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SubjectRe: [PATCH 1/3] drm/i915: allocate mock file pointer dynamically
On Mon, Mar 20, 2017 at 10:40:27AM +0100, Arnd Bergmann wrote:
> A struct file is a bit too large to put on the kernel stack in general
> and triggers a warning for low settings of CONFIG_FRAME_WARN:
>
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file':
> drivers/gpu/drm/i915/selftests/mock_drm.c:46:1: error: the frame size of 1328 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
> drivers/gpu/drm/i915/selftests/mock_drm.c: In function 'mock_file_free':
> drivers/gpu/drm/i915/selftests/mock_drm.c:54:1: error: the frame size of 1312 bytes is larger than 1280 bytes [-Werror=frame-larger-than=]
>
> It's also slightly dangerous to leave a reference to a stack object
> in the drm_file structure after leaving the stack frame.
> This changes the code to just allocate the object dynamically
> and release it when we are done with it.
>
> Fixes: 66d9cb5d805a ("drm/i915: Mock the GEM device for self-testing")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/gpu/drm/i915/selftests/mock_drm.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/selftests/mock_drm.c b/drivers/gpu/drm/i915/selftests/mock_drm.c
> index 113dec05c7dc..18514065c93d 100644
> --- a/drivers/gpu/drm/i915/selftests/mock_drm.c
> +++ b/drivers/gpu/drm/i915/selftests/mock_drm.c
> @@ -32,15 +32,15 @@ static inline struct inode fake_inode(struct drm_i915_private *i915)
> struct drm_file *mock_file(struct drm_i915_private *i915)
> {
> struct inode inode = fake_inode(i915);
> - struct file filp = {};
> + struct file *filp = kzalloc(sizeof(struct file), GFP_KERNEL);
> struct drm_file *file;
> int err;
>
> - err = drm_open(&inode, &filp);
> + err = drm_open(&inode, filp);

Aside: We should have a FIXME and/or merge David Herrmanns code to allow a
drm_file without a real struct file for kernel-internal use ...
-Daniel

> if (unlikely(err))
> return ERR_PTR(err);
>
> - file = filp.private_data;
> + file = filp->private_data;
> file->authenticated = true;
> return file;
> }
> @@ -48,7 +48,9 @@ struct drm_file *mock_file(struct drm_i915_private *i915)
> void mock_file_free(struct drm_i915_private *i915, struct drm_file *file)
> {
> struct inode inode = fake_inode(i915);
> - struct file filp = { .private_data = file };
> + struct file *filp = file->filp;
>
> - drm_release(&inode, &filp);
> + drm_release(&inode, filp);
> +
> + kfree(filp);
> }
> --
> 2.9.0
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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