x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP

For CONFIG_TRACE_BRANCH_PROFILING=y the likely/unlikely things get
overloaded and generate callouts to this code, and thus also when
AC=1.

Make it safe.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 4ad967453b6f..3ea65cdff30d 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -205,6 +205,8 @@ void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 void ftrace_likely_update(struct ftrace_likely_data *f, int val,
                           int expect, int is_constant)
 {
+        unsigned long flags = user_access_save();
+
         /* A constant is always correct */
         if (is_constant) {
                 f->constant++;
@@ -223,6 +225,8 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
                 f->data.correct++;
         else
                 f->data.incorrect++;
+
+        user_access_restore(flags);
 }
 EXPORT_SYMBOL(ftrace_likely_update);