Re: [PATCH v4 2/3] drm/printer: Allow NULL data in devcoredump printer

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 31 Jul 2024, Matthew Brost <matthew.brost@intel.com> wrote:
> Useful to determine size of devcoreump before writing it out.

I find it useful to have this special case documented, with an example,
so it's easier to see how handy this really is.

BR,
Jani.


>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  drivers/gpu/drm/drm_print.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c
> index cf24dfdeb6b2..a1a4de9f9c44 100644
> --- a/drivers/gpu/drm/drm_print.c
> +++ b/drivers/gpu/drm/drm_print.c
> @@ -100,8 +100,9 @@ void __drm_puts_coredump(struct drm_printer *p, const char *str)
>  			copy = iterator->remain;
>  
>  		/* Copy out the bit of the string that we need */
> -		memcpy(iterator->data,
> -			str + (iterator->start - iterator->offset), copy);
> +		if (iterator->data)
> +			memcpy(iterator->data,
> +				str + (iterator->start - iterator->offset), copy);
>  
>  		iterator->offset = iterator->start + copy;
>  		iterator->remain -= copy;
> @@ -110,7 +111,8 @@ void __drm_puts_coredump(struct drm_printer *p, const char *str)
>  
>  		len = min_t(ssize_t, strlen(str), iterator->remain);
>  
> -		memcpy(iterator->data + pos, str, len);
> +		if (iterator->data)
> +			memcpy(iterator->data + pos, str, len);
>  
>  		iterator->offset += len;
>  		iterator->remain -= len;
> @@ -140,8 +142,9 @@ void __drm_printfn_coredump(struct drm_printer *p, struct va_format *vaf)
>  	if ((iterator->offset >= iterator->start) && (len < iterator->remain)) {
>  		ssize_t pos = iterator->offset - iterator->start;
>  
> -		snprintf(((char *) iterator->data) + pos,
> -			iterator->remain, "%pV", vaf);
> +		if (iterator->data)
> +			snprintf(((char *) iterator->data) + pos,
> +				iterator->remain, "%pV", vaf);
>  
>  		iterator->offset += len;
>  		iterator->remain -= len;

-- 
Jani Nikula, Intel