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x86/alternative: PAUSE is not a NOP

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While chasing ghosts, I did notice that optimize_nops() was replacing
'REP NOP' aka 'PAUSE' with NOP2. This is clearly not right.

Fixes: 6c480f2221 ("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/
This commit is contained in:
Peter Zijlstra
2023-06-14 16:35:50 +02:00
committed by Borislav Petkov (AMD)
parent 9350a629e8
commit 2bd4aa9325
1 changed files with 4 additions and 1 deletions
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5
arch/x86/kernel/alternative.c
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@@ -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;