linux-kernel - Re: [PATCH] x86/retpoline: Remove the esp/rsp thunk

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Date:   Mon, 22 Jan 2018 22:21:47 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Waiman Long <longman@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jeff Law <law@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jiri Kosina <jikos@...nel.org>,
        Andy Lutomirski <luto@...capital.net>,
        Dave Hansen <dave.hansen@...el.com>,
        Kees Cook <keescook@...gle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Paul Turner <pjt@...gle.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH] x86/retpoline: Remove the esp/rsp thunk

On Mon, 2018-01-22 at 17:09 -0500, Waiman Long wrote:
> It doesn't make sense to have an indirect call thunk with esp/rsp as
> retpoline code won't work correctly with the stack pointer register.
> Removing it will help compiler writers to catch error in case such
> a thunk call is emitted incorrectly.
> 
> Fixes: 76b043848fd2 ("x86/retpoline: Add initial retpoline support")
> Suggested-by: Jeff Law <law@...hat.com>
> Signed-off-by: Waiman Long <longman@...hat.com>

Acked-by: David Woodhouse <dwmw@...zon.co.uk>

I spotted that and *almost* removed it a couple of times in other
refactoring, but after abandoning those I forgot to come back and do
just this. Thanks.

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