From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752835AbdBNK2g (ORCPT ); Tue, 14 Feb 2017 05:28:36 -0500 Received: from queue01a.mail.zen.net.uk ([212.23.3.234]:39468 "EHLO queue01a.mail.zen.net.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752047AbdBNK21 (ORCPT ); Tue, 14 Feb 2017 05:28:27 -0500 X-Greylist: delayed 1542 seconds by postgrey-1.27 at vger.kernel.org; Tue, 14 Feb 2017 05:28:27 EST Message-ID: <1487066503.2978.1.camel@linaro.org> Subject: Re: [BUGFIX PATCH 1/3] kprobes/arm: Allow to handle reentered kprobe on single-stepping From: "Jon Medhurst (Tixy)" To: Masami Hiramatsu , Russell King Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Ananth N Mavinakayanahalli , Ingo Molnar , Thomas Gleixner , "H . Peter Anvin" , Wang Nan , Catalin Marinas , Will Deacon , "David A . Long" , Sandeepa Prabhu Date: Tue, 14 Feb 2017 10:01:43 +0000 In-Reply-To: <148699820793.8505.2215835182494999847.stgit@devbox> References: <148699813647.8505.3671818093118978038.stgit@devbox> <148699820793.8505.2215835182494999847.stgit@devbox> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.4-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-smarthost03c-IP: [82.69.122.217] Feedback-ID: 82.69.122.217 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) > reentered kprobe is processing (KPROBE_REENTER), because > we already consumed a saved-area for the previous kprobe. > > Signed-off-by: Masami Hiramatsu > --- Acked-by: Jon Medhurst > 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(); >