branch-check: fix long->int truncation when profiling branches

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 <mingo@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 1f0d69a9fc815 ("tracing: profile likely and unlikely annotations")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 5ce911db7d884b99ba208cd97839e97f9c17978d..4f3dfabb680f904e47b4cdb4747f4c299a515218 100644 (file)
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -113,7 +113,7 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
 #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"))) \