[PATCH 3/4] drm/i915: introduce range_overflows utility macros

[Matthew Auld <matthew.auld@intel.com>]

In a number places we hand-roll the overflow sanity check for ranges, so
roll that into single macro, conceived by Chris, along with its typed
variant.

Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 20bc04d5e617..47b5a9f1c9ed 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -218,6 +218,18 @@ static inline const char *enableddisabled(bool v)
 	return v ? "enabled" : "disabled";
 }
 
+#define range_overflows(start, size, max) ({ \
+	typeof(start) start__ = (start); \
+	typeof(size) size__ = (size); \
+	typeof(max) max__ = (max); \
+	(void)(&start__ == &size__); \
+	(void)(&start__ == &max__); \
+	start > max || size > max - start; \
+})
+
+#define range_overflows_t(type, start, size, max) \
+	range_overflows(((type)start), ((type)size), ((type)max))
+
 enum pipe {
 	INVALID_PIPE = -1,
 	PIPE_A = 0,
-- 
2.9.3

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