From: Oleg Nesterov oleg@redhat.com
[ Upstream commit cefa72129e45313655d53a065b8055aaeb01a0c9 ]
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 rejects NOP with REP prefix as it treats them like word-sized branch instructions.
Fixes: 250bbd12c2fe ("uprobes/x86: Refuse to attach uprobe to "word-sized" branch insns") Reported-by: Seiji Nishikawa snishika@redhat.com Suggested-by: Denys Vlasenko dvlasenk@redhat.com Signed-off-by: Oleg Nesterov oleg@redhat.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org Link: https://lore.kernel.org/r/20221204173933.GA31544@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 ae9e806a11de..3b87bca027b4 100644 --- a/arch/x86/kernel/uprobes.c +++ b/arch/x86/kernel/uprobes.c @@ -735,8 +735,9 @@ 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); @@ -765,6 +766,7 @@ 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;