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

[Cavitt, Jonathan]

-----Original Message-----
From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Matthew Brost
Sent: Wednesday, July 31, 2024 2:32 PM
To: intel-xe at lists.freedesktop.org; dri-devel at lists.freedesktop.org
Cc: maarten.lankhorst at linux.intel.com; Vivi, Rodrigo <rodrigo.vivi at intel.com>
Subject: [PATCH v4 2/3] drm/printer: Allow NULL data in devcoredump printer
> 
> Useful to determine size of devcoreump before writing it out.
> 
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>

It seems this patch prevents us from copying strings into the data field if the data
field hasn't been initialized.  I'm not certain if it could ever be uninitialized at this
point, but I recognize it as good practice to check just in case regardless.

Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com>
-Jonathan Cavitt

> ---
>  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;
> -- 
> 2.34.1
> 
>