drm/xe/tracing: Fix a potential TP_printk UAF

The commit
afd2627 ("tracing: Check "%s" dereference via the field and not the TP_printk format")
exposes potential UAFs in the xe_bo_move trace event.

Fix those by avoiding dereferencing the
xe_mem_type_to_name[] array at TP_printk time.

Since some code refactoring has taken place, explicit backporting may
be needed for kernels older than 6.10.

Fixes: e46d3f8 ("drm/xe/trace: Extract bo, vm, vma traces")
Cc: Gustavo Sousa <[email protected]>
Cc: Lucas De Marchi <[email protected]>
Cc: Radhakrishna Sripada <[email protected]>
Cc: Matt Roper <[email protected]>
Cc: "Thomas Hellström" <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v6.11+
Signed-off-by: Thomas Hellström <[email protected]>
Reviewed-by: Jonathan Cavitt <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: Thomas Hellström

drivers/gpu/drm/xe/xe_trace_bo.h

@@ -60,24 +60,24 @@ TRACE_EVENT(xe_bo_move,
 	    TP_STRUCT__entry(
 		     __field(struct xe_bo *, bo)
 		     __field(size_t, size)
-		     __field(u32, new_placement)
-		     __field(u32, old_placement)
+		     __string(new_placement_name, xe_mem_type_to_name[new_placement])
+		     __string(old_placement_name, xe_mem_type_to_name[old_placement])
 		     __string(device_id, __dev_name_bo(bo))
 		     __field(bool, move_lacks_source)
 			),
 
 	    TP_fast_assign(
 		   __entry->bo      = bo;
 		   __entry->size = bo->size;
-		   __entry->new_placement = new_placement;
-		   __entry->old_placement = old_placement;
+		   __assign_str(new_placement_name);
+		   __assign_str(old_placement_name);
 		   __assign_str(device_id);
 		   __entry->move_lacks_source = move_lacks_source;
 		   ),
 	    TP_printk("move_lacks_source:%s, migrate object %p [size %zu] from %s to %s device_id:%s",
 		      __entry->move_lacks_source ? "yes" : "no", __entry->bo, __entry->size,
-		      xe_mem_type_to_name[__entry->old_placement],
-		      xe_mem_type_to_name[__entry->new_placement], __get_str(device_id))
+		      __get_str(old_placement_name),
+		      __get_str(new_placement_name), __get_str(device_id))
 );
 
 DECLARE_EVENT_CLASS(xe_vma,