From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759596Ab2IGIob (ORCPT ); Fri, 7 Sep 2012 04:44:31 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:42193 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751120Ab2IGIo2 (ORCPT ); Fri, 7 Sep 2012 04:44:28 -0400 X-AuditID: b753bd60-90ac1ba0000047ca-b2-5049b3e91406 X-AuditID: b753bd60-90ac1ba0000047ca-b2-5049b3e91406 Message-ID: <5049B3E7.1010208@hitachi.com> Date: Fri, 07 Sep 2012 17:44:23 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Masami Hiramatsu , Fengguang Wu Cc: Steven Rostedt , linux-kernel@vger.kernel.org, "H. Peter Anvin" , Peter Zijlstra , Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , Andrew Morton , yrl.pp-manager.tt@hitachi.com, Ingo Molnar , "H. Peter Anvin" Subject: Re: [PATCH -tip 4/4] [BUGFIX] kprobes/x86: Fix to support jprobes on ftrace-based kprobe References: <20120905143045.10329.64502.stgit@localhost.localdomain> <20120905143125.10329.90836.stgit@localhost.localdomain> In-Reply-To: <20120905143125.10329.90836.stgit@localhost.localdomain> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2012/09/05 23:31), Masami Hiramatsu wrote: > Fix kprobes/x86 to support jprobes on ftrace-based kprobes. > Because of -mfentry support of ftrace, ftrace is now put > on the beginning of function where jprobes are put. > > Originally ftrace-based kprobes doesn't support jprobe > because it will change regs->ip and ftrace doesn't support > changing IP and ftrace itself doesn't conflict jprobe. > However, ftrace -mfentry support moves mcount call on the > top of functions where jprobes are put. This means that > jprobe always conflicts with ftrace-based kprobe and fails. > > This patch allows ftrace-based kprobes to support jprobes > by allowing to modify regs->ip and kprobes breakpoint > handler also allows to skip singlestepping because there > is a ftrace call (not an original instruction). > > Signed-off-by: Masami Hiramatsu > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: Steven Rostedt This should have a below line... Reported-by: Fengguang Wu Thanks! > --- > > arch/x86/kernel/kprobes.c | 42 +++++++++++++++++++++++++++++------------- > kernel/kprobes.c | 3 --- > 2 files changed, 29 insertions(+), 16 deletions(-) > > diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c > index f49f60c..b7c2a85 100644 > --- a/arch/x86/kernel/kprobes.c > +++ b/arch/x86/kernel/kprobes.c > @@ -541,6 +541,8 @@ reenter_kprobe(struct kprobe *p, struct pt_regs *regs, struct kprobe_ctlblk *kcb > return 1; > } > > +static void __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs, > + struct kprobe_ctlblk *kcb); > /* > * Interrupts are disabled on entry as trap3 is an interrupt gate and they > * remain disabled throughout this function. > @@ -599,6 +601,12 @@ static int __kprobes kprobe_handler(struct pt_regs *regs) > } else if (kprobe_running()) { > p = __this_cpu_read(current_kprobe); > if (p->break_handler && p->break_handler(p, regs)) { > +#ifdef KPROBES_CAN_USE_FTRACE > + if (kprobe_ftrace(p)) { > + skip_singlestep(p, regs, kcb); > + return 1; > + } > +#endif > setup_singlestep(p, regs, kcb, 0); > return 1; > } > @@ -1053,6 +1061,21 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs) > } > > #ifdef KPROBES_CAN_USE_FTRACE > +static void __kprobes skip_singlestep(struct kprobe *p, struct pt_regs *regs, > + struct kprobe_ctlblk *kcb) > +{ > + /* > + * Emulate singlestep (and also recover regs->ip) > + * as if there is a 5byte nop > + */ > + regs->ip = (unsigned long)p->addr + MCOUNT_INSN_SIZE; > + if (unlikely(p->post_handler)) { > + kcb->kprobe_status = KPROBE_HIT_SSDONE; > + p->post_handler(p, regs, 0); > + } > + __this_cpu_write(current_kprobe, NULL); > +} > + > /* Ftrace callback handler for kprobes */ > void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > struct ftrace_ops *ops, struct pt_regs *regs) > @@ -1077,19 +1100,12 @@ void __kprobes kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip, > > __this_cpu_write(current_kprobe, p); > kcb->kprobe_status = KPROBE_HIT_ACTIVE; > - if (p->pre_handler) > - p->pre_handler(p, regs); > - > - if (unlikely(p->post_handler)) { > - /* > - * Emulate singlestep (and also recover regs->ip) > - * as if there is a 5byte nop > - */ > - regs->ip = ip + MCOUNT_INSN_SIZE; > - kcb->kprobe_status = KPROBE_HIT_SSDONE; > - p->post_handler(p, regs, 0); > - } > - __this_cpu_write(current_kprobe, NULL); > + if (!p->pre_handler || !p->pre_handler(p, regs)) > + skip_singlestep(p, regs, kcb); > + /* > + * If pre_handler returns !0, it sets regs->ip and > + * resets current kprobe. > + */ > } > end: > local_irq_restore(flags); > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 35b4315..098f396 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1418,9 +1418,6 @@ static __kprobes int check_kprobe_address_safe(struct kprobe *p, > /* Given address is not on the instruction boundary */ > if ((unsigned long)p->addr != ftrace_addr) > return -EILSEQ; > - /* break_handler (jprobe) can not work with ftrace */ > - if (p->break_handler) > - return -EINVAL; > p->flags |= KPROBE_FLAG_FTRACE; > #else /* !KPROBES_CAN_USE_FTRACE */ > return -EINVAL; > -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com