From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0551DC433E0 for ; Sun, 21 Mar 2021 12:55:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D1A62601FC for ; Sun, 21 Mar 2021 12:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229894AbhCUMzM (ORCPT ); Sun, 21 Mar 2021 08:55:12 -0400 Received: from mail.kernel.org ([198.145.29.99]:37458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229865AbhCUMyp (ORCPT ); Sun, 21 Mar 2021 08:54:45 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 440916192C; Sun, 21 Mar 2021 12:54:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616331282; bh=gxSLgsHjpoXlEVp0yZV3Q1ElINUeZsnQ2yc4m407QA0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=JNDOfNv3iRm7ZTNQzS9VSKStMvvU9YgG0X7VImdilLRbUkhraI2BYJpqJ2ewd8YSD RoadP0vYLncdibdS16voc3ysthzr1csAkU9s5avgayc9FXd0HpRC20KRELTTFaM7ku tfzq4f6h4yrlglAgo1HjZ0nJkzEJS/CkDHoiY04GdjyZ3NmuSf4yfcVgkhJ8/19Rlx ZQ1YIdKOo7NpIiSEuj/+28k0XaARVwPuLu9MngqhDmOrDXu2jLBOdnWtyXycsiePpA B2qzhk0kQhSpzzbw65/9ddrq5a/u4UhbkswGppa68XTT9ntaBR9sjPvoAjeujBJSBW QsMwUfNZxpdEw== Date: Sun, 21 Mar 2021 21:54:36 +0900 From: Masami Hiramatsu To: Masami Hiramatsu Cc: Steven Rostedt , Ingo Molnar , X86 ML , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, tglx@linutronix.de, kernel-team@fb.com, yhs@fb.com, Josh Poimboeuf , linux-ia64@vger.kernel.org Subject: Re: [PATCH -tip v3 08/11] kprobes: Setup instruction pointer in __kretprobe_trampoline_handler Message-Id: <20210321215436.2e0447bf4fc43471bcecc243@kernel.org> In-Reply-To: <161615659174.306069.12736134222759644948.stgit@devnote2> References: <161615650355.306069.17260992641363840330.stgit@devnote2> <161615659174.306069.12736134222759644948.stgit@devnote2> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, 19 Mar 2021 21:23:12 +0900 Masami Hiramatsu wrote: > To simplify the stacktrace with pt_regs from kretprobe handler, > set the correct return address to the instruction pointer in > the pt_regs before calling kretprobe handlers. > Oops, now I also find this breaks kretprobe for arm. It seems not enough registers stores. I need to fix the arm kprobe code too. In arch/arm/include/uapi/asm/ptrace.h, --- #define ARM_pc uregs[15] --- And in arch/arm/probes/kprobes/core.c, --- /* * When a retprobed function returns, trampoline_handler() is called, * calling the kretprobe's handler. We construct a struct pt_regs to * give a view of registers r0-r11 to the user return-handler. This is * not a complete pt_regs structure, but that should be plenty sufficient * for kretprobe handlers which should normally be interested in r0 only * anyway. */ void __naked __kprobes kretprobe_trampoline(void) { __asm__ __volatile__ ( "stmdb sp!, {r0 - r11} \n\t" --- So, changing regs->ARM_pc will break a stack entry. I need to expand it to r15. Thanks, > Suggested-by: Josh Poimboeuf > Signed-off-by: Masami Hiramatsu > --- > Changes in v3: > - Cast the correct_ret_addr to unsigned long. > --- > kernel/kprobes.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index cf19edc038e4..4ce3e6f5d28d 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1914,6 +1914,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, > BUG_ON(1); > } > > + /* Set the instruction pointer to the correct address */ > + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); > + > /* Run them. */ > first = current->kretprobe_instances.first; > while (first) { > -- Masami Hiramatsu