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Date: Thu, 28 Oct 2021 13:09:39 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: Ard Biesheuvel <ardb@kernel.org>, Mark Rutland <mark.rutland@arm.com>,
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In-Reply-To: <202110271430.2A3980217@keescook>

On Wed, Oct 27, 2021 at 03:27:59PM -0700, Kees Cook wrote:

> Right -- though wouldn't just adding __ro_after_init do the same?
> 
> DEFINE_STATIC_CALL(static_call_name, func_a) __ro_after_init;

That breaks modules (and your jump_label patch doing the same is
similarly broken).

When a module is loaded that uses the static_call(), it needs to
register it's .static_call_sites range with the static_call_key which
requires modifying it.