From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762545AbYALJVh (ORCPT ); Sat, 12 Jan 2008 04:21:37 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760190AbYALJVa (ORCPT ); Sat, 12 Jan 2008 04:21:30 -0500 Received: from rv-out-0910.google.com ([209.85.198.186]:25070 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760148AbYALJV3 (ORCPT ); Sat, 12 Jan 2008 04:21:29 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:user-agent:mime-version:to:cc:subject:content-type:content-transfer-encoding; b=uTwPxcP8YVGEQTAmZ42Y2opERgDeQDYMkXbj64CDJpx06wL8QtQS4quSjwyhsWUTbJPyI4CRxF/YWFQLALAVDDPSSEu3eQwGK08Ow6kW/dE4AHAAVWV8Y78+UVzdim5FTRc0nALJiBdDS7HJIY+MuFydlb3/sT1iw8FqQJkmYIk= Message-ID: <47888685.7050002@gmail.com> Date: Sat, 12 Jan 2008 14:51:09 +0530 From: Abhishek Sagar User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Masami Hiramatsu CC: LKML , Ingo Molnar , ananth@in.ibm.com, jkenisto@us.ibm.com Subject: [PATCH] x86: Fix singlestep handling in reenter_kprobe Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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;