Subject: Re: [PATCH v2 1/2] efi: add secure boot get helper

From: Chester Lin <[email-masked]>
Date: Wed, 14 Oct 2020 18:51:02 +0800

Hi Ard and Mimi,

On Wed, Oct 14, 2020 at 06:40:31PM +0800, Chester Lin wrote:
> Separate the get_sb_mode() from arch/x86 and treat it as a common function
> [rename to efi_get_secureboot_mode] so all EFI-based architectures can
> reuse the same logic.
> 
> Signed-off-by: Chester Lin <[email-masked]>
> ---
>  arch/x86/kernel/ima_arch.c | 47 ++------------------------------------
>  drivers/firmware/efi/efi.c | 43 ++++++++++++++++++++++++++++++++++
>  include/linux/efi.h        |  5 ++++
>  3 files changed, 50 insertions(+), 45 deletions(-)
> 
> diff --git a/arch/x86/kernel/ima_arch.c b/arch/x86/kernel/ima_arch.c
> index 7dfb1e808928..ed4623ecda6e 100644
> --- a/arch/x86/kernel/ima_arch.c
> +++ b/arch/x86/kernel/ima_arch.c
> @@ -8,49 +8,6 @@
>  
>  extern struct boot_params boot_params;
>  
> -static enum efi_secureboot_mode get_sb_mode(void)
> -{
> -	efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
> -	efi_status_t status;
> -	unsigned long size;
> -	u8 secboot, setupmode;
> -
> -	size = sizeof(secboot);
> -
> -	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
> -		pr_info("ima: secureboot mode unknown, no efi\n");
> -		return efi_secureboot_mode_unknown;
> -	}
> -
> -	/* Get variable contents into buffer */
> -	status = efi.get_variable(L"SecureBoot", &efi_variable_guid,
> -				  NULL, &size, &secboot);
> -	if (status == EFI_NOT_FOUND) {
> -		pr_info("ima: secureboot mode disabled\n");
> -		return efi_secureboot_mode_disabled;
> -	}
> -
> -	if (status != EFI_SUCCESS) {
> -		pr_info("ima: secureboot mode unknown\n");
> -		return efi_secureboot_mode_unknown;
> -	}
> -
> -	size = sizeof(setupmode);
> -	status = efi.get_variable(L"SetupMode", &efi_variable_guid,
> -				  NULL, &size, &setupmode);
> -
> -	if (status != EFI_SUCCESS)	/* ignore unknown SetupMode */
> -		setupmode = 0;
> -
> -	if (secboot == 0 || setupmode == 1) {
> -		pr_info("ima: secureboot mode disabled\n");
> -		return efi_secureboot_mode_disabled;
> -	}
> -
> -	pr_info("ima: secureboot mode enabled\n");
> -	return efi_secureboot_mode_enabled;
> -}
> -
>  bool arch_ima_get_secureboot(void)
>  {
>  	static enum efi_secureboot_mode sb_mode;
> @@ -60,7 +17,7 @@ bool arch_ima_get_secureboot(void)
>  		sb_mode = boot_params.secure_boot;
>  
>  		if (sb_mode == efi_secureboot_mode_unset)
> -			sb_mode = get_sb_mode();
> +			sb_mode = efi_get_secureboot_mode();
>  		initialized = true;
>  	}
>  
> @@ -70,7 +27,7 @@ bool arch_ima_get_secureboot(void)
>  		return false;
>  }
>  
> -/* secureboot arch rules */
> +/* secure and trusted boot arch rules */
>  static const char * const sb_arch_rules[] = {
>  #if !IS_ENABLED(CONFIG_KEXEC_SIG)
>  	"appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig",
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index 5e5480a0a32d..68ffa6a069c0 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c

I hope you don't mind that I temporarily move the get_sb_mode() to efi
since I'm not sure which place is better. Please let me know if any
suggestions.

Thanks,
Chester

> @@ -1022,3 +1022,46 @@ static int __init register_update_efi_random_seed(void)
>  }
>  late_initcall(register_update_efi_random_seed);
>  #endif
> +
> +enum efi_secureboot_mode efi_get_secureboot_mode(void)
> +{
> +	efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
> +	efi_status_t status;
> +	unsigned long size;
> +	u8 secboot, setupmode;
> +
> +	size = sizeof(secboot);
> +
> +	if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) {
> +		pr_info("ima: secureboot mode unknown, no efi\n");
> +		return efi_secureboot_mode_unknown;
> +	}
> +
> +	/* Get variable contents into buffer */
> +	status = efi.get_variable(L"SecureBoot", &efi_variable_guid,
> +				  NULL, &size, &secboot);
> +	if (status == EFI_NOT_FOUND) {
> +		pr_info("ima: secureboot mode disabled\n");
> +		return efi_secureboot_mode_disabled;
> +	}
> +
> +	if (status != EFI_SUCCESS) {
> +		pr_info("ima: secureboot mode unknown\n");
> +		return efi_secureboot_mode_unknown;
> +	}
> +
> +	size = sizeof(setupmode);
> +	status = efi.get_variable(L"SetupMode", &efi_variable_guid,
> +				  NULL, &size, &setupmode);
> +
> +	if (status != EFI_SUCCESS)	/* ignore unknown SetupMode */
> +		setupmode = 0;
> +
> +	if (secboot == 0 || setupmode == 1) {
> +		pr_info("ima: secureboot mode disabled\n");
> +		return efi_secureboot_mode_disabled;
> +	}
> +
> +	pr_info("ima: secureboot mode enabled\n");
> +	return efi_secureboot_mode_enabled;
> +}
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index d7c0e73af2b9..a73e5ae04672 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -1076,8 +1076,13 @@ static inline int efi_runtime_map_copy(void *buf, size_t bufsz)
>  
>  #ifdef CONFIG_EFI
>  extern bool efi_runtime_disabled(void);
> +extern enum efi_secureboot_mode efi_get_secureboot_mode(void);
>  #else
>  static inline bool efi_runtime_disabled(void) { return true; }
> +static inline enum efi_secureboot_mode efi_get_secureboot_mode(void)
> +{
> +	return efi_secureboot_mode_disabled;
> +}
>  #endif
>  
>  extern void efi_call_virt_check_flags(unsigned long flags, const char *call);
> -- 
> 2.26.1
> 

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