linux-kernel - Re: [PATCH 4/7] objtool: Add support for return trampoline call

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Message-ID: <20200402152717.GE20730@hirez.programming.kicks-ass.net>
Date:   Thu, 2 Apr 2020 17:27:17 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, jpoimboe@...hat.com,
        jthierry@...hat.com, tglx@...utronix.de
Subject: Re: [PATCH 4/7] objtool: Add support for return trampoline call

On Thu, Apr 02, 2020 at 10:22:17AM +0200, Alexandre Chartre wrote:
> With retpoline, the return instruction is used to branch to an address
> stored on the stack. So, unlike a regular return instruction, when a
> retpoline return instruction is reached the stack has been modified
> compared to what we have when the function was entered.
> 
> Provide the mechanism to explicitly call-out such return instruction
> so that objtool can correctly handle them.

https://lkml.kernel.org/r/20200331222703.GH2452@worktop.programming.kicks-ass.net

And also, the split out version:

  https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=core/objtool&id=ec9d9549901dfd2ff411676dfc624e50219e4d5a