Re: [PATCH v3 7/8] execmem: add support for cache of large ROX pages

From: Mike Rapoport <rppt@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Andreas Larsson <andreas@gaisler.com>,
	Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
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	Catalin Marinas <catalin.marinas@arm.com>,
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Subject: Re: [PATCH v3 7/8] execmem: add support for cache of large ROX pages
Date: Sun, 15 Sep 2024 16:48:27 +0300	[thread overview]
Message-ID: <Zublq4tR0q7lvicK@kernel.org> (raw)
In-Reply-To: <CAMj1kXG_Z=7B_eDAk3vhtDjfcnka3AoSKNzvFQDzpvYY2EyVfg@mail.gmail.com>

Hi Ard,

On Fri, Sep 13, 2024 at 05:00:42PM +0200, Ard Biesheuvel wrote:
> Hi Mike,
> 
> On Mon, 9 Sept 2024 at 08:51, Mike Rapoport <rppt@kernel.org> wrote:

...

> > +static void execmem_fill_trapping_insns(void *ptr, size_t size, bool writable)
> > +{
> > +       if (execmem_info->fill_trapping_insns)
> > +               execmem_info->fill_trapping_insns(ptr, size, writable);
> > +       else
> > +               memset(ptr, 0, size);
> 
> Does this really have to be a function pointer with a runtime check?
> 
> This could just be a __weak definition, with the arch providing an
> override if the memset() is not appropriate.

I prefer to keep this a method in execmem_info rather that have a __weak
definition that architectures can override.

This is not on the hot path, so I don't think a runtime check here would
matter. Still, I can fill in a default with memset at init time.

-- 
Sincerely yours,
Mike.