On 14/10/2016 16:18, Chris Wilson wrote:
In many places, we try to count pages using a 32 bit integer. That
implies if we are asked to create an object larger than 43bits, we will
subtly crash much later. Catch this on the boundary, and add a warning
to remind ourselves later on our exabyte systems.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 2 +-
drivers/gpu/drm/i915/i915_gem.c | 14 ++++++++++++--
2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index fe875b27a6bf..43eb1a72f19e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3107,7 +3107,7 @@ void i915_gem_object_free(struct drm_i915_gem_object *obj);
void i915_gem_object_init(struct drm_i915_gem_object *obj,
const struct drm_i915_gem_object_ops *ops);
struct drm_i915_gem_object *i915_gem_object_create(struct drm_device *dev,
- size_t size);
+ u64 size);
struct drm_i915_gem_object *i915_gem_object_create_from_data(
struct drm_device *dev, const void *data, size_t size);
void i915_gem_close_object(struct drm_gem_object *gem, struct drm_file *file);
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index fe92e28ea0a8..0d1dc04302ec 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -4131,14 +4131,24 @@ static const struct drm_i915_gem_object_ops i915_gem_object_ops = {
.put_pages = i915_gem_object_put_pages_gtt,
};
-struct drm_i915_gem_object *i915_gem_object_create(struct drm_device *dev,
- size_t size)
+struct drm_i915_gem_object *
+i915_gem_object_create(struct drm_device *dev, u64 size)
{
struct drm_i915_gem_object *obj;
struct address_space *mapping;
gfp_t mask;
int ret;
+ /* There is a prevalence of the assumption that we fit the object's
+ * page count inside a 32bit variable. Let's document this and catch
+ * if we ever need to fix it.
+ */
+ if (WARN_ON(size >> PAGE_SHIFT > INT_MAX))
+ return ERR_PTR(-E2BIG);
+
+ if (sizeof(size_t) < sizeof(u64) && size > INT_MAX)
+ return ERR_PTR(-E2BIG);
+
Shouldn't it be UINT_MAX in both cases?
We could try to future proof more maybe like
sizeof(typeof(obj->base.size)), is typeof can be used like that?
Something similar for sg API if possible. But then again, it could be
better future proofing to be hardcoded like you wrote it. Yes I think so.
Regards,
Tvrtko
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