linux-kernel - Re: [PATCH 01/14] x86/cfi: Wreck things...

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Message-ID: <20240930214218.aysuqlecl6olflow@treble>
Date: Mon, 30 Sep 2024 14:42:18 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, alyssa.milburn@...el.com,
	scott.d.constable@...el.com, joao@...rdrivepizza.com,
	andrew.cooper3@...rix.com, jose.marchesi@...cle.com,
	hjl.tools@...il.com, ndesaulniers@...gle.com,
	samitolvanen@...gle.com, nathan@...nel.org, ojeda@...nel.org,
	kees@...nel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH 01/14] x86/cfi: Wreck things...

On Sat, Sep 28, 2024 at 03:31:14PM +0200, Peter Zijlstra wrote:
> On Fri, Sep 27, 2024 at 04:15:27PM -0700, Josh Poimboeuf wrote:
> > Even better, require exported+indirect-called symbols to use
> > EXPORT_SYMBOL_TYPED, otherwise they get sealed.  I suppose we'd need to
> > add some module-to-vmlinux ENDBR validation to make sure modules don't
> > get broken by this.
> 
> So I like this idea. but yeah, this is going to be a bit tricky to
> validate.

If Module.symvers had EXPORT_SYMBOL[_GPL][_TYPED], objtool could read
that to decide whether a given module indirect branch is allowed.

Objtool is going to be getting support for reading Module.symvers anyway
for klp-build so it should actually be pretty easy.

-- 
Josh