[PATCH v4 2/3] powerpc/powernv: detect the secure boot mode of the system

[Nayna Jain <nayna@linux.ibm.com>]

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@linux.ibm.com>
---
 arch/powerpc/include/asm/secboot.h       | 21 ++++++++
 arch/powerpc/platforms/powernv/Makefile  |  2 +-
 arch/powerpc/platforms/powernv/secboot.c | 61 ++++++++++++++++++++++++
 3 files changed, 83 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@linux.ibm.com>
+ *
+ */
+#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 6651c742e530..6f4af607a915 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..9199e520ebed
--- /dev/null
+++ b/arch/powerpc/platforms/powernv/secboot.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain <nayna@linux.ibm.com>
+ *
+ * secboot.c
+ *      - util function to get powerpc secboot state
+ */
+#include <linux/uuid.h>
+#include <asm/opal.h>
+#include <asm/secboot.h>
+#include <asm/opal-secvar.h>
+
+bool get_powerpc_sb_mode(void)
+{
+	u8 secure_boot_name[] = "SecureBoot";
+	u8 setup_mode_name[] = "SetupMode";
+	u8 secboot, setupmode;
+	unsigned long size = sizeof(secboot);
+	int status;
+	unsigned long version;
+
+	status = opal_variable_version(&version);
+	if ((status != OPAL_SUCCESS) || (version != BACKEND_TC_COMPAT_V1)) {
+		pr_info("secboot: error retrieving compatible backend\n");
+		return false;
+	}
+
+	status = opal_get_variable(secure_boot_name, sizeof(secure_boot_name),
+				   NULL, NULL, &secboot, &size);
+
+	/*
+	 * For now assume all failures reading the SecureBoot variable implies
+	 * secure boot is not enabled. Later differentiate failure types.
+	 */
+	if (status != OPAL_SUCCESS) {
+		secboot = 0;
+		setupmode = 0;
+		goto out;
+	}
+
+	size = sizeof(setupmode);
+	status = opal_get_variable(setup_mode_name, sizeof(setup_mode_name),
+				   NULL, NULL,  &setupmode, &size);
+
+	/*
+	 * Failure to read the SetupMode variable does not prevent
+	 * secure boot mode
+	 */
+	if (status != OPAL_SUCCESS)
+		setupmode = 0;
+
+out:
+	if ((secboot == 0) || (setupmode == 1)) {
+		pr_info("secboot: secureboot mode disabled\n");
+		return false;
+	}
+
+	pr_info("secboot: secureboot mode enabled\n");
+	return true;
+}
-- 
2.20.1