Re: [PATCH v5] x86: Fallback {str|wcs}cmp RTM in the ncmp overflow case [BZ #28896]

["H.J. Lu" <hjl.tools@gmail.com>]

On Wed, May 25, 2022 at 12:52 PM Sunil Pandey <skpgkp2@gmail.com> wrote:
>
> On Thu, Feb 17, 2022 at 11:21 AM H.J. Lu via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
> >
> > On Thu, Feb 17, 2022 at 11:15 AM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> > >
> > > In the overflow fallback strncmp-avx2-rtm and wcsncmp-avx2-rtm would
> > > call strcmp-avx2 and wcsncmp-avx2 respectively. This would have
> > > not checks around vzeroupper and would trigger spurious
> > > aborts. This commit fixes that.
> > >
> > > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass on
> > > AVX2 machines with and without RTM.
> > >
> > > Co-authored-by: H.J. Lu <hjl.tools@gmail.com>
> > > ---
> > >  sysdeps/x86/Makefile                        |  2 +-
> > >  sysdeps/x86/tst-strncmp-rtm.c               | 17 ++++++++++++++++-
> > >  sysdeps/x86_64/multiarch/strcmp-avx2.S      |  8 ++------
> > >  sysdeps/x86_64/multiarch/strncmp-avx2-rtm.S |  1 +
> > >  sysdeps/x86_64/multiarch/strncmp-avx2.S     |  1 +
> > >  sysdeps/x86_64/multiarch/wcsncmp-avx2-rtm.S |  2 +-
> > >  sysdeps/x86_64/multiarch/wcsncmp-avx2.S     |  2 +-
> > >  7 files changed, 23 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
> > > index 6cf708335c..d110f7b7f2 100644
> > > --- a/sysdeps/x86/Makefile
> > > +++ b/sysdeps/x86/Makefile
> > > @@ -109,7 +109,7 @@ CFLAGS-tst-memset-rtm.c += -mrtm
> > >  CFLAGS-tst-strchr-rtm.c += -mrtm
> > >  CFLAGS-tst-strcpy-rtm.c += -mrtm
> > >  CFLAGS-tst-strlen-rtm.c += -mrtm
> > > -CFLAGS-tst-strncmp-rtm.c += -mrtm
> > > +CFLAGS-tst-strncmp-rtm.c += -mrtm -Wno-error
> > >  CFLAGS-tst-strrchr-rtm.c += -mrtm
> > >  endif
> > >
> > > diff --git a/sysdeps/x86/tst-strncmp-rtm.c b/sysdeps/x86/tst-strncmp-rtm.c
> > > index 09ed6fa0d6..9e20abaacc 100644
> > > --- a/sysdeps/x86/tst-strncmp-rtm.c
> > > +++ b/sysdeps/x86/tst-strncmp-rtm.c
> > > @@ -16,6 +16,7 @@
> > >     License along with the GNU C Library; if not, see
> > >     <https://www.gnu.org/licenses/>.  */
> > >
> > > +#include <stdint.h>
> > >  #include <tst-string-rtm.h>
> > >
> > >  #define LOOP 3000
> > > @@ -45,8 +46,22 @@ function (void)
> > >      return 1;
> > >  }
> > >
> > > +__attribute__ ((noinline, noclone))
> > > +static int
> > > +function_overflow (void)
> > > +{
> > > +  if (strncmp (string1, string2, SIZE_MAX) == 0)
> > > +    return 0;
> > > +  else
> > > +    return 1;
> > > +}
> > > +
> > >  static int
> > >  do_test (void)
> > >  {
> > > -  return do_test_1 ("strncmp", LOOP, prepare, function);
> > > +  int status = do_test_1 ("strncmp", LOOP, prepare, function);
> > > +  if (status != EXIT_SUCCESS)
> > > +    return status;
> > > +  status = do_test_1 ("strncmp", LOOP, prepare, function_overflow);
> > > +  return status;
> > >  }
> > > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > index 07a5a2c889..52ff5ad724 100644
> > > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > > @@ -193,10 +193,10 @@ L(ret_zero):
