linux-kernel - Re: [PATCH 10/18] objtool: Extricate ibt from stack validation

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Date:   Thu, 14 Apr 2022 10:05:50 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH 10/18] objtool: Extricate ibt from stack validation

On Thu, Apr 14, 2022 at 06:38:16PM +0200, Peter Zijlstra wrote:
> On Thu, Apr 14, 2022 at 08:44:49AM -0700, Josh Poimboeuf wrote:
> 
> > Ok.  That was subtle, it needs a comment or two.  I had the distinct
> > feeling I was introducing a bug, then I got distracted ;-)
> 
> Right, lemme try and not forget to write one ;-)

I'm rewriting the code anyway, I'll add some comments.

> > Doesn't the compiler give those special cases ENDBR anyway?  Just
> > wondering why we avoid the warning for those.
> 
> Sure, but this is about not scribbling that ENDBR with a NOP.

Right, but it only prints warnings for data sections, despite marking
others:

-                       dest = validate_ibt_reloc(file, reloc);
-                       if (is_data && dest && !dest->noendbr)
-                               warn_noendbr("data ", sec, reloc->offset, dest);


-- 
Josh