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x86/alternative: PAUSE is not a NOP
author
Peter Zijlstra
<peterz@infradead.org>
Wed, 14 Jun 2023 14:35:50 +0000
(16:35 +0200)
committer
Borislav Petkov (AMD)
<bp@alien8.de>
Wed, 14 Jun 2023 17:02:54 +0000
(19:02 +0200)
While chasing ghosts, I did notice that optimize_nops() was replacing
'REP NOP' aka 'PAUSE' with NOP2. This is clearly not right.
Fixes:
6c480f222128
("x86/alternative: Rewrite optimize_nops() some")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link:
https://lore.kernel.org/linux-next/20230524130104.GR83892@hirez.programming.kicks-ass.net/
arch/x86/kernel/alternative.c
patch
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diff --git
a/arch/x86/kernel/alternative.c
b/arch/x86/kernel/alternative.c
index
bbfbf7a
..
a7e1ec5
100644
(file)
--- a/
arch/x86/kernel/alternative.c
+++ b/
arch/x86/kernel/alternative.c
@@
-169,9
+169,12
@@
void text_poke_early(void *addr, const void *opcode, size_t len);
*/
static bool insn_is_nop(struct insn *insn)
{
- if (insn->opcode.bytes[0] == 0x90)
+ /* Anything NOP, but no REP NOP */
+ if (insn->opcode.bytes[0] == 0x90 &&
+ (!insn->prefixes.nbytes || insn->prefixes.bytes[0] != 0xF3))
return true;
+ /* NOPL */
if (insn->opcode.bytes[0] == 0x0F && insn->opcode.bytes[1] == 0x1F)
return true;