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Subject[RFC PATCH 2/6] uprobes/x86: Emulate nop's using ops->emulate()
Finally we can kill the ugly (and very limited) code in __skip_sstep().
Just change ttt_setup_xol_ops() to treat "nop" as jmp to the next insn.

Thanks to lib/insn.c, it is clever enough. OPCODE1() == 0x90 includes
"(rep;)+ nop;" at least, and (afaics) much more.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
arch/x86/kernel/uprobes.c | 20 +-------------------
1 files changed, 1 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 32ab147..dd5f51a 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -482,6 +482,7 @@ static int ttt_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
switch (OPCODE1(insn)) {
case 0xeb: /* jmp 8 */
case 0xe9: /* jmp 32 */
+ case 0x90: /* prefix* + nop; same as jmp with .disp = 0 */
break;
default:
return -ENOSYS;
@@ -717,29 +718,10 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
regs->flags &= ~X86_EFLAGS_TF;
}

-/*
- * Skip these instructions as per the currently known x86 ISA.
- * rep=0x66*; nop=0x90
- */
static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
{
- int i;
-
if (auprobe->ops->emulate)
return auprobe->ops->emulate(auprobe, regs);
-
- /* TODO: move this code into ->emulate() hook */
- for (i = 0; i < MAX_UINSN_BYTES; i++) {
- if (auprobe->insn[i] == 0x66)
- continue;
-
- if (auprobe->insn[i] == 0x90) {
- regs->ip += i + 1;
- return true;
- }
-
- break;
- }
return false;
}

--
1.5.5.1


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