From: Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: x86-64: Maintain 16-byte stack alignment
Date: Fri, 13 Jan 2017 16:39:27 +0800
Message-ID: <20170113083927.GC22022@gondor.apana.org.au>
References: <CA+55aFxJOzMim_d-O2E2yip8JWo0NdYs_72sNwFKSkTjy8q0Sw@mail.gmail.com>
 <CA+55aFzypqpMog8aTczWYok0MqOcMi4gGzCor6k-NdJzBoLWyQ@mail.gmail.com>
 <20170111043541.GA4944@gondor.apana.org.au>
 <CALCETrX_vWTWu=kh4Zawn2OuhPnLip8xTqBGjYU-BvpJ9=ruTg@mail.gmail.com>
 <CALCETrVb-NyKJajGEsLOrQqQrQ7cRm4sqLRxNr_yVE2-mjiDrg@mail.gmail.com>
 <20170112140215.rh247gwk55fjzmg7@treble>
 <CA+55aFxP+V6Wbq5Xw_NOksiWouEMg4gjBJgeGa-qFyxDMnTmcA@mail.gmail.com>
 <CALCETrVz-wEFVUwrpS8-Ln9SWnsF5KxkqJC-Br6wJ+e0LGM9UA@mail.gmail.com>
 <20170112201511.yj5ekqmj76r2yv6t@treble>
 <CALCETrXom8aY2XhpAyOtAwQQYF7wftBHJE_px1xr0iRmcYEJoA@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Andy Lutomirski <luto@amacapital.net>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <CALCETrXom8aY2XhpAyOtAwQQYF7wftBHJE_px1xr0iRmcYEJoA@mail.gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-crypto.vger.kernel.org

On Thu, Jan 12, 2017 at 05:46:55PM -0800, Andy Lutomirski wrote:
> 
> What I mean is: what guarantees that the stack is properly aligned for
> the subroutine call?  gcc promises to set up a stack frame, but does
> it promise that rsp will be properly aligned to call a C function?

Yes, as long as you don't go behind its back and start directly
pushing things onto the stack with inline asm.

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