From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933495AbdA0LEe (ORCPT ); Fri, 27 Jan 2017 06:04:34 -0500 Received: from mx2.suse.de ([195.135.220.15]:33242 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932872AbdA0LBL (ORCPT ); Fri, 27 Jan 2017 06:01:11 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, "Steven Rostedt (Red Hat)" , Jiri Slaby Subject: [PATCH 3.12 057/235] ftrace/x86_32: Set ftrace_stub to weak to prevent gcc from using short jumps to it Date: Fri, 27 Jan 2017 11:53:10 +0100 Message-Id: <7a2a5f7c2e9b4653385c2f0094e96ce3abc7b43a.1485514374.git.jslaby@suse.cz> X-Mailer: git-send-email 2.11.0 In-Reply-To: <5b46dc789ca2be4046e4e40a131858d386cac741.1485514374.git.jslaby@suse.cz> References: <5b46dc789ca2be4046e4e40a131858d386cac741.1485514374.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (Red Hat)" 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 847fa1a6d3d00f3bdf68ef5fa4a786f644a0dd67 upstream. With new binutils, gcc may get smart with its optimization and change a jmp from a 5 byte jump to a 2 byte one even though it was jumping to a global function. But that global function existed within a 2 byte radius, and gcc was able to optimize it. Unfortunately, that jump was also being modified when function graph tracing begins. Since ftrace expected that jump to be 5 bytes, but it was only two, it overwrote code after the jump, causing a crash. This was fixed for x86_64 with commit 8329e818f149, with the same subject as this commit, but nothing was done for x86_32. Fixes: d61f82d06672 ("ftrace: use dynamic patching for updating mcount calls") Reported-by: Colin Ian King Tested-by: Colin Ian King Signed-off-by: Steven Rostedt Signed-off-by: Jiri Slaby --- arch/x86/kernel/entry_32.S | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index 1f1c33d0a13c..a78db5ed8b3f 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -1113,8 +1113,8 @@ ftrace_graph_call: jmp ftrace_stub #endif -.globl ftrace_stub -ftrace_stub: +/* This is weak to keep gas from relaxing the jumps */ +WEAK(ftrace_stub) ret END(ftrace_caller) -- 2.11.0