drm/i915: Copy name string into ring buffer for intel_update/disable_plane tracepoints

Currently the intel_update_plane and intel_disable_plane tracepoints record
the address of plane->name in the ring buffer, and then when reading the
ring buffer uses %s to get the name. The issue with this, is that those two
events can be minutes, hours or even days apart. It is very dangerous to
dereference a string pointer without knowing if it still exists or not.

The proper way to handle this is to use the __string() macro in the
tracepoint which will save the string into the ring buffer at the time of
recording. Then there's no worries if the original string still exists in
memory when the ring buffer is read.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[vsyrjala: Rebase on top of drm-tip]
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190710171230.7471-1-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index cce426b23a240a8a30449b9a1b220c0de8ce92e3..da18b8d6b80c623a4baf0427ffdd7f874bb20099 100644 (file)
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -293,16 +293,16 @@ TRACE_EVENT(intel_update_plane,
 
            TP_STRUCT__entry(
                             __field(enum pipe, pipe)
-                            __field(const char *, name)
                             __field(u32, frame)
                             __field(u32, scanline)
                             __array(int, src, 4)
                             __array(int, dst, 4)
+                            __string(name, plane->name)
                             ),
 
            TP_fast_assign(
+                          __assign_str(name, plane->name);
                           __entry->pipe = crtc->pipe;
-                          __entry->name = plane->name;
                           __entry->frame = intel_crtc_get_vblank_counter(crtc);
                           __entry->scanline = intel_get_crtc_scanline(crtc);
                           memcpy(__entry->src, &plane->state->src, sizeof(__entry->src));
@@ -310,7 +310,7 @@ TRACE_EVENT(intel_update_plane,
                           ),
 
            TP_printk("pipe %c, plane %s, frame=%u, scanline=%u, " DRM_RECT_FP_FMT " -> " DRM_RECT_FMT,
-                     pipe_name(__entry->pipe), __entry->name,
+                     pipe_name(__entry->pipe), __get_str(name),
                      __entry->frame, __entry->scanline,
                      DRM_RECT_FP_ARG((const struct drm_rect *)__entry->src),
                      DRM_RECT_ARG((const struct drm_rect *)__entry->dst))
@@ -322,20 +322,20 @@ TRACE_EVENT(intel_disable_plane,
 
            TP_STRUCT__entry(
                             __field(enum pipe, pipe)
-                            __field(const char *, name)
                             __field(u32, frame)
                             __field(u32, scanline)
+                            __string(name, plane->name)
                             ),
 
            TP_fast_assign(
+                          __assign_str(name, plane->name);
                           __entry->pipe = crtc->pipe;
-                          __entry->name = plane->name;
                           __entry->frame = intel_crtc_get_vblank_counter(crtc);
                           __entry->scanline = intel_get_crtc_scanline(crtc);
                           ),
 
            TP_printk("pipe %c, plane %s, frame=%u, scanline=%u",
-                     pipe_name(__entry->pipe), __entry->name,
+                     pipe_name(__entry->pipe), __get_str(name),
                      __entry->frame, __entry->scanline)
 );