Commit acb5b8a2 authored Mar 16, 2008 by Yakov Lerner Committed by Ingo Molnar Apr 17, 2008

x86, kprobes: correct post-eip value in post_hander()



I was trying to get the address of instruction to be executed
next after the kprobed instruction.  But regs->eip in post_handler()
contains value which is useless to the user. It's pre-corrected value.
This value is difficult to use without access to resume_execution(), which
is not exported anyway.
I moved the invocation of post_handler() to *after* resume_execution().
Now regs->eip contains meaningful value in post_handler().

I do not think this change breaks any backward-compatibility.
To make meaning of the old value, post_handler() would need access to
resume_execution() which is not exported.  I have difficulty to believe
that previous, uncorrected, regs->eip can be meaningfully used in
post_handler().

Signed-off-by: Yakov Lerner <iler.ml@gmail.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 0f540910

arch/x86/kernel/kprobes.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -858,15 +858,15 @@ static int __kprobes post_kprobe_handler(struct pt_regs *regs)
		if (!cur)
		return 0;

		resume_execution(cur, regs, kcb);
		regs->flags \|= kcb->kprobe_saved_flags;
		trace_hardirqs_fixup_flags(regs->flags);

		if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
		kcb->kprobe_status = KPROBE_HIT_SSDONE;
		cur->post_handler(cur, regs, 0);
		}

		resume_execution(cur, regs, kcb);
		regs->flags \|= kcb->kprobe_saved_flags;
		trace_hardirqs_fixup_flags(regs->flags);

		/* Restore back the original saved kprobes variables and continue. */
		if (kcb->kprobe_status == KPROBE_REENTER) {
		restore_previous_kprobe(kcb);