linux-kernel - Re: [PATCH 20/25] MODSIGN: Provide module signing public keys to the kernel

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Message-ID: <5040CB1C.1010909@suse.cz>
Date:	Fri, 31 Aug 2012 16:33:00 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	David Howells <dhowells@...hat.com>
Cc:	rusty@...tcorp.com.au, dmitry.kasatkin@...el.com,
	zohar@...ux.vnet.ibm.com, jmorris@...ei.org,
	keyrings@...ux-nfs.org, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 20/25] MODSIGN: Provide module signing public keys to
 the kernel

On 16.8.2012 03:37, David Howells wrote:
> +asm(".section .init.data,\"aw\"\n"
> +    "modsign_public_keys:\n"
> +    ".incbin \"modsign.pub\"\n"
> +    "modsign_public_keys_end:"
> +    );
> +
> +/*
> + * We need to make sure ccache doesn't cache the .o file as it doesn't notice
> + * if modsign.pub changes.
> + */
> +static __initdata const char annoy_ccache[] = __TIME__ "foo";

This results in a different object file after each build, even if
modsign.pub is the same :(. How about generating a modsign-hash.c with
the following content

static __initdata const char annoy_ccache[] = "<some checksum of
modsign.pub, or the key fingerprint>";

and including it in modsign-pubkey.c with the preprocessor? When
changing the public key, modsign.hash.c would change as well and ccache
would notice it. But when doing a rebuild from the same source with the
same public key, the resulting object file would not change.

Thanks,
Michal
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