ci: compile-gate FreeBSD in the test pipeline

Assisted-by: GLM 5.3 Flash

.gitea/workflows/test.yml

@@ -56,6 +56,28 @@ jobs:
       - name: Build
         run: go build ./...
 
+      - name: FreeBSD build (amd64)
+        # The debugger's ptrace surface and the JIT substrate are the two
+        # FreeBSD-portable layers the tree carries; the forge has no FreeBSD
+        # runner, so a push can only compile-gate them. Running the ptrace
+        # suite needs real FreeBSD hardware.
+        env:
+          GOOS: freebsd
+          GOARCH: amd64
+        run: go build ./...
+
+      - name: FreeBSD build (arm64)
+        env:
+          GOOS: freebsd
+          GOARCH: arm64
+        run: go build ./...
+
+      - name: FreeBSD build (riscv64)
+        env:
+          GOOS: freebsd
+          GOARCH: riscv64
+        run: go build ./...
+
       - name: Format
         run: |
           perl -e '

CHANGELOG.md

@@ -9,7 +9,56 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
--
+- **The FreeBSD port of the debugger.**  `gasm debug` runs on FreeBSD on
+  amd64, arm64 and riscv64: the same interactive surface as on Linux —
+  breakpoints, hardware watchpoints (x86 debug registers, the arm64 debug
+  register file), single-stepping, register and memory access — behind the
+  kernel's own ptrace requests, with tracee memory through `PT_IO` and
+  stop reports through `PT_LWPINFO`.  The JIT substrate maps executable
+  memory through `golang.org/x/sys/unix`, so `verify` builds on FreeBSD
+  too.  The pipeline compile-gates all three architectures; live
+  validation awaits a FreeBSD machine.
+- **Workspace-wide navigation in the language server.**  `gasm lsp` indexes
+  the `.s` files under the workspace root beyond the documents the editor
+  has open, so go-to-definition, find references and workspace symbol search
+  reach files that were never opened.  An open buffer always shadows its
+  disk copy, and watched-file events together with a per-query freshness
+  check keep the index current.
+- **Quick fixes for the textflag include and the argument area.**  The
+  `missing-textflag-include` warning offers to add the include after the
+  last one in the file, and the `abi-argsize` warning offers to set the
+  TEXT argument area to the size the `// func` signature implies, computed
+  by the new `lint.ExpectedArgSize`.
+
+### Changed
+
+- **The corpus audit assembles like the build.**  A file's `//go:build`
+  constraint decides which target architectures attempt it: cpu_x86.s is
+  an x86 build alone, and the msan and goexperiment.runtimesecret trees
+  are compiled by no supported build, so they leave the measured set
+  instead of failing it.  The headline now reads "assemble for every
+  applicable target": every real-code GOROOT assembly file, the tree
+  without testdata, assembles for all four architectures (250 of 250,
+  100 %); over the whole tree including testdata the measure is 271 of
+  322 (84.2 %).
+
+### Fixed
+
+- **Rename edits land in their own documents.**  A rename collected the
+  ranges of every reference across the open documents but applied them all
+  to the document that started it, so renaming a symbol used in a second
+  file moved that file's text into the first.  Each edit now applies to the
+  document it was collected in.
+- **Negative numeric PC-relative jumps.**  `JMP -3(PC)`, the shape the
+  runtime's exit loops write (sys_linux_amd64.s, sys_netbsd_amd64.s),
+  resolved to nothing: only the forward forms counted.  A negative count
+  now walks the same instruction statements backwards, labels excluded,
+  byte-identical with the toolchain.
+- **The arm64 move-wide family reads its immediate as an unsigned
+  pattern.**  `MOVK $(40000<<48)` folds to a negative int64 and was
+  rejected; the toolchain picks the 16-bit lane from the 64-bit bit
+  pattern, so the encoder now does the same, and a zero immediate is
+  rejected where the toolchain rejects it.
 
 ## [0.35.0] - 2026-09-22
 

README.md

@@ -94,13 +94,16 @@ to give that syntax the tooling it deserves.
 - **Debugger.**  `gasm debug` is a source-level ptrace debugger with
   breakpoints (optionally conditional), hardware watchpoints, register and
   memory inspection, and headless script runs that report instruction and
-  label coverage.
+  label coverage; it runs on Linux (all four architectures) and FreeBSD
+  (amd64, arm64, riscv64).
 - **Language server.**  `gasm lsp` serves completion, hover, document symbols,
   push and pull diagnostics, semantic-token highlighting, go-to-definition,
   find references, rename, formatting, inlay hints, code actions, signature
   help, document highlights, workspace symbol search, #include document
   links and folding ranges over stdio; definition, references and rename
-  work across every open document.
+  work across every open document and the indexed workspace files beyond
+  them, and the quick fixes add a missing textflag.h include and set the
+  argument area from the // func signature.
 - **Comparators and audits.**  `gasm diff` compares the machine code of two
   assembly files byte-for-byte, `gasm profile` shows basic-block structure,
   `gasm audit-instructions` diffs the encoder against the installed toolchain,
@@ -127,10 +130,13 @@ can emit today is narrower, and a recognised but unencodable instruction is
 reported as an explicit error, never as a wrong byte.
 
 The same measurement runs over GOROOT's whole assembly corpus:
-`gasm audit-instructions --corpus` reports 291 of 353 attemptable files
-(82.4 %) assembling for every target architecture today (files named for
-other Go ports are counted but never attempted), with the top failure
-reasons per architecture; the number moves with every release.
+`gasm audit-instructions --corpus` reports every real-code GOROOT assembly
+file (the tree without testdata) assembling for every target its build
+admits: 250 of 250, 100 %. Over the whole tree including testdata the
+measure is 271 of 322 attemptable (84.2 %); files named for other Go ports
+are counted but never attempted, and `//go:build` constraints decide which
+targets attempt a file at all, exactly as the build does. The number moves
+with every release.
 
 ### Validation status
 
@@ -145,7 +151,7 @@ actually been executed.
 |---|---|---|
 | Encoding: byte-for-byte against `go tool asm` | native hardware | native hardware (the toolchain cross-assembles any GOARCH on any host) |
 | Execution: JIT calls, ABI checks, differential fuzzing | native hardware | qemu-user emulation |
-| Debugger: ptrace tracing, breakpoints, watchpoints, coverage | native hardware | emulation cannot run ptrace; the layer compiles and its architecture-neutral units run under `go test ./...`, nothing more |
+| Debugger: ptrace tracing, breakpoints, watchpoints, coverage | native hardware | emulation cannot run ptrace; the layer compiles and its architecture-neutral units run under `go test ./...`, nothing more. FreeBSD (amd64, arm64, riscv64) is in the same position: the port compiles behind the cross-build gate and its integration test is ready, but no FreeBSD machine has executed it |
 
 Consequences, stated plainly. An emulator is a model of a CPU, not the
 CPU: instruction semantics are implemented in software and can differ
@@ -215,9 +221,11 @@ The plan, in the order it is being worked:
   toolchain itself does not support; through ELF, Plan 9 assembly becomes
   usable outside Go entirely.
 - **Platforms: Linux and FreeBSD.**  Linux is supported today on all four
-  architectures and is where the binary builds.  FreeBSD follows: the
-  JIT's executable-memory mapping and the ptrace debugger layer are the
-  two pieces of porting work.  Other unix systems may follow those two.
+  architectures and is where the binary builds.  FreeBSD follows on amd64,
+  arm64 and riscv64: the JIT's executable-memory mapping and the ptrace
+  debugger layer are ported (the debugger's live validation awaits a
+  FreeBSD machine, as the validation status states).  Other unix systems
+  may follow those two.
 - **Four architectures, no more.**  amd64, arm64, riscv64 and loong64.
   No others are planned.
 

asm/arm64_assemble.go

@@ -3069,29 +3069,29 @@ func encodeARM64MoveWide(mnem string, baseOp uint32, ops []*ast.Operand) ([]byte
 	// base, so MOVZ and MOVN come along for free.
 	opc := baseOp >> 29 & 3
 	sf := baseOp >> 31 & 1
-	v := arm64Imm64(ops[0])
-	if v < 0 {
-		return nil, fmt.Errorf("%s: negative immediate %d", mnem, v)
+	// The toolchain's optab case 33, shared by the whole family in both
+	// widths: the immediate is one unsigned 64-bit pattern (a high-lane
+	// constant such as $(40000<<48) arrives negative through int64
+	// folding), it must occupy exactly one 16-bit lane, zero is rejected,
+	// and the W forms cannot reach the top half.
+	u := uint64(arm64Imm64(ops[0]))
+	if u == 0 {
+		return nil, fmt.Errorf("%s: zero immediate cannot be handled", mnem)
 	}
 	hw := -1
-	for i := range 4 {
-		if v>>(uint(i)*16)&0xFFFF != 0 {
-			hw = i
+	for lane := range 4 {
+		if u&^(uint64(0xFFFF)<<(lane*16)) == 0 {
+			hw = lane
 			break
 		}
 	}
 	if hw < 0 {
-		hw = 0 // zero: every chunk is zero, hw = 0 carries it
-	}
-	for i := hw + 1; i < 4; i++ {
-		if v>>(uint(i)*16)&0xFFFF != 0 {
-			return nil, fmt.Errorf("%s: immediate %d does not fit one 16-bit chunk", mnem, v)
-		}
+		return nil, fmt.Errorf("%s: immediate %#x does not fit one 16-bit chunk", mnem, u)
 	}
 	if sf == 0 && hw > 1 {
-		return nil, fmt.Errorf("%s: immediate %d out of range for the 32-bit form", mnem, v)
+		return nil, fmt.Errorf("%s: immediate %#x out of range for the 32-bit form", mnem, u)
 	}
-	return a64wordLE(a64MoveWide(sf, opc, uint32(hw), uint32(v>>uint(hw*16)&0xFFFF), uint32(rd))), nil
+	return a64wordLE(a64MoveWide(sf, opc, uint32(hw), uint32(u>>uint(hw*16)&0xFFFF), uint32(rd))), nil
 }
 
 // ---- Bitfield/EXTR encoding ----

asm/arm64_encode_test.go

@@ -1051,6 +1051,41 @@ func TestArm64MOVK(t *testing.T) {
 	}
 }
 
+// TestArm64MOVKHighLane pins the shifted high-lane immediate the arm64 test
+// kernels write: $(40000<<48) folds to a negative int64, and the toolchain
+// reads the value as an unsigned 64-bit pattern when it picks the lane.
+func TestArm64MOVKHighLane(t *testing.T) {
+	got := arm64Words(t, "\tMOVK $(40000<<48), R0\n\tMOVK $0x9c40000000000000, R1\n")
+	want := []uint32{
+		0xf2f38800, // MOVK $(40000<<48), R0 (go tool asm: f2f38800)
+		0xf2f38801, // MOVK hw=3
+		0xd65f03c0,
+	}
+	if len(got) != len(want) {
+		t.Fatalf("word count = %d, want %d", len(got), len(want))
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Errorf("word %d = %08x, want %08x", i, got[i], want[i])
+		}
+	}
+}
+
+// TestArm64MoveWideZeroImmediate pins the toolchain's rejection of a zero
+// immediate in the move-wide family (optab case 33: "zero shifts cannot be
+// handled"): every lane is zero, so no hw field can carry it.
+func TestArm64MoveWideZeroImmediate(t *testing.T) {
+	for _, mnem := range []string{"MOVK", "MOVZ", "MOVN"} {
+		f, errs := parser.Parse("test_arm64.s", "#include \"textflag.h\"\n\nTEXT ·f(SB), NOSPLIT, $0-0\n\t"+mnem+" $0, R0\n\tRET\n")
+		if len(errs) > 0 {
+			t.Fatalf("%s: parse: %v", mnem, errs)
+		}
+		if _, err := AssembleFileARM64(f); err == nil {
+			t.Errorf("%s $0: expected error, got nil", mnem)
+		}
+	}
+}
+
 // TestArm64LoadImm64 tests 64-bit immediate loading.
 func TestArm64LoadImm64(t *testing.T) {
 	src := `#include "textflag.h"

asm/assemble.go

@@ -543,11 +543,27 @@ func pcJumpOffset(op *ast.Operand) (int, bool) {
 // pcJumpTarget resolves a numeric jump at statement index j: N counts the
 // instruction statements after the jump itself (N = 0 is the jump's own
 // address, the classic park loop), and the target is the start of the Nth
-// one.  It reports false when the count runs past the end of the function.
+// one.  A negative N counts the same way backwards, before the jump: the
+// exit loops write JMP -3(PC) to land three instructions earlier.  Labels
+// count not, in either direction.  It reports false when the count runs
+// past the end of the function, or before its first instruction.
 func pcJumpTarget(t *ast.Text, j, n int, pcs []int) (int, bool) {
 	if n == 0 {
 		return pcs[j], true
 	}
+	if n < 0 {
+		seen := 0
+		for k := j - 1; k >= 0; k-- {
+			if _, ok := t.Body[k].(*ast.Instr); !ok {
+				continue
+			}
+			seen--
+			if seen == n {
+				return pcs[k], true
+			}
+		}
+		return 0, false
+	}
 	seen := 0
 	for k := j + 1; k < len(t.Body); k++ {
 		if _, ok := t.Body[k].(*ast.Instr); !ok {

asm/assemble_test.go

@@ -370,6 +370,58 @@ end:
 	}
 }
 
+// TestAssembleNumericPCJumps pins the numeric ±N(PC) branch operands: N
+// counts instruction statements, skipping labels, in both directions (the
+// runtime's exit loops write JMP -3(PC)), N = 0 parks on the jump itself.
+func TestAssembleNumericPCJumps(t *testing.T) {
+	fn := firstText(t, `
+#include "textflag.h"
+TEXT ·exit(SB), NOSPLIT, $0
+	MOVB $1, AL
+lab:
+	MOVB $2, AL
+	MOVB $3, AL
+	JMP -3(PC)
+	MOVB $4, AL
+park:
+	JMP 0(PC)
+	MOVB $5, AL
+	JMP 2(PC)
+	MOVB $6, AL
+	RET
+`)
+	code, _, err := Assemble(fn)
+	if err != nil {
+		t.Fatalf("Assemble: %v", err)
+	}
+	// From the Go-assembled function:
+	//   MOVB $1, AL       b001
+	//   MOVB $2, AL       b002
+	//   MOVB $3, AL       b003
+	//   JMP -3(PC)        ebf8      (three instructions back, past lab:)
+	//   MOVB $4, AL       b004
+	//   JMP 0(PC)         ebfe      (the park loop)
+	//   MOVB $5, AL       b005
+	//   JMP 2(PC)         eb02      (over MOVB $6 to the RET)
+	//   MOVB $6, AL       b006
+	//   RET               c3
+	want := []byte{
+		0xb0, 0x01,
+		0xb0, 0x02,
+		0xb0, 0x03,
+		0xeb, 0xf8,
+		0xb0, 0x04,
+		0xeb, 0xfe,
+		0xb0, 0x05,
+		0xeb, 0x02,
+		0xb0, 0x06,
+		0xc3,
+	}
+	if hexBytes(code) != hexBytes(want) {
+		t.Errorf("numeric-PC mismatch:\n got:  %s\n want: %s", hexBytes(code), hexBytes(want))
+	}
+}
+
 func TestAssemblePrefetch(t *testing.T) {
 	fn := firstText(t, `
 #include "textflag.h"

cmd/gasm/asmhdr_test.go

@@ -393,6 +393,52 @@ func TestRunCorpusAuditGOOS(t *testing.T) {
 	}
 }
 
+// TestRunCorpusAuditBuildConstraint covers the //go:build classification end
+// to end: a generic-named file whose constraint admits one target is
+// attempted there alone (cpu_x86.s on amd64), and a file whose constraint
+// admits none of the four targets is never attempted (the msan and
+// goexperiment trees).
+func TestRunCorpusAuditBuildConstraint(t *testing.T) {
+	dir := t.TempDir()
+	write := func(name, src string) {
+		t.Helper()
+		if err := os.WriteFile(filepath.Join(dir, name), []byte(src), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	write("x86.s", "//go:build 386 || amd64\n\nTEXT \xc2\xb7f(SB), NOSPLIT, $0\n\tRET\n")
+	write("racey.s", "//go:build race\n\nTEXT \xc2\xb7r(SB), NOSPLIT, $0\n\tRET\n")
+	write("plain.s", "TEXT \xc2\xb7p(SB), NOSPLIT, $0\n\tRET\n")
+
+	stats, err := runCorpusAudit(dir, nil)
+	if err != nil {
+		t.Fatalf("runCorpusAudit: %v", err)
+	}
+	tally := func(name string) *corpusTally {
+		for i, tg := range stats.targets {
+			if tg.name == name {
+				return stats.tallies[i]
+			}
+		}
+		t.Fatalf("no tally for %s", name)
+		return nil
+	}
+	if stats.narrowed != 1 || stats.excluded != 1 || stats.generic != 1 {
+		t.Errorf("buckets = narrowed %d, excluded %d, generic %d; want 1, 1, 1", stats.narrowed, stats.excluded, stats.generic)
+	}
+	if a := tally("amd64"); a.attempted != 2 || a.assembled != 2 {
+		t.Errorf("amd64 = %d/%d, want 2/2 (x86.s and plain.s)", a.assembled, a.attempted)
+	}
+	for _, name := range []string{"arm64", "riscv64", "loong64"} {
+		if a := tally(name); a.attempted != 1 || a.assembled != 1 {
+			t.Errorf("%s = %d/%d, want 1/1 (plain.s only)", name, a.assembled, a.attempted)
+		}
+	}
+	if stats.full != 2 {
+		t.Errorf("full = %d, want 2 (x86.s over its one target, plain.s over all four)", stats.full)
+	}
+}
+
 // TestGenerateGoAsmHeaderRuntime pins the generator against the real thing:
 // the runtime package of the ambient toolchain, whose header the toolchain's
 // own -asmhdr output was sampled from.  Skipped in short mode: it type-checks

cmd/gasm/audit.go

@@ -5,6 +5,7 @@ package main
 
 import (
 	"fmt"
+	"go/build/constraint"
 	"maps"
 	"os"
 	"os/exec"
@@ -476,8 +477,10 @@ type corpusStats struct {
 	root      string
 	files     int
 	generic   int // files attempted for all four architectures
+	narrowed  int // files whose //go:build admits a proper subset of the four
+	excluded  int // files whose //go:build admits none of the four: never compiled
 	otherPort int // files named for another Go port: never attempted
-	full      int // files that assembled for every target architecture
+	full      int // files that assembled for every applicable target architecture
 	targets   []corpusTarget
 	tallies   []*corpusTally
 }
@@ -573,6 +576,57 @@ func otherGOOSFile(path string) bool {
 	return false
 }
 
+// buildConstraint returns the file's leading //go:build expression, or nil
+// when the file carries none.  The constraint governs the same header block
+// go/build reads: blank lines and comments may precede it, and the first
+// line that is neither ends the block.  A constraint that does not parse
+// narrows nothing, so the file stays in the attempted set: the audit must
+// never exclude a file the toolchain would compile.
+func buildConstraint(src string) constraint.Expr {
+	for line := range strings.SplitSeq(src, "\n") {
+		t := strings.TrimSpace(line)
+		switch {
+		case t == "":
+			continue
+		case strings.HasPrefix(t, "//"):
+			if constraint.IsGoBuild(t) {
+				e, err := constraint.Parse(t)
+				if err != nil {
+					return nil
+				}
+				return e
+			}
+			continue
+		default:
+			return nil
+		}
+	}
+	return nil
+}
+
+// unixOS is go/build's unixOS set: the GOOSes the unix build tag admits.
+var unixOS = map[string]bool{
+	"aix": true, "android": true, "darwin": true, "dragonfly": true,
+	"freebsd": true, "hurd": true, "illumos": true, "ios": true,
+	"linux": true, "netbsd": true, "openbsd": true, "solaris": true,
+}
+
+// constraintTags answers the build tags a plain `go build` sets for a
+// target: the GOOS and GOARCH, gc, and unix on the unix-like GOOSes.  No
+// experiment, sanitiser or cgo tag is ever true: the audit models the
+// default build, and no GOROOT assembly file's constraint hinges on cgo.
+func constraintTags(goarch, goos string) func(string) bool {
+	return func(tag string) bool {
+		switch tag {
+		case goarch, goos, "gc":
+			return true
+		case "unix":
+			return unixOS[goos]
+		}
+		return false
+	}
+}
+
 func runCorpusAudit(root string, dirs includeDirs) (*corpusStats, error) {
 	files, err := asmFiles(root)
 	if err != nil {
@@ -590,8 +644,8 @@ func runCorpusAudit(root string, dirs includeDirs) (*corpusStats, error) {
 		tallies[i] = &corpusTally{reasons: map[string]int{}, example: map[string]string{}}
 	}
 	// full is the north-star number: a file counts when every architecture
-	// its name allows assembles it.
-	full, generic, otherPort := 0, 0, 0
+	// its build admits assembles it.
+	full, generic, otherPort, narrowedCount, excluded := 0, 0, 0, 0, 0
 
