From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Ingo Molnar" , "Steven Rostedt (VMware)" , "Mikulas Patocka" Date: Sun, 11 Nov 2018 19:49:05 +0000 Message-ID: Subject: [PATCH 3.16 114/366] branch-check: fix long->int truncation when profiling branches In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.16.61-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Mikulas Patocka commit 2026d35741f2c3ece73c11eb7e4a15d7c2df9ebe upstream. The function __builtin_expect returns long type (see the gcc documentation), and so do macros likely and unlikely. Unfortunatelly, when CONFIG_PROFILE_ANNOTATED_BRANCHES is selected, the macros likely and unlikely expand to __branch_check__ and __branch_check__ truncates the long type to int. This unintended truncation may cause bugs in various kernel code (we found a bug in dm-writecache because of it), so it's better to fix __branch_check__ to return long. Link: http://lkml.kernel.org/r/alpine.LRH.2.02.1805300818140.24812@file01.intranet.prod.int.rdu2.redhat.com Cc: Ingo Molnar Fixes: 1f0d69a9fc815 ("tracing: profile likely and unlikely annotations") Signed-off-by: Mikulas Patocka Signed-off-by: Steven Rostedt (VMware) [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- include/linux/compiler.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -105,7 +105,7 @@ void ftrace_likely_update(struct ftrace_ #define unlikely_notrace(x) __builtin_expect(!!(x), 0) #define __branch_check__(x, expect) ({ \ - int ______r; \ + long ______r; \ static struct ftrace_branch_data \ __attribute__((__aligned__(4))) \ __attribute__((section("_ftrace_annotated_branch"))) \