Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753969AbaGQSVz (ORCPT ); Thu, 17 Jul 2014 14:21:55 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.229]:50389 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751349AbaGQSVy (ORCPT ); Thu, 17 Jul 2014 14:21:54 -0400 Date: Thu, 17 Jul 2014 14:21:51 -0400 From: Steven Rostedt To: Masami Hiramatsu Cc: Josh Poimboeuf , Ingo Molnar , Namhyung Kim , Linux Kernel Mailing List , Ananth N Mavinakayanahalli , "H. Peter Anvin" Subject: Re: [PATCH ftrace/core v3 1/3] [BUGFIX]kprobes/ftrace: Recover original IP if pre_handler doesn't change it Message-ID: <20140717142151.51bde92c@gandalf.local.home> In-Reply-To: <20140715060021.12195.9680.stgit@kbuild-fedora.novalocal> References: <20140715060015.12195.74457.stgit@kbuild-fedora.novalocal> <20140715060021.12195.9680.stgit@kbuild-fedora.novalocal> X-Mailer: Claws Mail 3.10.1 (GTK+ 2.24.24; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.130:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This looks to require an acked-by from hpa. On Tue, 15 Jul 2014 06:00:21 +0000 Masami Hiramatsu wrote: > Recover original IP register if the pre_handler doesn't change it. > Since current kprobes doesn't expect that another ftrace handler > may change regs->ip, it sets kprobe.addr + MCOUNT_INSN_SIZE to > regs->ip and returns to ftrace. > This seems wrong behavior since kprobes can recover regs->ip > and safely pass it to other handler. s/other/another/ > > This adds a code which recovers original regs->ip passed from "... adds code which recovers the original ..." > ftrace right before returning ftrace, so that another ftrace user "... returning to ftrace, ..." > can change regs->ip. You say BUGFIX in the subject, but as nothing changes the regs->ip currently from ftrace, is this currently a real bug? -- Steve > > Signed-off-by: Masami Hiramatsu > --- > arch/x86/kernel/kprobes/ftrace.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c > index 717b02a..5f8f0b3 100644 > --- a/arch/x86/kernel/kprobes/ftrace.c > +++ b/arch/x86/kernel/kprobes/ftrace.c > @@ -27,7 +27,7 @@ > > static nokprobe_inline > int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, > - struct kprobe_ctlblk *kcb) > + struct kprobe_ctlblk *kcb, unsigned long orig_ip) > { > /* > * Emulate singlestep (and also recover regs->ip) > @@ -39,6 +39,8 @@ int __skip_singlestep(struct kprobe *p, struct pt_regs *regs, > p->post_handler(p, regs, 0); > } > __this_cpu_write(current_kprobe, NULL); > + if (orig_ip) > + regs->ip = orig_ip; > return 1; > } > > @@ -46,7 +48,7 @@ int skip_singlestep(struct kprobe *p, struct pt_regs *regs, > struct kprobe_ctlblk *kcb) > { > if (kprobe_ftrace(p)) > - return __skip_singlestep(p, regs, kcb); > + return __skip_singlestep(p, regs, kcb, 0); > else > return 0; > } > @@ -71,13 +73,14 @@ void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > if (kprobe_running()) { > kprobes_inc_nmissed_count(p); > } else { > + unsigned long orig_ip = regs->ip; > /* Kprobe handler expects regs->ip = ip + 1 as breakpoint hit */ > regs->ip = ip + sizeof(kprobe_opcode_t); > > __this_cpu_write(current_kprobe, p); > kcb->kprobe_status = KPROBE_HIT_ACTIVE; > if (!p->pre_handler || !p->pre_handler(p, regs)) > - __skip_singlestep(p, regs, kcb); > + __skip_singlestep(p, regs, kcb, orig_ip); > /* > * If pre_handler returns !0, it sets regs->ip and > * resets current kprobe. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/