 	// Header generation is created on first use, so a corpus with no
 	// go_asm.h includes never pays for a temp directory.
@@ -614,28 +668,78 @@ func runCorpusAudit(root string, dirs includeDirs) (*corpusStats, error) {
 		// invisible to a file-name rule).
 		goos := goosFromFilename(path)
 
+		// The GOOS the header generation type-checks under follows the
+		// file's name when the name carries one; the ambient GOOS is the
+		// honest guess otherwise.
+		namedArch := arch.FromFilename(path)
 		var wanted []int // indexes into targets
-		if a := arch.FromFilename(path); a != arch.Unknown {
+		other := false
+		switch {
+		case namedArch != arch.Unknown:
 			for i, tg := range targets {
-				if tg.a == a {
+				if tg.a == namedArch {
 					wanted = append(wanted, i)
 				}
 			}
-		} else if otherPortFile(path) {
+		case otherPortFile(path):
 			// A file named for a Go port gasm does not support (arm,
 			// 386, s390x, ...) or for another GOOS is compiled by no
 			// supported-arch build, so it is neither generic nor a
 			// per-arch attempt: counting it as generic would make the
 			// headline unreachably low for reasons no supported target
 			// can fix.
+			other = true
 			otherPort++
-		} else {
-			generic++
+		default:
 			for i := range targets {
 				wanted = append(wanted, i)
 			}
 		}
 
+		// A //go:build constraint narrows the set of targets the file is
+		// assembled for, the way the go command compiles the file only for
+		// the targets the expression admits: cpu_x86.s belongs to the x86
+		// build alone, and a file whose constraint admits none of the four
+		// targets (the goexperiment.runtimesecret and msan trees) is
+		// compiled by no supported build.  The tags mirror what a plain
+		// `go build` sets: the GOOS and GOARCH, gc, and unix on the
+		// unix-like GOOSes; no experiment, sanitiser or cgo tag is ever
+		// true.  The GOOS is the file's own when the name carries one,
+		// else the ambient one.
+		goosForEval := goos
+		if goosForEval == "" {
+			goosForEval = runtime.GOOS
+		}
+		narrowed := false
+		if len(wanted) > 0 {
+			if ce := buildConstraint(src); ce != nil {
+				kept := make([]int, 0, len(wanted))
+				for _, i := range wanted {
+					tg := targets[i]
+					if ce.Eval(constraintTags(goarchName(tg.a), goosForEval)) {
+						kept = append(kept, i)
+					}
+				}
+				if len(kept) < len(wanted) {
+					narrowed = true
+				}
+				wanted = kept
+			}
+		}
+
+		switch {
+		case other:
+			// already tallied above
+		case len(wanted) == 0:
+			excluded++
+		case namedArch != arch.Unknown:
+			// a per-arch attempt over the constraint's subset
+		case narrowed:
+			narrowedCount++
+		default:
+			generic++
+		}
+
 		// A file that includes go_asm.h parses against a per-target header:
 		// the defines differ per architecture (internal/cpu's layout, for
 		// one) and per GOOS (sys_darwin_arm64.s's trampoline constants,
@@ -719,6 +823,8 @@ func runCorpusAudit(root string, dirs includeDirs) (*corpusStats, error) {
 		root:      root,
 		files:     len(files),
 		generic:   generic,
+		narrowed:  narrowedCount,
+		excluded:  excluded,
 		otherPort: otherPort,
 		full:      full,
 		targets:   targets,
@@ -728,13 +834,15 @@ func runCorpusAudit(root string, dirs includeDirs) (*corpusStats, error) {
 
 // printCorpusStats renders the corpus audit report.
 func printCorpusStats(s *corpusStats, list bool) {
-	fmt.Printf("corpus %s: %d files (%d generic, attempted for all architectures; %d named for other Go ports, never attempted)\n", s.root, s.files, s.generic, s.otherPort)
+	fmt.Printf("corpus %s: %d files (%d generic, attempted for all architectures; %d narrowed by //go:build; %d excluded by //go:build; %d named for other Go ports, never attempted)\n",
+		s.root, s.files, s.generic, s.narrowed, s.excluded, s.otherPort)
 	// The rate is over the files a supported build would attempt: the
-	// other ports' files sit in the count for completeness but can never
-	// assemble, so counting them in the denominator would report the gap
-	// of architectures gasm deliberately does not target.
-	attemptable := max(s.files-s.otherPort, 1)
-	fmt.Printf("  assemble for every target architecture: %d of %d attemptable (%.1f%%)\n", s.full, attemptable, 100*float64(s.full)/float64(attemptable))
+	// other ports' files and the ones no supported target compiles sit in
+	// the count for completeness but can never assemble, so counting them
+	// in the denominator would report the gap of platforms gasm
+	// deliberately does not target.
+	attemptable := max(s.files-s.otherPort-s.excluded, 1)
+	fmt.Printf("  assemble for every applicable target: %d of %d attemptable (%.1f%%)\n", s.full, attemptable, 100*float64(s.full)/float64(attemptable))
 	for i, tg := range s.targets {
 		t := s.tallies[i]
 		fmt.Printf("  %s: %d/%d attempted\n", tg.name, t.assembled, t.attempted)

cmd/gasm/audit_test.go

@@ -4,6 +4,7 @@
 package main
 
 import (
+	"runtime"
 	"testing"
 
 	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
@@ -64,3 +65,62 @@ func TestGasmEncodable(t *testing.T) {
 		}
 	}
 }
+
+// TestBuildConstraint pins the //go:build reader: the constraint governs the
+// leading comment block, the first non-comment line ends it (a tag below a
+// #include governs nothing, exactly as go/build drops it), and a file
+// without one admits every target.
+func TestBuildConstraint(t *testing.T) {
+	admits := func(src, goarch, goos string) bool {
+		t.Helper()
+		e := buildConstraint(src)
+		if e == nil {
+			return true
+		}
+		return e.Eval(constraintTags(goarch, goos))
+	}
+	const ret = "TEXT \xc2\xb7f(SB), NOSPLIT, $0\n\tRET\n"
+	cases := []struct {
+		name         string
+		src          string
+		amd64, arm64 bool
+	}{
+		{"no constraint", ret, true, true},
+		{"x86 only", "//go:build 386 || amd64\n\n" + ret, true, false},
+		{"arm64 and linux", "//go:build arm64 && linux\n\n" + ret, false, true},
+		{"msan never", "//go:build msan\n\n" + ret, false, false},
+		{"experiment never", "//go:build goexperiment.runtimesecret\n\n" + ret, false, false},
+		{"below an include governs nothing", "#include \"textflag.h\"\n//go:build amd64\n" + ret, true, true},
+		{"unparsable narrows nothing", "//go:build (amd64\n" + ret, true, true},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := admits(c.src, "amd64", runtime.GOOS); got != c.amd64 {
+				t.Errorf("amd64 admission = %v, want %v", got, c.amd64)
+			}
+			if got := admits(c.src, "arm64", runtime.GOOS); got != c.arm64 {
+				t.Errorf("arm64 admission = %v, want %v", got, c.arm64)
+			}
+		})
+	}
+}
+
+// TestConstraintTags pins the tag set a plain `go build` sets: the GOOS and
+// GOARCH, gc, unix on the unix-like GOOSes; nothing else is ever true.
+func TestConstraintTags(t *testing.T) {
+	ok := constraintTags("amd64", "linux")
+	for _, tag := range []string{"amd64", "linux", "gc", "unix"} {
+		if !ok(tag) {
+			t.Errorf("tag %q = false, want true", tag)
+		}
+	}
+	for _, tag := range []string{"arm64", "freebsd", "darwin", "cgo", "race", "msan", "goexperiment.runtimesecret"} {
+		if ok(tag) {
+			t.Errorf("tag %q = true, want false", tag)
+		}
+	}
+	fb := constraintTags("arm64", "freebsd")
+	if !fb("unix") {
+		t.Error("unix on freebsd = false, want true")
+	}
+}

cmd/gasm/debug_other.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build !linux
+//go:build !(linux || (freebsd && (amd64 || arm64 || riscv64)))
 
 package main
 
@@ -11,6 +11,6 @@ import (
 )
 
 func cmdDebug(args []string) int {
-	fmt.Fprintln(os.Stderr, "gasm debug: the interactive debugger requires Linux (ptrace)")
+	fmt.Fprintln(os.Stderr, "gasm debug: the interactive debugger requires Linux or FreeBSD (ptrace)")
 	return 1
 }

cmd/gasm/debug_ptrace.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux
+//go:build linux || (freebsd && (amd64 || arm64 || riscv64))
 
 package main
 

debug/breakpoint.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux
+//go:build linux || (freebsd && (amd64 || arm64 || riscv64))
 
 package debug
 

debug/disasm_freebsd_amd64.go

@@ -0,0 +1,56 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && amd64
+
+package debug
+
+import (
+	"fmt"
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
+	"sourcedock.dev/petrbalvin/gasm-devkit/disasm"
+)
+
+// Disassemble decodes the instruction at the given address in the debuggee's
+// memory and returns its text representation and length in bytes.
+func (s *Session) Disassemble(addr uint64) (string, int, error) {
+	mem, err := s.ReadMemory(addr, 15)
+	if err != nil {
+		return "", 0, err
+	}
+	ins, err := disasm.Decode(arch.AMD64, mem, addr)
+	if err != nil {
+		return "", 0, err
+	}
+	return ins.Text, ins.Len, nil
+}
+
+// DisassembleN decodes up to n instructions starting at addr and returns
+// them as a formatted string with addresses and byte offsets.
+func (s *Session) DisassembleN(addr uint64, n int) string {
+	var result strings.Builder
+	pc := addr
+	for range n {
+		text, length, err := s.Disassemble(pc)
+		if err != nil {
+			result.WriteString(fmt.Sprintf("  %#08x: <error: %v>\n", pc, err))
+			break
+		}
+		result.WriteString(fmt.Sprintf("  %#08x: %s\n", pc, text))
+		if length == 0 {
+			length = 1
+		}
+		pc += uint64(length)
+	}
+	return result.String()
+}
+
+// isCallInsn reports whether disassembled text (x86asm.IntelSyntax) is a
+// call.  The first token must match exactly: a prefix test would also catch
+// unrelated mnemonics.
+func isCallInsn(text string) bool {
+	m, _, _ := strings.Cut(text, " ")
+	return strings.ToLower(m) == "call"
+}

debug/disasm_freebsd_arm64.go

@@ -0,0 +1,60 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && arm64
+
+package debug
+
+import (
+	"fmt"
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
+	"sourcedock.dev/petrbalvin/gasm-devkit/disasm"
+)
+
+// Disassemble decodes the instruction at the given address in the debuggee's
+// memory and returns its text representation and length in bytes.
+func (s *Session) Disassemble(addr uint64) (string, int, error) {
+	mem, err := s.ReadMemory(addr, 4)
+	if err != nil {
+		return "", 0, err
+	}
+	ins, err := disasm.Decode(arch.ARM64, mem, addr)
+	if err != nil {
+		return "", 0, err
+	}
+	return ins.Text, ins.Len, nil
+}
+
+// DisassembleN decodes up to n instructions starting at addr and returns
+// them as a formatted string with addresses and byte offsets.
+func (s *Session) DisassembleN(addr uint64, n int) string {
+	var result strings.Builder
+	pc := addr
+	for range n {
+		text, length, err := s.Disassemble(pc)
+		if err != nil {
+			result.WriteString(fmt.Sprintf("  %#08x: <error: %v>\n", pc, err))
+			break
+		}
+		result.WriteString(fmt.Sprintf("  %#08x: %s\n", pc, text))
+		if length == 0 {
+			length = 1
+		}
+		pc += uint64(length)
+	}
+	return result.String()
+}
+
+// isCallInsn reports whether disassembled text (arm64asm.GoSyntax) is a
+// call.  GoSyntax renders bl as CALL; the native mnemonic is accepted too.
+// The first token must match exactly so branches never match.
+func isCallInsn(text string) bool {
+	m, _, _ := strings.Cut(text, " ")
+	switch strings.ToLower(m) {
+	case "call", "bl":
+		return true
+	}
+	return false
+}

debug/disasm_freebsd_riscv64.go

@@ -0,0 +1,62 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && riscv64
+
+package debug
+
+import (
+	"fmt"
+	"strings"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/arch"
+	"sourcedock.dev/petrbalvin/gasm-devkit/disasm"
+)
+
+// Disassemble decodes the instruction at the given address in the debuggee's
+// memory and returns its text representation and length in bytes.
+func (s *Session) Disassemble(addr uint64) (string, int, error) {
+	mem, err := s.ReadMemory(addr, 4)
+	if err != nil {
+		return "", 0, err
+	}
+	ins, err := disasm.Decode(arch.RISCV, mem, addr)
+	if err != nil {
+		return "", 0, err
+	}
+	return ins.Text, ins.Len, nil
+}
+
+// DisassembleN decodes up to n instructions starting at addr and returns
+// them as a formatted string with addresses and byte offsets.
+func (s *Session) DisassembleN(addr uint64, n int) string {
+	var result strings.Builder
+	pc := addr
+	for range n {
+		text, length, err := s.Disassemble(pc)
+		if err != nil {
+			result.WriteString(fmt.Sprintf("  %#08x: <error: %v>\n", pc, err))
+			break
+		}
+		result.WriteString(fmt.Sprintf("  %#08x: %s\n", pc, text))
+		if length == 0 {
+			length = 1
+		}
+		pc += uint64(length)
+	}
+	return result.String()
+}
+
+// isCallInsn reports whether disassembled text (riscv64asm.GoSyntax) is a
+// call.  GoSyntax renders jal and jalr calls as CALL; the native mnemonics
+// are accepted too.  The first token must match exactly: a prefix test on
+// "bl" would catch branches on other architectures, and jalr as ret prints
+// RET, which must not be stepped over.
+func isCallInsn(text string) bool {
+	m, _, _ := strings.Cut(text, " ")
+	switch strings.ToLower(m) {
+	case "call", "jal", "jalr":
+		return true
+	}
+	return false
+}

debug/display_freebsd_amd64.go

@@ -0,0 +1,136 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && amd64
+
+package debug
+
+import "fmt"
+
+func printRegs(regs *Regs, codeBase, funcOff uint64) {
+	fmt.Printf("  RIP = %#016x  (func+%#x)\n", regs.RIP, regs.RIP-codeBase-funcOff)
+	fmt.Printf("  RSP = %#016x  RBP = %#016x\n", regs.RSP, regs.RBP)
+	fmt.Printf("  RAX = %#016x  RBX = %#016x\n", regs.RAX, regs.RBX)
+	fmt.Printf("  RCX = %#016x  RDX = %#016x\n", regs.RCX, regs.RDX)
+	fmt.Printf("  RSI = %#016x  RDI = %#016x\n", regs.RSI, regs.RDI)
+	fmt.Printf("  R8  = %#016x  R9  = %#016x\n", regs.R8, regs.R9)
+	fmt.Printf("  R10 = %#016x  R11 = %#016x\n", regs.R10, regs.R11)
+	fmt.Printf("  R12 = %#016x  R13 = %#016x\n", regs.R12, regs.R13)
+	fmt.Printf("  R14 = %#016x  R15 = %#016x\n", regs.R14, regs.R15)
+	fmt.Printf("  RFLAGS = %#x  [%s]\n", regs.RFLAGS, decodeRflags(regs.RFLAGS))
+}
+
+func printVectorRegs(v *VectorRegs) {
+	fmt.Println("\n  Vector registers (YMM):")
+	for i := 0; i < 16; i += 2 {
+		fmt.Printf("  YMM%-2d = ", i)
+		printYMM(v.YMM[i][:])
+		fmt.Printf("  YMM%-2d = ", i+1)
+		printYMM(v.YMM[i+1][:])
+		fmt.Println()
+	}
+}
+
+func printYMM(b []byte) {
+	for j := 0; j < 32; j += 4 {
+		v := uint32(b[j]) | uint32(b[j+1])<<8 | uint32(b[j+2])<<16 | uint32(b[j+3])<<24
+		fmt.Printf("%08x ", v)
+	}
+}
+
+func decodeRflags(f uint64) string {
+	var flags string
+	if f&1 != 0 {
+		flags += "CF "
+	}
+	if f&(1<<2) != 0 {
+		flags += "PF "
+	}
+	if f&(1<<4) != 0 {
+		flags += "AF "
+	}
+	if f&(1<<6) != 0 {
+		flags += "ZF "
+	}
+	if f&(1<<7) != 0 {
+		flags += "SF "
+	}
+	if f&(1<<8) != 0 {
+		flags += "TF "
+	}
+	if f&(1<<9) != 0 {
+		flags += "IF "
+	}
+	if f&(1<<10) != 0 {
+		flags += "DF "
+	}
+	if f&(1<<11) != 0 {
+		flags += "OF "
+	}
+	if flags == "" {
+		return "none"
+	}
+	return flags[:len(flags)-1]
+}
+
+// SetReg modifies a register value in the debuggee.
+func (s *Session) SetReg(name string, value uint64) error {
+	regs, err := s.GetRegs()
+	if err != nil {
+		return err
+	}
+	switch name {
+	case "rax", "eax", "ax", "al":
+		regs.RAX = value
+	case "rbx", "ebx", "bx", "bl":
+		regs.RBX = value
+	case "rcx", "ecx", "cx", "cl":
+		regs.RCX = value
+	case "rdx", "edx", "dx", "dl":
+		regs.RDX = value
+	case "rsi", "esi", "si":
+		regs.RSI = value
+	case "rdi", "edi", "di":
+		regs.RDI = value
+	case "rbp", "ebp", "bp":
+		regs.RBP = value
+	case "rsp", "esp", "sp":
+		regs.RSP = value
+	case "r8":
+		regs.R8 = value
+	case "r9":
+		regs.R9 = value
+	case "r10":
+		regs.R10 = value
+	case "r11":
+		regs.R11 = value
+	case "r12":
+		regs.R12 = value
+	case "r13":
+		regs.R13 = value
+	case "r14":
+		regs.R14 = value
+	case "r15":
+		regs.R15 = value
+	case "rip", "eip":
+		regs.RIP = value
+	default:
+		return fmt.Errorf("debug: unknown register %q", name)
+	}
+	return s.SetRegs(&regs)
+}
+
+// archReturnAddr reads the return address of the current frame (amd64
+// ABI0 convention).  A function that contains a CALL (or has a frame) is
+// assembled with the prologue PUSHQ BP; MOVQ SP, BP, so mid-function the
+// word at SP is the saved caller BP, a stack address, and the return
+// address sits further up.  Walk the stack from SP and take the first word
+// that lies in an executable mapping: stack and data words never do, a
+// return address always does.  FreeBSD exposes no mapping list, so the
+// walk degenerates to the raw entry convention, [SP] before any push.
+func archReturnAddr(s *Session, regs *Regs) (uint64, error) {
+	return s.Peek(regs.RSP)
+}
+
+// archSPLabel returns the SP register name for display.
+func archSPLabel() string { return "RSP" }

