linux-kernel - Re: [PATCH v2 2/4] x86/elf: Support a new ELF aux vector AT

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Date:   Fri, 27 Nov 2020 10:30:44 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Borislav Petkov <bp@...e.de>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Dave Martin <Dave.Martin@....com>
Cc:     mtk.manpages@...il.com, tglx@...utronix.de, mingo@...nel.org,
        luto@...nel.org, x86@...nel.org, len.brown@...el.com,
        dave.hansen@...el.com, hjl.tools@...il.com, Dave.Martin@....com,
        mpe@...erman.id.au, tony.luck@...el.com, ravi.v.shankar@...el.com,
        libc-alpha@...rceware.org, linux-arch@...r.kernel.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
        Fenghua Yu <fenghua.yu@...el.com>
Subject: Re: [PATCH v2 2/4] x86/elf: Support a new ELF aux vector
 AT_MINSIGSTKSZ

Hey Dave Marin,

On 11/26/20 6:44 PM, Borislav Petkov wrote:
> On Thu, Nov 19, 2020 at 11:02:35AM -0800, Chang S. Bae wrote:
>> Historically, signal.h defines MINSIGSTKSZ (2KB) and SIGSTKSZ (8KB), for
>> use by all architectures with sigaltstack(2). Over time, the hardware state
>> size grew, but these constants did not evolve. Today, literal use of these
>> constants on several architectures may result in signal stack overflow, and
>> thus user data corruption.
>>
>> A few years ago, the ARM team addressed this issue by establishing
>> getauxval(AT_MINSIGSTKSZ), such that the kernel can supply at runtime value
>> that is an appropriate replacement on the current and future hardware.
>>
>> Add getauxval(AT_MINSIGSTKSZ) support to x86, analogous to the support
>> added for ARM in commit 94b07c1f8c39 ("arm64: signal: Report signal frame
>> size to userspace via auxv").
> 
> I don't see it documented here:
> 
> https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man3/getauxval.3
> 
> Dunno, now that two architectures will have it, maybe that is good
> enough reason to document it.
> 
> Adding Michael.

Commit 94b07c1f8c39 was your, Dave. Might I convince you to write a 
patch for getauxval(3)?

Thanks,


Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/