feat(debug): port the debugger to FreeBSD

Assisted-by: GLM 5.3 Flash
2026-09-25 21:46:40 +02:00
parent b9015e1c2e
commit b306c210c6
28 changed files with 2444 additions and 15 deletions
@@ -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