[PATCH 3/4] powerpc/powernv: Detect the secure boot mode of the system

[Claudio Carvalho]

From: Nayna Jain <nayna@xxxxxxxxxxxxx>

PowerNV secure boot defines different IMA policies based on the secure
boot state of the system.

This patch defines a function to detect the secure boot state of the
system.

Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
---
 arch/powerpc/include/asm/secboot.h       | 21 +++++++++
 arch/powerpc/platforms/powernv/Makefile  |  2 +-
 arch/powerpc/platforms/powernv/secboot.c | 54 ++++++++++++++++++++++++
 3 files changed, 76 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/include/asm/secboot.h
 create mode 100644 arch/powerpc/platforms/powernv/secboot.c

diff --git a/arch/powerpc/include/asm/secboot.h b/arch/powerpc/include/asm/secboot.h
new file mode 100644
index 000000000000..1904fb4a3352
--- /dev/null
+++ b/arch/powerpc/include/asm/secboot.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * PowerPC secure boot definitions
+ *
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain <nayna@xxxxxxxxxxxxx>
+ *
+ */
+#ifndef POWERPC_SECBOOT_H
+#define POWERPC_SECBOOT_H
+
+#if defined(CONFIG_OPAL_SECVAR)
+extern bool get_powerpc_sb_mode(void);
+#else
+static inline bool get_powerpc_sb_mode(void)
+{
+	return false;
+}
+#endif
+
+#endif
diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
index 1511d836fd19..a36e22f8ecf8 100644
--- a/arch/powerpc/platforms/powernv/Makefile
+++ b/arch/powerpc/platforms/powernv/Makefile
@@ -16,4 +16,4 @@ obj-$(CONFIG_PERF_EVENTS) += opal-imc.o
 obj-$(CONFIG_PPC_MEMTRACE)	+= memtrace.o
 obj-$(CONFIG_PPC_VAS)	+= vas.o vas-window.o vas-debug.o
 obj-$(CONFIG_OCXL_BASE)	+= ocxl.o
-obj-$(CONFIG_OPAL_SECVAR)	+= opal-secvar.o
+obj-$(CONFIG_OPAL_SECVAR)	+= opal-secvar.o secboot.o
diff --git a/arch/powerpc/platforms/powernv/secboot.c b/arch/powerpc/platforms/powernv/secboot.c
new file mode 100644
index 000000000000..afb1552636c5
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/secboot.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain <nayna@xxxxxxxxxxxxx>
+ *
+ * secboot.c
+ *      - util functions to get powerpc secboot state
+ *
+ */
+#include <linux/efi.h>
+#include <asm/secboot.h>
+
+bool get_powerpc_sb_mode(void)
+{
+	efi_char16_t efi_SecureBoot_name[] = L"SecureBoot";
+	efi_char16_t efi_SetupMode_name[] = L"SetupMode";
+	efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID;
+	efi_status_t status;
+	u8 secboot, setupmode;
+	unsigned long size = sizeof(secboot);
+
+	status = efi.get_variable(efi_SecureBoot_name, &efi_variable_guid,
+				  NULL, &size, &secboot);
+
+	/*
+	 * For now assume all failures reading the SecureBoot variable implies
+	 * secure boot is not enabled. Later differentiate failure types.
+	 */
+	if (status != EFI_SUCCESS) {
+		secboot = 0;
+		setupmode = 0;
+		goto out;
+	}
+
+	size = sizeof(setupmode);
+	status = efi.get_variable(efi_SetupMode_name, &efi_variable_guid,
+				  NULL, &size, &setupmode);
+
+	/*
+	 * Failure to read the SetupMode variable does not prevent
+	 * secure boot mode
+	 */
+	if (status != EFI_SUCCESS)
+		setupmode = 0;
+
+out:
+	if ((secboot == 0) || (setupmode == 1)) {
+		pr_info("ima: secureboot mode disabled\n");
+		return false;
+	}
+
+	pr_info("ima: secureboot mode enabled\n");
+	return true;
+}
-- 
2.20.1