1 files changed, 217 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c b/arch/powerpc/platforms/pseries/plpks-secvar.c
new file mode 100644
index 000000000000..257fd1f8bc19
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/plpks-secvar.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+// Secure variable implementation using the PowerVM LPAR Platform KeyStore (PLPKS)
+//
+// Copyright 2022, 2023 IBM Corporation
+// Authors: Russell Currey
+//          Andrew Donnellan
+//          Nayna Jain
+
+#define pr_fmt(fmt) "secvar: "fmt
+
+#include <linux/printk.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/kobject.h>
+#include <linux/nls.h>
+#include <asm/machdep.h>
+#include <asm/secvar.h>
+#include <asm/plpks.h>
+
+// Config attributes for sysfs
+#define PLPKS_CONFIG_ATTR(name, fmt, func)			\
+	static ssize_t name##_show(struct kobject *kobj,	\
+				   struct kobj_attribute *attr,	\
+				   char *buf)			\
+	{							\
+		return sysfs_emit(buf, fmt, func());		\
+	}							\
+	static struct kobj_attribute attr_##name = __ATTR_RO(name)
+
+PLPKS_CONFIG_ATTR(version, "%u\n", plpks_get_version);
+PLPKS_CONFIG_ATTR(max_object_size, "%u\n", plpks_get_maxobjectsize);
+PLPKS_CONFIG_ATTR(total_size, "%u\n", plpks_get_totalsize);
+PLPKS_CONFIG_ATTR(used_space, "%u\n", plpks_get_usedspace);
+PLPKS_CONFIG_ATTR(supported_policies, "%08x\n", plpks_get_supportedpolicies);
+PLPKS_CONFIG_ATTR(signed_update_algorithms, "%016llx\n", plpks_get_signedupdatealgorithms);
+
+static const struct attribute *config_attrs[] = {
+	&attr_version.attr,
+	&attr_max_object_size.attr,
+	&attr_total_size.attr,
+	&attr_used_space.attr,
+	&attr_supported_policies.attr,
+	&attr_signed_update_algorithms.attr,
+	NULL,
+};
+
+static u32 get_policy(const char *name)
+{
+	if ((strcmp(name, "db") == 0) ||
+	    (strcmp(name, "dbx") == 0) ||
+	    (strcmp(name, "grubdb") == 0) ||
+	    (strcmp(name, "grubdbx") == 0) ||
+	    (strcmp(name, "sbat") == 0))
+		return (PLPKS_WORLDREADABLE | PLPKS_SIGNEDUPDATE);
+	else
+		return PLPKS_SIGNEDUPDATE;
+}
+
+static const char * const plpks_var_names[] = {
+	"PK",
+	"KEK",
+	"db",
+	"dbx",
+	"grubdb",
+	"grubdbx",
+	"sbat",
+	"moduledb",
+	"trustedcadb",
+	NULL,
+};
+
+static int plpks_get_variable(const char *key, u64 key_len, u8 *data,
+			      u64 *data_size)
+{
+	struct plpks_var var = {0};
+	int rc = 0;
+
+	// We subtract 1 from key_len because we don't need to include the
+	// null terminator at the end of the string
+	var.name = kcalloc(key_len - 1, sizeof(wchar_t), GFP_KERNEL);
+	if (!var.name)
+		return -ENOMEM;
+	rc = utf8s_to_utf16s(key, key_len - 1, UTF16_LITTLE_ENDIAN, (wchar_t *)var.name,
+			     key_len - 1);
+	if (rc < 0)
+		goto err;
+	var.namelen = rc * 2;
+
+	var.os = PLPKS_VAR_LINUX;
+	if (data) {
+		var.data = data;
+		var.datalen = *data_size;
+	}
+	rc = plpks_read_os_var(&var);
+
+	if (rc)
+		goto err;
+
+	*data_size = var.datalen;
+
+err:
+	kfree(var.name);
+	if (rc && rc != -ENOENT) {
+		pr_err("Failed to read variable '%s': %d\n", key, rc);
+		// Return -EIO since userspace probably doesn't care about the
+		// specific error
+		rc = -EIO;
+	}
+	return rc;
+}
+
+static int plpks_set_variable(const char *key, u64 key_len, u8 *data,
+			      u64 data_size)
+{
+	struct plpks_var var = {0};
+	int rc = 0;
+	u64 flags;
+
+	// Secure variables need to be prefixed with 8 bytes of flags.
