1 files changed, 45 insertions, 16 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index d95ec2876bbb..c90f55d80f86 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -181,6 +181,17 @@ static int __init set_trace_boot_options(char *str)
 }
 __setup("trace_options=", set_trace_boot_options);
 
+static char trace_boot_clock_buf[MAX_TRACER_SIZE] __initdata;
+static char *trace_boot_clock __initdata;
+
+static int __init set_trace_boot_clock(char *str)
+{
+        strlcpy(trace_boot_clock_buf, str, MAX_TRACER_SIZE);
+        trace_boot_clock = trace_boot_clock_buf;
+        return 0;
+}
+__setup("trace_clock=", set_trace_boot_clock);
+
 
 unsigned long long ns2usecs(cycle_t nsec)
 {
@@ -4746,25 +4757,10 @@ static int tracing_clock_show(struct seq_file *m, void *v)
         return 0;
 }
 
-static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
-                                   size_t cnt, loff_t *fpos)
+static int tracing_set_clock(struct trace_array *tr, const char *clockstr)
 {
-        struct seq_file *m = filp->private_data;
-        struct trace_array *tr = m->private;
-        char buf[64];
-        const char *clockstr;
         int i;
 
-        if (cnt >= sizeof(buf))
-                return -EINVAL;
-
-        if (copy_from_user(&buf, ubuf, cnt))
-                return -EFAULT;
-
-        buf[cnt] = 0;
-
-        clockstr = strstrip(buf);
-
         for (i = 0; i < ARRAY_SIZE(trace_clocks); i++) {
                 if (strcmp(trace_clocks[i].name, clockstr) == 0)
                         break;
@@ -4792,6 +4788,32 @@ static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
 
         mutex_unlock(&trace_types_lock);
 
+        return 0;
+}
+
+static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
+                                   size_t cnt, loff_t *fpos)
+{
+        struct seq_file *m = filp->private_data;
+        struct trace_array *tr = m->private;
+        char buf[64];
+        const char *clockstr;
+        int ret;
+
+        if (cnt >= sizeof(buf))
+                return -EINVAL;
+
+        if (copy_from_user(&buf, ubuf, cnt))
+                return -EFAULT;
+
+        buf[cnt] = 0;
+
+        clockstr = strstrip(buf);
+
+        ret = tracing_set_clock(tr, clockstr);
+        if (ret)
+                return ret;
+
         *fpos += cnt;
 
         return cnt;
@@ -6574,6 +6596,13 @@ __init static int tracer_alloc_buffers(void)
 
         trace_init_cmdlines();
 
+        if (trace_boot_clock) {
+                ret = tracing_set_clock(&global_trace, trace_boot_clock);
+                if (ret < 0)
+                        pr_warning("Trace clock %s not defined, going back to default\n",
+                                   trace_boot_clock);
+        }
+
         /*
          * register_tracer() might reference current_trace, so it
          * needs to be set before we register anything. This is