[PATCH v5 2/7] drm: add parameter-order checking to drm memory allocators

[Dave Gordon]

After the recent addition of drm_malloc_gfp(), it was noticed that
some callers of these functions has swapped the parameters in the
call - it's supposed to be 'number of members' and 'sizeof(element)',
but a few callers had got the size first and the count second. This
isn't otherwise detected because they're both type 'size_t', and
the implementation at present just multiplies them anyway, so the
result is still right. But some future implementation might treat
them differently (e.g. allowing 0 elements but not zero size), so
let's add some compile-time checks and complain if the second (size)
parameter isn't a sizeof() expression, or at least a compile-time
constant.

This patch also fixes those callers where the order was wrong.

Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>Cc: dri-
Cc: dri-devel at lists.freedesktop.org
---
 drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c |  2 +-
 drivers/gpu/drm/i915/i915_gem_execbuffer.c   |  8 ++++----
 include/drm/drm_mem_util.h                   | 30 +++++++++++++++++++++++++---
 3 files changed, 32 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
index 1aba01a..9ae4a71 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
@@ -340,7 +340,7 @@ int etnaviv_ioctl_gem_submit(struct drm_device *dev, void *data,
 	 */
 	bos = drm_malloc_ab(args->nr_bos, sizeof(*bos));
 	relocs = drm_malloc_ab(args->nr_relocs, sizeof(*relocs));
-	stream = drm_malloc_ab(1, args->stream_size);
+	stream = drm_malloc_ab(args->stream_size, sizeof(*stream));
 	cmdbuf = etnaviv_gpu_cmdbuf_new(gpu, ALIGN(args->stream_size, 8) + 8,
 					args->nr_bos);
 	if (!bos || !relocs || !stream || !cmdbuf) {
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 18a5dcc..865876d 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1687,8 +1687,8 @@ static bool only_mappable_for_reloc(unsigned int flags)
 	}
 
 	/* Copy in the exec list from userland */
-	exec_list = drm_malloc_ab(sizeof(*exec_list), args->buffer_count);
-	exec2_list = drm_malloc_ab(sizeof(*exec2_list), args->buffer_count);
+	exec_list = drm_malloc_ab(args->buffer_count, sizeof(*exec_list));
+	exec2_list = drm_malloc_ab(args->buffer_count, sizeof(*exec2_list));
 	if (exec_list == NULL || exec2_list == NULL) {
 		DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
 			  args->buffer_count);
@@ -1776,8 +1776,8 @@ static bool only_mappable_for_reloc(unsigned int flags)
 		return -EINVAL;
 	}
 
-	exec2_list = drm_malloc_gfp(sizeof(*exec2_list),
-				    args->buffer_count,
+	exec2_list = drm_malloc_gfp(args->buffer_count,
+				    sizeof(*exec2_list),
 				    GFP_TEMPORARY);
 	if (exec2_list == NULL) {
 		DRM_DEBUG("Failed to allocate exec list for %d buffers\n",
diff --git a/include/drm/drm_mem_util.h b/include/drm/drm_mem_util.h
index 741ce75..886ff0a 100644
--- a/include/drm/drm_mem_util.h
+++ b/include/drm/drm_mem_util.h
@@ -29,7 +29,7 @@
 
 #include <linux/vmalloc.h>
 
-static __inline__ void *drm_calloc_large(size_t nmemb, size_t size)
+static __inline__ void *__drm_calloc_large(size_t nmemb, const size_t size)
 {
 	if (size != 0 && nmemb > SIZE_MAX / size)
 		return NULL;
@@ -41,8 +41,15 @@ static __inline__ void *drm_calloc_large(size_t nmemb, size_t size)
 			 GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO, PAGE_KERNEL);
 }
 
+#define	drm_calloc_large(nmemb, size)					\
+({									\
+	BUILD_BUG_ON_MSG(!__builtin_constant_p(size),			\
+		"Non-constant 'size' - check argument ordering?");	\
+	__drm_calloc_large(nmemb, size);				\
+})
+
 /* Modeled after cairo's malloc_ab, it's like calloc but without the zeroing. */
-static __inline__ void *drm_malloc_ab(size_t nmemb, size_t size)
+static __inline__ void *__drm_malloc_ab(size_t nmemb, const size_t size)
 {
 	if (size != 0 && nmemb > SIZE_MAX / size)
 		return NULL;
@@ -54,8 +61,18 @@ static __inline__ void *drm_malloc_ab(size_t nmemb, size_t size)
 			 GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL);
 }
 
-static __inline__ void *drm_malloc_gfp(size_t nmemb, size_t size, gfp_t gfp)
+#define	drm_malloc_ab(nmemb, size)					\
+({									\
+	BUILD_BUG_ON_MSG(!__builtin_constant_p(size),			\
+		"Non-constant 'size' - check argument ordering?");	\
+	__drm_malloc_ab(nmemb, size);					\
+})
+
+static __inline__ void *__drm_malloc_gfp(size_t nmemb, const size_t size, gfp_t gfp)
 {
+	BUILD_BUG_ON_MSG(!__builtin_constant_p(size),
+		"Non-constant 'size' - check argument ordering?");
+
 	if (size != 0 && nmemb > SIZE_MAX / size)
 		return NULL;
 
@@ -73,6 +90,13 @@ static __inline__ void *drm_malloc_gfp(size_t nmemb, size_t size, gfp_t gfp)
 			 gfp | __GFP_HIGHMEM, PAGE_KERNEL);
 }
 
+#define	drm_malloc_gfp(nmemb, size, gfp)				\
+({									\
+	BUILD_BUG_ON_MSG(!__builtin_constant_p(size),			\
+		"Non-constant 'size' - check argument ordering?");	\
+	__drm_malloc_gfp(nmemb, size, gfp);				\
+})
+
 static __inline void drm_free_large(void *ptr)
 {
 	kvfree(ptr);
-- 
1.9.1