debug/display_freebsd_arm64.go

@@ -0,0 +1,127 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && arm64
+
+package debug
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+func printRegs(regs *Regs, codeBase, funcOff uint64) {
+	fmt.Printf("  PC  = %#016x  (func+%#x)\n", regs.PC, regs.PC-codeBase-funcOff)
+	fmt.Printf("  SP  = %#016x  FP  = %#016x\n", regs.SP, regs.X29)
+	fmt.Printf("  LR  = %#016x\n", regs.X30)
+	fmt.Printf("  X0  = %#016x  X1  = %#016x\n", regs.X0, regs.X1)
+	fmt.Printf("  X2  = %#016x  X3  = %#016x\n", regs.X2, regs.X3)
+	fmt.Printf("  X4  = %#016x  X5  = %#016x\n", regs.X4, regs.X5)
+	fmt.Printf("  X6  = %#016x  X7  = %#016x\n", regs.X6, regs.X7)
+	fmt.Printf("  X8  = %#016x  X9  = %#016x\n", regs.X8, regs.X9)
+	fmt.Printf("  X10 = %#016x  X11 = %#016x\n", regs.X10, regs.X11)
+	fmt.Printf("  X12 = %#016x  X13 = %#016x\n", regs.X12, regs.X13)
+	fmt.Printf("  X14 = %#016x  X15 = %#016x\n", regs.X14, regs.X15)
+	fmt.Printf("  X16 = %#016x  X17 = %#016x\n", regs.X16, regs.X17)
+	fmt.Printf("  X18 = %#016x  X19 = %#016x\n", regs.X18, regs.X19)
+	fmt.Printf("  X20 = %#016x  X21 = %#016x\n", regs.X20, regs.X21)
+	fmt.Printf("  X22 = %#016x  X23 = %#016x\n", regs.X22, regs.X23)
+	fmt.Printf("  X24 = %#016x  X25 = %#016x\n", regs.X24, regs.X25)
+	fmt.Printf("  X26 = %#016x  X27 = %#016x\n", regs.X26, regs.X27)
+	fmt.Printf("  X28 = %#016x  PSTATE = %#x\n", regs.X28, regs.PSTATE)
+}
+
+func printVectorRegs(v *VectorRegs) {
+	fmt.Println("\n  Vector registers (V0-V31):")
+	for i := 0; i < 32; i += 2 {
+		fmt.Printf("  V%-2d  = %016x%016x\n", i, binary.LittleEndian.Uint64(v.V[i][8:16]), binary.LittleEndian.Uint64(v.V[i][0:8]))
+		fmt.Printf("  V%-2d  = %016x%016x\n", i+1, binary.LittleEndian.Uint64(v.V[i+1][8:16]), binary.LittleEndian.Uint64(v.V[i+1][0:8]))
+	}
+}
+
+// SetReg modifies a register value in the debuggee.
+func (s *Session) SetReg(name string, value uint64) error {
+	regs, err := s.GetRegs()
+	if err != nil {
+		return err
+	}
+	switch name {
+	case "x0":
+		regs.X0 = value
+	case "x1":
+		regs.X1 = value
+	case "x2":
+		regs.X2 = value
+	case "x3":
+		regs.X3 = value
+	case "x4":
+		regs.X4 = value
+	case "x5":
+		regs.X5 = value
+	case "x6":
+		regs.X6 = value
+	case "x7":
+		regs.X7 = value
+	case "x8":
+		regs.X8 = value
+	case "x9":
+		regs.X9 = value
+	case "x10":
+		regs.X10 = value
+	case "x11":
+		regs.X11 = value
+	case "x12":
+		regs.X12 = value
+	case "x13":
+		regs.X13 = value
+	case "x14":
+		regs.X14 = value
+	case "x15":
+		regs.X15 = value
+	case "x16":
+		regs.X16 = value
+	case "x17":
+		regs.X17 = value
+	case "x18":
+		regs.X18 = value
+	case "x19":
+		regs.X19 = value
+	case "x20":
+		regs.X20 = value
+	case "x21":
+		regs.X21 = value
+	case "x22":
+		regs.X22 = value
+	case "x23":
+		regs.X23 = value
+	case "x24":
+		regs.X24 = value
+	case "x25":
+		regs.X25 = value
+	case "x26":
+		regs.X26 = value
+	case "x27":
+		regs.X27 = value
+	case "x28":
+		regs.X28 = value
+	case "x29", "fp":
+		regs.X29 = value
+	case "x30", "lr":
+		regs.X30 = value
+	case "sp":
+		regs.SP = value
+	case "pc":
+		regs.PC = value
+	default:
+		return fmt.Errorf("debug: unknown register %q", name)
+	}
+	return s.SetRegs(&regs)
+}
+
+// archReturnAddr reads the return address from LR (arm64 convention).
+func archReturnAddr(s *Session, regs *Regs) (uint64, error) {
+	return regs.X30, nil
+}
+
+// archSPLabel returns the SP register name for display.
+func archSPLabel() string { return "SP" }

debug/display_freebsd_riscv64.go

@@ -0,0 +1,121 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && riscv64
+
+package debug
+
+import "fmt"
+
+func printRegs(regs *Regs, codeBase, funcOff uint64) {
+	fmt.Printf("  PC  = %#016x  (func+%#x)\n", regs.PC, regs.PC-codeBase-funcOff)
+	fmt.Printf("  SP  = %#016x  FP  = %#016x\n", regs.Sp, regs.S0)
+	fmt.Printf("  RA  = %#016x\n", regs.Ra)
+	fmt.Printf("  A0  = %#016x  A1  = %#016x\n", regs.A0, regs.A1)
+	fmt.Printf("  A2  = %#016x  A3  = %#016x\n", regs.A2, regs.A3)
+	fmt.Printf("  A4  = %#016x  A5  = %#016x\n", regs.A4, regs.A5)
+	fmt.Printf("  A6  = %#016x  A7  = %#016x\n", regs.A6, regs.A7)
+	fmt.Printf("  T0  = %#016x  T1  = %#016x\n", regs.T0, regs.T1)
+	fmt.Printf("  T2  = %#016x  T3  = %#016x\n", regs.T2, regs.T3)
+	fmt.Printf("  T4  = %#016x  T5  = %#016x\n", regs.T4, regs.T5)
+	fmt.Printf("  T6  = %#016x\n", regs.T6)
+	fmt.Printf("  S1  = %#016x  S2  = %#016x\n", regs.S1, regs.S2)
+	fmt.Printf("  S3  = %#016x  S4  = %#016x\n", regs.S3, regs.S4)
+	fmt.Printf("  S5  = %#016x  S6  = %#016x\n", regs.S5, regs.S6)
+	fmt.Printf("  S7  = %#016x  S8  = %#016x\n", regs.S7, regs.S8)
+	fmt.Printf("  S9  = %#016x  S10 = %#016x\n", regs.S9, regs.S10)
+	fmt.Printf("  S11 = %#016x\n", regs.S11)
+}
+
+func printVectorRegs(v *VectorRegs) {
+	fmt.Println("\n  FP registers (F0-F31):")
+	for i := 0; i < 32; i += 2 {
+		fmt.Printf("  F%-2d  = %#018x  F%-2d  = %#018x\n", i, v.F[i], i+1, v.F[i+1])
+	}
+	fmt.Printf("  FCSR = %#x\n", v.FCSR)
+}
+
+// SetReg modifies a register value in the debuggee.
+func (s *Session) SetReg(name string, value uint64) error {
+	regs, err := s.GetRegs()
+	if err != nil {
+		return err
+	}
+	switch name {
+	case "pc":
+		regs.PC = value
+	case "ra", "x1":
+		regs.Ra = value
+	case "sp", "x2":
+		regs.Sp = value
+	case "gp", "x3":
+		regs.Gp = value
+	case "tp", "x4":
+		regs.Tp = value
+	case "t0", "x5":
+		regs.T0 = value
+	case "t1", "x6":
+		regs.T1 = value
+	case "t2", "x7":
+		regs.T2 = value
+	case "s0", "fp", "x8":
+		regs.S0 = value
+	case "s1", "x9":
+		regs.S1 = value
+	case "a0", "x10":
+		regs.A0 = value
+	case "a1", "x11":
+		regs.A1 = value
+	case "a2", "x12":
+		regs.A2 = value
+	case "a3", "x13":
+		regs.A3 = value
+	case "a4", "x14":
+		regs.A4 = value
+	case "a5", "x15":
+		regs.A5 = value
+	case "a6", "x16":
+		regs.A6 = value
+	case "a7", "x17":
+		regs.A7 = value
+	case "s2", "x18":
+		regs.S2 = value
+	case "s3", "x19":
+		regs.S3 = value
+	case "s4", "x20":
+		regs.S4 = value
+	case "s5", "x21":
+		regs.S5 = value
+	case "s6", "x22":
+		regs.S6 = value
+	case "s7", "x23":
+		regs.S7 = value
+	case "s8", "x24":
+		regs.S8 = value
+	case "s9", "x25":
+		regs.S9 = value
+	case "s10", "x26":
+		regs.S10 = value
+	case "s11", "x27":
+		regs.S11 = value
+	case "t3", "x28":
+		regs.T3 = value
+	case "t4", "x29":
+		regs.T4 = value
+	case "t5", "x30":
+		regs.T5 = value
+	case "t6", "x31":
+		regs.T6 = value
+	default:
+		return fmt.Errorf("debug: unknown register %q", name)
+	}
+	return s.SetRegs(&regs)
+}
+
+// archReturnAddr reads the return address from RA (riscv64 convention).
+func archReturnAddr(s *Session, regs *Regs) (uint64, error) {
+	return regs.Ra, nil
+}
+
+// archSPLabel returns the SP register name for display.
+func archSPLabel() string { return "SP" }

debug/ptrace_freebsd.go

@@ -0,0 +1,288 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && (amd64 || arm64 || riscv64)
+
+package debug
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"syscall"
+	"time"
+
+	"golang.org/x/sys/unix"
+)
+
+// Session is a ptrace debugging session controlling one debuggee process.
+// The FreeBSD implementation sits behind the same surface as the Linux one:
+// PT_TRACE_ME from the debuggee, PT_CONTINUE/PT_STEP from the tracer, and
+// tracee memory through PT_IO (FreeBSD has no /proc/pid/mem to fall back
+// on, so PT_IO is the only supported route).
+type Session struct {
+	pid      int
+	cmd      *exec.Cmd
+	stopped  bool
+	exited   bool
+	codeBase uint64   // base address of the JIT code in the debuggee
+	tmpDir   string   // scratch directory of the session, removed on Kill
+	wpSlots  [16]bool // hardware watchpoint slots in use (DR0-DR3, arm64 dbw 0-15)
+	// lastSignal holds the signal of the most recent stop when that stop
+	// was a genuine signal-delivery-stop the caller must see (a fault such
+	// as SIGSEGV, SIGBUS, SIGFPE or SIGILL); 0 for breakpoint traps,
+	// single-steps, SIGSTOP and suppressed runtime signals.
+	lastSignal syscall.Signal
+}
+
+// Launch starts the debuggee subprocess (gasm debug --target ...) and
+// attaches to it via ptrace.
+func Launch(gasmBin, asmPath, funcName string, args []byte) (*Session, error) {
+	sess, _, err := LaunchWithBuffers(gasmBin, asmPath, funcName, args, "")
+	return sess, err
+}
+
+// LaunchWithBuffers is like Launch but also allocates buffers in the debuggee.
+//
+// It pins the calling goroutine to its OS thread and leaves it pinned: the
+// debuggee's PT_TRACE_ME binds the tracer relation to the forking thread,
+// and every ptrace request on the session must come from that same thread.
+// All Session methods must therefore be called from the goroutine that
+// launched the session (the REPL and coverage loops do exactly that).
+func LaunchWithBuffers(gasmBin, asmPath, funcName string, args []byte, bufSpec string) (*Session, []uint64, error) {
+	runtime.LockOSThread() // ptrace requests must stay on the forking thread
+	self, err := os.Executable()
+	if err != nil {
+		return nil, nil, fmt.Errorf("debug: cannot find gasm binary: %w", err)
+	}
+	if gasmBin != "" {
+		self = gasmBin
+	}
+
+	tmpDir, err := os.MkdirTemp("", "gasm-debug-*")
+	if err != nil {
+		return nil, nil, fmt.Errorf("debug: tempdir: %w", err)
+	}
+	argsFile := filepath.Join(tmpDir, "args.bin")
+	if err := os.WriteFile(argsFile, args, 0o644); err != nil {
+		os.RemoveAll(tmpDir)
+		return nil, nil, fmt.Errorf("debug: write args: %w", err)
+	}
+
+	if bufSpec != "" {
+		if err := os.WriteFile(filepath.Join(tmpDir, "bufspec"), []byte(bufSpec), 0o644); err != nil {
+			os.RemoveAll(tmpDir)
+			return nil, nil, fmt.Errorf("debug: write bufspec: %w", err)
+		}
+	}
+
+	cmd := exec.Command(self, "debug", "--func", funcName, "--args", argsFile, asmPath)
+	cmd.Env = append(os.Environ(), "GASM_DEBUG_TARGET=1", "GASM_DEBUG_TMP="+tmpDir)
+	cmd.Stdout = nil
+	cmd.Stderr = os.Stderr
+	cmd.SysProcAttr = &syscall.SysProcAttr{}
+
+	if err := cmd.Start(); err != nil {
+		os.RemoveAll(tmpDir)
+		return nil, nil, fmt.Errorf("debug: start debuggee: %w", err)
+	}
+
+	s := &Session{pid: cmd.Process.Pid, cmd: cmd, tmpDir: tmpDir}
+
+	readyFile := filepath.Join(tmpDir, "ready")
+	for range 500 {
+		if _, err := os.Stat(readyFile); err == nil {
+			break
+		}
+		time.Sleep(5 * time.Millisecond)
+	}
+
+	// The debuggee parks itself with SIGSTOP once the JIT code is mapped.
+	// A Go tracee also reports SIGURG preemption as signal-delivery-stops,
+	// so the wait loops until a stop the debugger cares about instead of
+	// assuming the first event is the SIGSTOP.
+	if _, err := s.waitStopped(); err != nil {
+		cmd.Process.Kill()
+		os.RemoveAll(tmpDir)
+		return nil, nil, fmt.Errorf("debug: wait for debuggee: %w", err)
+	}
+	s.stopped = true
+
+	// The debuggee reports its JIT mapping in the codebase file; that is
+	// the supported path on FreeBSD, where no /proc/pid/maps exists to
+	// scan for the RWX region as a fallback.
+	if data, err := os.ReadFile(filepath.Join(tmpDir, "codebase")); err == nil {
+		fmt.Sscanf(string(data), "%d", &s.codeBase)
+	}
+
+	var bufAddrs []uint64
+	if bufSpec != "" {
+		addrFile := filepath.Join(tmpDir, "bufaddrs")
+		if data, err := os.ReadFile(addrFile); err == nil {
+			for line := range strings.SplitSeq(strings.TrimSpace(string(data)), "\n") {
+				var addr uint64
+				if _, err := fmt.Sscanf(line, "%d", &addr); err == nil {
+					bufAddrs = append(bufAddrs, addr)
+				}
+			}
+		}
+	}
+
+	return s, bufAddrs, nil
+}
+
+// waitStopped consumes ptrace-stop events until one the debugger cares
+// about arrives: SIGTRAP (a breakpoint or a completed single-step), the
+// debuggee's own SIGSTOP, or a genuine signal-delivery-stop.  A Go tracee's
+// runtime raises SIGURG for asynchronous preemption, and every signal on a
+// traced thread surfaces as a signal-delivery-stop, so SIGURG is suppressed
+// and the tracee resumed without it.  Every other signal (SIGSEGV, SIGBUS,
+// SIGFPE, SIGILL, ...) is returned to the caller: resuming with signal 0
+// would restart the faulting instruction and fault forever, so a faulting
+// kernel must surface as a stop the caller reports.
+func (s *Session) waitStopped() (syscall.Signal, error) {
+	for {
+		var ws syscall.WaitStatus
+		if _, err := syscall.Wait4(s.pid, &ws, syscall.WUNTRACED, nil); err != nil {
+			return 0, err
+		}
+		if ws.Exited() {
+			s.exited = true
+			return 0, fmt.Errorf("debuggee exited with status %d", ws.ExitStatus())
+		}
+		if ws.Signaled() {
+			s.exited = true
+			return 0, fmt.Errorf("debuggee killed by signal %v", ws.Signal())
+		}
+		switch sig := ws.StopSignal(); sig {
+		case syscall.SIGTRAP, syscall.SIGSTOP:
+			s.stopped = true
+			s.lastSignal = 0
+			return sig, nil
+		case syscall.SIGURG:
+			// Go runtime asynchronous preemption: resume the tracee
+			// without delivering the signal.
+			s.lastSignal = 0
+			if err := unix.PtraceCont(s.pid, 0); err != nil {
+				return 0, fmt.Errorf("debug: PT_CONTINUE: %w", err)
+			}
+		default:
+			// A genuine signal-delivery-stop.  Report it; the caller
+			// decides how to proceed.
+			s.stopped = true
+			s.lastSignal = sig
+			return sig, nil
+		}
+	}
+}
+
+// LastSignal returns the signal of the most recent stop when that stop was
+// a genuine signal-delivery-stop (a fault such as SIGSEGV, SIGFPE, SIGILL
+// or SIGBUS), and 0 for breakpoint traps, single-steps, SIGSTOP and
+// suppressed runtime signals.
+func (s *Session) LastSignal() syscall.Signal { return s.lastSignal }
+
+// Peek reads a word (8 bytes) from the debuggee's memory at addr, through
+// PT_IO with PIOD_READ_D.
+func (s *Session) Peek(addr uint64) (uint64, error) {
+	var buf [8]byte
+	if _, err := unix.PtraceIO(unix.PIOD_READ_D, s.pid, uintptr(addr), buf[:], len(buf)); err != nil {
+		return 0, fmt.Errorf("debug: read mem %#x: %w", addr, err)
+	}
+	return uint64(buf[0]) | uint64(buf[1])<<8 | uint64(buf[2])<<16 | uint64(buf[3])<<24 |
+		uint64(buf[4])<<32 | uint64(buf[5])<<40 | uint64(buf[6])<<48 | uint64(buf[7])<<56, nil
+}
+
+// Poke writes a word (8 bytes) to the debuggee's memory at addr, through
+// PT_IO with PIOD_WRITE_D.
+func (s *Session) Poke(addr, val uint64) error {
+	buf := []byte{byte(val), byte(val >> 8), byte(val >> 16), byte(val >> 24),
+		byte(val >> 32), byte(val >> 40), byte(val >> 48), byte(val >> 56)}
+	if _, err := unix.PtraceIO(unix.PIOD_WRITE_D, s.pid, uintptr(addr), buf, len(buf)); err != nil {
+		return fmt.Errorf("debug: write mem %#x: %w", addr, err)
+	}
+	return nil
+}
+
+// ReadMemory reads len bytes from the debuggee's memory at addr in one
+// PT_IO request, the shape the request is built for.
+func (s *Session) ReadMemory(addr uint64, length int) ([]byte, error) {
+	out := make([]byte, length)
+	n, err := unix.PtraceIO(unix.PIOD_READ_D, s.pid, uintptr(addr), out, length)
+	return out[:n], err
+}
+
+// WriteMemory writes bytes to the debuggee's memory at addr in one PT_IO
+// request.
+func (s *Session) WriteMemory(addr uint64, data []byte) error {
+	_, err := unix.PtraceIO(unix.PIOD_WRITE_D, s.pid, uintptr(addr), data, len(data))
+	return err
+}
+
+// Step executes a single instruction in the debuggee.
+func (s *Session) Step() error {
+	if s.exited {
+		return fmt.Errorf("debug: debuggee has exited")
+	}
+	if err := unix.PtraceSingleStep(s.pid); err != nil {
+		return fmt.Errorf("debug: PT_STEP: %w", err)
+	}
+	_, err := s.waitStopped()
+	return err
+}
+
+// Continue resumes execution until the next breakpoint or exit.
+func (s *Session) Continue() error {
+	if s.exited {
+		return fmt.Errorf("debug: debuggee has exited")
+	}
+	if err := unix.PtraceCont(s.pid, 0); err != nil {
+		return fmt.Errorf("debug: PT_CONTINUE: %w", err)
+	}
+	_, err := s.waitStopped()
+	return err
+}
+
+// Exited returns true if the debuggee has terminated.
+func (s *Session) Exited() bool { return s.exited }
+
+// Pid returns the debuggee's process ID.
+func (s *Session) Pid() int { return s.pid }
+
+// CodeBase returns the base address of the JIT code in the debuggee.
+func (s *Session) CodeBase() uint64 { return s.codeBase }
+
+// Kill terminates the debuggee and removes the session's scratch
+// directory, so a successful session leaves no gasm-debug-* debris behind.
+func (s *Session) Kill() {
+	if !s.exited {
+		syscall.Kill(s.pid, syscall.SIGKILL)
+		syscall.Wait4(s.pid, nil, 0, nil)
+		s.exited = true
+	}
+	if s.cmd != nil && s.cmd.Process != nil {
+		s.cmd.Wait()
+	}
+	if s.tmpDir != "" {
+		os.RemoveAll(s.tmpDir)
+		s.tmpDir = ""
+	}
+}
+
+// execRange is one executable mapping of the debuggee.
+type execRange struct {
+	lo, hi uint64
+}
+
+// execRanges is a stub on FreeBSD: there is no /proc/pid/maps to parse,
+// and procfs(5) is not guaranteed to be mounted.  The callers degrade
+// gracefully: archReturnAddr falls back to the raw stack convention and
+// the mapping scan is skipped.
+func execRanges(pid int) []execRange { return nil }
+
+// findRWXMapping is a stub on FreeBSD for the same reason: the codebase
+// handshake file is the supported way the JIT region is located.
+func findRWXMapping(pid int) uint64 { return 0 }

