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

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Message-ID: <20161123092735.GA2071@wunner.de>
Date:   Wed, 23 Nov 2016 10:27:35 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     David Howells <dhowells@...hat.com>
Cc:     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]

On Wed, Nov 23, 2016 at 12:23:12AM +0000, David Howells wrote:
> From: Josh Boyer <jwboyer@...oraproject.org>
> 
> UEFI machines can be booted in Secure Boot mode.  Add a EFI_SECURE_BOOT bit
> that can be passed to efi_enabled() to find out whether secure boot is
> enabled.
> 
> This will be used by the SysRq+x handler, registered by the x86 arch, to find
> out whether secure boot mode is enabled so that it can be disabled.
> 
> Signed-off-by: Josh Boyer <jwboyer@...oraproject.org>
> Signed-off-by: David Howells <dhowells@...hat.com>
> ---
> 
>  arch/x86/kernel/setup.c |    7 +++++++
>  include/linux/efi.h     |    1 +
>  2 files changed, 8 insertions(+)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 9c337b0e8ba7..522915d6de1f 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1160,6 +1160,13 @@ void __init setup_arch(char **cmdline_p)
>  
>  	io_delay_init();
>  
> +#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.  Also, CONFIG_EFI_STUB might be more apt than
CONFIG_EFI.

Thanks,

Lukas

>  	/*
>  	 * Parse the ACPI tables for possible boot-time SMP configuration.
>  	 */
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index ff01ad6f2823..d95bb9e69974 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1066,6 +1066,7 @@ extern int __init efi_setup_pcdp_console(char *);
>  #define EFI_ARCH_1		7	/* First arch-specific bit */
>  #define EFI_DBG			8	/* Print additional debug info at runtime */
>  #define EFI_NX_PE_DATA		9	/* Can runtime data regions be mapped non-executable? */
> +#define EFI_SECURE_BOOT		10	/* Are we in Secure Boot mode? */
>  
>  #ifdef CONFIG_EFI
>  /*
>