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