On 04/08, Jiri Olsa wrote:
>
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -608,6 +608,16 @@ static void riprel_post_xol(struct arch_uprobe *auprobe,
> struct pt_regs *regs)
> *sr = utask->autask.saved_scratch_register;
> }
> }
> +
> +static int is_nop5_insn(uprobe_opcode_t *insn)
> +{
> + return !memcmp(insn, x86_nops[5], 5);
> +}
> +
> +static bool emulate_nop5_insn(struct arch_uprobe *auprobe)
> +{
> + return is_nop5_insn((uprobe_opcode_t *) &auprobe->insn);
> +}
Why do we need 2 functions? Can't branch_setup_xol_ops() just use
is_nop5_insn(insn->kaddr) ?
> #else /* 32-bit: */
> /*
> * No RIP-relative addressing on 32-bit
> @@ -621,6 +631,10 @@ 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;
> +}
Hmm, why? I mean, why we can't emulate x86_nops[5] if !CONFIG_X86_64 ?
OTOH. What if the kernel is 64-bit, but the probed task is 32-bit and it
uses the 64-bit version of BYTES_NOP5?
Perhaps this is fine, I simply don't know, so let me ask...
> @@ -852,6 +866,8 @@ static int branch_setup_xol_ops(struct arch_uprobe
> *auprobe, struct insn *insn)
> break;
>
> case 0x0f:
> + if (emulate_nop5_insn(auprobe))
> + goto setup;
I think this will work, but if we want to emulate nop5, then perhaps
we can do the same for other nops?
For the moment, lets forget about compat tasks on a 64-bit kernel, can't
we simply do something like below?
Oleg.
---
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 9194695662b2..76d2cceca6c4 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -840,12 +840,16 @@ static int branch_setup_xol_ops(struct arch_uprobe
*auprobe, struct insn *insn)
insn_byte_t p;
int i;
+ /* prefix* + nop[i]; same as jmp with .offs = 0 */
+ for (i = 1; i <= ASM_NOP_MAX; ++i) {
+ if (!memcmp(insn->kaddr, x86_nops[i], i))
+ goto setup;
+ }
+
switch (opc1) {
case 0xeb: /* jmp 8 */
case 0xe9: /* jmp 32 */
break;
- case 0x90: /* prefix* + nop; same as jmp with .offs = 0 */
- goto setup;
case 0xe8: /* call relative */
branch_clear_offset(auprobe, insn);
