drm/panfrost: Add a no execute flag for BO allocations

Executable buffers have an alignment restriction that they can't cross
16MB boundary as the GPU program counter is 24-bits. This restriction is
currently not handled and we just get lucky. As current userspace
assumes all BOs are executable, that has to remain the default. So add a
new PANFROST_BO_NOEXEC flag to allow userspace to indicate which BOs are
not executable.

There is also a restriction that executable buffers cannot start or end
on a 4GB boundary. This is mostly avoided as there is only 4GB of space
currently and the beginning is already blocked out for NULL ptr
detection. Add support to handle this restriction fully regardless of
the current constraints.

For existing userspace, all created BOs remain executable, but the GPU
VA alignment will be increased to the size of the BO. This shouldn't
matter as there is plenty of GPU VA space.

Cc: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Cc: Boris Brezillon <boris.brezillon@collabora.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190808222200.13176-6-robh@kernel.org

1 files changed, 48 insertions, 2 deletions

diff --git a/drivers/gpu/drm/panfrost/panfrost_gem.c b/drivers/gpu/drm/panfrost/panfrost_gem.c
index d0b0f5f2270e..1a3bde3dc662 100644
--- a/drivers/gpu/drm/panfrost/panfrost_gem.c
+++ b/drivers/gpu/drm/panfrost/panfrost_gem.c
@@ -31,13 +31,25 @@ static int panfrost_gem_open(struct drm_gem_object *obj, struct drm_file *file_p
 {
 	int ret;
 	size_t size = obj->size;
-	u64 align = size >= SZ_2M ? SZ_2M >> PAGE_SHIFT : 0;
+	u64 align;
 	struct panfrost_gem_object *bo = to_panfrost_bo(obj);
 	struct panfrost_device *pfdev = obj->dev->dev_private;
+	unsigned long color = bo->noexec ? PANFROST_BO_NOEXEC : 0;
+
+	/*
+	 * Executable buffers cannot cross a 16MB boundary as the program
+	 * counter is 24-bits. We assume executable buffers will be less than
+	 * 16MB and aligning executable buffers to their size will avoid
+	 * crossing a 16MB boundary.
+	 */
+	if (!bo->noexec)
+		align = size >> PAGE_SHIFT;
+	else
+		align = size >= SZ_2M ? SZ_2M >> PAGE_SHIFT : 0;
 
 	spin_lock(&pfdev->mm_lock);
 	ret = drm_mm_insert_node_generic(&pfdev->mm, &bo->node,
-					 size >> PAGE_SHIFT, align, 0, 0);
+					 size >> PAGE_SHIFT, align, color, 0);
 	if (ret)
 		goto out;
 
@@ -98,16 +110,50 @@ struct drm_gem_object *panfrost_gem_create_object(struct drm_device *dev, size_t
 	return &obj->base.base;
 }
 
+struct panfrost_gem_object *
+panfrost_gem_create_with_handle(struct drm_file *file_priv,
+				struct drm_device *dev, size_t size,
+				u32 flags,
+				uint32_t *handle)
+{
+	int ret;
+	struct drm_gem_shmem_object *shmem;
+	struct panfrost_gem_object *bo;
+
+	shmem = drm_gem_shmem_create(dev, size);
+	if (IS_ERR(shmem))
+		return ERR_CAST(shmem);
+
+	bo = to_panfrost_bo(&shmem->base);
+	bo->noexec = !!(flags & PANFROST_BO_NOEXEC);
+
+	/*
+	 * Allocate an id of idr table where the obj is registered
+	 * and handle has the id what user can see.
+	 */
+	ret = drm_gem_handle_create(file_priv, &shmem->base, handle);
+	/* drop reference from allocate - handle holds it now. */
+	drm_gem_object_put_unlocked(&shmem->base);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return bo;
+}
+
 struct drm_gem_object *
 panfrost_gem_prime_import_sg_table(struct drm_device *dev,
 				   struct dma_buf_attachment *attach,
 				   struct sg_table *sgt)
 {
 	struct drm_gem_object *obj;
+	struct panfrost_gem_object *bo;
 
 	obj = drm_gem_shmem_prime_import_sg_table(dev, attach, sgt);
 	if (IS_ERR(obj))
 		return ERR_CAST(obj);
 
+	bo = to_panfrost_bo(obj);
+	bo->noexec = true;
+
 	return obj;
 }