Re: [PATCH] drm/exynos: fix accidental on-stack copy of exynos_drm_plane

[Marek Szyprowski <m.szyprowski@samsung.com>]

On 14.12.2023 13:32, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> gcc rightfully complains about excessive stack usage in the fimd_win_set_pixfmt()
> function:
>
> drivers/gpu/drm/exynos/exynos_drm_fimd.c: In function 'fimd_win_set_pixfmt':
> drivers/gpu/drm/exynos/exynos_drm_fimd.c:750:1: error: the frame size of 1032 bytes is larger than 1024 byte
> drivers/gpu/drm/exynos/exynos5433_drm_decon.c: In function 'decon_win_set_pixfmt':
> drivers/gpu/drm/exynos/exynos5433_drm_decon.c:381:1: error: the frame size of 1032 bytes is larger than 1024 bytes
>
> There is really no reason to copy the large exynos_drm_plane
> structure to the stack before using one of its members, so just
> use a pointer instead.
>
> Fixes: 6f8ee5c21722 ("drm/exynos: fimd: Make plane alpha configurable")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>


> ---
>   drivers/gpu/drm/exynos/exynos5433_drm_decon.c | 4 ++--
>   drivers/gpu/drm/exynos/exynos_drm_fimd.c      | 4 ++--
>   2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos5433_drm_decon.c b/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
> index 4d986077738b..bce027552474 100644
> --- a/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
> +++ b/drivers/gpu/drm/exynos/exynos5433_drm_decon.c
> @@ -319,9 +319,9 @@ static void decon_win_set_bldmod(struct decon_context *ctx, unsigned int win,
>   static void decon_win_set_pixfmt(struct decon_context *ctx, unsigned int win,
>   				 struct drm_framebuffer *fb)
>   {
> -	struct exynos_drm_plane plane = ctx->planes[win];
> +	struct exynos_drm_plane *plane = &ctx->planes[win];
>   	struct exynos_drm_plane_state *state =
> -		to_exynos_plane_state(plane.base.state);
> +		to_exynos_plane_state(plane->base.state);
>   	unsigned int alpha = state->base.alpha;
>   	unsigned int pixel_alpha;
>   	unsigned long val;
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fimd.c b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> index 8dde7b1e9b35..5bdc246f5fad 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_fimd.c
> @@ -661,9 +661,9 @@ static void fimd_win_set_bldmod(struct fimd_context *ctx, unsigned int win,
>   static void fimd_win_set_pixfmt(struct fimd_context *ctx, unsigned int win,
>   				struct drm_framebuffer *fb, int width)
>   {
> -	struct exynos_drm_plane plane = ctx->planes[win];
> +	struct exynos_drm_plane *plane = &ctx->planes[win];
>   	struct exynos_drm_plane_state *state =
> -		to_exynos_plane_state(plane.base.state);
> +		to_exynos_plane_state(plane->base.state);
>   	uint32_t pixel_format = fb->format->format;
>   	unsigned int alpha = state->base.alpha;
>   	u32 val = WINCONx_ENWIN;

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland