From: "H.J. Lu" <hjl.tools@gmail.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: GNU C Library <libc-alpha@sourceware.org>,
Libc-stable Mailing List <libc-stable@sourceware.org>
Subject: Re: [PATCH v3 1/7] x86: Fix __wcsncmp_avx2 in strcmp-avx2.S [BZ# 28755]
Date: Wed, 26 Jan 2022 14:05:20 -0800 [thread overview]
Message-ID: <CAMe9rOp4c0QdrUX_KXEwY531G=6yJmSowSWJr7boKLynwX5ZjQ@mail.gmail.com> (raw)
In-Reply-To: <CAMe9rOoSyQpp=u=B2+OXXfxqJvdCOyd0GKj-sx=tv4iQW_dNug@mail.gmail.com>
On Mon, Jan 10, 2022 at 6:15 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Mon, Jan 10, 2022 at 1:36 PM Noah Goldstein via Libc-alpha
> <libc-alpha@sourceware.org> wrote:
> >
> > Fixes [BZ# 28755] for wcsncmp by redirecting length >= 2^56 to
> > __wcscmp_avx2. For x86_64 this covers the entire address range so any
> > length larger could not possibly be used to bound `s1` or `s2`.
> >
> > test-strcmp, test-strncmp, test-wcscmp, and test-wcsncmp all pass.
> >
> > Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
> > ---
> > sysdeps/x86_64/multiarch/strcmp-avx2.S | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > index a45f9d2749..9c73b5899d 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
> > @@ -87,6 +87,16 @@ ENTRY (STRCMP)
> > je L(char0)
> > jb L(zero)
> > # ifdef USE_AS_WCSCMP
> > +# ifndef __ILP32__
> > + movq %rdx, %rcx
> > + /* Check if length could overflow when multiplied by
> > + sizeof(wchar_t). Checking top 8 bits will cover all potential
> > + overflow cases as well as redirect cases where its impossible to
> > + length to bound a valid memory region. In these cases just use
> > + 'wcscmp'. */
> > + shrq $56, %rcx
> > + jnz __wcscmp_avx2
> > +# endif
> > /* Convert units: from wide to byte char. */
> > shl $2, %RDX_LP
> > # endif
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> Thanks.
>
> --
> H.J.
I am backporting this to 2.34 branch.
--
H.J.
next prev parent reply other threads:[~2022-01-26 22:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220109122946.2754917-1-goldstein.w.n@gmail.com>
[not found] ` <20220110213540.1258344-1-goldstein.w.n@gmail.com>
[not found] ` <20220110213540.1258344-2-goldstein.w.n@gmail.com>
[not found] ` <CAMe9rOqXMUQj_EUcisf_xr+cN2VVUJEY2p1DibS9tjkDS5vmSA@mail.gmail.com>
2022-01-26 22:04 ` [PATCH v3 2/7] x86: Fix __wcsncmp_evex in strcmp-evex.S " H.J. Lu
2022-04-29 22:05 ` Sunil Pandey
[not found] ` <CAMe9rOoSyQpp=u=B2+OXXfxqJvdCOyd0GKj-sx=tv4iQW_dNug@mail.gmail.com>
2022-01-26 22:05 ` H.J. Lu [this message]
2022-01-27 4:29 ` [PATCH v3 1/7] x86: Fix __wcsncmp_avx2 in strcmp-avx2.S " H.J. Lu
2022-01-27 5:10 ` H.J. Lu
2022-01-27 5:52 ` Noah Goldstein
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