linux-kernel - Re: [PATCH 1/8] x86,kcfi: Fix EXPORT

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Message-ID: <20241105142720.GG10375@noisy.programming.kicks-ass.net>
Date: Tue, 5 Nov 2024 15:27:20 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Christoph Hellwig <hch@...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, jpoimboe@...nel.org,
	alexei.starovoitov@...il.com, ebiggers@...nel.org,
	samitolvanen@...gle.com, kees@...nel.org
Subject: Re: [PATCH 1/8] x86,kcfi: Fix EXPORT_SYMBOL vs kCFI

On Tue, Nov 05, 2024 at 06:16:01AM -0800, Christoph Hellwig wrote:
> On Tue, Nov 05, 2024 at 12:39:02PM +0100, Peter Zijlstra wrote:
> > The expectation is that all EXPORT'ed symbols are free to have their
> > address taken and called indirectly.
> 
> I don't think that is the case at all.  The is a relatively small number
> of exported symbols that are called indirectly.  I'd much rather mark
> those explicitly.

I'm not claiming they have their address taken -- just saying that
traditionally this has always been a valid thing to do.

Anyway, I raised this point last time, and I think back then the
consensus was to explicitly mark those you should not be able to call.

But irrespective of all that, this just makes sure all the .S functions
are on equal footing with the C functions as generated by the compiler.

Once that's done, we can look at adding to the EXPORT family.