From patchwork Tue Jun 9 17:44:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 224619 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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 34265C433E1 for ; Tue, 9 Jun 2020 18:19:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0B2602068D for ; Tue, 9 Jun 2020 18:19:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591726784; bh=3XDvXZld3h/2dX04iqm+4ls4antOHtFKxEtomIO23CY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=C4XV3N84jeyIfaImgq8XW5g6WpOdcoxcYMPcgNaoF7YUkQGzPC6+UiNzaSxTcIYWv aJ2hzctuPam2pK0kwsFCojENAf+HhyeydEYd8HOSH3/Qu9kKCo4uYntaLl8ALsEHBX 3UuKSvjD8gQO2cT4qIvzj7ayvfkL2f2uMHZJJHqk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388856AbgFISTb (ORCPT ); Tue, 9 Jun 2020 14:19:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:36092 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732550AbgFIRtn (ORCPT ); Tue, 9 Jun 2020 13:49:43 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 864C720801; Tue, 9 Jun 2020 17:49:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591724983; bh=3XDvXZld3h/2dX04iqm+4ls4antOHtFKxEtomIO23CY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pjw3OcJcp6+hlROmUQVnu8ab/cPVtlGkapfORifQ6YWtpIJikZDEzuPmsWQaaTNxs AG+zcD3VuxO4Y65OBgSNcRgc2wsh4uN6JBsNDo99Z8n91JGETcpl+/KjSt+0qJdyQK jRxCecL5G3GtmObbwFVy6ciYbZiQmqkJXhJvYCqs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Sven Schnelle , Vasily Gorbik , Sasha Levin Subject: [PATCH 4.14 05/46] s390/ftrace: save traced function caller Date: Tue, 9 Jun 2020 19:44:21 +0200 Message-Id: <20200609174023.361913754@linuxfoundation.org> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200609174022.938987501@linuxfoundation.org> References: <20200609174022.938987501@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vasily Gorbik [ Upstream commit b4adfe55915d8363e244e42386d69567db1719b9 ] A typical backtrace acquired from ftraced function currently looks like the following (e.g. for "path_openat"): arch_stack_walk+0x15c/0x2d8 stack_trace_save+0x50/0x68 stack_trace_call+0x15a/0x3b8 ftrace_graph_caller+0x0/0x1c 0x3e0007e3c98 <- ftraced function caller (should be do_filp_open+0x7c/0xe8) do_open_execat+0x70/0x1b8 __do_execve_file.isra.0+0x7d8/0x860 __s390x_sys_execve+0x56/0x68 system_call+0xdc/0x2d8 Note random "0x3e0007e3c98" stack value as ftraced function caller. This value causes either imprecise unwinder result or unwinding failure. That "0x3e0007e3c98" comes from r14 of ftraced function stack frame, which it haven't had a chance to initialize since the very first instruction calls ftrace code ("ftrace_caller"). (ftraced function might never save r14 as well). Nevertheless according to s390 ABI any function is called with stack frame allocated for it and r14 contains return address. "ftrace_caller" itself is called with "brasl %r0,ftrace_caller". So, to fix this issue simply always save traced function caller onto ftraced function stack frame. Reported-by: Sven Schnelle Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin --- arch/s390/kernel/mcount.S | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/s390/kernel/mcount.S b/arch/s390/kernel/mcount.S index 0cfd5a83a1da..151f001a90ff 100644 --- a/arch/s390/kernel/mcount.S +++ b/arch/s390/kernel/mcount.S @@ -40,6 +40,7 @@ EXPORT_SYMBOL(_mcount) ENTRY(ftrace_caller) .globl ftrace_regs_caller .set ftrace_regs_caller,ftrace_caller + stg %r14,(__SF_GPRS+8*8)(%r15) # save traced function caller lgr %r1,%r15 #ifndef CC_USING_HOTPATCH aghi %r0,MCOUNT_RETURN_FIXUP