[v3] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

[PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 5 months, 3 weeks ago

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the new TRAILING_OVERLAP() helper to fix the following warning:

drivers/gpu/drm/nouveau/nvif/fifo.c:29:42: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM)
and a set of members that would otherwise follow it. This overlays
the trailing members onto the FAM while preserving the original
memory layout.

Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
Changes in v3:
 - Use the new TRAILING_OVERLAP() helper.

Changes in v2:
 - Adjust heap allocation.

 drivers/gpu/drm/nouveau/nvif/fifo.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nvif/fifo.c b/drivers/gpu/drm/nouveau/nvif/fifo.c
index a463289962b2..b0ab80995d98 100644
--- a/drivers/gpu/drm/nouveau/nvif/fifo.c
+++ b/drivers/gpu/drm/nouveau/nvif/fifo.c
@@ -25,13 +25,12 @@ static int
 nvif_fifo_runlists(struct nvif_device *device)
 {
 	struct nvif_object *object = &device->object;
-	struct {
-		struct nv_device_info_v1 m;
+	TRAILING_OVERLAP(struct nv_device_info_v1, m, data,
 		struct {
 			struct nv_device_info_v1_data runlists;
 			struct nv_device_info_v1_data runlist[64];
 		} v;
-	} *a;
+	) *a;
 	int ret, i;
 
 	if (device->runlist)
-- 
2.43.0

Re: [PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Kees Cook 1 month ago

On Thu, 14 Aug 2025 15:01:07 +0900, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
> 
> drivers/gpu/drm/nouveau/nvif/fifo.c:29:42: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning
      https://git.kernel.org/kees/c/2d4909bae919

Take care,

-- 
Kees Cook

Re: [PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 1 month ago

Hi all,

Friendly ping: who can take this, please?

Thanks
-Gustavo

On 8/14/25 15:01, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
> 
> drivers/gpu/drm/nouveau/nvif/fifo.c:29:42: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> This helper creates a union between a flexible-array member (FAM)
> and a set of members that would otherwise follow it. This overlays
> the trailing members onto the FAM while preserving the original
> memory layout.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
> Changes in v3:
>   - Use the new TRAILING_OVERLAP() helper.
> 
> Changes in v2:
>   - Adjust heap allocation.
> 
>   drivers/gpu/drm/nouveau/nvif/fifo.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvif/fifo.c b/drivers/gpu/drm/nouveau/nvif/fifo.c
> index a463289962b2..b0ab80995d98 100644
> --- a/drivers/gpu/drm/nouveau/nvif/fifo.c
> +++ b/drivers/gpu/drm/nouveau/nvif/fifo.c
> @@ -25,13 +25,12 @@ static int
>   nvif_fifo_runlists(struct nvif_device *device)
>   {
>   	struct nvif_object *object = &device->object;
> -	struct {
> -		struct nv_device_info_v1 m;
> +	TRAILING_OVERLAP(struct nv_device_info_v1, m, data,
>   		struct {
>   			struct nv_device_info_v1_data runlists;
>   			struct nv_device_info_v1_data runlist[64];
>   		} v;
> -	} *a;
> +	) *a;
>   	int ret, i;
>   
>   	if (device->runlist)

Re: [PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Danilo Krummrich 1 month ago

On 1/6/26 7:08 AM, Gustavo A. R. Silva wrote:
> Friendly ping: who can take this, please?
For some reason this patch wasn't tagged for applying in my inbox -- seems like
it slipped through.

I was about to pick it up, but recognized just in time that Kees already took it
through his hardening tree.

Sorry for the delay; thanks Kees for picking it up. Even though already applied,
please consider this patch:

	Acked-by: Danilo Krummrich <dakr@kernel.org>

Thanks,
Danilo

Re: [PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Kees Cook 1 month ago

On Tue, Jan 06, 2026 at 09:14:36PM +0100, Danilo Krummrich wrote:
> On 1/6/26 7:08 AM, Gustavo A. R. Silva wrote:
> > Friendly ping: who can take this, please?
> For some reason this patch wasn't tagged for applying in my inbox -- seems like
> it slipped through.
> 
> I was about to pick it up, but recognized just in time that Kees already took it
> through his hardening tree.

Ah great!

> Sorry for the delay; thanks Kees for picking it up. Even though already applied,
> please consider this patch:
> 
> 	Acked-by: Danilo Krummrich <dakr@kernel.org>

Thanks! I had figured it was slipping through the cracks so I snagged
it. I'll add your Ack. :) If you'd rather take it, just say the word and
I can drop it from my tree.

-Kees

-- 
Kees Cook

Re: [PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Gustavo A. R. Silva 1 month ago


On 1/7/26 05:21, Kees Cook wrote:
> On Tue, Jan 06, 2026 at 09:14:36PM +0100, Danilo Krummrich wrote:
>> On 1/6/26 7:08 AM, Gustavo A. R. Silva wrote:
>>> Friendly ping: who can take this, please?
>> For some reason this patch wasn't tagged for applying in my inbox -- seems like
>> it slipped through.
>>
>> I was about to pick it up, but recognized just in time that Kees already took it
>> through his hardening tree.
> 
> Ah great!
> 
>> Sorry for the delay; thanks Kees for picking it up. Even though already applied,
>> please consider this patch:
>>
>> 	Acked-by: Danilo Krummrich <dakr@kernel.org>
> 
> Thanks! I had figured it was slipping through the cracks so I snagged
> it. I'll add your Ack. :) If you'd rather take it, just say the word and
> I can drop it from my tree.

Thank you both!

-Gustavo

Re: [PATCH v3][next] drm/nouveau: fifo: Avoid -Wflex-array-member-not-at-end warning

Posted by Justin Stitt 4 months, 3 weeks ago

Hi,

On Thu, Aug 14, 2025 at 03:01:07PM +0900, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
> 
> drivers/gpu/drm/nouveau/nvif/fifo.c:29:42: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> This helper creates a union between a flexible-array member (FAM)
> and a set of members that would otherwise follow it. This overlays
> the trailing members onto the FAM while preserving the original
> memory layout.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

I took a look at the modified structure layout with the union from the
macro using pahole and found the layouts and sizes to be equivalent --
all the while fixing the warning you demonstrated.

Reviewed-by: Justin Stitt <justinstitt@google.com>

> ---
> Changes in v3:
>  - Use the new TRAILING_OVERLAP() helper.

There's really starting to be a lot of these helper macros!

> 
> Changes in v2:
>  - Adjust heap allocation.
> 
>  drivers/gpu/drm/nouveau/nvif/fifo.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nvif/fifo.c b/drivers/gpu/drm/nouveau/nvif/fifo.c
> index a463289962b2..b0ab80995d98 100644
> --- a/drivers/gpu/drm/nouveau/nvif/fifo.c
> +++ b/drivers/gpu/drm/nouveau/nvif/fifo.c
> @@ -25,13 +25,12 @@ static int
>  nvif_fifo_runlists(struct nvif_device *device)
>  {
>  	struct nvif_object *object = &device->object;
> -	struct {
> -		struct nv_device_info_v1 m;
> +	TRAILING_OVERLAP(struct nv_device_info_v1, m, data,
>  		struct {
>  			struct nv_device_info_v1_data runlists;
>  			struct nv_device_info_v1_data runlist[64];
>  		} v;
> -	} *a;
> +	) *a;
>  	int ret, i;
>  
>  	if (device->runlist)
> -- 
> 2.43.0
> 
>

Thanks
Justin