From: Mikulas Patocka Date: Wed, 30 May 2018 12:19:22 +0000 (-0400) Subject: branch-check: fix long->int truncation when profiling branches X-Git-Tag: v4.18-rc1~116^2~1 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=2026d35741f2c3ece73c11eb7e4a15d7c2df9ebe;p=linux.git branch-check: fix long->int truncation when profiling branches 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 Cc: stable@vger.kernel.org Fixes: 1f0d69a9fc815 ("tracing: profile likely and unlikely annotations") Signed-off-by: Mikulas Patocka Signed-off-by: Steven Rostedt (VMware) --- diff --git a/include/linux/compiler.h b/include/linux/compiler.h index ab4711c63601..42506e4d1f53 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -21,7 +21,7 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, #define unlikely_notrace(x) __builtin_expect(!!(x), 0) #define __branch_check__(x, expect, is_constant) ({ \ - int ______r; \ + long ______r; \ static struct ftrace_likely_data \ __attribute__((__aligned__(4))) \ __attribute__((section("_ftrace_annotated_branch"))) \