debug/ptrace_freebsd_amd64.go

@@ -0,0 +1,160 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && amd64
+
+package debug
+
+import (
+	"encoding/binary"
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// GetRegs reads the general-purpose registers of the stopped debuggee and
+// converts the FreeBSD struct reg into the portable layout.
+func (s *Session) GetRegs() (Regs, error) {
+	var ur unix.Reg
+	if err := unix.PtraceGetRegs(s.pid, &ur); err != nil {
+		return Regs{}, fmt.Errorf("debug: PT_GETREGS: %w", err)
+	}
+	return Regs{
+		R15:    uint64(ur.R15),
+		R14:    uint64(ur.R14),
+		R13:    uint64(ur.R13),
+		R12:    uint64(ur.R12),
+		R11:    uint64(ur.R11),
+		R10:    uint64(ur.R10),
+		R9:     uint64(ur.R9),
+		R8:     uint64(ur.R8),
+		RDI:    uint64(ur.Rdi),
+		RSI:    uint64(ur.Rsi),
+		RBP:    uint64(ur.Rbp),
+		RBX:    uint64(ur.Rbx),
+		RDX:    uint64(ur.Rdx),
+		RCX:    uint64(ur.Rcx),
+		RAX:    uint64(ur.Rax),
+		RIP:    uint64(ur.Rip),
+		CS:     uint64(ur.Cs),
+		RFLAGS: uint64(ur.Rflags),
+		RSP:    uint64(ur.Rsp),
+		SS:     uint64(ur.Ss),
+		FS:     uint64(ur.Fs),
+		GS:     uint64(ur.Gs),
+		DS:     uint64(ur.Ds),
+		ES:     uint64(ur.Es),
+	}, nil
+}
+
+// SetRegs writes the general-purpose registers of the stopped debuggee.
+func (s *Session) SetRegs(regs *Regs) error {
+	// Read-modify-write keeps the fields FreeBSD owns (trapno, err) intact.
+	var ur unix.Reg
+	if err := unix.PtraceGetRegs(s.pid, &ur); err != nil {
+		return fmt.Errorf("debug: PT_GETREGS: %w", err)
+	}
+	ur.R15 = int64(regs.R15)
+	ur.R14 = int64(regs.R14)
+	ur.R13 = int64(regs.R13)
+	ur.R12 = int64(regs.R12)
+	ur.R11 = int64(regs.R11)
+	ur.R10 = int64(regs.R10)
+	ur.R9 = int64(regs.R9)
+	ur.R8 = int64(regs.R8)
+	ur.Rdi = int64(regs.RDI)
+	ur.Rsi = int64(regs.RSI)
+	ur.Rbp = int64(regs.RBP)
+	ur.Rbx = int64(regs.RBX)
+	ur.Rdx = int64(regs.RDX)
+	ur.Rcx = int64(regs.RCX)
+	ur.Rax = int64(regs.RAX)
+	ur.Rip = int64(regs.RIP)
+	ur.Cs = int64(regs.CS)
+	ur.Rflags = int64(regs.RFLAGS)
+	ur.Rsp = int64(regs.RSP)
+	ur.Ss = int64(regs.SS)
+	return unix.PtraceSetRegs(s.pid, &ur)
+}
+
+// FPRegs holds the x87 FPU and SSE (XMM) register state, the FXSAVE image
+// the FreeBSD struct fpreg mirrors: XMM0-15 at the same offsets.
+type FPRegs struct {
+	XMM [16][16]byte // XMM0-15
+}
+
+// GetFPRegs retrieves the FPU/SSE register state via PT_GETFPREGS.  The
+// FreeBSD struct fpreg mirrors the FXSAVE image: the x87 environment and
+// stack in Env/Acc, XMM0-15 in Xacc.
+func (s *Session) GetFPRegs() (FPRegs, error) {
+	var fp FPRegs
+	var fr unix.FpReg
+	if err := unix.PtraceGetFpRegs(s.pid, &fr); err != nil {
+		return fp, fmt.Errorf("debug: PT_GETFPREGS: %w", err)
+	}
+	for i := range 16 {
+		copy(fp.XMM[i][:], fr.Xacc[i][:])
+	}
+	return fp, nil
+}
+
+// VectorRegs holds the YMM register state.
+type VectorRegs struct {
+	YMM [16][32]byte // YMM0-15 (full 256-bit values)
+}
+
+// The XSAVE area the PT_GETXSTATE request returns follows the architectural
+// layout (Intel SDM vol 1, "XSAVE"): the 512-byte legacy FXSAVE image (x87
+// state in 0-159, XMM0-15 in 160-511), then the 64-byte xsave header whose
+// first 8 bytes are xstate_bv, then one component per set feature bit, each
+// 64-byte aligned.  The YMM high halves are the first extended component,
+// at offset 576; XFEATURE_STATE_BIT_AVX is bit 2 of xstate_bv.
+const (
+	xsaveXMMOffset    = 160
+	xsaveHeaderOffset = 512
+	xsaveBVOffset     = xsaveHeaderOffset
+	ymmOffset         = xsaveHeaderOffset + 64 // 576
+	ymmSize           = 256                    // 16 registers, 16 bytes each
+	xfeatureMaskYMM   = 1 << 2
+	xstateMaxBuffer   = 4096 // PT_GETXSTATE_INFO bounds the size far below this
+)
+
+// GetVectorRegs retrieves the YMM registers via PT_GETXSTATE.  The low
+// (XMM) halves always come from the legacy image; the high halves are
+// copied only when xstate_bv reports the AVX state, and read as zero
+// otherwise.  When the request fails the FP image still provides correct
+// XMM halves, so that is the fallback.
+func (s *Session) GetVectorRegs() (VectorRegs, error) {
+	var v VectorRegs
+	buf := make([]byte, xstateMaxBuffer)
+	n, _, errno := unix.Syscall6(
+		unix.SYS_PTRACE,
+		uintptr(unix.PT_GETXSTATE),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(&buf[0])),
+		0, 0,
+	)
+	if errno != 0 {
+		fp, err := s.GetFPRegs()
+		if err != nil {
+			return v, err
+		}
+		for i := range 16 {
+			copy(v.YMM[i][:16], fp.XMM[i][:])
+		}
+		return v, nil
+	}
+	for i := range 16 {
+		copy(v.YMM[i][:16], buf[xsaveXMMOffset+16*i:xsaveXMMOffset+16*i+16])
+	}
+	if int(n) >= ymmOffset+ymmSize {
+		if binary.LittleEndian.Uint64(buf[xsaveBVOffset:xsaveBVOffset+8])&xfeatureMaskYMM != 0 {
+			for i := range 16 {
+				copy(v.YMM[i][16:], buf[ymmOffset+16*i:ymmOffset+16*i+16])
+			}
+		}
+	}
+	return v, nil
+}

debug/ptrace_freebsd_arm64.go

@@ -0,0 +1,114 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && arm64
+
+package debug
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+// GetRegs reads the general-purpose registers of the stopped debuggee and
+// converts the FreeBSD struct reg (x[30], lr, sp, elr, spsr) into the
+// portable layout.
+func (s *Session) GetRegs() (Regs, error) {
+	var ur unix.Reg
+	if err := unix.PtraceGetRegs(s.pid, &ur); err != nil {
+		return Regs{}, fmt.Errorf("debug: PT_GETREGS: %w", err)
+	}
+	return Regs{
+		X0:     ur.X[0],
+		X1:     ur.X[1],
+		X2:     ur.X[2],
+		X3:     ur.X[3],
+		X4:     ur.X[4],
+		X5:     ur.X[5],
+		X6:     ur.X[6],
+		X7:     ur.X[7],
+		X8:     ur.X[8],
+		X9:     ur.X[9],
+		X10:    ur.X[10],
+		X11:    ur.X[11],
+		X12:    ur.X[12],
+		X13:    ur.X[13],
+		X14:    ur.X[14],
+		X15:    ur.X[15],
+		X16:    ur.X[16],
+		X17:    ur.X[17],
+		X18:    ur.X[18],
+		X19:    ur.X[19],
+		X20:    ur.X[20],
+		X21:    ur.X[21],
+		X22:    ur.X[22],
+		X23:    ur.X[23],
+		X24:    ur.X[24],
+		X25:    ur.X[25],
+		X26:    ur.X[26],
+		X27:    ur.X[27],
+		X28:    ur.X[28],
+		X29:    ur.X[29],
+		X30:    ur.Lr,
+		SP:     ur.Sp,
+		PC:     ur.Elr,
+		PSTATE: uint64(ur.Spsr),
+	}, nil
+}
+
+// SetRegs writes the general-purpose registers of the stopped debuggee.
+func (s *Session) SetRegs(regs *Regs) error {
+	var ur unix.Reg
+	ur.X = [30]uint64{
+		regs.X0, regs.X1, regs.X2, regs.X3, regs.X4, regs.X5, regs.X6,
+		regs.X7, regs.X8, regs.X9, regs.X10, regs.X11, regs.X12, regs.X13,
+		regs.X14, regs.X15, regs.X16, regs.X17, regs.X18, regs.X19, regs.X20,
+		regs.X21, regs.X22, regs.X23, regs.X24, regs.X25, regs.X26, regs.X27,
+		regs.X28, regs.X29,
+	}
+	ur.Lr = regs.X30
+	ur.Sp = regs.SP
+	ur.Elr = regs.PC
+	ur.Spsr = uint32(regs.PSTATE)
+	return unix.PtraceSetRegs(s.pid, &ur)
+}
+
+// FPRegs holds the arm64 FP/NEON register state: the 32 128-bit V
+// registers, then FPSR and FPCR (the user_fpsimd shape).
+type FPRegs struct {
+	V    [32][16]byte // V0-V31 (128-bit NEON/FP registers)
+	FPSR uint32
+	FPCR uint32
+}
+
+// GetFPRegs retrieves the FP/NEON register state via PT_GETFPREGS.  The
+// FreeBSD struct fpreg holds the 32 128-bit V registers followed by FPSR
+// and FPCR, the user_fpsimd shape.
+func (s *Session) GetFPRegs() (FPRegs, error) {
+	var fp FPRegs
+	var fr unix.FpReg
+	if err := unix.PtraceGetFpRegs(s.pid, &fr); err != nil {
+		return fp, fmt.Errorf("debug: PT_GETFPREGS: %w", err)
+	}
+	for i := range 32 {
+		copy(fp.V[i][:], fr.Q[i][:])
+	}
+	return fp, nil
+}
+
+// VectorRegs holds the full SIMD register state.
+type VectorRegs struct {
+	V [32][16]byte // V0-V31 (128-bit)
+}
+
+// GetVectorRegs retrieves the SIMD registers.
+func (s *Session) GetVectorRegs() (VectorRegs, error) {
+	var v VectorRegs
+	fp, err := s.GetFPRegs()
+	if err != nil {
+		return v, err
+	}
+	copy(v.V[:][:], fp.V[:][:])
+	return v, nil
+}

debug/ptrace_freebsd_riscv64.go

@@ -0,0 +1,115 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && riscv64
+
+package debug
+
+import (
+	"fmt"
+
+	"golang.org/x/sys/unix"
+)
+
+// GetRegs reads the general-purpose registers of the stopped debuggee and
+// converts the FreeBSD struct reg into the portable layout.  Sstatus rides
+// the kernel's struct but the portable surface carries the GPRs and PC.
+func (s *Session) GetRegs() (Regs, error) {
+	var ur unix.Reg
+	if err := unix.PtraceGetRegs(s.pid, &ur); err != nil {
+		return Regs{}, fmt.Errorf("debug: PT_GETREGS: %w", err)
+	}
+	return Regs{
+		PC:  ur.Sepc,
+		Ra:  ur.Ra,
+		Sp:  ur.Sp,
+		Gp:  ur.Gp,
+		Tp:  ur.Tp,
+		T0:  ur.T[0],
+		T1:  ur.T[1],
+		T2:  ur.T[2],
+		S0:  ur.S[0],
+		S1:  ur.S[1],
+		A0:  ur.A[0],
+		A1:  ur.A[1],
+		A2:  ur.A[2],
+		A3:  ur.A[3],
+		A4:  ur.A[4],
+		A5:  ur.A[5],
+		A6:  ur.A[6],
+		A7:  ur.A[7],
+		S2:  ur.S[2],
+		S3:  ur.S[3],
+		S4:  ur.S[4],
+		S5:  ur.S[5],
+		S6:  ur.S[6],
+		S7:  ur.S[7],
+		S8:  ur.S[8],
+		S9:  ur.S[9],
+		S10: ur.S[10],
+		S11: ur.S[11],
+		T3:  ur.T[3],
+		T4:  ur.T[4],
+		T5:  ur.T[5],
+		T6:  ur.T[6],
+	}, nil
+}
+
+// SetRegs writes the general-purpose registers of the stopped debuggee.
+// Read-modify-write keeps sstatus, which the kernel owns, intact.
+func (s *Session) SetRegs(regs *Regs) error {
+	var ur unix.Reg
+	if err := unix.PtraceGetRegs(s.pid, &ur); err != nil {
+		return fmt.Errorf("debug: PT_GETREGS: %w", err)
+	}
+	ur.Sepc = regs.PC
+	ur.Ra = regs.Ra
+	ur.Sp = regs.Sp
+	ur.Gp = regs.Gp
+	ur.Tp = regs.Tp
+	ur.T = [7]uint64{regs.T0, regs.T1, regs.T2, regs.T3, regs.T4, regs.T5, regs.T6}
+	ur.S = [12]uint64{regs.S0, regs.S1, regs.S2, regs.S3, regs.S4, regs.S5,
+		regs.S6, regs.S7, regs.S8, regs.S9, regs.S10, regs.S11}
+	ur.A = [8]uint64{regs.A0, regs.A1, regs.A2, regs.A3, regs.A4, regs.A5, regs.A6, regs.A7}
+	return unix.PtraceSetRegs(s.pid, &ur)
+}
+
+// FPRegs holds the RISC-V FP register state (32 64-bit FP registers plus
+// fcsr).
+type FPRegs struct {
+	F    [32]uint64 // F0-F31 (64-bit FP registers)
+	FCSR uint32
+}
+
+// GetFPRegs retrieves the FP register state via PT_GETFPREGS.  The FreeBSD
+// struct fpreg carries each 64-bit FP register in a 128-bit slot (fp_x is
+// the flat [64]-word area the x/sys type renders as [32][2]); the low word
+// holds the register, and FCSR rides the tail.
+func (s *Session) GetFPRegs() (FPRegs, error) {
+	var fp FPRegs
+	var fr unix.FpReg
+	if err := unix.PtraceGetFpRegs(s.pid, &fr); err != nil {
+		return fp, fmt.Errorf("debug: PT_GETFPREGS: %w", err)
+	}
+	for i := range 32 {
+		fp.F[i] = fr.X[i][0]
+	}
+	fp.FCSR = uint32(fr.Fcsr)
+	return fp, nil
+}
+
+// VectorRegs holds the FP register state shown by the regs command
+// (riscv64 has 32 64-bit FP registers and fcsr).
+type VectorRegs struct {
+	F    [32]uint64
+	FCSR uint32
+}
+
+// GetVectorRegs retrieves the FP registers.
+func (s *Session) GetVectorRegs() (VectorRegs, error) {
+	fp, err := s.GetFPRegs()
+	if err != nil {
+		return VectorRegs{}, err
+	}
+	return VectorRegs{F: fp.F, FCSR: fp.FCSR}, nil
+}

debug/ptrace_integration_freebsd_test.go

@@ -0,0 +1,91 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && amd64
+
+package debug
+
+import (
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/verify"
+)
+
+// TestLaunchAndBreakpoint is the FreeBSD twin of the Linux integration
+// test: it drives the whole launch, breakpoint, trap and register-rewind
+// flow end to end.  It needs a real FreeBSD kernel (ptrace does not work
+// under emulation), so it only runs where it can.
+func TestLaunchAndBreakpoint(t *testing.T) {
+	if runtime.GOARCH != "amd64" {
+		t.Skip("runs only on amd64 hosts")
+	}
+	// The tracer is the OS thread that forked the debuggee (PT_TRACE_ME
+	// binds the relation to that thread); every ptrace request must come
+	// from the same thread, so pin the test goroutine to one thread.
+	runtime.LockOSThread()
+	defer runtime.UnlockOSThread()
+
+	bin := filepath.Join(t.TempDir(), "gasm")
+	out, err := exec.Command("go", "build", "-o", bin, "sourcedock.dev/petrbalvin/gasm-devkit/cmd/gasm").CombinedOutput()
+	if err != nil {
+		t.Fatalf("build gasm: %v: %s", err, out)
+	}
+
+	const kernelPath = "../testdata/verify/basic_amd64.s"
+	k, err := verify.Load(kernelPath)
+	if err != nil {
+		t.Fatalf("Load: %v", err)
+	}
+	t.Cleanup(k.Close)
+	fl, err := k.Func("wideCopy")
+	if err != nil {
+		t.Fatalf("Func: %v", err)
+	}
+
+	sess, err := Launch(bin, kernelPath, "wideCopy", make([]byte, fl.Args))
+	if err != nil {
+		t.Fatalf("Launch: %v", err)
+	}
+	t.Cleanup(sess.Kill)
+
+	bm := NewBreakpoints(sess)
+	entry := sess.CodeBase() + uint64(fl.Offset)
+	if _, err := bm.Set(entry, "entry"); err != nil {
+		t.Fatalf("Set: %v", err)
+	}
+
+	// The INT3 must be visible in the debuggee's memory.
+	word, err := sess.Peek(entry)
+	if err != nil {
+		t.Fatalf("Peek: %v", err)
+	}
+	if b := word & 0xFF; b != 0xCC {
+		t.Fatalf("int3 not patched: first byte %#02x at %#x", b, entry)
+	}
+
+	// The debuggee raises a second SIGSTOP after the launch barrier (the
+	// child's RunTarget marks its entry), so like the REPL and the cover
+	// mode the test keeps resuming until the breakpoint trap arrives.
+	for range 10 {
+		if err := sess.Continue(); err != nil {
+			t.Fatalf("Continue: %v", err)
+		}
+		if sess.Exited() {
+			t.Fatal("debuggee exited instead of trapping on the breakpoint")
+		}
+		regs, err := sess.GetRegs()
+		if err != nil {
+			t.Fatalf("GetRegs: %v", err)
+		}
+		if bp := bm.HandleTrap(&regs); bp != nil {
+			if bp.Addr != entry {
+				t.Fatalf("trap at %#x, want %#x", bp.Addr, entry)
+			}
+			return // trap on the entry breakpoint: the whole flow works
+		}
+	}
+	t.Fatal("no breakpoint trap after 10 resumes")
+}

