[PATCH v1] x86: Fallback {str|wcs}cmp RTM in the ncmp overflow case [BZ #28896]

[Noah Goldstein]

On Tue, Feb 15, 2022 at 10:30 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Feb 15, 2022 at 8:28 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.
>
> Include a testcase?
Added test case in V2. Don't have the hardware to check it though,
can you?
>
> > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all
> > pass. Note not tested on a machine that supports RTM (non
> > available).
> > ---
> >  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 +-
> >  5 files changed, 6 insertions(+), 8 deletions(-)
> >
> > 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
> >
>
>
> --
> H.J.