[PATCH v6 2/9] powerpc: detect the secure boot mode of the system

Nayna Jain
2019-09-27T14:26:34Z

Secure boot on PowerNV 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.

The PPC_SECURE_BOOT config represents the base enablement of secureboot
on POWER.

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
---
arch/powerpc/Kconfig | 10 ++++
arch/powerpc/include/asm/secure_boot.h | 31 ++++++++++
arch/powerpc/kernel/Makefile | 2 +
arch/powerpc/kernel/secure_boot.c | 82 ++++++++++++++++++++++++++
4 files changed, 125 insertions(+)
create mode 100644 arch/powerpc/include/asm/secure_boot.h
create mode 100644 arch/powerpc/kernel/secure_boot.c

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 77f6ebf97113..2c54beb29f1a 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -912,6 +912,16 @@ config PPC_MEM_KEYS

If unsure, say y.

+config PPC_SECURE_BOOT
+ prompt "Enable secure boot support"
+ bool
+ depends on PPC_POWERNV
+ help
+ Systems with firmware secure boot enabled needs to define security
+ policies to extend secure boot to the OS. This config allows user
+ to enable OS secure boot on systems that have firmware support for
+ it. If in doubt say N.
+
endmenu

config ISA_DMA_API
diff --git a/arch/powerpc/include/asm/secure_boot.h b/arch/powerpc/include/asm/secure_boot.h
new file mode 100644
index 000000000000..4e8e2b08a993
--- /dev/null
+++ b/arch/powerpc/include/asm/secure_boot.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Secure boot definitions
+ *
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+#ifndef _ASM_POWER_SECURE_BOOT_H
+#define _ASM_POWER_SECURE_BOOT_H
+
+#ifdef CONFIG_PPC_SECURE_BOOT
+
+#define SECURE_BOOT_MASK 0xFFFFFFFF00000000
+
+bool is_powerpc_os_secureboot_enabled(void);
+int get_powerpc_os_sb_node(struct device_node **node);
+
+#else
+
+static inline bool is_powerpc_os_secureboot_enabled(void)
+{
+ return false;
+}
+
+static inline int get_powerpc_os_sb_node(struct device_node **node)
+{
+ return -ENOENT;
+}
+
+#endif
+#endif
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index ea0c69236789..875b0785a20e 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -157,6 +157,8 @@ endif
obj-$(CONFIG_EPAPR_PARAVIRT) += epapr_paravirt.o epapr_hcalls.o
obj-$(CONFIG_KVM_GUEST) += kvm.o kvm_emul.o

+obj-$(CONFIG_PPC_SECURE_BOOT) += secure_boot.o
+
# Disable GCOV, KCOV & sanitizers in odd or sensitive code
GCOV_PROFILE_prom_init.o := n
KCOV_INSTRUMENT_prom_init.o := n
diff --git a/arch/powerpc/kernel/secure_boot.c b/arch/powerpc/kernel/secure_boot.c
new file mode 100644
index 000000000000..45ca19f5e836
--- /dev/null
+++ b/arch/powerpc/kernel/secure_boot.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 IBM Corporation
+ * Author: Nayna Jain
+ */
+#include <linux/types.h>
+#include <linux/of.h>
+#include <asm/secure_boot.h>
+
+static struct device_node *get_powerpc_fw_sb_node(void)
+{
+ return of_find_node_by_name(NULL, "ibm,secureboot");
+}
+
+bool is_powerpc_os_sb_supported(void)
+{
+ struct device_node *node = NULL;
+
+ node = get_powerpc_fw_sb_node();
+ if (node && of_device_is_compatible(node, "ibm,secureboot-v3"))
+ return true;
+
+ return false;
+}
+
+int get_powerpc_os_sb_node(struct device_node **node)
+{
+ struct device_node *fwsbnode;
+
+ if (!is_powerpc_os_sb_supported())
+ return -ENOTSUPP;
+
+ fwsbnode = get_powerpc_fw_sb_node();
+ if (!fwsbnode)
+ return -ENOENT;
+
+ *node = of_find_node_by_name(fwsbnode, "secvar");
+ if (*node)
+ return 0;
+
+ return -ENOENT;
+}
+
+bool is_powerpc_os_secureboot_enabled(void)
+{
+ struct device_node *node;
+ u64 sbmode = 0;
+ int rc;
+
+ rc = get_powerpc_os_sb_node(&node);
+ if (rc == -ENOTSUPP)
+ goto disabled;
+
+ /* Fail secure for any failure related to secvar */
+ if (rc) {
+ pr_err("Expected secure variables support, fail secure\n");
+ goto enabled;
+ }
+
+ if (!of_device_is_available(node)) {
+ pr_err("Secure variables support is in error state, fail secure\n");
+ goto enabled;
+ }
+
+ rc = of_property_read_u64(node, "os-secure-mode", &sbmode);
+ if (rc)
+ goto enabled;
+
+ sbmode = be64_to_cpu(sbmode);
+
+ /* checks for the secure mode enforcing bit */
+ if (!(sbmode & SECURE_BOOT_MASK))
+ goto disabled;
+
+enabled:
+ pr_info("secureboot mode enabled\n");
+ return true;
+
+disabled:
+ pr_info("secureboot mode disabled\n");
+ return false;
+}
--
2.20.1