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Date: Wed, 15 Feb 2017 00:32:59 +0900 From: Masami Hiramatsu <mhiramat@...nel.org> To: "Jon Medhurst (Tixy)" <tixy@...aro.org> Cc: Russell King <linux@...linux.org.uk>, linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>, Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>, Ingo Molnar <mingo@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, "H . Peter Anvin" <hpa@...or.com>, Wang Nan <wangnan0@...wei.com>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, "David A . Long" <dave.long@...aro.org>, Sandeepa Prabhu <sandeepa.s.prabhu@...il.com> Subject: Re: [BUGFIX PATCH 1/3] kprobes/arm: Allow to handle reentered kprobe on single-stepping On Tue, 14 Feb 2017 10:01:43 +0000 "Jon Medhurst (Tixy)" <tixy@...aro.org> wrote: > On Tue, 2017-02-14 at 00:03 +0900, Masami Hiramatsu wrote: > > This is arm port of commit 6a5022a56ac3 ("kprobes/x86: Allow to > > handle reentered kprobe on single-stepping") > > > > Since the FIQ handlers can interrupt in the single stepping > > (or preparing the single stepping, do_debug etc.), we should > > consider a kprobe is hit in the NMI handler. Even in that > > case, the kprobe is allowed to be reentered as same as the > > kprobes hit in kprobe handlers > > (KPROBE_HIT_ACTIVE or KPROBE_HIT_SSDONE). > > > > The real issue will happen when a kprobe hit while another > > Could to with 'is' being inserted above ^^^ > (I know this is a copy of the x86 commit message) Ah! yes, it should be corrected. > > > reentered kprobe is processing (KPROBE_REENTER), because > > we already consumed a saved-area for the previous kprobe. > > > > Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org> > > --- > > Acked-by: Jon Medhurst <tixy@...aro.org> Thank you! > > > arch/arm/probes/kprobes/core.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c > > index a4ec240..264fedb 100644 > > --- a/arch/arm/probes/kprobes/core.c > > +++ b/arch/arm/probes/kprobes/core.c > > @@ -270,6 +270,7 @@ void __kprobes kprobe_handler(struct pt_regs *regs) > > switch (kcb->kprobe_status) { > > case KPROBE_HIT_ACTIVE: > > case KPROBE_HIT_SSDONE: > > + case KPROBE_HIT_SS: > > /* A pre- or post-handler probe got us here. */ > > kprobes_inc_nmissed_count(p); > > save_previous_kprobe(kcb); > > @@ -278,6 +279,11 @@ void __kprobes kprobe_handler(struct pt_regs *regs) > > singlestep(p, regs, kcb); > > restore_previous_kprobe(kcb); > > break; > > + case KPROBE_REENTER: > > + /* A nested probe was hit in FIQ, it is a BUG */ > > + pr_warn("Unrecoverable kprobe detected at %p.\n", > > + p->addr); > > + /* fall through */ > > default: > > /* impossible cases */ > > BUG(); > > -- Masami Hiramatsu <mhiramat@...nel.org>
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