debug/regs_freebsd_amd64.go

@@ -0,0 +1,98 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && amd64
+
+package debug
+
+// Regs holds the full general-purpose register set of a traced process
+// (the FreeBSD amd64 struct reg layout, sys/x86/include/reg.h).  FreeBSD
+// reports segment selectors (FS/GS/ES/DS), not the bases the Linux ptrace
+// surface carries, and has no ORIG_RAX slot.
+type Regs struct {
+	R15    uint64
+	R14    uint64
+	R13    uint64
+	R12    uint64
+	RBP    uint64
+	RBX    uint64
+	R11    uint64
+	R10    uint64
+	R9     uint64
+	R8     uint64
+	RAX    uint64
+	RCX    uint64
+	RDX    uint64
+	RSI    uint64
+	RDI    uint64
+	RIP    uint64
+	CS     uint64
+	RFLAGS uint64
+	RSP    uint64
+	SS     uint64
+	FS     uint64
+	GS     uint64
+	DS     uint64
+	ES     uint64
+}
+
+// GetPC returns the program counter.
+func (r *Regs) GetPC() uint64 { return r.RIP }
+
+// SetPC sets the program counter.
+func (r *Regs) SetPC(pc uint64) { r.RIP = pc }
+
+// GetSP returns the stack pointer.
+func (r *Regs) GetSP() uint64 { return r.RSP }
+
+// RegValue returns the value of the named register, or false if unknown.
+func (r *Regs) RegValue(name string) (uint64, bool) {
+	switch name {
+	case "rax", "eax", "ax", "al":
+		return r.RAX, true
+	case "rbx", "ebx", "bx", "bl":
+		return r.RBX, true
+	case "rcx", "ecx", "cx", "cl":
+		return r.RCX, true
+	case "rdx", "edx", "dx", "dl":
+		return r.RDX, true
+	case "rsi", "esi", "si":
+		return r.RSI, true
+	case "rdi", "edi", "di":
+		return r.RDI, true
+	case "rbp", "ebp", "bp":
+		return r.RBP, true
+	case "rsp", "esp", "sp":
+		return r.RSP, true
+	case "r8":
+		return r.R8, true
+	case "r9":
+		return r.R9, true
+	case "r10":
+		return r.R10, true
+	case "r11":
+		return r.R11, true
+	case "r12":
+		return r.R12, true
+	case "r13":
+		return r.R13, true
+	case "r14":
+		return r.R14, true
+	case "r15":
+		return r.R15, true
+	case "rip", "eip":
+		return r.RIP, true
+	default:
+		return 0, false
+	}
+}
+
+// breakpointInsn is the software breakpoint instruction.
+var breakpointInsn = []byte{0xCC} // INT3
+
+// breakpointPCAdjust is how far PC is past the breakpoint instruction after
+// a trap.  INT3 leaves the hardware PC on the following instruction (Intel
+// SDM vol 3, "Debug Exceptions") and the FreeBSD T_BPTFLT path delivers
+// that frame unmodified (sys/amd64/amd64/trap.c), so the trap address is
+// PC-1, the same correction the Linux side applies.
+const breakpointPCAdjust = 1

debug/regs_freebsd_arm64.go

@@ -0,0 +1,139 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && arm64
+
+package debug
+
+// Regs holds the full general-purpose register set of a traced process
+// (the FreeBSD arm64 struct reg layout, sys/arm64/include/reg.h: x[30], lr,
+// sp, elr, spsr).
+type Regs struct {
+	X0     uint64
+	X1     uint64
+	X2     uint64
+	X3     uint64
+	X4     uint64
+	X5     uint64
+	X6     uint64
+	X7     uint64
+	X8     uint64
+	X9     uint64
+	X10    uint64
+	X11    uint64
+	X12    uint64
+	X13    uint64
+	X14    uint64
+	X15    uint64
+	X16    uint64
+	X17    uint64
+	X18    uint64
+	X19    uint64
+	X20    uint64
+	X21    uint64
+	X22    uint64
+	X23    uint64
+	X24    uint64
+	X25    uint64
+	X26    uint64
+	X27    uint64
+	X28    uint64
+	X29    uint64 // FP (frame pointer)
+	X30    uint64 // LR (link register)
+	SP     uint64
+	PC     uint64
+	PSTATE uint64
+}
+
+// GetPC returns the program counter.
+func (r *Regs) GetPC() uint64 { return r.PC }
+
+// SetPC sets the program counter.
+func (r *Regs) SetPC(pc uint64) { r.PC = pc }
+
+// GetSP returns the stack pointer.
+func (r *Regs) GetSP() uint64 { return r.SP }
+
+// RegValue returns the value of the named register, or false if unknown.
+func (r *Regs) RegValue(name string) (uint64, bool) {
+	switch name {
+	case "x0":
+		return r.X0, true
+	case "x1":
+		return r.X1, true
+	case "x2":
+		return r.X2, true
+	case "x3":
+		return r.X3, true
+	case "x4":
+		return r.X4, true
+	case "x5":
+		return r.X5, true
+	case "x6":
+		return r.X6, true
+	case "x7":
+		return r.X7, true
+	case "x8":
+		return r.X8, true
+	case "x9":
+		return r.X9, true
+	case "x10":
+		return r.X10, true
+	case "x11":
+		return r.X11, true
+	case "x12":
+		return r.X12, true
+	case "x13":
+		return r.X13, true
+	case "x14":
+		return r.X14, true
+	case "x15":
+		return r.X15, true
+	case "x16":
+		return r.X16, true
+	case "x17":
+		return r.X17, true
+	case "x18":
+		return r.X18, true
+	case "x19":
+		return r.X19, true
+	case "x20":
+		return r.X20, true
+	case "x21":
+		return r.X21, true
+	case "x22":
+		return r.X22, true
+	case "x23":
+		return r.X23, true
+	case "x24":
+		return r.X24, true
+	case "x25":
+		return r.X25, true
+	case "x26":
+		return r.X26, true
+	case "x27":
+		return r.X27, true
+	case "x28":
+		return r.X28, true
+	case "x29", "fp":
+		return r.X29, true
+	case "x30", "lr":
+		return r.X30, true
+	case "sp":
+		return r.SP, true
+	case "pc":
+		return r.PC, true
+	default:
+		return 0, false
+	}
+}
+
+// breakpointInsn is the software breakpoint instruction (BRK #0).
+var breakpointInsn = []byte{0x00, 0x00, 0x20, 0xD4} // BRK #0
+
+// breakpointPCAdjust is how far PC is past the breakpoint instruction after
+// a trap: 0.  The BRK synchronous exception leaves ELR_EL0 on the BRK
+// itself (ARM DDI 0487), and the FreeBSD EXCP_BRKPT_EL0 handler delivers
+// the frame's elr unmodified (sys/arm64/arm64/trap.c), so the trap address
+// is the PC as reported.
+const breakpointPCAdjust = 0

debug/regs_freebsd_riscv64.go

@@ -0,0 +1,134 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && riscv64
+
+package debug
+
+// Regs holds the full general-purpose register set of a traced process
+// (the FreeBSD riscv64 struct reg layout: ra, sp, gp, tp, t0-t6, s0-s11,
+// a0-a7, sepc, sstatus).
+type Regs struct {
+	PC  uint64 // sepc
+	Ra  uint64 // x1 (return address)
+	Sp  uint64 // x2
+	Gp  uint64 // x3
+	Tp  uint64 // x4
+	T0  uint64 // x5
+	T1  uint64 // x6
+	T2  uint64 // x7
+	S0  uint64 // x8 (frame pointer)
+	S1  uint64 // x9
+	A0  uint64 // x10
+	A1  uint64 // x11
+	A2  uint64 // x12
+	A3  uint64 // x13
+	A4  uint64 // x14
+	A5  uint64 // x15
+	A6  uint64 // x16
+	A7  uint64 // x17
+	S2  uint64 // x18
+	S3  uint64 // x19
+	S4  uint64 // x20
+	S5  uint64 // x21
+	S6  uint64 // x22
+	S7  uint64 // x23
+	S8  uint64 // x24
+	S9  uint64 // x25
+	S10 uint64 // x26
+	S11 uint64 // x27
+	T3  uint64 // x28
+	T4  uint64 // x29
+	T5  uint64 // x30
+	T6  uint64 // x31
+}
+
+// GetPC returns the program counter.
+func (r *Regs) GetPC() uint64 { return r.PC }
+
+// SetPC sets the program counter.
+func (r *Regs) SetPC(pc uint64) { r.PC = pc }
+
+// GetSP returns the stack pointer.
+func (r *Regs) GetSP() uint64 { return r.Sp }
+
+// RegValue returns the value of the named register, or false if unknown.
+func (r *Regs) RegValue(name string) (uint64, bool) {
+	switch name {
+	case "pc":
+		return r.PC, true
+	case "ra", "x1":
+		return r.Ra, true
+	case "sp", "x2":
+		return r.Sp, true
+	case "gp", "x3":
+		return r.Gp, true
+	case "tp", "x4":
+		return r.Tp, true
+	case "t0", "x5":
+		return r.T0, true
+	case "t1", "x6":
+		return r.T1, true
+	case "t2", "x7":
+		return r.T2, true
+	case "s0", "fp", "x8":
+		return r.S0, true
+	case "s1", "x9":
+		return r.S1, true
+	case "a0", "x10":
+		return r.A0, true
+	case "a1", "x11":
+		return r.A1, true
+	case "a2", "x12":
+		return r.A2, true
+	case "a3", "x13":
+		return r.A3, true
+	case "a4", "x14":
+		return r.A4, true
+	case "a5", "x15":
+		return r.A5, true
+	case "a6", "x16":
+		return r.A6, true
+	case "a7", "x17":
+		return r.A7, true
+	case "s2", "x18":
+		return r.S2, true
+	case "s3", "x19":
+		return r.S3, true
+	case "s4", "x20":
+		return r.S4, true
+	case "s5", "x21":
+		return r.S5, true
+	case "s6", "x22":
+		return r.S6, true
+	case "s7", "x23":
+		return r.S7, true
+	case "s8", "x24":
+		return r.S8, true
+	case "s9", "x25":
+		return r.S9, true
+	case "s10", "x26":
+		return r.S10, true
+	case "s11", "x27":
+		return r.S11, true
+	case "t3", "x28":
+		return r.T3, true
+	case "t4", "x29":
+		return r.T4, true
+	case "t5", "x30":
+		return r.T5, true
+	case "t6", "x31":
+		return r.T6, true
+	default:
+		return 0, false
+	}
+}
+
+// breakpointInsn is the software breakpoint instruction (EBREAK).
+var breakpointInsn = []byte{0x73, 0x00, 0x10, 0x00} // ebreak
+
+// breakpointPCAdjust is how far PC is past the breakpoint instruction after
+// a trap: 0.  The EBREAK synchronous exception leaves sepc on the ebreak
+// itself (RISC-V privileged architecture), so the trap address is the PC as
+// reported.
+const breakpointPCAdjust = 0

debug/repl.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux
+//go:build linux || (freebsd && (amd64 || arm64 || riscv64))
 
 package debug
 

debug/stopinfo_freebsd.go

@@ -0,0 +1,73 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && (amd64 || arm64 || riscv64)
+
+package debug
+
+import (
+	"encoding/binary"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// FreeBSD TRAP_* si_code values (sys/signal.h).  A breakpoint (INT3, BRK,
+// EBREAK) arrives as TRAP_BRKPT on every supported architecture; TRAP_TRACE
+// is shared by the completed single-step and the hardware watchpoint hit,
+// so the watchpoint layer disambiguates from the debug registers.
+const (
+	trapBRKPT = 1 // TRAP_BRKPT
+	trapTRACE = 2 // TRAP_TRACE
+)
+
+// StopReason describes why the debuggee stopped.
+type StopReason int
+
+const (
+	StopNone       StopReason = iota
+	StopBreakpoint            // software breakpoint hit
+	StopWatchpoint            // hardware watchpoint triggered
+	StopSingleStep            // single-step completed
+	StopSignal                // stopped by a signal
+	StopExited                // process exited
+)
+
+// StopInfo returns the reason the debuggee stopped and the faulting address
+// (for watchpoints, the watched address that was accessed).  FreeBSD has no
+// PTRACE_GETSIGINFO; the stop's signal information comes from PT_LWPINFO,
+// whose pl_siginfo carries the siginfo the kernel delivered.  A ptrace stop
+// with no signal behind it (a completed single-step, the initial attach)
+// fills no siginfo at all.
+func (s *Session) StopInfo() (StopReason, uint64) {
+	if s.exited {
+		return StopExited, 0
+	}
+	var info unix.PtraceLwpInfoStruct
+	if err := unix.PtraceLwpInfo(s.pid, &info); err != nil {
+		return StopNone, 0
+	}
+	// The siginfo layout is the FreeBSD siginfo_t: three leading ints
+	// (signo, errno, code), then the union, 8-byte aligned, whose _fault
+	// member puts the address at byte offset 16.  The read is byte-wise
+	// because the blob's alignment is not guaranteed.
+	si := (*[64]byte)(unsafe.Pointer(&info.Siginfo))
+	signo := int32(binary.LittleEndian.Uint32(si[0:4]))
+	code := int32(binary.LittleEndian.Uint32(si[8:12]))
+	switch {
+	case signo == 0:
+		// A pure ptrace stop: single-step completion, attach, or the
+		// events the kernel resolves internally.
+		return StopSingleStep, 0
+	case signo != int32(syscall.SIGTRAP):
+		return StopSignal, uint64(code)
+	case code == trapBRKPT:
+		return StopBreakpoint, 0
+	case code == trapTRACE:
+		addr := binary.LittleEndian.Uint64(si[16:24])
+		return archStopTrace(s, addr)
+	default:
+		return StopSingleStep, 0
+	}
+}

debug/target_freebsd.go

@@ -0,0 +1,195 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && (amd64 || arm64 || riscv64)
+
+package debug
+
+import (
+	"encoding/hex"
+	"fmt"
+	"os"
+	"runtime"
+	"strconv"
+	"strings"
+	"syscall"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/asm"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+	"sourcedock.dev/petrbalvin/gasm-devkit/verify"
+)
+
+// mapRWX maps code into a read-write-execute region.
+func mapRWX(code []byte) ([]byte, error) {
+	const pageSize = 4096
+	size := (len(code) + pageSize - 1) &^ (pageSize - 1)
+	mem, err := syscall.Mmap(-1, 0, size,
+		syscall.PROT_READ|syscall.PROT_WRITE|syscall.PROT_EXEC,
+		syscall.MAP_PRIVATE|syscall.MAP_ANON)
+	if err != nil {
+		return nil, err
+	}
+	copy(mem, code)
+	return mem, nil
+}
+
+// setupBuffers allocates buffers in the debuggee's memory.
+func setupBuffers(spec string, args []byte, tmpDir string) ([]byte, error) {
+	type bufSpec struct {
+		name    string
+		size    int
+		pattern string
+	}
+	var specs []bufSpec
+	for part := range strings.SplitSeq(spec, ",") {
+		fields := strings.SplitN(part, ":", 3)
+		if len(fields) != 3 {
+			continue
+		}
+		size, err := strconv.Atoi(fields[1])
+		if err != nil || size <= 0 {
+			continue
+		}
+		specs = append(specs, bufSpec{name: fields[0], size: size, pattern: fields[2]})
+	}
+
+	if len(specs) == 0 {
+		return args, nil
+	}
+
+	var bufAddrs []uint64
+	for _, s := range specs {
+		buf, err := syscall.Mmap(-1, 0, s.size,
+			syscall.PROT_READ|syscall.PROT_WRITE,
+			syscall.MAP_PRIVATE|syscall.MAP_ANON)
+		if err != nil {
+			return nil, fmt.Errorf("mmap buffer %s: %w", s.name, err)
+		}
+		fillBuffer(buf, s.pattern)
+		bufAddrs = append(bufAddrs, uint64(uintptr(unsafe.Pointer(&buf[0]))))
+	}
+
+	addrFile, err := os.Create(tmpDir + "/bufaddrs")
+	if err != nil {
+		return nil, err
+	}
+	for _, addr := range bufAddrs {
+		fmt.Fprintf(addrFile, "%d\n", addr)
+	}
+	addrFile.Close()
+
+	return args, nil
+}
+
+// fillBuffer fills a buffer with the specified pattern.
+func fillBuffer(buf []byte, pattern string) {
+	switch pattern {
+	case "zero":
+	case "ones":
+		for i := range buf {
+			buf[i] = 0xFF
+		}
+	case "seq":
+		for i := range buf {
+			buf[i] = byte(i)
+		}
+	default:
+		if data, err := hex.DecodeString(pattern); err == nil && len(data) > 0 {
+			for i := range buf {
+				buf[i] = data[i%len(data)]
+			}
+		}
+	}
+}
+
+// RunTarget is the debuggee entry point (gasm debug --target).
+func RunTarget(asmPath, funcName, argsFile, tmpDir string) error {
+	src, err := os.ReadFile(asmPath)
+	if err != nil {
+		return fmt.Errorf("debug target: %w", err)
+	}
+	file, errs := parser.Parse(asmPath, string(src))
+	if len(errs) > 0 {
+		return fmt.Errorf("debug target: parse: %v", errs[0])
+	}
+	img, err := asm.AssembleFile(file)
+	if err != nil {
+		return fmt.Errorf("debug target: assemble: %w", err)
+	}
+
+	var fl *asm.FuncLayout
+	for i := range img.Funcs {
+		if img.Funcs[i].Name == funcName {
+			fl = &img.Funcs[i]
+			break
+		}
+	}
+	if fl == nil {
+		return fmt.Errorf("debug target: function %q not found", funcName)
+	}
+
+	code := img.Bytes()
+	exec, err := mapRWX(code)
+	if err != nil {
+		return fmt.Errorf("debug target: mmap: %w", err)
+	}
+
+	codeBase := uintptr(unsafe.Pointer(&exec[0]))
+	if err := os.WriteFile(tmpDir+"/codebase", []byte(fmt.Sprintf("%d", codeBase)), 0o644); err != nil {
+		return fmt.Errorf("debug target: write codebase: %w", err)
+	}
+
+	meta := fmt.Sprintf("%d %d %d", fl.Offset, fl.Size, fl.Args)
+	os.WriteFile(tmpDir+"/funcmeta", []byte(meta), 0o644)
+
+	labelsFile, _ := os.Create(tmpDir + "/labels")
+	if labelsFile != nil {
+		for label, off := range fl.Labels {
+			fmt.Fprintf(labelsFile, "%s %d\n", label, off)
+		}
+		labelsFile.Close()
+	}
+
+	args, err := os.ReadFile(argsFile)
+	if err != nil {
+		return fmt.Errorf("debug target: read args: %w", err)
+	}
+	if len(args) < fl.Args {
+		padded := make([]byte, fl.Args)
+		copy(padded, args)
+		args = padded
+	}
+
+	bufSpecFile := tmpDir + "/bufspec"
+	if bufSpec, err := os.ReadFile(bufSpecFile); err == nil && len(bufSpec) > 0 {
+		args, err = setupBuffers(string(bufSpec), args, tmpDir)
+		if err != nil {
+			return fmt.Errorf("debug target: setup buffers: %w", err)
+		}
+	}
+
+	runtime.LockOSThread()
+
+	if _, _, errno := unix.RawSyscall(unix.SYS_PTRACE, uintptr(unix.PT_TRACE_ME), 0, 0); errno != 0 {
+		return fmt.Errorf("debug target: PT_TRACE_ME: %v", errno)
+	}
+	os.WriteFile(tmpDir+"/ready", []byte("ok"), 0o644)
+	syscall.Kill(syscall.Getpid(), syscall.SIGSTOP)
+
+	os.WriteFile(tmpDir+"/entry", []byte("ok"), 0o644)
+	syscall.Kill(syscall.Getpid(), syscall.SIGSTOP)
+
+	fnAddr := codeBase + uintptr(fl.Offset)
+	stackArgs := make([]byte, fl.Args)
+	copy(stackArgs, args)
+
+	if _, callErr := verify.Call(fnAddr, stackArgs); callErr != nil {
+		os.Exit(1)
+	}
+	// Success returns to the caller, which exits with status 0; the JIT
+	// code has already run to its own trampoline by the time Call returns.
+	return nil
+}

debug/tracer.go

@@ -1,7 +1,7 @@
 // Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
 // SPDX-License-Identifier: BSD-3-Clause
 
