linux-kernel - Re: [PATCH 6/6] efi: Add EFI_SECURE

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Date:   Wed, 23 Nov 2016 10:07:21 +0000
From:   David Howells <dhowells@...hat.com>
To:     Lukas Wunner <lukas@...ner.de>
Cc:     dhowells@...hat.com, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Josh Boyer <jwboyer@...oraproject.org>,
        keyrings@...r.kernel.org
Subject: Re: [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2]

Lukas Wunner <lukas@...ner.de> wrote:

> > +#ifdef CONFIG_EFI
> > +	if (boot_params.secure_boot) {
> > +		set_bit(EFI_SECURE_BOOT, &efi.flags);
> > +		pr_info("Secure boot enabled\n");
> > +	}
> > +#endif
> > +
> 
> Section 20 of Documentation/CodingStyle recommends IS_ENABLED()
> instead of #ifdef.

The problem is this:

	arch/x86/include/asm/bitops.h:75: undefined reference to `efi'

To quote section 20: "... Thus, you still have to use an #ifdef if the code
inside the block references symbols that will not exist if the condition is
not met."

> Also, CONFIG_EFI_STUB might be more apt than CONFIG_EFI.

Other stuff in the same function is contingent on CONFIG_EFI.  EFI_STUB is to
do with how the thing can be booted, I think - not whether EFI support is
enabled.

David