linux-kernel - Re: [PATCH 4/6] efi: Get the secure boot status

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Message-ID: <20161122203631.GB1844@wunner.de>
Date:   Tue, 22 Nov 2016 21:36:31 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     David Howells <dhowells@...hat.com>
Cc:     Matthew Garrett <matthew.garrett@...ula.com>,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org
Subject: Re: [PATCH 4/6] efi: Get the secure boot status

On Tue, Nov 22, 2016 at 02:52:01PM +0000, David Howells wrote:
> Lukas Wunner <lukas@...ner.de> wrote:
> > You dropped the efi_system_table_t *sys_table_arg argument but this
> > isn't defined anywhere as a static global.
> 
> It seems to me that passing this value in on x86 is probably a bad idea as
> it's not mixed-mode safe.  Should I just pass NULL there in that case?

It's safe, it's merely a pointer below 4 Gig.  Just on dereference it
needs to be cast to the correct variant.  Passing in sys_table_arg is
done all over the place in the EFI stub, see e.g. efi_printk().

Best regards,

Lukas