[PATCH RFCv2 11/18] uprobes/x86: Add support to emulate nop5 instruction

Jiri Olsa
2025-02-24T14:04:00Z

Adding support to emulate nop5 as the original uprobe instruction.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
arch/x86/kernel/uprobes.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 8d4eb8133221..e8aebbda83bc 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -308,6 +308,11 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool
return -ENOTSUPP;
}

+static int is_nop5_insn(uprobe_opcode_t *insn)
+{
+ return !memcmp(insn, x86_nops[5], 5);
+}
+
#ifdef CONFIG_X86_64

asm (
@@ -927,6 +932,11 @@ void arch_uprobe_clear_state(struct mm_struct *mm)
node = next;
}
}
+
+static bool emulate_nop5_insn(struct arch_uprobe *auprobe)
+{
+ return is_nop5_insn((uprobe_opcode_t *) &auprobe->insn);
+}
#else /* 32-bit: */
/*
* No RIP-relative addressing on 32-bit
@@ -940,6 +950,10 @@ static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
}
+static bool emulate_nop5_insn(struct arch_uprobe *auprobe)
+{
+ return false;
+}
#endif /* CONFIG_X86_64 */

struct uprobe_xol_ops {
@@ -1171,6 +1185,8 @@ static int branch_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
break;

case 0x0f:
+ if (emulate_nop5_insn(auprobe))
+ goto setup;
if (insn->opcode.nbytes != 2)
return -ENOSYS;
/*
--
2.48.1