66 lines
1.9 KiB
Go
66 lines
1.9 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
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package debug
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import (
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"fmt"
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"strings"
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"sourcedock.dev/petrbalvin/gasm-sdk/arch"
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"sourcedock.dev/petrbalvin/gasm-sdk/disasm"
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)
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// Disassemble decodes the instruction at the given address in the debuggee's
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// memory and returns its text representation and length in bytes. An amd64
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// instruction is up to 15 bytes long, but the read must not reach past the
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// end of the mapping: when the full 15-byte window crosses into unmapped
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// memory the window shrinks, because an instruction at the mapping's end is
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// by construction no longer than the readable bytes that hold it.
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func (s *Session) Disassemble(addr uint64) (string, int, error) {
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var lastErr error
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for _, n := range []int{15, 8, 4, 2, 1} {
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mem, err := s.ReadMemory(addr, n)
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if err != nil {
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lastErr = err
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continue
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}
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ins, derr := disasm.Decode(arch.AMD64, mem, addr)
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if derr != nil {
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return "", 0, derr
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}
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return ins.Text, ins.Len, nil
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}
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return "", 0, lastErr
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}
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// DisassembleN decodes up to n instructions starting at addr and returns
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// them as a formatted string with addresses and byte offsets.
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func (s *Session) DisassembleN(addr uint64, n int) string {
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var result strings.Builder
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pc := addr
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for range n {
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text, length, err := s.Disassemble(pc)
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if err != nil {
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result.WriteString(fmt.Sprintf(" %#08x: <error: %v>\n", pc, err))
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break
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}
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result.WriteString(fmt.Sprintf(" %#08x: %s\n", pc, text))
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if length == 0 {
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length = 1
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}
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pc += uint64(length)
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}
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return result.String()
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}
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// isCallInsn reports whether disassembled text (x86asm.IntelSyntax) is a
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// call. The first token must match exactly: a prefix test would also catch
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// unrelated mnemonics.
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func isCallInsn(text string) bool {
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m, _, _ := strings.Cut(text, " ")
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return strings.ToLower(m) == "call"
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}
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