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[PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2]

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  [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2] David Howells <dhowells@redhat.com> - 2016-11-23 01:30 +0100
    Re: [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2] Lukas Wunner <lukas@wunner.de> - 2016-11-23 10:30 +0100
      Re: [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2] David Howells <dhowells@redhat.com> - 2016-11-23 11:10 +0100
        Re: [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2] David Howells <dhowells@redhat.com> - 2016-11-23 11:20 +0100

#1528035 — [PATCH 6/6] efi: Add EFI_SECURE_BOOT bit [ver #2]

From: Josh Boyer <jwboyer@fedoraproject.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@fedoraproject.org>
Signed-off-by: David Howells <dhowells@redhat.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
+
 	/*
 	 * 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
 /*

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#1528237

On Wed, Nov 23, 2016 at 12:23:12AM +0000, David Howells wrote:
> From: Josh Boyer <jwboyer@fedoraproject.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@fedoraproject.org>
> Signed-off-by: David Howells <dhowells@redhat.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
>  /*
> 

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#1528276

Lukas Wunner <lukas@wunner.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

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#1528278

David Howells <dhowells@redhat.com> 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."

Okay, I take that back - it does actually work.  However, should I follow the
scheme of the rest of the file?

David

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