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

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Date:   Thu, 26 Nov 2020 18:44:18 +0100
From:   Borislav Petkov <bp@...e.de>
To:     "Chang S. Bae" <chang.seok.bae@...el.com>,
        Michael Kerrisk <mtk.manpages@...il.com>
Cc:     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

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.

-- 
Regards/Gruss,
    Boris.

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