Commit 2bd4aa93 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Borislav Petkov (AMD)
Browse files

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: 6c480f22 ("x86/alternative: Rewrite optimize_nops() some")
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/linux-next/20230524130104.GR83892@hirez.programming.kicks-ass.net/
parent 9350a629

arch/x86/kernel/alternative.c

+4 −1
Original line number Diff line number Diff line
@@ -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;