powerpc/pseries: Detect secure and trusted boot state of the system.

The device-tree properties to check secure and trusted boot state are
different for guests (pseries) compared to baremetal (powernv).

This patch updates the existing is_ppc_secureboot_enabled() and
is_ppc_trustedboot_enabled() functions to add support for pseries.

For pseries the secureboot and trustedboot state are exposed via
device-tree properties /ibm,secure-boot and /ibm,trusted-boot.

The values of ibm,secure-boot under pseries are interpreted as:

  0   - Disabled
  1   - Enabled in Log-only mode. This patch interprets this value as
        disabled, since audit mode is currently not supported for
	Linux.
  2   - Enabled and enforced.
  3-9 - Enabled and enforcing; requirements are at the discretion of
        the operating system.

The values of ibm,trusted-boot under pseries are interpreted as:
  0 - Disabled
  1 - Enabled
Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
[mpe: Drop machdep.h inclusion, tweak change log slightly]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1594813921-12425-1-git-send-email-nayna@linux.ibm.com

arch/powerpc/kernel/secure_boot.c

@@ -23,12 +23,19 @@ bool is_ppc_secureboot_enabled(void)
 {
 	struct device_node *node;
 	bool enabled = false;
+	u32 secureboot;
 
 	node = get_ppc_fw_sb_node();
 	enabled = of_property_read_bool(node, "os-secureboot-enforcing");
-
 	of_node_put(node);
 
+	if (enabled)
+		goto out;
+
+	if (!of_property_read_u32(of_root, "ibm,secure-boot", &secureboot))
+		enabled = (secureboot > 1);
+
+out:
 	pr_info("Secure boot mode %s\n", enabled ? "enabled" : "disabled");
 
 	return enabled;
@@ -38,12 +45,19 @@ bool is_ppc_trustedboot_enabled(void)
 {
 	struct device_node *node;
 	bool enabled = false;
+	u32 trustedboot;
 
 	node = get_ppc_fw_sb_node();
 	enabled = of_property_read_bool(node, "trusted-enabled");
-
 	of_node_put(node);
 
+	if (enabled)
+		goto out;
+
+	if (!of_property_read_u32(of_root, "ibm,trusted-boot", &trustedboot))
+		enabled = (trustedboot > 0);
+
+out:
 	pr_info("Trusted boot mode %s\n", enabled ? "enabled" : "disabled");
 
 	return enabled;