linux-kernel - Re: [PATCH 3/3] x86/alternative: make kernel ITS thunks read-only

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Message-ID: <aDdIZ9vBQ3JQoIN5@kernel.org>
Date: Wed, 28 May 2025 20:31:19 +0300
From: Mike Rapoport <rppt@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Jürgen Groß <jgross@...e.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org, xin@...or.com,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, stable@...r.kernel.org
Subject: Re: [PATCH 3/3] x86/alternative: make kernel ITS thunks read-only

On Wed, May 28, 2025 at 05:58:21PM +0200, Peter Zijlstra wrote:
> On Wed, May 28, 2025 at 03:30:33PM +0200, Jürgen Groß wrote:
> 
> > Have a look at its_fini_mod().
> 
> Oh, that's what you mean. But this still isn't very nice, you now have
> restore_rox() without make_temp_rw(), which was the intended usage
> pattern.
> 
> Bah, I hate how execmem works different for !PSE, Mike, you see a sane
> way to fix this?

The least ugly thing I could think of is to replace the current pattern of

	execmem_alloc()
	exemem_make_temp_rw()
	/* update */
	execmem_restore_rox()

with

	execmem_alloc_rw()
	/* update */
	execmem_protect()

but I still haven't got to try it.

-- 
Sincerely yours,
Mike.