linux-kernel - Re: [PATCH 2/2] x86/asm: Fix inline asm call constraints for clang

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Message-ID: <7e39ef18-3e60-8cc9-ec4f-1cd02ade171f@zytor.com>
Date:   Wed, 20 Sep 2017 10:46:24 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Potapenko <glider@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>
Subject: Re: [PATCH 2/2] x86/asm: Fix inline asm call constraints for clang

On 09/20/17 10:38, Dmitry Vyukov wrote:
> 
> I think we need just the frame itself and RSP pointing below this
> frame. If we don't have a frame, CALL instruction will smash whatever
> RSP happens to point to. Compiler doesn't have to setup RSP to point
> below used part of stack in leaf functions.
> 

In the kernel it does.  Redzoning is not allowed in the kernel, because
interrupts or exceptions would also smash the redzone.

	-hpa