1 files changed, 71 insertions, 15 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c2e2c2310374..4f1dade56981 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -704,7 +704,7 @@ __update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 void
 update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 {
-        struct ring_buffer *buf = tr->buffer;
+        struct ring_buffer *buf;
 
         if (trace_stop_count)
                 return;
@@ -719,6 +719,7 @@ update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu)
 
         arch_spin_lock(&ftrace_max_lock);
 
+        buf = tr->buffer;
         tr->buffer = max_tr.buffer;
         max_tr.buffer = buf;
 
@@ -2400,6 +2401,27 @@ static void test_ftrace_alive(struct seq_file *m)
         seq_printf(m, "#          MAY BE MISSING FUNCTION EVENTS\n");
 }
 
+#ifdef CONFIG_TRACER_MAX_TRACE
+static void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter)
+{
+        if (iter->trace->allocated_snapshot)
+                seq_printf(m, "#\n# * Snapshot is allocated *\n#\n");
+        else
+                seq_printf(m, "#\n# * Snapshot is freed *\n#\n");
+
+        seq_printf(m, "# Snapshot commands:\n");
+        seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n");
+        seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n");
+        seq_printf(m, "#                      Takes a snapshot of the main buffer.\n");
+        seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)\n");
+        seq_printf(m, "#                      (Doesn't have to be '2' works with any number that\n");
+        seq_printf(m, "#                       is not a '0' or '1')\n");
+}
+#else
+/* Should never be called */
+static inline void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter) { }
+#endif
+
 static int s_show(struct seq_file *m, void *v)
 {
         struct trace_iterator *iter = v;
@@ -2411,7 +2433,9 @@ static int s_show(struct seq_file *m, void *v)
                         seq_puts(m, "#\n");
                         test_ftrace_alive(m);
                 }
-                if (iter->trace && iter->trace->print_header)
+                if (iter->snapshot && trace_empty(iter))
+                        print_snapshot_help(m, iter);
+                else if (iter->trace && iter->trace->print_header)
                         iter->trace->print_header(m);
                 else
                         trace_default_header(m);
@@ -2857,11 +2881,25 @@ static int set_tracer_option(struct tracer *trace, char *cmp, int neg)
         return -EINVAL;
 }
 
-static void set_tracer_flags(unsigned int mask, int enabled)
+/* Some tracers require overwrite to stay enabled */
+int trace_keep_overwrite(struct tracer *tracer, u32 mask, int set)
+{
+        if (tracer->enabled && (mask & TRACE_ITER_OVERWRITE) && !set)
+                return -1;
+
+        return 0;
+}
+
+int set_tracer_flag(unsigned int mask, int enabled)
 {
         /* do nothing if flag is already set */
         if (!!(trace_flags & mask) == !!enabled)
-                return;
+                return 0;
+
+        /* Give the tracer a chance to approve the change */
+        if (current_trace->flag_changed)
+                if (current_trace->flag_changed(current_trace, mask, !!enabled))
+                        return -EINVAL;
 
         if (enabled)
                 trace_flags |= mask;
@@ -2871,18 +2909,24 @@ static void set_tracer_flags(unsigned int mask, int enabled)
         if (mask == TRACE_ITER_RECORD_CMD)
                 trace_event_enable_cmd_record(enabled);
 
-        if (mask == TRACE_ITER_OVERWRITE)
+        if (mask == TRACE_ITER_OVERWRITE) {
                 ring_buffer_change_overwrite(global_trace.buffer, enabled);
+#ifdef CONFIG_TRACER_MAX_TRACE
+                ring_buffer_change_overwrite(max_tr.buffer, enabled);
+#endif
+        }
 
         if (mask == TRACE_ITER_PRINTK)
                 trace_printk_start_stop_comm(enabled);
+
+        return 0;
 }
 
 static int trace_set_options(char *option)
 {
         char *cmp;
         int neg = 0;
-        int ret = 0;
+        int ret = -ENODEV;
         int i;
 
         cmp = strstrip(option);
@@ -2892,19 +2936,20 @@ static int trace_set_options(char *option)
                 cmp += 2;
         }
 
+        mutex_lock(&trace_types_lock);
+
         for (i = 0; trace_options[i]; i++) {
                 if (strcmp(cmp, trace_options[i]) == 0) {
-                        set_tracer_flags(1 << i, !neg);
+                        ret = set_tracer_flag(1 << i, !neg);
                         break;
                 }
         }
 
         /* If no option could be set, test the specific tracer options */
-        if (!trace_options[i]) {
-                mutex_lock(&trace_types_lock);
+        if (!trace_options[i])
                 ret = set_tracer_option(current_trace, cmp, neg);
-                mutex_unlock(&trace_types_lock);
-        }
+
+        mutex_unlock(&trace_types_lock);
 
         return ret;
 }
@@ -2914,6 +2959,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
                         size_t cnt, loff_t *ppos)
 {
         char buf[64];
+        int ret;
 
         if (cnt >= sizeof(buf))
                 return -EINVAL;
@@ -2923,7 +2969,9 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 
         buf[cnt] = 0;
 
-        trace_set_options(buf);
+        ret = trace_set_options(buf);
+        if (ret < 0)
+                return ret;
 
         *ppos += cnt;
 
@@ -3227,6 +3275,9 @@ static int tracing_set_tracer(const char *buf)
                 goto out;
 
         trace_branch_disable();
+
+        current_trace->enabled = false;
+
         if (current_trace->reset)
                 current_trace->reset(tr);
 
@@ -3271,6 +3322,7 @@ static int tracing_set_tracer(const char *buf)
         }
 
         current_trace = t;
+        current_trace->enabled = true;
         trace_branch_enable(tr);
  out:
         mutex_unlock(&trace_types_lock);
@@ -4144,8 +4196,6 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
         default:
                 if (current_trace->allocated_snapshot)
                         tracing_reset_online_cpus(&max_tr);
-                else
-                        ret = -EINVAL;
                 break;
         }
 
@@ -4759,7 +4809,13 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
 
         if (val != 0 && val != 1)
                 return -EINVAL;
-        set_tracer_flags(1 << index, val);
+
+        mutex_lock(&trace_types_lock);
+        ret = set_tracer_flag(1 << index, val);
+        mutex_unlock(&trace_types_lock);
+
+        if (ret < 0)
+                return ret;
 
         *ppos += cnt;