diff mbox series

[v2] drm/i915: Copy name string into ring buffer for intel_update/disable_plane tracepoints

Message ID 20190710171230.7471-1-ville.syrjala@linux.intel.com (mailing list archive)
State New, archived
Headers show
Series [v2] drm/i915: Copy name string into ring buffer for intel_update/disable_plane tracepoints | expand

Commit Message

Ville Syrjala July 10, 2019, 5:12 p.m. UTC 
From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

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>
---
 drivers/gpu/drm/i915/i915_trace.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Comments

Ville Syrjala July 11, 2019, 7:55 p.m. UTC | #1 
On Wed, Jul 10, 2019 at 08:12:30PM +0300, Ville Syrjala wrote:
> From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> 
> 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>

CI is happy (not that we test this stuff) and I'm happy (the tracepoints
still work) -> pushed to drm-intel-next-queued. Thanks for the patch.

> ---
>  drivers/gpu/drm/i915/i915_trace.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
> index cce426b23a24..da18b8d6b80c 100644
> --- 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)
>  );
>  
> -- 
> 2.21.0
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index cce426b23a24..da18b8d6b80c 100644
--- 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)
 );