tracing: Prevent buffer overwrite disabled for latency tracers

[pandora-kernel.git] / kernel / trace / trace.c

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0c6ce44..17edb14 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2636,11 +2636,25 @@ 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;
@@ -2656,6 +2670,8 @@ static void set_tracer_flags(unsigned int mask, int enabled)
                ring_buffer_change_overwrite(max_tr.buffer, enabled);
 #endif
        }
+
+       return 0;
 }
 
 static ssize_t
@@ -2686,7 +2702,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 
        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;
                }
        }
@@ -3022,6 +3038,9 @@ static int tracing_set_tracer(const char *buf)
                goto out;
 
        trace_branch_disable();
+
+       current_trace->enabled = false;
+
        if (current_trace && current_trace->reset)
                current_trace->reset(tr);
        if (current_trace && current_trace->use_max_tr) {
@@ -3051,6 +3070,7 @@ static int tracing_set_tracer(const char *buf)
                        goto out;
        }
 
+       current_trace->enabled = true;
        trace_branch_enable(tr);
  out:
        mutex_unlock(&trace_types_lock);
@@ -4387,9 +4407,12 @@ trace_options_core_write(struct file *filp, const char __user *ubuf, size_t cnt,
                return -EINVAL;
 
        mutex_lock(&trace_types_lock);
-       set_tracer_flags(1 << index, val);
+       ret = set_tracer_flag(1 << index, val);
        mutex_unlock(&trace_types_lock);
 
+       if (ret < 0)
+               return ret;
+
        *ppos += cnt;
 
        return cnt;