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Message-ID: <20221204173933.GA31544@redhat.com>
Date: Sun, 4 Dec 2022 18:39:33 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Masami Hiramatsu <mhiramat@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>
Cc: Denys Vlasenko <dvlasenk@...hat.com>,
Seiji Nishikawa <snishika@...hat.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v2] uprobes/x86: allow to probe a "nop" insn with 0x66 prefix
Intel icc -hotpatch inserts 2-byte "0x66 0x90" NOP at the start of each
function to reserve extra space for hot-patching, and currently it is not
possible to probe these functions because branch_setup_xol_ops() wrongly
nacks NOP with REP prefix.
Fixes: 250bbd12c2fe ("uprobes/x86: Refuse to attach uprobe to "word-sized" branch insns")
Reported-by: Seiji Nishikawa <snishika@...hat.com>
Suggested-by: Denys Vlasenko <dvlasenk@...hat.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Signed-off-by: Oleg Nesterov <oleg@...hat.com>
---
arch/x86/kernel/uprobes.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index b63cf8f7745e..6c07f6daaa22 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -722,8 +722,9 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
switch (opc1) {
case 0xeb: /* jmp 8 */
case 0xe9: /* jmp 32 */
- case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
break;
+ case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
+ goto setup;
case 0xe8: /* call relative */
branch_clear_offset(auprobe, insn);
@@ -753,6 +754,7 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
return -ENOTSUPP;
}
+setup:
auprobe->branch.opc1 = opc1;
auprobe->branch.ilen = insn->length;
auprobe->branch.offs = insn->immediate.value;
--
2.25.1.362.g51ebf55
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