2 files changed, 57 insertions, 2 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9243dd84f4d6..fcd3bfbe74e8 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -751,12 +751,25 @@ and is between 256 and 4096 characters. It is defined in the file
                         ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 
         ftrace=[tracer]
-                        [ftrace] will set and start the specified tracer
+                        [FTRACE] will set and start the specified tracer
                         as early as possible in order to facilitate early
                         boot debugging.
 
         ftrace_dump_on_oops
-                        [ftrace] will dump the trace buffers on oops.
+                        [FTRACE] will dump the trace buffers on oops.
+
+        ftrace_filter=[function-list]
+                        [FTRACE] Limit the functions traced by the function
+                        tracer at boot up. function-list is a comma separated
+                        list of functions. This list can be changed at run
+                        time by the set_ftrace_filter file in the debugfs
+                        tracing directory. 
+
+        ftrace_notrace=[function-list]
+                        [FTRACE] Do not trace the functions specified in
+                        function-list. This list can be changed at run time
+                        by the set_ftrace_notrace file in the debugfs
+                        tracing directory.
 
         gamecon.map[2|3]=
                         [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 140699a9a8a7..2074e5b7766b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -32,6 +32,7 @@
 #include <trace/events/sched.h>
 
 #include <asm/ftrace.h>
+#include <asm/setup.h>
 
 #include "trace_output.h"
 #include "trace_stat.h"
@@ -2369,6 +2370,45 @@ void ftrace_set_notrace(unsigned char *buf, int len, int reset)
         ftrace_set_regex(buf, len, reset, 0);
 }
 
+/*
+ * command line interface to allow users to set filters on boot up.
+ */
+#define FTRACE_FILTER_SIZE              COMMAND_LINE_SIZE
+static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
+static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
+
+static int __init set_ftrace_notrace(char *str)
+{
+        strncpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
+        return 1;
+}
+__setup("ftrace_notrace=", set_ftrace_notrace);
+
+static int __init set_ftrace_filter(char *str)
+{
+        strncpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
+        return 1;
+}
+__setup("ftrace_filter=", set_ftrace_filter);
+
+static void __init set_ftrace_early_filter(char *buf, int enable)
+{
+        char *func;
+
+        while (buf) {
+                func = strsep(&buf, ",");
+                ftrace_set_regex(func, strlen(func), 0, enable);
+        }
+}
+
+static void __init set_ftrace_early_filters(void)
+{
+        if (ftrace_filter_buf[0])
+                set_ftrace_early_filter(ftrace_filter_buf, 1);
+        if (ftrace_notrace_buf[0])
+                set_ftrace_early_filter(ftrace_notrace_buf, 0);
+}
+
 static int
 ftrace_regex_release(struct inode *inode, struct file *file, int enable)
 {
@@ -2829,6 +2869,8 @@ void __init ftrace_init(void)
         if (ret)
                 pr_warning("Failed to register trace ftrace module notifier\n");
 
+        set_ftrace_early_filters();
+
         return;
  failed:
         ftrace_disabled = 1;