linux-kernel - Re: x86-64: Maintain 16-byte stack alignment

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Message-ID: <20170113083841.GB22022@gondor.apana.org.au>
Date:   Fri, 13 Jan 2017 16:38:41 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Andy Lutomirski <luto@...capital.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: x86-64: Maintain 16-byte stack alignment

On Thu, Jan 12, 2017 at 01:40:54PM -0800, Linus Torvalds wrote:
> 
> The 8-byte alignment mainly makes sense when the basic call sequence
> just adds 8 bytes, and you have functions without frames (that still
> call other functions).

The question is does it really make sense to save those 8 bytes
of padding on x86-64 when arm64 apparently also requires 16-byte
stack alignment.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt