efi: add secure boot get helper

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 <clin@suse.com>

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",

drivers/firmware/efi/efi.c

@@ -1015,3 +1015,46 @@ 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;
+}

include/linux/efi.h

@@ -1084,8 +1084,13 @@ 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);