diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2025-09-24 15:27:03 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2025-10-14 13:43:11 +0200 |
| commit | 044f721ccd33103349eebbb960825584bc6d8e23 (patch) | |
| tree | 3e9c6be0aa5d332a7e50798611fafdd60b7a7a1e /tools/objtool/arch | |
| parent | 76e1851a1bc28e760d6acc7a54ec9dce05717028 (diff) | |
objtool/x86: Fix NOP decode
For x86_64 the kernel consistently uses 2 instructions for all NOPs:
90 - NOP
0f 1f /0 - NOPL
Notably:
- REP NOP is PAUSE, not a NOP instruction.
- 0f {0c...0f} is reserved space,
except for 0f 0d /1, which is PREFETCHW, not a NOP.
- 0f {19,1c...1f} is reserved space,
except for 0f 1f /0, which is NOPL.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Diffstat (limited to 'tools/objtool/arch')
| -rw-r--r-- | tools/objtool/arch/x86/decode.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index ef6e96db8ce4..204e2ad1fada 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -494,6 +494,12 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec break; case 0x90: + if (rex_b) /* XCHG %r8, %rax */ + break; + + if (prefix == 0xf3) /* REP NOP := PAUSE */ + break; + insn->type = INSN_NOP; break; @@ -547,13 +553,14 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec } else if (op2 == 0x0b || op2 == 0xb9) { - /* ud2 */ + /* ud2, ud1 */ insn->type = INSN_BUG; - } else if (op2 == 0x0d || op2 == 0x1f) { + } else if (op2 == 0x1f) { - /* nopl/nopw */ - insn->type = INSN_NOP; + /* 0f 1f /0 := NOPL */ + if (modrm_reg == 0) + insn->type = INSN_NOP; } else if (op2 == 0x1e) { |