-//go:build linux
+//go:build linux || (freebsd && (amd64 || arm64 || riscv64))
 
 package debug
 

debug/watchpoint_freebsd_amd64.go

@@ -0,0 +1,190 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && amd64
+
+package debug
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// Hardware watchpoint support via x86-64 debug registers (DR0-DR3, DR7),
+// read and written as one blob through PT_GETDBREGS/PT_SETDBREGS.  The
+// FreeBSD struct dbreg is the raw DR file: dr[16], where DR0-DR3 are the
+// address registers, DR6 the status and DR7 the control (sys/x86/include/
+// reg.h; the DBREG_DRX accessor indexes the same array).
+
+// dbreg mirrors FreeBSD's struct dbreg for PT_GETDBREGS/PT_SETDBREGS.
+type dbreg struct {
+	Dr [16]uint64
+}
+
+// dbreg indices of the registers the watchpoint layer drives.
+const (
+	drStatus  = 6 // DR6: the trap status register
+	drControl = 7 // DR7: the debug control register
+)
+
+// WatchpointType selects what triggers the watchpoint.
+type WatchpointType int
+
+const (
+	WatchWrite WatchpointType = 1 // trigger on write
+	WatchRead  WatchpointType = 3 // trigger on read or write
+)
+
+// maxWatchpoints reports the number of hardware watchpoint slots the
+// architecture provides: four address registers, DR0-DR3.
+func maxWatchpoints() int { return 4 }
+
+// getDbRegs reads the debug register file of the stopped debuggee.
+func (s *Session) getDbRegs() (*dbreg, error) {
+	var dr dbreg
+	if _, _, errno := unix.Syscall6(
+		unix.SYS_PTRACE,
+		uintptr(unix.PT_GETDBREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(&dr)),
+		0, 0,
+	); errno != 0 {
+		return nil, errno
+	}
+	return &dr, nil
+}
+
+// setDbRegs writes the debug register file of the stopped debuggee.
+func (s *Session) setDbRegs(dr *dbreg) error {
+	if _, _, errno := unix.Syscall6(
+		unix.SYS_PTRACE,
+		uintptr(unix.PT_SETDBREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(dr)),
+		0, 0,
+	); errno != 0 {
+		return errno
+	}
+	return nil
+}
+
+// archStopTrace classifies a TRAP_TRACE stop.  On amd64 the kernel
+// delivers both the completed single-step and the debug-register hit
+// through T_TRCTRAP with TRAP_TRACE (sys/amd64/amd64/trap.c), and DR6's
+// B0-B3 bits name the watchpoint that fired.
+func archStopTrace(s *Session, siAddr uint64) (StopReason, uint64) {
+	dr, err := s.getDbRegs()
+	if err != nil {
+		return StopSingleStep, 0
+	}
+	if status := dr.Dr[drStatus]; status&0xF != 0 {
+		for slot := range 4 {
+			if status&(1<<slot) != 0 && dr.Dr[slot] != 0 {
+				return StopWatchpoint, dr.Dr[slot]
+			}
+		}
+	}
+	return StopSingleStep, 0
+}
+
+// FindFreeWatchpointSlot returns the index of the first free watchpoint slot
+// (0-3), or -1 if all four hardware watchpoints are in use.
+func (s *Session) FindFreeWatchpointSlot() int {
+	for i := range 4 {
+		if !s.wpSlots[i] {
+			return i
+		}
+	}
+	return -1
+}
+
+// IsWatchpointSlotUsed reports whether slot (0-3) currently holds a watchpoint.
+func (s *Session) IsWatchpointSlotUsed(slot int) bool {
+	if slot < 0 || slot > 3 {
+		return false
+	}
+	return s.wpSlots[slot]
+}
+
+// SetWatchpoint installs a hardware watchpoint on the given address.
+// DR7's encoding is architectural: a 2-bit local/global enable pair per
+// slot at bit 2*slot, the R/W field at 16+4*slot and the length field at
+// 18+4*slot (Intel SDM vol 3, "Debug Registers").
+func (s *Session) SetWatchpoint(slot int, addr uint64, typ WatchpointType, size int) error {
+	if slot < 0 || slot > 3 {
+		return fmt.Errorf("debug: watchpoint slot must be 0-3")
+	}
+	if s.wpSlots[slot] {
+		return fmt.Errorf("debug: watchpoint slot %d already in use", slot)
+	}
+
+	var lenBits uint64
+	switch size {
+	case 1:
+		lenBits = 0
+	case 2:
+		lenBits = 1
+	case 4:
+		lenBits = 3
+	case 8:
+		lenBits = 2
+	default:
+		return fmt.Errorf("debug: watchpoint size must be 1, 2, 4, or 8")
+	}
+
+	dr, err := s.getDbRegs()
+	if err != nil {
+		return fmt.Errorf("debug: read debug registers: %w", err)
+	}
+	dr.Dr[slot] = addr
+
+	dr7 := dr.Dr[drControl]
+	enableBit := uint64(1) << (2 * slot)
+	rwBits := uint64(typ) << (16 + 4*slot)
+	lenField := lenBits << (18 + 4*slot)
+	mask := ^((uint64(1) << (2 * slot)) | (uint64(3) << (16 + 4*slot)) | (uint64(3) << (18 + 4*slot)))
+	dr.Dr[drControl] = (dr7 & mask) | enableBit | rwBits | lenField
+
+	if err := s.setDbRegs(dr); err != nil {
+		return fmt.Errorf("debug: set debug registers: %w", err)
+	}
+	s.wpSlots[slot] = true
+	return nil
+}
+
+// ClearWatchpoint removes a hardware watchpoint.
+func (s *Session) ClearWatchpoint(slot int) error {
+	if slot < 0 || slot > 3 {
+		return fmt.Errorf("debug: watchpoint slot must be 0-3")
+	}
+	if !s.wpSlots[slot] {
+		return fmt.Errorf("debug: watchpoint slot %d is not in use", slot)
+	}
+	dr, err := s.getDbRegs()
+	if err != nil {
+		return err
+	}
+	dr.Dr[slot] = 0
+	dr.Dr[drControl] &^= uint64(1) << (2 * slot)
+	if err := s.setDbRegs(dr); err != nil {
+		return err
+	}
+	s.wpSlots[slot] = false
+	return nil
+}
+
+// ClearAllWatchpoints removes all hardware watchpoints.
+func (s *Session) ClearAllWatchpoints() error {
+	for slot := range maxWatchpoints() {
+		if s.wpSlots[slot] {
+			if err := s.ClearWatchpoint(slot); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}

debug/watchpoint_freebsd_arm64.go

@@ -0,0 +1,205 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && arm64
+
+package debug
+
+import (
+	"fmt"
+	"unsafe"
+
+	"golang.org/x/sys/unix"
+)
+
+// Hardware watchpoint support via arm64 debug registers, read and written
+// as one blob through PT_GETDBREGS/PT_SETDBREGS.  The FreeBSD struct dbreg
+// (sys/arm64/include/reg.h) opens with the debug-facility header and then
+// carries 16 breakpoint and 16 watchpoint pairs of {address, control}.
+
+// dbreg mirrors FreeBSD's struct dbreg for PT_GETDBREGS/PT_SETDBREGS.
+type dbreg struct {
+	DbDebugVer  uint8
+	DbNbkpts    uint8
+	DbNwtpts    uint8
+	_           [5]byte
+	DbBreakregs [16]struct {
+		Addr uint64
+		Ctrl uint32
+		_    uint32
+	}
+	DbWatchregs [16]struct {
+		Addr uint64
+		Ctrl uint32
+		_    uint32
+	}
+}
+
+// WatchpointType selects what triggers the watchpoint.
+type WatchpointType int
+
+const (
+	WatchWrite WatchpointType = 1 // trigger on write
+	WatchRead  WatchpointType = 3 // trigger on read or write
+)
+
+// maxWatchpoints reports the number of hardware watchpoint slots the
+// architecture provides: DBGWVR0-DBGWCR15.
+func maxWatchpoints() int { return 16 }
+
+// getDbRegs reads the debug register file of the stopped debuggee.
+func (s *Session) getDbRegs() (*dbreg, error) {
+	var dr dbreg
+	if _, _, errno := unix.Syscall6(
+		unix.SYS_PTRACE,
+		uintptr(unix.PT_GETDBREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(&dr)),
+		0, 0,
+	); errno != 0 {
+		return nil, errno
+	}
+	return &dr, nil
+}
+
+// setDbRegs writes the debug register file of the stopped debuggee.
+func (s *Session) setDbRegs(dr *dbreg) error {
+	if _, _, errno := unix.Syscall6(
+		unix.SYS_PTRACE,
+		uintptr(unix.PT_SETDBREGS),
+		uintptr(s.pid),
+		0,
+		uintptr(unsafe.Pointer(dr)),
+		0, 0,
+	); errno != 0 {
+		return errno
+	}
+	return nil
+}
+
+// archStopTrace classifies a TRAP_TRACE stop.  On arm64 the kernel
+// delivers both the software single step and the watchpoint hit through
+// EXCP_SOFTSTP_EL0/EXCP_WATCHPT_EL0 with TRAP_TRACE (sys/arm64/arm64/
+// trap.c); the watchpoint address rides the FAR register, so a stop whose
+// reported address falls inside an armed watchpoint's byte range is a
+// watchpoint and everything else is a single step.
+func archStopTrace(s *Session, siAddr uint64) (StopReason, uint64) {
+	dr, err := s.getDbRegs()
+	if err != nil {
+		return StopSingleStep, 0
+	}
+	for slot := range 16 {
+		ctrl := uint64(dr.DbWatchregs[slot].Ctrl)
+		if ctrl&1 == 0 || dr.DbWatchregs[slot].Addr == 0 {
+			continue
+		}
+		if bas := (ctrl >> 5) & 0xFF; bas != 0 && siAddr >= dr.DbWatchregs[slot].Addr && siAddr < dr.DbWatchregs[slot].Addr+8 {
+			return StopWatchpoint, siAddr
+		}
+	}
+	return StopSingleStep, 0
+}
+
+// FindFreeWatchpointSlot returns the index of the first free watchpoint
+// slot, or -1 if all of them are in use.
+func (s *Session) FindFreeWatchpointSlot() int {
+	for i := range maxWatchpoints() {
+		if !s.wpSlots[i] {
+			return i
+		}
+	}
+	return -1
+}
+
+// IsWatchpointSlotUsed reports whether slot currently holds a watchpoint.
+func (s *Session) IsWatchpointSlotUsed(slot int) bool {
+	if slot < 0 || slot >= maxWatchpoints() {
+		return false
+	}
+	return s.wpSlots[slot]
+}
+
+// SetWatchpoint installs a hardware watchpoint on the given address.  The
+// control word is the architectural DBGWCR (ARM DDI 0487): bit 0 enables,
+// bits 3-4 select the access type (10 store, 11 load+store) and bits 5-12
+// are the byte-address select, so the watch stays 8-byte aligned and names
+// its watched bytes through BAS.
+func (s *Session) SetWatchpoint(slot int, addr uint64, typ WatchpointType, size int) error {
+	if slot < 0 || slot >= maxWatchpoints() {
+		return fmt.Errorf("debug: watchpoint slot must be 0-%d", maxWatchpoints()-1)
+	}
+	if s.wpSlots[slot] {
+		return fmt.Errorf("debug: watchpoint slot %d already in use", slot)
+	}
+	var bas uint64
+	switch size {
+	case 1:
+		bas = 0x01
+	case 2:
+		bas = 0x03
+	case 4:
+		bas = 0x0F
+	case 8:
+		bas = 0xFF
+	default:
+		return fmt.Errorf("debug: watchpoint size must be 1, 2, 4, or 8")
+	}
+
+	dr, err := s.getDbRegs()
+	if err != nil {
+		return fmt.Errorf("debug: read debug registers: %w", err)
+	}
+	if uint8(slot) >= dr.DbNwtpts && dr.DbNwtpts != 0 {
+		return fmt.Errorf("debug: slot %d exceeds available watchpoints (%d)", slot, dr.DbNwtpts)
+	}
+	ctrl := uint64(1) // enable
+	switch typ {
+	case WatchWrite:
+		ctrl |= 2 << 3 // store only
+	case WatchRead:
+		ctrl |= 3 << 3 // load+store
+	}
+	ctrl |= bas << 5
+	dr.DbWatchregs[slot].Addr = addr
+	dr.DbWatchregs[slot].Ctrl = uint32(ctrl)
+
+	if err := s.setDbRegs(dr); err != nil {
+		return fmt.Errorf("debug: set debug registers: %w", err)
+	}
+	s.wpSlots[slot] = true
+	return nil
+}
+
+// ClearWatchpoint removes a hardware watchpoint.
+func (s *Session) ClearWatchpoint(slot int) error {
+	if slot < 0 || slot >= maxWatchpoints() {
+		return fmt.Errorf("debug: watchpoint slot must be 0-%d", maxWatchpoints()-1)
+	}
+	if !s.wpSlots[slot] {
+		return fmt.Errorf("debug: watchpoint slot %d is not in use", slot)
+	}
+	dr, err := s.getDbRegs()
+	if err != nil {
+		return err
+	}
+	dr.DbWatchregs[slot].Addr = 0
+	dr.DbWatchregs[slot].Ctrl = 0
+	if err := s.setDbRegs(dr); err != nil {
+		return err
+	}
+	s.wpSlots[slot] = false
+	return nil
+}
+
+// ClearAllWatchpoints removes all hardware watchpoints.
+func (s *Session) ClearAllWatchpoints() error {
+	for slot := range maxWatchpoints() {
+		if s.wpSlots[slot] {
+			if err := s.ClearWatchpoint(slot); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}

debug/watchpoint_freebsd_riscv64.go

@@ -0,0 +1,50 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build freebsd && riscv64
+
+package debug
+
+import "fmt"
+
+// The architecture has hardware watchpoint triggers, but FreeBSD exposes
+// no PT_GETDBREGS request for riscv64, so there is no supported way to arm
+// one: the watchpoint layer is honestly empty here.
+
+// WatchpointType selects what triggers the watchpoint.
+type WatchpointType int
+
+const (
+	WatchWrite WatchpointType = 1 // trigger on write
+	WatchRead  WatchpointType = 3 // trigger on read or write
+)
+
+// maxWatchpoints reports the number of hardware watchpoint slots the
+// platform provides: FreeBSD exposes none for riscv64.
+func maxWatchpoints() int { return 0 }
+
+// archStopTrace classifies a TRAP_TRACE stop; with no watchpoint layer a
+// trace stop is always a completed single step.
+func archStopTrace(s *Session, siAddr uint64) (StopReason, uint64) {
+	return StopSingleStep, 0
+}
+
+// FindFreeWatchpointSlot returns -1: no slots exist.
+func (s *Session) FindFreeWatchpointSlot() int { return -1 }
+
+// IsWatchpointSlotUsed reports whether slot currently holds a watchpoint.
+func (s *Session) IsWatchpointSlotUsed(slot int) bool { return false }
+
+// SetWatchpoint is unsupported: FreeBSD exposes no debug register request
+// for riscv64.
+func (s *Session) SetWatchpoint(slot int, addr uint64, typ WatchpointType, size int) error {
+	return fmt.Errorf("debug: hardware watchpoints are not supported on freebsd/riscv64")
+}
+
+// ClearWatchpoint is unsupported for the same reason.
+func (s *Session) ClearWatchpoint(slot int) error {
+	return fmt.Errorf("debug: hardware watchpoints are not supported on freebsd/riscv64")
+}
+
+// ClearAllWatchpoints is a no-op: no watchpoint can be armed.
+func (s *Session) ClearAllWatchpoints() error { return nil }

docs/ARCHITECTURE.md

@@ -246,11 +246,18 @@ document store, republishes diagnostics on every change, and provides:
   pseudo-registers, labels, immediates, comments, directives, textflag macros);
 - **navigation**: go-to-definition from a label reference to its definition,
   find references, document highlights of every use of the symbol under the
-  cursor, rename, and workspace symbol search over the open documents;
+  cursor, rename, and workspace symbol search over the open documents and
+  the indexed workspace files: the `.s` files under the workspace root that
+  the editor has never opened, where an open buffer shadows its disk copy
+  and watched-file events plus a per-query freshness check keep the index
+  current;
 - **assists**: document formatting through the `format` package, inlay hints
   (the frame size after the TEXT argument area), signature help (the callee's
   `// func` signature while the cursor is on a `CALL`), and code actions
-  offering quick fixes for the `missing-ret` and `unused-label` diagnostics.
+  offering quick fixes for the `missing-ret` and `unused-label` diagnostics,
+  the `missing-textflag-include` warning (the include after the last one in
+  the file) and the `abi-argsize` warning (the argument area set to the size
+  the `// func` signature implies).
 - **document information**: pull diagnostics (`textDocument/diagnostic`),
   #include document links (resolved against the document directory, then
   `$GOROOT/pkg/include`) and folding ranges (one collapsible region per
@@ -572,7 +579,9 @@ AST, so neither depends on an encoding.
   --ground-truth`, `go list -json -export` locates the archives of the packages
   a GOOBJ object references, and `_gen` parses
   `$GOROOT/src/cmd/internal/obj/<arch>/anames.go` to rebuild the tables.
-- **Linux process interfaces** for the dynamic work: `mmap` and `mprotect` for
-  the JIT mapping, ptrace with `/proc/pid/mem` for the debugger.  That is why
+- **Linux and FreeBSD process interfaces** for the dynamic work: `mmap` and
+  `mprotect` for the JIT mapping, ptrace for the debugger — with tracee
+  memory through `/proc/pid/mem` on Linux and through `PT_IO` on FreeBSD,
+  and the tracee's stop reports read from `PT_LWPINFO` there.  That is why
   `verify` runs a JIT check only when the host architecture matches the
-  kernel's, and why `debug` is Linux-only.
+  kernel's, and why `debug` is bounded to those two kernels.

docs/CLI.md

@@ -287,7 +287,8 @@ Usage: gasm debug <file.s> --func <name>
 The debugger re-executes the binary it is running as (`os.Executable()`) for the
 traced child, so the child is the same `gasm`, whether it is installed on `$PATH`
 or run with `go run ./cmd/gasm`; nothing has to be installed first. Requires
-Linux (ptrace), and all four architectures are supported.
+Linux or FreeBSD (ptrace): all four architectures on Linux, amd64, arm64 and
+riscv64 on FreeBSD.
 
 REPL commands:
 
@@ -455,7 +456,13 @@ semantic tokens, go-to-definition, find references, rename, document
 formatting, inlay hints, code actions, signature help, document highlights,
 workspace symbol search, #include document links, and folding ranges for
 function bodies. Definition, references and rename work across every open
-document.
+document and the wider workspace on disk: the server indexes the `.s` files
+under the workspace root that the editor has never opened, an open buffer
+always shadows its disk copy, and watched-file events together with a
+per-query freshness check keep the index current. The quick fixes add the
+missing `#include "textflag.h"`, set the TEXT argument area to the size the
+`// func` signature implies, add a missing `RET`, and remove an unused
+label.
 
