tracing: Prevent buffer overwrite disabled for latency tracers
commit 613f04a0f51e6e68ac6fe571ab79da3c0a5eb4da upstream.
The latency tracers require the buffers to be in overwrite mode,
otherwise they get screwed up. Force the buffers to stay in overwrite
mode when latency tracers are enabled.
Added a flag_changed() method to the tracer structure to allow
the tracers to see what flags are being changed, and also be able
to prevent the change from happing.
[Backported for 3.4-stable. Re-added current_trace NULL checks; removed
allocated_snapshot field; adapted to tracing_trace_options_write without
trace_set_options.]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Lingzhu Xiang <lxiang@redhat.com>
Reviewed-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a786b6a..8beda39 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2743,11 +2743,25 @@
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;
@@ -2759,6 +2773,8 @@
if (mask == TRACE_ITER_OVERWRITE)
ring_buffer_change_overwrite(global_trace.buffer, enabled);
+
+ return 0;
}
static ssize_t
@@ -2768,7 +2784,7 @@
char buf[64];
char *cmp;
int neg = 0;
- int ret = 0;
+ int ret = -ENODEV;
int i;
if (cnt >= sizeof(buf))
@@ -2789,7 +2805,7 @@
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;
}
}
@@ -2800,7 +2816,7 @@
mutex_unlock(&trace_types_lock);
- if (ret)
+ if (ret < 0)
return ret;
*ppos += cnt;
@@ -3125,6 +3141,9 @@
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) {
@@ -3154,6 +3173,7 @@
goto out;
}
+ current_trace->enabled = true;
trace_branch_enable(tr);
out:
mutex_unlock(&trace_types_lock);
@@ -4490,9 +4510,12 @@
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;