From patchwork Thu Jul 29 14:07:48 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 12408857 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=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 6CC03C4338F for ; Thu, 29 Jul 2021 14:09:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 568D3601FF for ; Thu, 29 Jul 2021 14:09:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238649AbhG2OJt (ORCPT ); Thu, 29 Jul 2021 10:09:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:57276 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238857AbhG2OH4 (ORCPT ); Thu, 29 Jul 2021 10:07:56 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 09D8A6054F; Thu, 29 Jul 2021 14:07:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627567673; bh=3BqLLykrOHv7GrNy26CHO6BhcUQk9jcyV1ViRuIHq5w=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rjTxoVNx+0CPwjmljDa3NUqVrbGdoOjCvICs8nqofQ/XQychD9hg5X6ssibECY6tn 67q1Gd8e2eHBEmzpynESsCXjopJoU79oZHuQdKNWSfZe7Nd+/7nQDKcRUaQjm6U5Hs lSehCLOUB8VGPS13FYbmJA5NdhDAE/3CXUSePAX/vyodSvZ+cTWLnysDE+Qrw6GvZp 9iwcAWEtSgY7JXG05r17TKwsnbSaKsmvoqjD99sRblYqfN2rHdkBuT4HDRLBRyd0VB 8AxLrgrlo7pKw2LcLxNzJK0ccb8M/cX0gSItxBy5NCsFgBxH8kuBKSbE9FYtLaZmDA blciR1p3Yix+A== From: Masami Hiramatsu To: Steven Rostedt , Josh Poimboeuf , Ingo Molnar Cc: X86 ML , Masami Hiramatsu , Daniel Xu , linux-kernel@vger.kernel.org, bpf@vger.kernel.org, kuba@kernel.org, mingo@redhat.com, ast@kernel.org, Thomas Gleixner , Borislav Petkov , Peter Zijlstra , kernel-team@fb.com, yhs@fb.com, linux-ia64@vger.kernel.org, Abhishek Sagar , Andrii Nakryiko Subject: [PATCH -tip v10 12/16] kprobes: Enable stacktrace from pt_regs in kretprobe handler Date: Thu, 29 Jul 2021 23:07:48 +0900 Message-Id: <162756766854.301564.16064835736239439658.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <162756755600.301564.4957591913842010341.stgit@devnote2> References: <162756755600.301564.4957591913842010341.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Since the ORC unwinder from pt_regs requires setting up regs->ip correctly, set the correct return address to the regs->ip before calling user kretprobe handler. This allows the kretrprobe handler to trace stack from the kretprobe's pt_regs by stack_trace_save_regs() (eBPF will do this), instead of stack tracing from the handler context by stack_trace_save() (ftrace will do this). Suggested-by: Josh Poimboeuf Signed-off-by: Masami Hiramatsu Tested-by: Andrii Nakryiko Acked-by: Josh Poimboeuf --- Changes in v9: - Update comment to explain specifically why this is necessary. Changes in v8: - Update comment to clarify why this is needed. Changes in v3: - Cast the correct_ret_addr to unsigned long. --- kernel/kprobes.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 833f07f33115..ebc587b9a346 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1937,6 +1937,13 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, BUG_ON(1); } + /* + * Set the return address as the instruction pointer, because if the + * user handler calls stack_trace_save_regs() with this 'regs', + * the stack trace will start from the instruction pointer. + */ + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); + /* Run the user handler of the nodes. */ first = current->kretprobe_instances.first; while (first) {