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x86: fix singlestep handling in reenter_kprobe

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Highlight peculiar cases in singles-step kprobe handling.

In reenter_kprobe(), a breakpoint in KPROBE_HIT_SS case can only occur
when single-stepping a breakpoint on which a probe was installed. Since
such probes are single-stepped inline, identifying these cases is
unambiguous. All other cases leading up to KPROBE_HIT_SS are possible
bugs. Identify and WARN_ON such cases.

Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Abhishek Sagar 2008-01-30 13:33:13 +01:00 committed by Ingo Molnar
parent 0723a69a63
commit fb8830e72d
1 changed files with 13 additions and 15 deletions
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28
arch/x86/kernel/kprobes.c
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@ -443,17 +443,6 @@ void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
*sara = (unsigned long) &kretprobe_trampoline;
}
static void __kprobes recursive_singlestep(struct kprobe *p,
struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
save_previous_kprobe(kcb);
set_current_kprobe(p, regs, kcb);
kprobes_inc_nmissed_count(p);
prepare_singlestep(p, regs);
kcb->kprobe_status = KPROBE_REENTER;
}
static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
struct kprobe_ctlblk *kcb)
{
@ -492,20 +481,29 @@ static int __kprobes reenter_kprobe(struct kprobe *p, struct pt_regs *regs,
break;
#endif
case KPROBE_HIT_ACTIVE:
recursive_singlestep(p, regs, kcb);
save_previous_kprobe(kcb);
set_current_kprobe(p, regs, kcb);
kprobes_inc_nmissed_count(p);
prepare_singlestep(p, regs);
kcb->kprobe_status = KPROBE_REENTER;
break;
case KPROBE_HIT_SS:
if (*p->ainsn.insn == BREAKPOINT_INSTRUCTION) {
if (p == kprobe_running()) {
regs->flags &= ~TF_MASK;
regs->flags |= kcb->kprobe_saved_flags;
return 0;
} else {
recursive_singlestep(p, regs, kcb);
/* A probe has been hit in the codepath leading up
* to, or just after, single-stepping of a probed
* instruction. This entire codepath should strictly
* reside in .kprobes.text section. Raise a warning
* to highlight this peculiar case.
*/
}
break;
default:
/* impossible cases */
WARN_ON(1);
return 0;
}
return 1;