+	// We only want to perform the write if we have at least one byte of data.
+	if (data_size <= sizeof(flags))
+		return -EINVAL;
+
+	// We subtract 1 from key_len because we don't need to include the
+	// null terminator at the end of the string
+	var.name = kcalloc(key_len - 1, sizeof(wchar_t), GFP_KERNEL);
+	if (!var.name)
+		return -ENOMEM;
+	rc = utf8s_to_utf16s(key, key_len - 1, UTF16_LITTLE_ENDIAN, (wchar_t *)var.name,
+			     key_len - 1);
+	if (rc < 0)
+		goto err;
+	var.namelen = rc * 2;
+
+	// Flags are contained in the first 8 bytes of the buffer, and are always big-endian
+	flags = be64_to_cpup((__be64 *)data);
+
+	var.datalen = data_size - sizeof(flags);
+	var.data = data + sizeof(flags);
+	var.os = PLPKS_VAR_LINUX;
+	var.policy = get_policy(key);
+
+	// Unlike in the read case, the plpks error code can be useful to
+	// userspace on write, so we return it rather than just -EIO
+	rc = plpks_signed_update_var(&var, flags);
+
+err:
+	kfree(var.name);
+	return rc;
+}
+
+// PLPKS dynamic secure boot doesn't give us a format string in the same way OPAL does.
+// Instead, report the format using the SB_VERSION variable in the keystore.
+// The string is made up by us, and takes the form "ibm,plpks-sb-v<n>" (or "ibm,plpks-sb-unknown"
+// if the SB_VERSION variable doesn't exist). Hypervisor defines the SB_VERSION variable as a
+// "1 byte unsigned integer value".
+static ssize_t plpks_secvar_format(char *buf, size_t bufsize)
+{
+	struct plpks_var var = {0};
+	ssize_t ret;
+	u8 version;
+
+	var.component = NULL;
+	// Only the signed variables have null bytes in their names, this one doesn't
+	var.name = "SB_VERSION";
+	var.namelen = strlen(var.name);
+	var.datalen = 1;
+	var.data = &version;
+
+	// Unlike the other vars, SB_VERSION is owned by firmware instead of the OS
+	ret = plpks_read_fw_var(&var);
+	if (ret) {
+		if (ret == -ENOENT) {
+			ret = snprintf(buf, bufsize, "ibm,plpks-sb-unknown");
+		} else {
+			pr_err("Error %ld reading SB_VERSION from firmware\n", ret);
+			ret = -EIO;
+		}
+		goto err;
+	}
+
+	ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version);
+err:
+	return ret;
+}
+
+static int plpks_max_size(u64 *max_size)
+{
+	// The max object size reported by the hypervisor is accurate for the
+	// object itself, but we use the first 8 bytes of data on write as the
+	// signed update flags, so the max size a user can write is larger.
+	*max_size = (u64)plpks_get_maxobjectsize() + sizeof(u64);
+
+	return 0;
+}
+
+
+static const struct secvar_operations plpks_secvar_ops = {
+	.get = plpks_get_variable,
+	.set = plpks_set_variable,
+	.format = plpks_secvar_format,
+	.max_size = plpks_max_size,
+	.config_attrs = config_attrs,
+	.var_names = plpks_var_names,
+};
+
+static int plpks_secvar_init(void)
+{
+	if (!plpks_is_available())
+		return -ENODEV;
+
+	return set_secvar_ops(&plpks_secvar_ops);
+}
+machine_device_initcall(pseries, plpks_secvar_init);