1 files changed, 75 insertions, 17 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8ac204360a39..63dbc7ff213f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -323,12 +323,21 @@ static const char *trace_options[] = {
         "printk-msg-only",
         "context-info",
         "latency-format",
-        "global-clock",
         "sleep-time",
         "graph-time",
         NULL
 };
 
+static struct {
+        u64 (*func)(void);
+        const char *name;
+} trace_clocks[] = {
+        { trace_clock_local,    "local" },
+        { trace_clock_global,   "global" },
+};
+
+int trace_clock_id;
+
 /*
  * ftrace_max_lock is used to protect the swapping of buffers
  * when taking a max snapshot. The buffers themselves are
@@ -2159,22 +2168,6 @@ static void set_tracer_flags(unsigned int mask, int enabled)
                 trace_flags |= mask;
         else
                 trace_flags &= ~mask;
-
-        if (mask == TRACE_ITER_GLOBAL_CLK) {
-                u64 (*func)(void);
-
-                if (enabled)
-                        func = trace_clock_global;
-                else
-                        func = trace_clock_local;
-
-                mutex_lock(&trace_types_lock);
-                ring_buffer_set_clock(global_trace.buffer, func);
-
-                if (max_tr.buffer)
-                        ring_buffer_set_clock(max_tr.buffer, func);
-                mutex_unlock(&trace_types_lock);
-        }
 }
 
 static ssize_t
@@ -3142,6 +3135,62 @@ tracing_mark_write(struct file *filp, const char __user *ubuf,
         return cnt;
 }
 
+static ssize_t tracing_clock_read(struct file *filp, char __user *ubuf,
+                                  size_t cnt, loff_t *ppos)
+{
+        char buf[64];
+        int bufiter = 0;
+        int i;
+
+        for (i = 0; i < ARRAY_SIZE(trace_clocks); i++)
+                bufiter += snprintf(buf + bufiter, sizeof(buf) - bufiter,
+                        "%s%s%s%s", i ? " " : "",
+                        i == trace_clock_id ? "[" : "", trace_clocks[i].name,
+                        i == trace_clock_id ? "]" : "");
+        bufiter += snprintf(buf + bufiter, sizeof(buf) - bufiter, "\n");
+
+        return simple_read_from_buffer(ubuf, cnt, ppos, buf, bufiter);
+}
+
+static ssize_t tracing_clock_write(struct file *filp, const char __user *ubuf,
+                                   size_t cnt, loff_t *fpos)
+{
+        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;
+        }
+        if (i == ARRAY_SIZE(trace_clocks))
+                return -EINVAL;
+
+        trace_clock_id = i;
+
+        mutex_lock(&trace_types_lock);
+
+        ring_buffer_set_clock(global_trace.buffer, trace_clocks[i].func);
+        if (max_tr.buffer)
+                ring_buffer_set_clock(max_tr.buffer, trace_clocks[i].func);
+
+        mutex_unlock(&trace_types_lock);
+
+        *fpos += cnt;
+
+        return cnt;
+}
+
 static const struct file_operations tracing_max_lat_fops = {
         .open           = tracing_open_generic,
         .read           = tracing_max_lat_read,
@@ -3179,6 +3228,12 @@ static const struct file_operations tracing_mark_fops = {
         .write          = tracing_mark_write,
 };
 
+static const struct file_operations trace_clock_fops = {
+        .open           = tracing_open_generic,
+        .read           = tracing_clock_read,
+        .write          = tracing_clock_write,
+};
+
 struct ftrace_buffer_info {
         struct trace_array      *tr;
         void                    *spare;
@@ -3918,6 +3973,9 @@ static __init int tracer_init_debugfs(void)
         trace_create_file("saved_cmdlines", 0444, d_tracer,
                         NULL, &tracing_saved_cmdlines_fops);
 
+        trace_create_file("trace_clock", 0644, d_tracer, NULL,
+                          &trace_clock_fops);
+
 #ifdef CONFIG_DYNAMIC_FTRACE
         trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
                         &ftrace_update_tot_cnt, &tracing_dyn_info_fops);