linux-kernel - Re: [PATCH 2/6] arm/efi: Allow invocation of arbitrary runtime services [ver #2]

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Message-ID: <5320.1479893643@warthog.procyon.org.uk>
Date:   Wed, 23 Nov 2016 09:34:03 +0000
From:   David Howells <dhowells@...hat.com>
To:     lukas@...ner.de
Cc:     dhowells@...hat.com, linux-efi@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] arm/efi: Allow invocation of arbitrary runtime services [ver #2]

David Howells <dhowells@...hat.com> wrote:

> +#define efi_call_runtime(f, ...)	sys_table_arg->runtime->f(__VA_ARGS__)

Turns out it's not that simple - of course.  runtime->get_variable is just a
void pointer.  The old arm stub was casting it by virtue of assignment to a
function pointer variable.

The x86_64 appears to be doing bypassing all the compile-time type checking by
passing the arguments through an ellipsis and then fixing up the argument list
in the ->call() function.

What I've changed the ARM and ARM64 things to is:

	#define efi_call_runtime(f, ...)	((efi_##f##_t *)sys_table_arg->runtime->f)(__VA_ARGS__)

David