tracing, x86: add low level support for ftrace return tracing
Impact: add infrastructure for function-return tracing
Add low level support for ftrace return tracing.
This plug-in stores return addresses on the thread_info structure of
the current task.
The index of the current return address is initialized when the task
is the first one (init) and when a process forks (the child). It is
not needed when a task does a sys_execve because after this syscall,
it still needs to return on the kernel functions it called.
Note that the code of return_to_handler has been suggested by Steven
Rostedt as almost all of the ideas of improvements in this V3.
For purpose of security, arch/x86/kernel/process_32.c is not traced
because __switch_to() changes the current task during its execution.
That could cause inconsistency in the stored return address of this
function even if I didn't have any crash after testing with tracing on
this function enabled.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 1f5608c..dcbbf72 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -268,6 +268,26 @@
/*
+ * Structure that defines a return function trace.
+ */
+struct ftrace_retfunc {
+ unsigned long ret; /* Return address */
+ unsigned long func; /* Current function */
+ unsigned long long calltime;
+ unsigned long long rettime;
+};
+
+#ifdef CONFIG_FUNCTION_RET_TRACER
+/* Type of a callback handler of tracing return function */
+typedef void (*trace_function_return_t)(struct ftrace_retfunc *);
+
+extern void register_ftrace_return(trace_function_return_t func);
+/* The current handler in use */
+extern trace_function_return_t ftrace_function_return;
+extern void unregister_ftrace_return(void);
+#endif
+
+/*
* Structure which defines the trace of an initcall.
* You don't have to fill the func field since it is
* only used internally by the tracer.