On Thu, 9 Jul 2026 14:22:25 +0000 Pu Hu <[email protected]> wrote: > From: Pu Hu <[email protected]> > > A kprobe can be hit while another kprobe is in KPROBE_HIT_SS state. This > can happen when tracing or perf code runs from the debug exception path > while the first kprobe is preparing or executing its out-of-line > single-step instruction. > > Currently arm64 treats a kprobe hit in KPROBE_HIT_SS as unrecoverable, > the same as a hit in KPROBE_REENTER. This is too strict. A hit in > KPROBE_HIT_SS is still a one-level reentry and can be handled by saving > the current kprobe state and setting up single-step for the new probe, > just like reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. > > The truly unrecoverable case is hitting another kprobe while already in > KPROBE_REENTER, because the reentry save area has already been consumed. > > Move KPROBE_HIT_SS to the recoverable reentry cases and leave > KPROBE_REENTER as the unrecoverable nested reentry case. > > This mirrors the x86 fix in commit 6a5022a56ac3 > ("kprobes/x86: Allow to handle reentered kprobe on single-stepping"). >
Hi, as Sashiko commented, we have to save the saved_irqflag to prev_kprobbe. https://sashiko.dev/#/patchset/20260709142215.226872-1-hupu%40transsion.com?part=2 Thank you, > Signed-off-by: Pu Hu <[email protected]> > Signed-off-by: Hongyan Xia <[email protected]> > --- > arch/arm64/kernel/probes/kprobes.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/probes/kprobes.c > b/arch/arm64/kernel/probes/kprobes.c > index 798e4b091d1a..2ca5916eca2f 100644 > --- a/arch/arm64/kernel/probes/kprobes.c > +++ b/arch/arm64/kernel/probes/kprobes.c > @@ -240,10 +240,16 @@ static int __kprobes reenter_kprobe(struct kprobe *p, > switch (kcb->kprobe_status) { > case KPROBE_HIT_SSDONE: > case KPROBE_HIT_ACTIVE: > + case KPROBE_HIT_SS: > + /* > + * A probe can be hit while another kprobe is preparing or > + * executing its XOL single-step instruction. This is still a > + * recoverable one-level reentry, so handle it in the same way > as > + * reentry from KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE. > + */ > kprobes_inc_nmissed_count(p); > setup_singlestep(p, regs, kcb, 1); > break; > - case KPROBE_HIT_SS: > case KPROBE_REENTER: > pr_warn("Failed to recover from reentered kprobes.\n"); > dump_kprobe(p); > -- > 2.43.0 > -- Masami Hiramatsu (Google) <[email protected]>
