On Sat, May 26, 2018 at 08:28:18AM -0300, Mauro Carvalho Chehab wrote:
> Em Sat, 26 May 2018 03:24:00 +0300
> Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> escreveu:
>
> > Hi Mauro,
> >
> > On Saturday, 26 May 2018 02:39:16 EEST Laurent Pinchart wrote:
> > > On Saturday, 26 May 2018 02:10:27 EEST Mauro Carvalho Chehab wrote:
> > > > Em Sun, 20 May 2018 15:10:50 +0300 Laurent Pinchart escreveu:
> > > >> Hi Mauro,
> > > >>
> > > >> The following changes since commit
> > > >>
> > > >> 8ed8bba70b4355b1ba029b151ade84475dd12991:
> > > >> media: imx274: remove non-indexed pointers from mode_table (2018-05-17
> > > >>
> > > >> 06:22:08 -0400)
> > > >>
> > > >> are available in the Git repository at:
> > > >> git://linuxtv.org/pinchartl/media.git v4l2/vsp1/next
> > > >>
> > > >> for you to fetch changes up to 429f256501652c90a4ed82f2416618f82a77d37c:
> > > >> media: vsp1: Move video configuration to a cached dlb (2018-05-20
> > > >> 09:46:51 +0300)
> > > >>
> > > >> The branch passes the VSP and DU test suites, both on its own and when
> > > >> merged with the drm-next branch.
> > > >
> > > > This series added a new warning:
> > > >
> > > > drivers/media/platform/vsp1/vsp1_dl.c:69: warning: Function parameter or
> > > > member 'refcnt' not described in 'vsp1_dl_body'
> > >
> > > We'll fix that. Kieran, as you authored the code, would you like to give it
> > > a go ?
> > >
> > > > To the already existing one:
> > > >
> > > > drivers/media/platform/vsp1/vsp1_drm.c:336 vsp1_du_pipeline_setup_brx()
> > > > error: we previously assumed 'pipe->brx' could be null (see line 244)
> > >
> > > That's still on my todo list. I tried to give it a go but received plenty of
> > > SQL errors. How do you run smatch ?
> >
> > Nevermind, I found out what was wrong (had to specify the data directory
> > manually).
> >
> > I've reproduced the issue and created a minimal test case.
> >
> > 1. struct vsp1_pipeline;
> > 2.
> > 3. struct vsp1_entity {
> > 4. struct vsp1_pipeline *pipe;
> > 5. struct vsp1_entity *sink;
> > 6. unsigned int source_pad;
> > 7. };
> > 8.
> > 9. struct vsp1_pipeline {
> > 10. struct vsp1_entity *brx;
> > 11. };
> > 12.
> > 13. struct vsp1_brx {
> > 14. struct vsp1_entity entity;
> > 15. };
> > 16.
> > 17. struct vsp1_device {
> > 18. struct vsp1_brx *bru;
> > 19. struct vsp1_brx *brs;
> > 20. };
> > 21.
> > 22. unsigned int frob(struct vsp1_device *vsp1, struct vsp1_pipeline *pipe)
> > 23. {
> > 24. struct vsp1_entity *brx;
> > 25.
> > 26. if (pipe->brx)
> > 27. brx = pipe->brx;
> > 28. else if (!vsp1->bru->entity.pipe)
> > 29. brx = &vsp1->bru->entity;
> > 30. else
> > 31. brx = &vsp1->brs->entity;
> > 32.
> > 33. if (brx != pipe->brx)
> > 34. pipe->brx = brx;
> > 35.
> > 36. return pipe->brx->source_pad;
> > 37. }
> >
> > The reason why smatch complains is that it has no guarantee that vsp1->brs is
> > not NULL. It's quite tricky:
> >
> > - On line 26, smatch assumes that pipe->brx can be NULL
> > - On line 27, brx is assigned a non-NULL value (as pipe->brx is not NULL due
> > to line 26)
> > - On line 28, smatch assumes that vsp1->bru is not NULL
> > - On line 29, brx is assigned a non-NULL value (as vsp1->bru is not NULL due
> > to line 28)
> > - On line 31, brx is assigned a possibly NULL value (as there's no information
> > regarding vsp1->brs)
> > - On line 34, pipe->brx is not assigned a non-NULL value if brx is NULL
> > - On line 36 pipe->brx is dereferenced
> >
> > The problem comes from the fact that smatch assumes that vsp1->brs isn't NULL.
> > Adding a "(void)vsp1->brs->entity;" statement on line 25 makes the warning
> > disappear.
> >
I will respond to the other emails in this thread. You guys are
basically spot on. All this analysis is 100% correct. Btw, if you want
to see Smatch's internal state you can do:
#include "/home/whatever/smatch/check_debug.h"
else if (!vsp1->bru->entity.pipe) {
__smatch_implied(&vsp1->bru->entity);
And it tells you what Smatch thinks it is at that point. The
__smatch_about() output can also be useful.
regards,
dan carpenter