 ## version
 

go.mod

@@ -2,4 +2,7 @@ module sourcedock.dev/petrbalvin/gasm-devkit
 
 go 1.27.1
 
-require golang.org/x/arch v0.30.0
+require (
+	golang.org/x/arch v0.30.0
+	golang.org/x/sys v0.48.0
+)

go.sum

@@ -1,4 +1,4 @@
-golang.org/x/arch v0.29.0 h1:8sSET5wB0+exBm0FGmOtdHMqjlRdV2DRD3/IV6OZgho=
-golang.org/x/arch v0.29.0/go.mod h1:0X+GdSIP+kL5wPmpK7sdkEVTt2XoYP0cSjQSbZBwOi8=
 golang.org/x/arch v0.30.0 h1:sB9h+1gRGa2+LauFSV0tm8bK1J2yo1bx6/Uyi/P6DTU=
 golang.org/x/arch v0.30.0/go.mod h1:0X+GdSIP+kL5wPmpK7sdkEVTt2XoYP0cSjQSbZBwOi8=
+golang.org/x/sys v0.48.0 h1:bbX/i/6MgT9BVLM9RT1thmxL04yeTAhbEz4SyadbXoo=
+golang.org/x/sys v0.48.0/go.mod h1:hNLxWAXmnKAxqDtdwIYC4bM9oQPEecfsnNMuSxOs3og=

lint/abi.go

@@ -11,6 +11,15 @@ import (
 	"strings"
 )
 
+// ExpectedArgSize computes the argument-area size (parameters plus results,
+// laid out with Go's alignment rules on a 64-bit target) implied by the
+// `// func …` signature in a doc comment.  It returns ok=false when there is
+// no parseable signature or it uses a type whose size cannot be determined
+// (a named type), so the caller can skip the fix rather than guess.
+func ExpectedArgSize(doc string) (int64, bool) {
+	return abiExpectedArgSize(doc)
+}
+
 // abiExpectedArgSize computes the argument-area size (parameters plus results,
 // laid out with Go's alignment rules on a 64-bit target) from the `// func …`
 // signature in a TEXT function's doc comment.  It returns ok=false when there

lsp/handlers.go

@@ -11,6 +11,7 @@ import (
 	"regexp"
 	"runtime"
 	"slices"
+	"strconv"
 	"strings"
 	"unicode"
 	"unicode/utf16"
@@ -127,8 +128,8 @@ func (s *Server) openASTs() []openAST {
 
 // definition returns the location of the named label or function: a local
 // label in the current document wins, then the TEXT functions of every open
-// document are searched, so a `CALL ·helper(SB)` jumps to its definition in
-// another file.
+// document and indexed workspace file are searched, so a `CALL ·helper(SB)`
+// jumps to its definition even when the defining file was never opened.
 func (s *Server) definition(p definitionParams) []Location {
 	text := s.docs[p.TextDocument.URI]
 	word, _ := wordAt(text, p.Position)
@@ -156,15 +157,15 @@ func (s *Server) definition(p definitionParams) []Location {
 		}
 	}
 
-	// Function definitions across the open workspace.
-	for _, of := range s.openASTs() {
-		for _, d := range of.file.Decls {
+	// Function definitions across the workspace.
+	for _, u := range s.scanUnits() {
+		for _, d := range u.file.Decls {
 			t, ok := d.(*ast.Text)
 			if !ok || !realSymbol(t.Name) {
 				continue
 			}
 			if t.Name.Name == name {
-				return []Location{{URI: of.uri, Range: clientRange(s.docs[of.uri], symRange(t.Name))}}
+				return []Location{{URI: u.uri, Range: clientRange(u.text, symRange(t.Name))}}
 			}
 		}
 	}
@@ -172,10 +173,11 @@ func (s *Server) definition(p definitionParams) []Location {
 }
 
 // references returns all locations where the symbol under the cursor appears
-// across every open document.  The current document matches labels and any
-// operand name, as before; other documents only match SB-qualified operand
-// references and the definition itself, because a bare name is a
-// function-local label whose repeats in other files are unrelated.
+// across every open document and indexed workspace file.  The current
+// document matches labels and any operand name, as before; every other
+// source only matches SB-qualified operand references and the definition
+// itself, because a bare name is a function-local label whose repeats in
+// other files are unrelated.
 func (s *Server) references(p referenceParams) []Location {
 	text := s.docs[p.TextDocument.URI]
 	word, _ := wordAt(text, p.Position)
@@ -186,22 +188,22 @@ func (s *Server) references(p referenceParams) []Location {
 	uri := p.TextDocument.URI
 
 	var out []Location
-	for _, of := range s.openASTs() {
-		sameDoc := of.uri == uri
-		for _, d := range of.file.Decls {
+	for _, u := range s.scanUnits() {
+		sameDoc := u.uri == uri
+		for _, d := range u.file.Decls {
 			t, ok := d.(*ast.Text)
 			if !ok || !realSymbol(t.Name) {
 				continue
 			}
 			// Include the definition if requested.
 			if p.Context.IncludeDeclaration && t.Name.Name == name {
-				out = append(out, Location{URI: of.uri, Range: clientRange(s.docs[of.uri], symRange(t.Name))})
+				out = append(out, Location{URI: u.uri, Range: clientRange(u.text, symRange(t.Name))})
 			}
 			for _, stmt := range t.Body {
 				switch st := stmt.(type) {
 				case *ast.Label:
 					if sameDoc && st.Name.Text == name {
-						out = append(out, Location{URI: of.uri, Range: clientRange(s.docs[of.uri], tokenRange(st.Name))})
+						out = append(out, Location{URI: u.uri, Range: clientRange(u.text, tokenRange(st.Name))})
 					}
 				case *ast.Instr:
 					for _, op := range st.Operands {
@@ -215,8 +217,8 @@ func (s *Server) references(p referenceParams) []Location {
 						// identifier, `·`/package prefix included, so a
 						// rename replaces the whole spelling.
 						out = append(out, Location{
-							URI: of.uri,
-							Range: clientRange(s.docs[of.uri], Range{
+							URI: u.uri,
+							Range: clientRange(u.text, Range{
 								Start: Position{Line: op.Pos.Line - 1, Character: op.Pos.Column - 1},
 								End:   Position{Line: op.Pos.Line - 1, Character: op.Pos.Column - 1 + symIdentLen(op.Addr.Sym)},
 							}),
@@ -229,7 +231,9 @@ func (s *Server) references(p referenceParams) []Location {
 	return out
 }
 
-// rename renames a label across the document.
+// rename renames a label across every document the references reach.  Each
+// edit is grouped under the URI it belongs to: a range collected in another
+// file must never be applied to the document that started the rename.
 func (s *Server) rename(p renameParams) *WorkspaceEdit {
 	text := s.docs[p.TextDocument.URI]
 	word, _ := wordAt(text, p.Position)
@@ -244,13 +248,11 @@ func (s *Server) rename(p renameParams) *WorkspaceEdit {
 	if len(refs) == 0 {
 		return nil
 	}
-	edits := make([]TextEdit, 0, len(refs))
+	edits := make(map[string][]TextEdit, len(refs))
 	for _, loc := range refs {
-		edits = append(edits, TextEdit{Range: loc.Range, NewText: p.NewName})
-	}
-	return &WorkspaceEdit{
-		Changes: map[string][]TextEdit{p.TextDocument.URI: edits},
+		edits[loc.URI] = append(edits[loc.URI], TextEdit{Range: loc.Range, NewText: p.NewName})
 	}
+	return &WorkspaceEdit{Changes: edits}
 }
 
 // documentFormatting returns a single edit that replaces the whole document
@@ -385,6 +387,61 @@ func (s *Server) codeActions(p codeActionParams) []CodeAction {
 					}
 				}
 			}
+		case "missing-textflag-include":
+			// Offer to #include the header that defines the flag macros:
+			// after the last existing include, or at the top of the file
+			// when there is none.
+			insertLine := 0
+			lines := strings.Split(text, "\n")
+			for i, line := range lines {
+				if includeRe.MatchString(line) {
+					insertLine = i + 1
+				}
+			}
+			actions = append(actions, CodeAction{
+				Title: `Add #include "textflag.h"`,
+				Kind:  "quickfix",
+				Edit: &WorkspaceEdit{
+					Changes: map[string][]TextEdit{p.TextDocument.URI: {{
+						Range:   Range{Start: Position{Line: insertLine, Character: 0}, End: Position{Line: insertLine, Character: 0}},
+						NewText: "#include \"textflag.h\"\n",
+					}}},
+				},
+			})
+		case "abi-argsize":
+			// Offer to set the TEXT argument area to the size the // func
+			// signature implies.  The diagnostic's range covers the TEXT
+			// keyword, so a line match picks the function it belongs to.
+			f, _ := parser.Parse(uriPath(p.TextDocument.URI), text)
+			if f == nil {
+				continue
+			}
+			for _, d := range f.Decls {
+				t, ok := d.(*ast.Text)
+				if !ok || t.Keyword.Pos.Line-1 != int(diag.Range.Start.Line) {
+					continue
+				}
+				want, ok := lint.ExpectedArgSize(t.Doc)
+				if !ok || t.Args == nil || !t.Args.Imm.HasVal || t.Args.Imm.Val == want {
+					continue
+				}
+				// The parser records the argument area with its leading
+				// minus, so the replacement spans the whole `-16` shape.
+				rng := clientRange(text, Range{
+					Start: Position{Line: t.Args.Pos.Line - 1, Character: t.Args.Pos.Column - 1},
+					End:   Position{Line: t.Args.Pos.Line - 1, Character: t.Args.Pos.Column - 1 + runeLen(t.Args.Raw)},
+				})
+				actions = append(actions, CodeAction{
+					Title: fmt.Sprintf("Set arg size to %d", want),
+					Kind:  "quickfix",
+					Edit: &WorkspaceEdit{
+						Changes: map[string][]TextEdit{p.TextDocument.URI: {{
+							Range:   rng,
+							NewText: "-" + strconv.FormatInt(want, 10),
+						}}},
+					},
+				})
+			}
 		}
 	}
 	return actions
@@ -510,19 +567,16 @@ func (s *Server) documentHighlights(p documentHighlightParams) []DocumentHighlig
 	return out
 }
 
-// workspaceSymbols searches all open documents for symbols matching the query.
+// workspaceSymbols searches all open documents and indexed workspace files
+// for symbols matching the query.
 func (s *Server) workspaceSymbols(p workspaceSymbolParams) []WorkspaceSymbol {
 	if p.Query == "" {
 		return nil
 	}
 	query := strings.ToLower(p.Query)
 	var out []WorkspaceSymbol
-	for uri, text := range s.docs {
-		f, _ := parser.Parse(uriPath(uri), text)
-		if f == nil {
-			continue
-		}
-		for _, d := range f.Decls {
+	for _, u := range s.scanUnits() {
+		for _, d := range u.file.Decls {
 			switch dd := d.(type) {
 			case *ast.Text:
 				// A malformed TEXT line is kept in the tree under a "?"
@@ -535,7 +589,7 @@ func (s *Server) workspaceSymbols(p workspaceSymbolParams) []WorkspaceSymbol {
 					out = append(out, WorkspaceSymbol{
 						Name:     dd.Name.Name,
 						Kind:     symFunction,
-						Location: Location{URI: uri, Range: clientRange(text, symRange(dd.Name))},
+						Location: Location{URI: u.uri, Range: clientRange(u.text, symRange(dd.Name))},
 					})
 				}
 			case *ast.Globl:
@@ -543,7 +597,7 @@ func (s *Server) workspaceSymbols(p workspaceSymbolParams) []WorkspaceSymbol {
 					out = append(out, WorkspaceSymbol{
 						Name:     dd.Name.Name,
 						Kind:     symConstant,
-						Location: Location{URI: uri, Range: clientRange(text, symRange(dd.Name))},
+						Location: Location{URI: u.uri, Range: clientRange(u.text, symRange(dd.Name))},
 					})
 				}
 			case *ast.Data:
@@ -551,7 +605,7 @@ func (s *Server) workspaceSymbols(p workspaceSymbolParams) []WorkspaceSymbol {
 					out = append(out, WorkspaceSymbol{
 						Name:     dd.Name.Name,
 						Kind:     symConstant,
-						Location: Location{URI: uri, Range: clientRange(text, symRange(dd.Name))},
+						Location: Location{URI: u.uri, Range: clientRange(u.text, symRange(dd.Name))},
 					})
 				}
 			}

lsp/protocol.go

@@ -309,6 +309,56 @@ type ServerCapabilities struct {
 	DiagnosticProvider         map[string]any `json:"diagnosticProvider,omitempty"`
 	DocumentLinkProvider       map[string]any `json:"documentLinkProvider,omitempty"`
 	FoldingRangeProvider       bool           `json:"foldingRangeProvider,omitempty"`
+	Workspace                  map[string]any `json:"workspace,omitempty"`
+}
+
+// --- workspace ----------------------------------------------------------------
+
+// initializeParams carries the workspace roots the client announces.
+type initializeParams struct {
+	RootURI          string            `json:"rootUri"`
+	WorkspaceFolders []workspaceFolder `json:"workspaceFolders"`
+}
+
+// workspaceFolder is one root folder the client opened.
+type workspaceFolder struct {
+	URI  string `json:"uri"`
+	Name string `json:"name"`
+}
+
+// roots returns the workspace roots as filesystem paths: the workspace
+// folders when the client sends them, else the root URI.
+func (p initializeParams) roots() []string {
+	var out []string
+	for _, f := range p.WorkspaceFolders {
+		if path := uriPath(f.URI); path != "" {
+			out = append(out, path)
+		}
+	}
+	if len(out) == 0 && p.RootURI != "" {
+		if path := uriPath(p.RootURI); path != "" {
+			out = append(out, path)
+		}
+	}
+	return out
+}
+
+// didChangeWatchedFilesParams announces on-disk changes the client watched.
+type didChangeWatchedFilesParams struct {
+	Changes []fileEvent `json:"changes"`
+}
+
+// File change types (LSP FileChangeType).
+const (
+	fileCreated = 1
+	fileChanged = 2
+	fileDeleted = 3
+)
+
+// fileEvent is one created, changed or deleted file.
+type fileEvent struct {
+	URI  string `json:"uri"`
+	Type int    `json:"type"`
 }
 
 // --- pull diagnostics ---------------------------------------------------------

lsp/server.go

@@ -24,6 +24,7 @@ type Server struct {
 	out     io.Writer
 	mu      sync.Mutex // guards writes to out
 	docs    map[string]string
+	ws      workspaceIndex // the on-disk workspace beyond the open documents
 	version string         // reported in the initialize result ("" omits it)
 }
 
@@ -169,6 +170,11 @@ func (s *Server) dispatch(msg *rpcMessage) (exit bool) {
 
 	switch msg.Method {
 	case "initialize":
+		var ip initializeParams
+		if len(msg.Params) > 0 {
+			json.Unmarshal(msg.Params, &ip)
+		}
+		s.ws.roots = ip.roots()
 		info := map[string]string{"name": "gasm"}
 		if s.version != "" {
 			info["version"] = s.version
@@ -198,6 +204,7 @@ func (s *Server) dispatch(msg *rpcMessage) (exit bool) {
 				DiagnosticProvider:        map[string]any{"interFileDependencies": false, "workspaceDiagnostics": false},
 				DocumentLinkProvider:      map[string]any{},
 				FoldingRangeProvider:      true,
+				Workspace:                 map[string]any{"didChangeWatchedFiles": map[string]any{}},
 			},
 			ServerInfo: info,
 		})
@@ -308,6 +315,14 @@ func (s *Server) dispatch(msg *rpcMessage) (exit bool) {
 		json.Unmarshal(msg.Params, &p)
 		s.respond(msg.ID, s.workspaceSymbols(p))
 
+	case "workspace/didChangeWatchedFiles":
+		var p didChangeWatchedFilesParams
+		if json.Unmarshal(msg.Params, &p) == nil {
+			for _, ch := range p.Changes {
+				s.ws.watched(uriPath(ch.URI), ch.Type == fileDeleted)
+			}
+		}
+
 	case "shutdown":
 		s.respond(msg.ID, nil)
 

lsp/server_test.go

@@ -1014,6 +1014,134 @@ func TestCodeActionsTargetsFlaggedFunctionOnly(t *testing.T) {
 	}
 }
 
+// TestCodeActionInsertsTextflagInclude offers the include a file must carry
+// when it uses flag macros: at the top of the file when there is no include
+// yet, after the last one otherwise.
+func TestCodeActionInsertsTextflagInclude(t *testing.T) {
+	doc := "TEXT \u00b7f(SB), NOSPLIT, $0\n\tRET\n"
+	withInclude := "#include \"go_asm.h\"\n\nTEXT \u00b7f(SB), NOSPLIT, $0\n\tRET\n"
+	in := session("file:///f_amd64.s", doc) +
+		frame(30, "textDocument/codeAction", map[string]any{
+			"textDocument": map[string]any{"uri": "file:///f_amd64.s"},
+			"range":        map[string]any{"start": map[string]any{"line": 0, "character": 0}, "end": map[string]any{"line": 1, "character": 0}},
+			"context": map[string]any{"diagnostics": []map[string]any{
+				{"code": "missing-textflag-include", "range": map[string]any{"start": map[string]any{"line": 0, "character": 0}, "end": map[string]any{"line": 0, "character": 4}}},
+			}},
+		}) +
+		frame(nil, "textDocument/didChange", map[string]any{
+			"textDocument":   map[string]any{"uri": "file:///f_amd64.s", "version": 2},
+			"contentChanges": []map[string]any{{"text": withInclude}},
+		}) +
+		frame(31, "textDocument/codeAction", map[string]any{
+			"textDocument": map[string]any{"uri": "file:///f_amd64.s"},
+			"range":        map[string]any{"start": map[string]any{"line": 0, "character": 0}, "end": map[string]any{"line": 3, "character": 0}},
+			"context": map[string]any{"diagnostics": []map[string]any{
+				{"code": "missing-textflag-include", "range": map[string]any{"start": map[string]any{"line": 2, "character": 0}, "end": map[string]any{"line": 2, "character": 4}}},
+			}},
+		}) +
+		frame(nil, "exit", nil)
+	msgs := run(t, in)
+
+	resp := findByID(msgs, 30)
+	if resp == nil {
+		t.Fatal("no codeAction response")
+	}
+	var actions []CodeAction
+	if err := json.Unmarshal(mustResult(t, resp), &actions); err != nil {
+		t.Fatal(err)
+	}
+	if len(actions) != 1 {
+		t.Fatalf("actions = %d, want 1", len(actions))
+	}
+	edits := actions[0].Edit.Changes["file:///f_amd64.s"]
+	if len(edits) != 1 || edits[0].Range.Start.Line != 0 || edits[0].Range.Start.Character != 0 {
+		t.Fatalf("edit = %+v, want an insertion at line 0 character 0", edits)
+	}
+	if got := applyEdits(doc, edits); !strings.HasPrefix(got, "#include \"textflag.h\"\nTEXT \u00b7f") {
+		t.Errorf("edited document = %q, want the include as the first line", got)
+	}
+
+	resp = findByID(msgs, 31)
+	if resp == nil {
+		t.Fatal("no codeAction response for the with-include variant")
+	}
+	actions = nil
+	if err := json.Unmarshal(mustResult(t, resp), &actions); err != nil {
+		t.Fatal(err)
+	}
+	if len(actions) != 1 || actions[0].Edit.Changes["file:///f_amd64.s"][0].Range.Start.Line != 1 {
+		t.Fatalf("actions = %+v, want one insertion after the last include (line 1)", actions)
+	}
+}
+
+// TestCodeActionFixesArgSize offers the argument area the // func signature
+// implies; without a parseable signature there is nothing to offer.
+func TestCodeActionFixesArgSize(t *testing.T) {
+	doc := "// func Add(x int64) int64\n" +
+		"TEXT \u00b7Add(SB), NOSPLIT, $0-8\n" +
+		"\tMOVQ x+0(FP), AX\n" +
+		"\tADDQ y+8(FP), AX\n" +
+		"\tMOVQ AX, ret+16(FP)\n" +
+		"\tRET\n"
+	bare := "TEXT \u00b7Bare(SB), NOSPLIT, $0-8\n\tRET\n"
+	in := session("file:///f_amd64.s", doc) +
+		frame(32, "textDocument/codeAction", map[string]any{
+			"textDocument": map[string]any{"uri": "file:///f_amd64.s"},
+			"range":        map[string]any{"start": map[string]any{"line": 1, "character": 0}, "end": map[string]any{"line": 1, "character": 4}},
+			"context": map[string]any{"diagnostics": []map[string]any{
+				{"code": "abi-argsize", "range": map[string]any{"start": map[string]any{"line": 1, "character": 0}, "end": map[string]any{"line": 1, "character": 4}}},
+			}},
+		}) +
+		frame(nil, "textDocument/didChange", map[string]any{
+			"textDocument":   map[string]any{"uri": "file:///f_amd64.s", "version": 2},
+			"contentChanges": []map[string]any{{"text": bare}},
+		}) +
+		frame(33, "textDocument/codeAction", map[string]any{
+			"textDocument": map[string]any{"uri": "file:///f_amd64.s"},
+			"range":        map[string]any{"start": map[string]any{"line": 0, "character": 0}, "end": map[string]any{"line": 0, "character": 4}},
+			"context": map[string]any{"diagnostics": []map[string]any{
+				{"code": "abi-argsize", "range": map[string]any{"start": map[string]any{"line": 0, "character": 0}, "end": map[string]any{"line": 0, "character": 4}}},
+			}},
+		}) +
+		frame(nil, "exit", nil)
+	msgs := run(t, in)
+
+	resp := findByID(msgs, 32)
+	if resp == nil {
+		t.Fatal("no codeAction response")
+	}
+	var actions []CodeAction
+	if err := json.Unmarshal(mustResult(t, resp), &actions); err != nil {
+		t.Fatal(err)
+	}
+	if len(actions) != 1 {
+		t.Fatalf("actions = %d, want 1", len(actions))
+	}
+	if actions[0].Title != "Set arg size to 16" {
+		t.Errorf("action title = %q, want Set arg size to 16", actions[0].Title)
+	}
+	edits := actions[0].Edit.Changes["file:///f_amd64.s"]
+	if len(edits) != 1 || edits[0].NewText != "-16" || edits[0].Range.Start.Line != 1 {
+		t.Fatalf("edit = %+v, want -16 on line 1", edits)
+	}
+	if got := applyEdits(doc, edits); !strings.Contains(got, "$0-16") {
+		t.Errorf("edited document = %q, want $0-16", got)
+	}
+
+	// No // func signature, no offer: the expected size cannot be computed.
+	resp = findByID(msgs, 33)
+	if resp == nil {
+		t.Fatal("no codeAction response for the bare variant")
+	}
+	actions = nil
+	if err := json.Unmarshal(mustResult(t, resp), &actions); err != nil {
+		t.Fatal(err)
+	}
+	if len(actions) != 0 {
+		t.Fatalf("actions = %+v, want none without a // func signature", actions)
+	}
+}
+
 // TestCrossFileDefinitionAndReferences opens two documents: docA calls
 // ·helper(SB), docB defines it.  Definition must jump to docB and references
 // must collect the call site in docA plus the definition in docB.
@@ -1074,3 +1202,49 @@ func TestCrossFileDefinitionAndReferences(t *testing.T) {
 		t.Errorf("references by uri = %v, want one in each file", byURI)
 	}
 }
+
+// TestRenameGroupsEditsByDocument pins the grouping contract: every edit is
+// applied to the document it was collected in, so a cross-file rename never
+// corrupts the origin buffer.
+func TestRenameGroupsEditsByDocument(t *testing.T) {
+	docA := "TEXT \u00b7caller(SB), NOSPLIT, $0\n" +
+		"\tCALL \u00b7helper(SB)\n" +
+		"\tRET\n"
+	docB := "TEXT \u00b7helper(SB), NOSPLIT, $0\n" +
+		"\tRET\n"
+	uriA := "file:///rename_a_amd64.s"
+	uriB := "file:///rename_b_amd64.s"
+	in := frame(1, "initialize", map[string]any{}) +
+		frame(nil, "initialized", map[string]any{}) +
+		frame(nil, "textDocument/didOpen", map[string]any{
+			"textDocument": map[string]any{"uri": uriA, "languageId": "gasm", "version": 1, "text": docA},
+		}) +
+		frame(nil, "textDocument/didOpen", map[string]any{
+			"textDocument": map[string]any{"uri": uriB, "languageId": "gasm", "version": 1, "text": docB},
+		}) +
+		frame(2, "textDocument/rename", map[string]any{
+			"textDocument": map[string]any{"uri": uriA},
+			"position":     map[string]any{"line": 1, "character": 8}, // on helper in CALL ·helper(SB)
+			"newName":      "renamed",
+		}) + frame(nil, "exit", nil)
+	msgs := run(t, in)
+	resp := findByID(msgs, 2)
+	if resp == nil {
+		t.Fatal("no rename response")
+	}
+	var edit WorkspaceEdit
+	if err := json.Unmarshal(mustResult(t, resp), &edit); err != nil {
+		t.Fatal(err)
+	}
+	if len(edit.Changes[uriA]) != 1 || len(edit.Changes[uriB]) != 1 {
+		t.Fatalf("edits per uri = %d and %d, want one each", len(edit.Changes[uriA]), len(edit.Changes[uriB]))
+	}
+	gotA := applyEdits(docA, edit.Changes[uriA])
+	gotB := applyEdits(docB, edit.Changes[uriB])
+	if !strings.Contains(gotA, "CALL renamed(SB)") || strings.Contains(gotA, "renamed(SB), NOSPLIT") {
+		t.Errorf("caller document rename wrong: %q", gotA)
+	}
+	if !strings.Contains(gotB, "TEXT renamed(SB)") {
+		t.Errorf("helper document rename wrong: %q", gotB)
+	}
+}