> > >         .p2align 4,, 5
> > >  L(one_or_less):
> > >         jb      L(ret_zero)
> > > -#  ifdef USE_AS_WCSCMP
> > >         /* 'nbe' covers the case where length is negative (large
> > >            unsigned).  */
> > > -       jnbe    __wcscmp_avx2
> > > +       jnbe    OVERFLOW_STRCMP
> > > +#  ifdef USE_AS_WCSCMP
> > >         movl    (%rdi), %edx
> > >         xorl    %eax, %eax
> > >         cmpl    (%rsi), %edx
> > > @@ -205,10 +205,6 @@ L(one_or_less):
> > >         negl    %eax
> > >         orl     $1, %eax
> > >  #  else
> > > -       /* 'nbe' covers the case where length is negative (large
> > > -          unsigned).  */
> > > -
> > > -       jnbe    __strcmp_avx2
> > >         movzbl  (%rdi), %eax
> > >         movzbl  (%rsi), %ecx
> > >         subl    %ecx, %eax
> > > diff --git a/sysdeps/x86_64/multiarch/strncmp-avx2-rtm.S b/sysdeps/x86_64/multiarch/strncmp-avx2-rtm.S
> > > index 37d1224bb9..68bad365ba 100644
> > > --- a/sysdeps/x86_64/multiarch/strncmp-avx2-rtm.S
> > > +++ b/sysdeps/x86_64/multiarch/strncmp-avx2-rtm.S
> > > @@ -1,3 +1,4 @@
> > >  #define STRCMP __strncmp_avx2_rtm
> > >  #define USE_AS_STRNCMP 1
> > > +#define OVERFLOW_STRCMP        __strcmp_avx2_rtm
> > >  #include "strcmp-avx2-rtm.S"
> > > diff --git a/sysdeps/x86_64/multiarch/strncmp-avx2.S b/sysdeps/x86_64/multiarch/strncmp-avx2.S
> > > index 1678bcc235..f138e9f1fd 100644
> > > --- a/sysdeps/x86_64/multiarch/strncmp-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/strncmp-avx2.S
> > > @@ -1,3 +1,4 @@
> > >  #define STRCMP __strncmp_avx2
> > >  #define USE_AS_STRNCMP 1
> > > +#define OVERFLOW_STRCMP __strcmp_avx2
> > >  #include "strcmp-avx2.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wcsncmp-avx2-rtm.S b/sysdeps/x86_64/multiarch/wcsncmp-avx2-rtm.S
> > > index 4e88c70cc6..f467582cbe 100644
> > > --- a/sysdeps/x86_64/multiarch/wcsncmp-avx2-rtm.S
> > > +++ b/sysdeps/x86_64/multiarch/wcsncmp-avx2-rtm.S
> > > @@ -1,5 +1,5 @@
> > >  #define STRCMP __wcsncmp_avx2_rtm
> > >  #define USE_AS_STRNCMP 1
> > >  #define USE_AS_WCSCMP 1
> > > -
> > > +#define OVERFLOW_STRCMP        __wcscmp_avx2_rtm
> > >  #include "strcmp-avx2-rtm.S"
> > > diff --git a/sysdeps/x86_64/multiarch/wcsncmp-avx2.S b/sysdeps/x86_64/multiarch/wcsncmp-avx2.S
> > > index 4fa1de4d3f..e9ede522b8 100644
> > > --- a/sysdeps/x86_64/multiarch/wcsncmp-avx2.S
> > > +++ b/sysdeps/x86_64/multiarch/wcsncmp-avx2.S
> > > @@ -1,5 +1,5 @@
> > >  #define STRCMP __wcsncmp_avx2
> > >  #define USE_AS_STRNCMP 1
> > >  #define USE_AS_WCSCMP 1
> > > -
> > > +#define OVERFLOW_STRCMP        __wcscmp_avx2
> > >  #include "strcmp-avx2.S"
> > > --
> > > 2.25.1
> > >
> >
> > LGTM.
> >
> > Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
> >
> > Thanks.
> >
> > --
> > H.J.
>
> I would like to backport this patch to release branches.
> Any comments or objections?
>
> Patch attached, it fixes BZ# 29127.
>
> --Sunil

LGTM.

Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

Thanks.

-- 
H.J.