linux-kernel - Re: [PATCH v6 3/6] x86/elf: Support a new ELF aux vector AT

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Date:   Wed, 10 Mar 2021 18:43:10 +0100
From:   Borislav Petkov <bp@...e.de>
To:     "Bae, Chang Seok" <chang.seok.bae@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "luto@...nel.org" <luto@...nel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "Brown, Len" <len.brown@...el.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "hjl.tools@...il.com" <hjl.tools@...il.com>,
        "Dave.Martin@....com" <Dave.Martin@....com>,
        "jannh@...gle.com" <jannh@...gle.com>,
        "mpe@...erman.id.au" <mpe@...erman.id.au>,
        "carlos@...hat.com" <carlos@...hat.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "libc-alpha@...rceware.org" <libc-alpha@...rceware.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v6 3/6] x86/elf: Support a new ELF aux vector
 AT_MINSIGSTKSZ

On Wed, Mar 10, 2021 at 04:34:40PM +0000, Bae, Chang Seok wrote:
> Yeah, right. While this attempts to fix the issue, it involves the ABI change.
> Len and I think PATCH5 [1] is rather a backport candidate as it gives a more
> reasonable behavior.

Yap, patch 5 is more conservative, sure.

I guess I can take it out of the set and send it Linuswards now.

> > That source code needs some special markup to look like source code -
> > currently, the result looks bad.
> 
> How about this code:

No, build the docs by doing

make htmldocs

and look at the result.

Btw, you should always look at the result before sending it out.

> Rewrote like this:
> 
> AT_SYSINFO is used for locating the vsyscall entry point.  It is not exported
> on 64-bit mode.
> 
> AT_SYSINFO_EHDR is the start address of the page containing the vDSO.
> 
> AT_MINSIGSTKSZ denotes the minimum stack size required by the kernel to
> deliver a signal to user-space.  AT_MINSIGSTKSZ comprehends the space consumed
> by the kernel to accommodate the user context for the current hardware
> configuration.  It does not comprehend subsequent user-space stack
> consumption, which must be added by the user.  (e.g. Above, user-space adds
> SIGSTKSZ to AT_MINSIGSTKSZ.)

Better.

Thx.

-- 
Regards/Gruss,
    Boris.

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