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help / color / mirror / Atom feedFrom: Thomas Munro <[email protected]>
To: Andres Freund <[email protected]>
Cc: Nathan Bossart <[email protected]>
Cc: Heikki Linnakangas <[email protected]>
Cc: Mats Kindahl <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: glibc qsort() vulnerability
Date: Thu, 8 Feb 2024 15:38:10 +1300
Message-ID: <CA+hUKGLbC4O56rtFM69Tx6StT3PcVio9K2GisjZp=z6O20Q3sw@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <CA+14426g2Wa9QuUpmakwPxXFWG_1FaY0AsApkvcTBy-YfS6uaw@mail.gmail.com>
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<20240206205305.GB3891538@nathanxps13>
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<CA+14425TqyUZ3-O7zYsW6u85yY5diCz-p_TPQ2bZovn-N-fQ9A@mail.gmail.com>
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On Thu, Feb 8, 2024 at 3:06 PM Andres Freund <[email protected]> wrote:
> On 2024-02-07 19:52:11 -0600, Nathan Bossart wrote:
> > On Wed, Feb 07, 2024 at 04:42:07PM -0800, Andres Freund wrote:
> > > On 2024-02-07 16:21:24 -0600, Nathan Bossart wrote:
> > >> The assembly for that looks encouraging, but I still need to actually test
> > >> it...
> > >
> > > Possible. For 16bit upcasting to 32bit is clearly the best way. For 32 bit
> > > that doesn't work, given the 32bit return, so we need something more.
> >
> > For the same compASC() test, I see an ~8.4% improvement with your int64
> > code
>
> Just to be clear, that code unfortuntely isn't correct, the return value is a
> 32 bit integer, so the 64bit difference doesn't help. In contrast to the 16bit
> case.
Perhaps you could wrap it in a branch-free sign() function so you get
a narrow answer?
https://stackoverflow.com/questions/14579920/fast-sign-of-integer-in-c
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To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: glibc qsort() vulnerability
In-Reply-To: <CA+hUKGLbC4O56rtFM69Tx6StT3PcVio9K2GisjZp=z6O20Q3sw@mail.gmail.com>
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