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authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2013-08-31 01:04:07 -0400
committerSteven Rostedt <rostedt@goodmis.org>2013-09-03 19:36:26 -0400
commit59338f754a55f07857342dbcd81652a4f091d72f (patch)
treed060266252fcf0dd8fbb399d6c3f26aab6be756e /kernel/trace
parentccfe9e42e451232dd17a230d1b4e979c3d15311e (diff)
ftrace: Fix a slight race in modifying what function callback gets traced
There's a slight race when going from a list function to a non list function. That is, when only one callback is registered to the function tracer, it gets called directly by the mcount trampoline. But if this function has filters, it may be called by the wrong functions. As the list ops callback that handles multiple callbacks that are registered to ftrace, it also handles what functions they call. While the transaction is taking place, use the list function always, and after all the updates are finished (only the functions that should be traced are being traced), then we can update the trampoline to call the function directly. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/ftrace.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index a6d098c6df3f..03cf44ac54d3 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1978,12 +1978,27 @@ int __weak ftrace_arch_code_modify_post_process(void)
void ftrace_modify_all_code(int command)
{
+ int update = command & FTRACE_UPDATE_TRACE_FUNC;
+
+ /*
+ * If the ftrace_caller calls a ftrace_ops func directly,
+ * we need to make sure that it only traces functions it
+ * expects to trace. When doing the switch of functions,
+ * we need to update to the ftrace_ops_list_func first
+ * before the transition between old and new calls are set,
+ * as the ftrace_ops_list_func will check the ops hashes
+ * to make sure the ops are having the right functions
+ * traced.
+ */
+ if (update)
+ ftrace_update_ftrace_func(ftrace_ops_list_func);
+
if (command & FTRACE_UPDATE_CALLS)
ftrace_replace_code(1);
else if (command & FTRACE_DISABLE_CALLS)
ftrace_replace_code(0);
- if (command & FTRACE_UPDATE_TRACE_FUNC)
+ if (update && ftrace_trace_function != ftrace_ops_list_func)
ftrace_update_ftrace_func(ftrace_trace_function);
if (command & FTRACE_START_FUNC_RET)