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

[Matthew Brost]

On Wed, Jul 31, 2024 at 04:22:03PM -0600, Cavitt, Jonathan wrote:
> -----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.
> 

That's not the intent. The intent to call the print functions with NULL
data so the printer can calculate the size of buffer required to print
out all the devcoredump data.

Matt

> 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
> > 
> >