lsp/workspace.go

@@ -0,0 +1,164 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package lsp
+
+import (
+	"cmp"
+	"io/fs"
+	"net/url"
+	"os"
+	"path/filepath"
+	"slices"
+	"strings"
+	"time"
+
+	"sourcedock.dev/petrbalvin/gasm-devkit/ast"
+	"sourcedock.dev/petrbalvin/gasm-devkit/parser"
+)
+
+// workspaceIndex indexes the .s files under the workspace roots that the
+// client has not opened.  Every workspace-scoped answer (definition,
+// references, workspace symbols) reads it after the open documents, so a
+// symbol resolves to and collects references from files the editor has never
+// shown.  An open buffer always shadows its disk copy: the entry stays in the
+// index but is skipped at query time, because the buffer may hold unsaved
+// edits the disk has never seen.
+//
+// Freshness does not rest on the client's watched-file events alone: every
+// query re-stats the indexed files and re-reads the ones whose stat identity
+// changed.  Watched-file events remain necessary for files created after the
+// build, which a stat of the known set cannot discover.  The index builds on
+// first use, since the roots arrive with initialize.  The server serves one
+// message at a time, so the index needs no lock.
+type workspaceIndex struct {
+	roots []string
+	built bool
+	files map[string]*workspaceFile // keyed by absolute path
+}
+
+// workspaceFile is one indexed on-disk file: its content, the parsed tree and
+// the stat identity the freshness check compares.
+type workspaceFile struct {
+	text    string
+	modTime time.Time
+	size    int64
+	file    *ast.File
+}
+
+// ensure builds the index on first use and refreshes it on every query
+// afterwards: a stat per file, a re-read only for the ones that changed.
+func (w *workspaceIndex) ensure() {
+	if !w.built {
+		w.built = true
+		w.files = make(map[string]*workspaceFile)
+		for _, root := range w.roots {
+			w.walk(root)
+		}
+		return
+	}
+	for path := range w.files {
+		w.load(path)
+	}
+}
+
+// walk adds every .s file below root, skipping the directories the go tool
+// itself ignores (hidden and underscore-prefixed names, testdata): the index
+// covers the buildable surface, not the whole tree.
+func (w *workspaceIndex) walk(root string) {
+	filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return nil // an unreadable entry never breaks the scan
+		}
+		if d.IsDir() {
+			if path != root && skipDir(d.Name()) {
+				return fs.SkipDir
+			}
+			return nil
+		}
+		if strings.HasSuffix(path, ".s") {
+			w.load(path)
+		}
+		return nil
+	})
+}
+
+// skipDir reports whether a directory is outside the buildable surface.
+func skipDir(name string) bool {
+	return name == "testdata" || strings.HasPrefix(name, ".") || strings.HasPrefix(name, "_")
+}
+
+// load reads one path into the index, or evicts it when it has disappeared.
+// A file whose stat identity still matches is left untouched.
+func (w *workspaceIndex) load(path string) {
+	st, err := os.Stat(path)
+	if err != nil || st.IsDir() {
+		delete(w.files, path)
+		return
+	}
+	if ef, ok := w.files[path]; ok && ef.size == st.Size() && ef.modTime.Equal(st.ModTime()) {
+		return
+	}
+	text, err := os.ReadFile(path)
+	if err != nil {
+		delete(w.files, path)
+		return
+	}
+	// Parsing is tolerant: a file with syntax errors still contributes its
+	// usable declarations, exactly as an open buffer mid-edit does.
+	body := string(text)
+	f, _ := parser.Parse(path, body)
+	w.files[path] = &workspaceFile{text: body, modTime: st.ModTime(), size: st.Size(), file: f}
+}
+
+// watched applies one client watched-file event: the named file is re-read
+// (created or changed) or evicted (deleted).  Events for anything but .s
+// files are ignored, and an event arriving before the first build no-ops:
+// the build then reads the disk state that already includes it.
+func (w *workspaceIndex) watched(path string, deleted bool) {
+	if !w.built || !strings.HasSuffix(path, ".s") {
+		return
+	}
+	if deleted {
+		delete(w.files, path)
+		return
+	}
+	w.load(path)
+}
+
+// scanUnit is one parseable source the workspace answers draw from: an open
+// buffer or an indexed disk file.
+type scanUnit struct {
+	uri  string
+	text string
+	file *ast.File
+}
+
+// scanUnits returns every source the workspace answers cover, in URI order
+// for deterministic results: the open documents, then the indexed disk files
+// that no open buffer shadows.
+func (s *Server) scanUnits() []scanUnit {
+	open := make(map[string]bool, len(s.docs))
+	for uri := range s.docs {
+		open[uriPath(uri)] = true
+	}
+	units := make([]scanUnit, 0, len(s.docs))
+	for _, of := range s.openASTs() {
+		units = append(units, scanUnit{uri: of.uri, text: s.docs[of.uri], file: of.file})
+	}
+	s.ws.ensure()
+	for path, ef := range s.ws.files {
+		if ef.file == nil || open[path] {
+			continue
+		}
+		units = append(units, scanUnit{uri: fileToURI(path), text: ef.text, file: ef.file})
+	}
+	slices.SortFunc(units, func(a, b scanUnit) int { return cmp.Compare(a.uri, b.uri) })
+	return units
+}
+
+// fileToURI renders an absolute path as a file URI, percent-encoding the
+// characters the URI rules reserve.
+func fileToURI(path string) string {
+	return (&url.URL{Scheme: "file", Path: path}).String()
+}

lsp/workspace_test.go

@@ -0,0 +1,251 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: BSD-3-Clause
+
+package lsp
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// diskWorkspace writes one helper file on disk and returns the workspace root
+// and the caller document that references ·helper and ·late by symbol.
+func diskWorkspace(t *testing.T) (root, callerURI string, caller string) {
+	t.Helper()
+	root = t.TempDir()
+	helper := "TEXT \u00b7helper(SB), NOSPLIT, $0\n\tRET\n"
+	if err := os.WriteFile(filepath.Join(root, "helper_amd64.s"), []byte(helper), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	caller = "TEXT \u00b7caller(SB), NOSPLIT, $0\n" +
+		"\tCALL \u00b7helper(SB)\n" +
+		"\tCALL \u00b7late(SB)\n" +
+		"\tRET\n"
+	callerURI = "file://" + root + "/caller_amd64.s"
+	return root, callerURI, caller
+}
+
+// openCaller frames the initialize/didOpen scripting around the caller doc.
+func openCaller(root, callerURI, caller string) string {
+	return frame(1, "initialize", map[string]any{"rootUri": "file://" + root}) +
+		frame(nil, "initialized", map[string]any{}) +
+		frame(nil, "textDocument/didOpen", map[string]any{
+			"textDocument": map[string]any{"uri": callerURI, "languageId": "gasm", "version": 1, "text": caller},
+		})
+}
+
+// TestDefinitionReachesDiskFile checks that go-to-definition resolves a
+// symbol to a workspace file the editor has never opened.
+func TestDefinitionReachesDiskFile(t *testing.T) {
+	root, callerURI, caller := diskWorkspace(t)
+	in := openCaller(root, callerURI, caller) +
+		frame(2, "textDocument/definition", map[string]any{
+			"textDocument": map[string]any{"uri": callerURI},
+			"position":     map[string]any{"line": 1, "character": 8}, // on helper in CALL ·helper(SB)
+		}) + frame(nil, "exit", nil)
+	msgs := run(t, in)
+	resp := findByID(msgs, 2)
+	if resp == nil {
+		t.Fatal("no definition response")
+	}
+	var locs []Location
+	if err := json.Unmarshal(mustResult(t, resp), &locs); err != nil {
+		t.Fatal(err)
+	}
+	wantURI := fileToURI(filepath.Join(root, "helper_amd64.s"))
+	if len(locs) != 1 || locs[0].URI != wantURI || locs[0].Range.Start.Line != 0 {
+		t.Fatalf("definition = %+v, want the TEXT in %s line 0", locs, wantURI)
+	}
+}
+
+// TestReferencesReachDiskFiles checks that find references collects the call
+// site in the open document plus the definition in the unopened disk file.
+func TestReferencesReachDiskFiles(t *testing.T) {
+	root, callerURI, caller := diskWorkspace(t)
+	in := openCaller(root, callerURI, caller) +
+		frame(2, "textDocument/references", map[string]any{
+			"textDocument": map[string]any{"uri": callerURI},
+			"position":     map[string]any{"line": 1, "character": 8}, // on helper in CALL ·helper(SB)
+			"context":      map[string]any{"includeDeclaration": true},
+		}) + frame(nil, "exit", nil)
+	msgs := run(t, in)
+	resp := findByID(msgs, 2)
+	if resp == nil {
+		t.Fatal("no references response")
+	}
+	var locs []Location
+	if err := json.Unmarshal(mustResult(t, resp), &locs); err != nil {
+		t.Fatal(err)
+	}
+	byURI := map[string]int{}
+	for _, l := range locs {
+		byURI[l.URI]++
+	}
+	if byURI[callerURI] != 1 || byURI[fileToURI(filepath.Join(root, "helper_amd64.s"))] != 1 {
+		t.Fatalf("references by uri = %v, want the call in the open document and the definition on disk", byURI)
+	}
+}
+
+// TestWorkspaceSymbolsReachesDiskFiles checks the workspace symbol search
+// against a file the editor has never opened.
+func TestWorkspaceSymbolsReachesDiskFiles(t *testing.T) {
+	root, callerURI, caller := diskWorkspace(t)
+	in := openCaller(root, callerURI, caller) +
+		frame(2, "workspace/symbol", map[string]any{"query": "helper"}) +
+		frame(nil, "exit", nil)
+	msgs := run(t, in)
+	resp := findByID(msgs, 2)
+	if resp == nil {
+		t.Fatal("no workspace/symbol response")
+	}
+	var syms []WorkspaceSymbol
+	if err := json.Unmarshal(mustResult(t, resp), &syms); err != nil {
+		t.Fatal(err)
+	}
+	if len(syms) != 1 || syms[0].Name != "helper" ||
+		syms[0].Location.URI != fileToURI(filepath.Join(root, "helper_amd64.s")) {
+		t.Fatalf("symbols = %+v, want helper from the disk file", syms)
+	}
+}
+
+// TestOpenBufferShadowsDiskFile pins the shadowing rule: when an open buffer
+// carries unsaved edits, the answers come from the buffer, never from the
+// stale disk copy.
+func TestOpenBufferShadowsDiskFile(t *testing.T) {
+	root, callerURI, caller := diskWorkspace(t)
+	helperURI := "file://" + root + "/helper_amd64.s"
+	// The buffer moved the definition to line 1; the disk copy has line 0.
+	buffered := "\nTEXT \u00b7helper(SB), NOSPLIT, $0\n\tRET\n"
+	in := openCaller(root, callerURI, caller) +
+		frame(nil, "textDocument/didOpen", map[string]any{
+			"textDocument": map[string]any{"uri": helperURI, "languageId": "gasm", "version": 1, "text": buffered},
+		}) +
+		frame(2, "textDocument/definition", map[string]any{
+			"textDocument": map[string]any{"uri": callerURI},
+			"position":     map[string]any{"line": 1, "character": 8},
+		}) +
+		frame(3, "textDocument/references", map[string]any{
+			"textDocument": map[string]any{"uri": callerURI},
+			"position":     map[string]any{"line": 1, "character": 8},
+			"context":      map[string]any{"includeDeclaration": true},
+		}) + frame(nil, "exit", nil)
+	msgs := run(t, in)
+
+	dresp := findByID(msgs, 2)
+	if dresp == nil {
+		t.Fatal("no definition response")
+	}
+	var locs []Location
+	if err := json.Unmarshal(mustResult(t, dresp), &locs); err != nil {
+		t.Fatal(err)
+	}
+	if len(locs) != 1 || locs[0].URI != helperURI || locs[0].Range.Start.Line != 1 {
+		t.Fatalf("definition = %+v, want the buffered TEXT on line 1", locs)
+	}
+
+	rresp := findByID(msgs, 3)
+	if rresp == nil {
+		t.Fatal("no references response")
+	}
+	locs = nil
+	if err := json.Unmarshal(mustResult(t, rresp), &locs); err != nil {
+		t.Fatal(err)
+	}
+	if len(locs) != 2 {
+		t.Fatalf("references = %+v, want the call and the buffered definition", locs)
+	}
+	for _, l := range locs {
+		if l.URI == helperURI && l.Range.Start.Line != 1 {
+			t.Errorf("reference in the opened file points at line %d, want the buffered line 1", l.Range.Start.Line)
+		}
+	}
+}
+
+// TestWatchedFileEventsUpdateIndex pins the one case a per-query refresh
+// cannot cover: a file created after the build is unknown to the index until
+// the client's watched-file event names it.  The steps run through dispatch
+// directly, because the file must appear on disk between two requests.
+func TestWatchedFileEventsUpdateIndex(t *testing.T) {
+	root, callerURI, caller := diskWorkspace(t)
+	latePath := filepath.Join(root, "late_amd64.s")
+	lateURI := "file://" + latePath
+
+	var buf bytes.Buffer
+	srv := New(strings.NewReader(""), &buf)
+	request := func(id int, method string, params any) *rpcMessage {
+		t.Helper()
+		raw, err := json.Marshal(params)
+		if err != nil {
+			t.Fatal(err)
+		}
+		var msgID *json.RawMessage
+		if id > 0 {
+			msgID = rawID(t, id)
+		}
+		srv.dispatch(&rpcMessage{ID: msgID, Method: method, Params: raw})
+		msgs := readFrames(t, &buf)
+		buf.Reset()
+		if id > 0 {
+			return findByID(msgs, id)
+		}
+		return nil
+	}
+	definitionOnLate := func(id int) []Location {
+		t.Helper()
+		resp := request(id, "textDocument/definition", map[string]any{
+			"textDocument": map[string]any{"uri": callerURI},
+			"position":     map[string]any{"line": 2, "character": 8}, // on late in CALL ·late(SB)
+		})
+		var locs []Location
+		if err := json.Unmarshal(mustResult(t, resp), &locs); err != nil {
+			t.Fatal(err)
+		}
+		return locs
+	}
+
+	request(1, "initialize", map[string]any{"rootUri": "file://" + root})
+	request(0, "textDocument/didOpen", map[string]any{
+		"textDocument": map[string]any{"uri": callerURI, "languageId": "gasm", "version": 1, "text": caller},
+	})
+
+	// The first request builds the index; the late file does not exist yet.
+	if locs := definitionOnLate(2); len(locs) != 0 {
+		t.Fatalf("definition before the file exists = %+v, want no result", locs)
+	}
+
+	if err := os.WriteFile(latePath, []byte("TEXT \u00b7late(SB), NOSPLIT, $0\n\tRET\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	request(0, "workspace/didChangeWatchedFiles", map[string]any{
+		"changes": []map[string]any{{"uri": lateURI, "type": fileCreated}},
+	})
+	if locs := definitionOnLate(4); len(locs) != 1 || locs[0].URI != fileToURI(latePath) {
+		t.Fatalf("definition after the created event = %+v, want late_amd64.s", locs)
+	}
+
+	if err := os.Remove(latePath); err != nil {
+		t.Fatal(err)
+	}
+	request(0, "workspace/didChangeWatchedFiles", map[string]any{
+		"changes": []map[string]any{{"uri": lateURI, "type": fileDeleted}},
+	})
+	if locs := definitionOnLate(6); len(locs) != 0 {
+		t.Fatalf("definition after the deleted event = %+v, want no result", locs)
+	}
+}
+
+// TestFileToURIRoundTrip pins the URI encoding of the disk entries: the
+// constructed URI decodes back to the path it came from.
+func TestFileToURIRoundTrip(t *testing.T) {
+	const path = "/tmp/Repositáře/kernels/helper.s"
+	if got := uriPath(fileToURI(path)); got != path {
+		t.Errorf("fileToURI round trip = %q, want %q", got, path)
+	}
+	if got := fileToURI("/plain/k.s"); got != "file:///plain/k.s" {
+		t.Errorf("fileToURI plain = %q", got)
+	}
+}

verify/jit.go

@@ -19,6 +19,8 @@ import (
 	"fmt"
 	"syscall"
 	"unsafe"
+
+	"golang.org/x/sys/unix"
 )
 
 // Executable maps a copy of code into a read-execute memory region suitable
@@ -49,8 +51,9 @@ func Map(code []byte) (*Executable, error) {
 	}
 	copy(mem, code)
 
-	// Remove write permission (W^X).
-	if err := syscall.Mprotect(mem, syscall.PROT_READ|syscall.PROT_EXEC); err != nil {
+	// Remove write permission (W^X).  x/sys carries Mprotect on every
+	// platform the package builds for; the stdlib syscall one is Linux-only.
+	if err := unix.Mprotect(mem, syscall.PROT_READ|syscall.PROT_EXEC); err != nil {
 		syscall.Munmap(mem)
 		return nil, fmt.Errorf("verify: mprotect: %w", err)
 	}