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 <[EMAIL PROTECTED]>
---
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index 93aff49..afb5c96 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -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;
--
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