On 7/10/2026 5:38 PM, Masami Hiramatsu wrote: > On Fri, 10 Jul 2026 06:32:55 +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 change also requires saving saved_irqflag in struct prev_kprobe. >> When a nested kprobe calls kprobes_save_local_irqflag(), it overwrites >> kcb->saved_irqflag with the currently masked DAIF value, losing the >> outer kprobe's original DAIF state. Without this fix, when the outer >> kprobe's single-step finishes, kprobes_restore_local_irqflag() applies >> the wrong DAIF mask and leaves interrupts permanently disabled. >> >> Extend struct prev_kprobe with a saved_irqflag field and save/restore it >> alongside kp and status. This ensures the outer kprobe's original >> interrupt state is preserved across reentry. >> >> This mirrors the x86 fix in commit 6a5022a56ac3 >> ("kprobes/x86: Allow to handle reentered kprobe on single-stepping"). >> > > OK, this looks good to me. > > Reviewed-by: Masami Hiramatsu (Google) <[email protected]> > > for this series. > > Will, Catalin, can you pick this series? > > Thanks! >
Hi Will, Catalin, Just a gentle ping on this series. Masami has kindly reviewed it and provided his Reviewed-by tag. I was wondering if you had a chance to take a look, or if there is anything else I should address before it can be picked up. No rush, and apologies for the reminder if this is already on your radar. Thanks a lot for your time! Thanks, Pu Hu
