Re: [PATCH v1] x86: Fix bug in strncmp-evex and strncmp-avx2 [BZ #28895]

[Noah Goldstein <goldstein.w.n@gmail.com>]

On Tue, Feb 15, 2022 at 10:48 AM Andreas Schwab <schwab@linux-m68k.org> wrote:
>
> On Feb 15 2022, Noah Goldstein via Libc-alpha wrote:
>
> > diff --git a/string/test-strncmp.c b/string/test-strncmp.c
> > index 831cb77893..501055de0c 100644
> > --- a/string/test-strncmp.c
> > +++ b/string/test-strncmp.c
> > @@ -423,6 +423,29 @@ check3 (void)
> >       }
> >  }
> >
> > +
> > +static void
> > +check4 (void)
> > +{
> > +  /* To trigger bug 28895; We need 1) both s1 and s2 to be within 32 bytes of
> > +     the end of the page. 2) For there to be no mismatch/null byte before the
> > +     first page cross. 3) For length (`n`) to be large enough for one string to
> > +     cross the page. And 4) for there to be either mismatch/null bytes before
> > +     the start of the strings.  */
> > +
> > +  size_t size = 10;
> > +  CHAR *s1 = (CHAR *)(buf1 + (getpagesize () & 0xffa) / sizeof (CHAR));
> > +  CHAR *s2 = (CHAR *)(buf2 + (getpagesize () & 0xfed) / sizeof (CHAR));
>
> s/&/-/
?
>
> --
> Andreas Schwab, schwab@linux-m68k.org
> GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
> "And now for something completely different."