[PATCH] drm/amdgpu: Fix format character cut-off issues in amdgpu_vcn_early_init()

[Lazar, Lijo]

On 3/20/2024 2:15 PM, Srinivasan Shanmugam wrote:
> The issue was present in the lines where 'fw_name' was being formatted.
> This fix ensures that the output is not truncated
> 
> Fixes the below with gcc W=1:
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c: In function ‘amdgpu_vcn_early_init’:
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:102:66: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
>   102 |                 snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
>       |                                                                  ^
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:102:17: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 40
>   102 |                 snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:102:66: warning: ‘snprintf’ output may be truncated before the last format character [-Wformat-truncation=]
>   102 |                 snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
>       |                                                                  ^
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:102:17: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 40
>   102 |                 snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
>       |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:105:73: warning: ‘.bin’ directive output may be truncated writing 4 bytes into a region of size between 2 and 31 [-Wformat-truncation=]
>   105 |                         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s_%d.bin", ucode_prefix, i);
>       |                                                                         ^~~~
> drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:105:25: note: ‘snprintf’ output between 14 and 43 bytes into a destination of size 40
>   105 |                         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s_%d.bin", ucode_prefix, i);
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Christian König <christian.koenig at amd.com>
> Suggested-by: Lijo Lazar <lijo.lazar at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
> index 9c514a606a2f..f994ee6c548d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
> @@ -94,7 +94,7 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work);
>  int amdgpu_vcn_early_init(struct amdgpu_device *adev)
>  {
>  	char ucode_prefix[30];

Hi Srini,

Sorry, if I miscommunicated. Suggestion was to reduce prefix size to 25
as the max prefix length is possibly length of dimgrey_cavefish_vcn.

With fw_name[42] also, you may run into 43 bytes (30 prefix + 13 for
others) warning.

Thanks,
Lijo

> -	char fw_name[40];
> +	char fw_name[42];
>  	int r, i;
>  
>  	for (i = 0; i < adev->vcn.num_vcn_inst; i++) {