From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757973AbaKUC33 (ORCPT ); Thu, 20 Nov 2014 21:29:29 -0500 Received: from mail4.hitachi.co.jp ([133.145.228.5]:45112 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757877AbaKUC31 (ORCPT ); Thu, 20 Nov 2014 21:29:27 -0500 Subject: [PATCH ftrace/core v6 1/5] kprobes/ftrace: Recover original IP if pre_handler doesn't change it From: Masami Hiramatsu To: Steven Rostedt , Josh Poimboeuf Cc: Ananth N Mavinakayanahalli , Jiri Kosina , Seth Jennings , Linux Kernel Mailing List , Petr Mladek , Vojtech Pavlik , Namhyung Kim , Miroslav Benes , Ingo Molnar Date: Fri, 21 Nov 2014 05:25:09 -0500 Message-ID: <20141121102509.11844.64671.stgit@localhost.localdomain> In-Reply-To: <20141121102502.11844.82696.stgit@localhost.localdomain> References: <20141121102502.11844.82696.stgit@localhost.localdomain> User-Agent: StGit/0.17-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 another handler. This adds a code which recovers original regs->ip passed from ftrace right before returning to ftrace, so that another ftrace user can change regs->ip. Signed-off-by: Masami Hiramatsu --- Changes in v4: - Fix description and remove bugfix tag. --- 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.