Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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>
+11
-4
+11
-4
tools/objtool/arch/x86/decode.c
+11
-4
tools/objtool/arch/x86/decode.c
···
494
494
break;
495
495
496
496
case 0x90:
497
+
if (rex_b) /* XCHG %r8, %rax */
498
+
break;
499
+
500
+
if (prefix == 0xf3) /* REP NOP := PAUSE */
501
+
break;
502
+
497
503
insn->type = INSN_NOP;
498
504
break;
499
505
···
553
547
554
548
} else if (op2 == 0x0b || op2 == 0xb9) {
555
549
556
-
/* ud2 */
550
+
/* ud2, ud1 */
557
551
insn->type = INSN_BUG;
558
552
559
-
} else if (op2 == 0x0d || op2 == 0x1f) {
553
+
} else if (op2 == 0x1f) {
560
554
561
-
/* nopl/nopw */
562
-
insn->type = INSN_NOP;
555
+
/* 0f 1f /0 := NOPL */
556
+
if (modrm_reg == 0)
557
+
insn->type = INSN_NOP;
563
558
564
559
} else if (op2 == 0x1e) {
565
560