[Mesa-dev] [PATCH 2/2] i965/tiled_memcpy: Protect against wrong alignments

[Jason Ekstrand]

On Tue, Apr 5, 2016 at 10:12 AM, Roland Scheidegger <sroland at vmware.com>
wrote:

> Am 05.04.2016 um 03:04 schrieb Jason Ekstrand:
> > It's possible, when doing an x-tiled copy, to end up with a case where
> the
> > bytes parameter is equal to 16 but the pointer is not actually aligned.
> > This causes asserts in debug mode and segfaults in release builds due to
> > doing an aligned operation on an unaligned pointer.
> >
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93962
> > ---
> >  src/mesa/drivers/dri/i965/intel_tiled_memcpy.c | 48
> +++++++++++++-------------
> >  1 file changed, 24 insertions(+), 24 deletions(-)
> >
> > diff --git a/src/mesa/drivers/dri/i965/intel_tiled_memcpy.c
> b/src/mesa/drivers/dri/i965/intel_tiled_memcpy.c
> > index 19079d0..823d8b0 100644
> > --- a/src/mesa/drivers/dri/i965/intel_tiled_memcpy.c
> > +++ b/src/mesa/drivers/dri/i965/intel_tiled_memcpy.c
> > @@ -85,19 +85,19 @@ rgba8_copy_aligned_dst(void *dst, const void *src,
> size_t bytes)
> >     uint8_t const *s = src;
> >
> >  #ifdef __SSSE3__
> > -   if (bytes == 16) {
> > -      assert(!(((uintptr_t)dst) & 0xf));
> > -      rgba8_copy_16_aligned_dst(d+ 0, s+ 0);
> > -      return dst;
> > -   }
> > +   if ((((uintptr_t)dst) & 0xf) == 0) {
> > +      if (bytes == 16) {
> > +         rgba8_copy_16_aligned_dst(d+ 0, s+ 0);
> > +         return dst;
> > +      }
> >
> > -   if (bytes == 64) {
> > -      assert(!(((uintptr_t)dst) & 0xf));
> > -      rgba8_copy_16_aligned_dst(d+ 0, s+ 0);
> > -      rgba8_copy_16_aligned_dst(d+16, s+16);
> > -      rgba8_copy_16_aligned_dst(d+32, s+32);
> > -      rgba8_copy_16_aligned_dst(d+48, s+48);
> > -      return dst;
> > +      if (bytes == 64) {
> > +         rgba8_copy_16_aligned_dst(d+ 0, s+ 0);
> > +         rgba8_copy_16_aligned_dst(d+16, s+16);
> > +         rgba8_copy_16_aligned_dst(d+32, s+32);
> > +         rgba8_copy_16_aligned_dst(d+48, s+48);
> > +         return dst;
> > +      }
> >     }
> >  #endif
> >
> > @@ -123,19 +123,19 @@ rgba8_copy_aligned_src(void *dst, const void *src,
> size_t bytes)
> >     uint8_t const *s = src;
> >
> >  #ifdef __SSSE3__
> > -   if (bytes == 16) {
> > -      assert(!(((uintptr_t)src) & 0xf));
> > -      rgba8_copy_16_aligned_src(d+ 0, s+ 0);
> > -      return dst;
> > -   }
> > +   if ((((uintptr_t)src) & 0xf) == 0) {
> > +      if (bytes == 16) {
> > +         rgba8_copy_16_aligned_src(d+ 0, s+ 0);
> > +         return dst;
> > +      }
> >
> > -   if (bytes == 64) {
> > -      assert(!(((uintptr_t)src) & 0xf));
> > -      rgba8_copy_16_aligned_src(d+ 0, s+ 0);
> > -      rgba8_copy_16_aligned_src(d+16, s+16);
> > -      rgba8_copy_16_aligned_src(d+32, s+32);
> > -      rgba8_copy_16_aligned_src(d+48, s+48);
> > -      return dst;
> > +      if (bytes == 64) {
> > +         rgba8_copy_16_aligned_src(d+ 0, s+ 0);
> > +         rgba8_copy_16_aligned_src(d+16, s+16);
> > +         rgba8_copy_16_aligned_src(d+32, s+32);
> > +         rgba8_copy_16_aligned_src(d+48, s+48);
> > +         return dst;
> > +      }
> >     }
> >  #endif
> >
> >
>
> Looks alright to me.


Does that count as a revie? :-)


> Do you plan on reapplying the code which was
> reverted due to bug 93962 mentioned there?
> (Though honestly that code was part 2 of a 4-part series and I was only
> really interested in parts 3 and 4 which noone ever reviewed... I think
> they'd still have value today but maybe that's just me...)
>

Yes, that was my plan.  The real bug still existed if you built with
-mssse3.  Now that we've gotten it sorted out, the sse2 code should be fine
as long as we make the corresponding change there..  It'd be nice to get
that merged since I think you'd have to work pretty hard to find a machine
with a GPU that works with the i965 driver and doesn't support SSE2.
--Jason


> Roland
>
>
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