The following commit has been merged into the x86/alternatives branch of tip:
Commit-ID: 2bd4aa9325821551648cf9738d6aa3a49317d7e5
Gitweb: https://git.kernel.org/tip/2bd4aa9325821551648cf9738d6aa3a49317d7e5
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Wed, 14 Jun 2023 16:35:50 +02:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Wed, 14 Jun 2023 19:02:54 +02:00
x86/alternative: PAUSE is not a NOP
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@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Link: https://lore.kernel.org/linux-next/20230524130104.GR83892@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
---
arch/x86/kernel/alternative.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index bbfbf7a..a7e1ec5 100644
--- 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;
|