petrbalvin
b5d6f1b46a
The Go runtime can migrate the debuggee's target-mode goroutine off the process leader before PTRACE_TRACEME, which left the trace relation on a thread the session never addressed: its stops starved the waits on the leader, and a kill sequence that resumed nothing and then blocked in Wait4 hung the whole package. The debuggee now reports the traced thread in the launch handshake and parks with a thread-directed stop, every ptrace request and wait addresses that thread, a SIGURG arriving on a single-step resumes it as a single-step again instead of letting the tracee run uncontrolled, a resume rejected with ESRCH lifts a group-stop with SIGCONT and retries once, and Kill resumes, kills and reaps through non-blocking waits so it returns for a tracee in any state. Assisted-by: GLM 5.3
123 lines
3.2 KiB
Go
123 lines
3.2 KiB
Go
// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build linux && riscv64
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package debug
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import (
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"fmt"
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"os"
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"runtime"
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"syscall"
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"unsafe"
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"sourcedock.dev/petrbalvin/gasm-sdk/asm"
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"sourcedock.dev/petrbalvin/gasm-sdk/parser"
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"sourcedock.dev/petrbalvin/gasm-sdk/verify"
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)
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// RunTarget is the debuggee entry point (gasm debug --target). A failure
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// is marked in the handshake directory before the process exits, so the
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// debugger's readiness poll fails fast on a dead debuggee instead of
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// waiting out its whole budget.
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func RunTarget(asmPath, funcName, argsFile, tmpDir string) error {
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err := runTarget(asmPath, funcName, argsFile, tmpDir)
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if err != nil {
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markDead(tmpDir, err.Error())
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}
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return err
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}
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func runTarget(asmPath, funcName, argsFile, tmpDir string) error {
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src, err := os.ReadFile(asmPath)
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if err != nil {
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return fmt.Errorf("debug target: %w", err)
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}
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file, errs := parser.Parse(asmPath, string(src))
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if len(errs) > 0 {
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return fmt.Errorf("debug target: parse: %v", errs[0])
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}
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img, err := asm.AssembleFileRISCV(file)
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if err != nil {
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return fmt.Errorf("debug target: assemble: %w", err)
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}
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var fl *asm.FuncLayout
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for i := range img.Funcs {
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if img.Funcs[i].Name == funcName {
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fl = &img.Funcs[i]
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break
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}
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}
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if fl == nil {
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return fmt.Errorf("debug target: function %q not found", funcName)
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}
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code := img.Bytes()
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exec, err := mapRWX(code)
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if err != nil {
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return fmt.Errorf("debug target: mmap: %w", err)
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}
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codeBase := uintptr(unsafe.Pointer(&exec[0]))
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if err := os.WriteFile(tmpDir+"/codebase", []byte(fmt.Sprintf("%d", codeBase)), 0o644); err != nil {
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return fmt.Errorf("debug target: write codebase: %w", err)
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}
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meta := fmt.Sprintf("%d %d %d", fl.Offset, fl.Size, fl.Args)
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os.WriteFile(tmpDir+"/funcmeta", []byte(meta), 0o644)
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labelsFile, _ := os.Create(tmpDir + "/labels")
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if labelsFile != nil {
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for label, off := range fl.Labels {
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fmt.Fprintf(labelsFile, "%s %d\n", label, off)
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}
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labelsFile.Close()
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}
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args, err := os.ReadFile(argsFile)
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if err != nil {
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return fmt.Errorf("debug target: read args: %w", err)
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}
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if len(args) < fl.Args {
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padded := make([]byte, fl.Args)
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copy(padded, args)
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args = padded
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}
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bufSpecFile := tmpDir + "/bufspec"
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if bufSpec, err := os.ReadFile(bufSpecFile); err == nil && len(bufSpec) > 0 {
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args, err = setupBuffers(string(bufSpec), args, tmpDir)
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if err != nil {
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return fmt.Errorf("debug target: setup buffers: %w", err)
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}
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}
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runtime.LockOSThread()
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if _, _, errno := syscall.Syscall(syscall.SYS_PTRACE, uintptr(syscall.PTRACE_TRACEME), 0, 0); errno != 0 {
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return fmt.Errorf("debug target: PTRACE_TRACEME: %v", errno)
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}
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// The tracer must address the thread that called PTRACE_TRACEME, which
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// is not necessarily the process leader: report it before readiness.
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os.WriteFile(tmpDir+"/tracetid", []byte(fmt.Sprintf("%d", syscall.Gettid())), 0o644)
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os.WriteFile(tmpDir+"/ready", []byte("ok"), 0o644)
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parkSelf()
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os.WriteFile(tmpDir+"/entry", []byte("ok"), 0o644)
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parkSelf()
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fnAddr := codeBase + uintptr(fl.Offset)
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stackArgs := make([]byte, fl.Args)
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copy(stackArgs, args)
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_, callErr := verify.Call(fnAddr, stackArgs)
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if callErr != nil {
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os.Exit(1)
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}
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os.Exit(0)
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return nil
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}
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