linux-kernel - Re: [tip: x86/core] objtool: Find unused ENDBR instructions

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Message-ID: <20220317222254.lm2f2337jejcf3uu@treble>
Date:   Thu, 17 Mar 2022 15:22:54 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tip-commits@...r.kernel.org" 
        <linux-tip-commits@...r.kernel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [tip: x86/core] objtool: Find unused ENDBR instructions

On Tue, Mar 15, 2022 at 03:39:52PM +0000, David Laight wrote:
> From: Peter Zijlstra
> > 
> > objtool: Find unused ENDBR instructions
> > 
> > Find all ENDBR instructions which are never referenced and stick them
> > in a section such that the kernel can poison them, sealing the
> > functions from ever being an indirect call target.
> 
> Thought, what happens if the only indirect call is from
> code in a module?

Then <boom>, I guess.  Is it safe to assume in-tree modules don't need
to do indirect calls to exported functions?  I guess we'll find out :-)

-- 
Josh