ftrace: return error on failed modified text.
Have the ftrace_modify_code return error values:
-EFAULT on error of reading the address
-EINVAL if what is read does not match what it expected
-EPERM if the write fails to update after a successful match.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 0e95295..79fa10c 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -72,13 +72,33 @@
extern unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr);
extern int ftrace_dyn_arch_init(void *data);
extern int ftrace_mcount_set(unsigned long *data);
-extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
- unsigned char *new_code);
extern int ftrace_update_ftrace_func(ftrace_func_t func);
extern void ftrace_caller(void);
extern void ftrace_call(void);
extern void mcount_call(void);
+/**
+ * ftrace_modify_code - modify code segment
+ * @ip: the address of the code segment
+ * @old_code: the contents of what is expected to be there
+ * @new_code: the code to patch in
+ *
+ * This is a very sensitive operation and great care needs
+ * to be taken by the arch. The operation should carefully
+ * read the location, check to see if what is read is indeed
+ * what we expect it to be, and then on success of the compare,
+ * it should write to the location.
+ *
+ * Return must be:
+ * 0 on success
+ * -EFAULT on error reading the location
+ * -EINVAL on a failed compare of the contents
+ * -EPERM on error writing to the location
+ * Any other value will be considered a failure.
+ */
+extern int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+ unsigned char *new_code);
+
extern int skip_trace(unsigned long ip);
extern void ftrace_release(void *start, unsigned long size);