--- /dev/null
+What: /sys/firmware/secvar
+Date: August 2019
+Contact: Nayna Jain <nayna@linux.ibm.com>
+Description: This directory is created if the POWER firmware supports OS
+ secureboot, thereby secure variables. It exposes interface
+ for reading/writing the secure variables
+
+What: /sys/firmware/secvar/vars
+Date: August 2019
+Contact: Nayna Jain <nayna@linux.ibm.com>
+Description: This directory lists all the secure variables that are supported
+ by the firmware.
+
+What: /sys/firmware/secvar/format
+Date: August 2019
+Contact: Nayna Jain <nayna@linux.ibm.com>
+Description: A string indicating which backend is in use by the firmware.
+ This determines the format of the variable and the accepted
+ format of variable updates.
+
+What: /sys/firmware/secvar/vars/<variable name>
+Date: August 2019
+Contact: Nayna Jain <nayna@linux.ibm.com>
+Description: Each secure variable is represented as a directory named as
+ <variable_name>. The variable name is unique and is in ASCII
+ representation. The data and size can be determined by reading
+ their respective attribute files.
+
+What: /sys/firmware/secvar/vars/<variable_name>/size
+Date: August 2019
+Contact: Nayna Jain <nayna@linux.ibm.com>
+Description: An integer representation of the size of the content of the
+ variable. In other words, it represents the size of the data.
+
+What: /sys/firmware/secvar/vars/<variable_name>/data
+Date: August 2019
+Contact: Nayna Jain h<nayna@linux.ibm.com>
+Description: A read-only file containing the value of the variable. The size
+ of the file represents the maximum size of the variable data.
+
+What: /sys/firmware/secvar/vars/<variable_name>/update
+Date: August 2019
+Contact: Nayna Jain <nayna@linux.ibm.com>
+Description: A write-only file that is used to submit the new value for the
+ variable. The size of the file represents the maximum size of
+ the variable data that can be written.
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2019 IBM Corporation <nayna@linux.ibm.com>
+ *
+ * This code exposes secure variables to user via sysfs
+ */
+
+#define pr_fmt(fmt) "secvar-sysfs: "fmt
+
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/string.h>
+#include <linux/of.h>
+#include <asm/secvar.h>
+
+#define NAME_MAX_SIZE 1024
+
+static struct kobject *secvar_kobj;
+static struct kset *secvar_kset;
+
+static ssize_t format_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ ssize_t rc = 0;
+ struct device_node *node;
+ const char *format;
+
+ node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
+ if (!of_device_is_available(node))
+ return -ENODEV;
+
+ rc = of_property_read_string(node, "format", &format);
+ if (rc)
+ return rc;
+
+ rc = sprintf(buf, "%s\n", format);
+
+ of_node_put(node);
+
+ return rc;
+}
+
+
+static ssize_t size_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ uint64_t dsize;
+ int rc;
+
+ rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
+ if (rc) {
+ pr_err("Error retrieving %s variable size %d\n", kobj->name,
+ rc);
+ return rc;
+ }
+
+ return sprintf(buf, "%llu\n", dsize);
+}
+
+static ssize_t data_read(struct file *filep, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf, loff_t off,
+ size_t count)
+{
+ uint64_t dsize;
+ char *data;
+ int rc;
+
+ rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
+ if (rc) {
+ pr_err("Error getting %s variable size %d\n", kobj->name, rc);
+ return rc;
+ }
+ pr_debug("dsize is %llu\n", dsize);
+
+ data = kzalloc(dsize, GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, data, &dsize);
+ if (rc) {
+ pr_err("Error getting %s variable %d\n", kobj->name, rc);
+ goto data_fail;
+ }
+
+ rc = memory_read_from_buffer(buf, count, &off, data, dsize);
+
+data_fail:
+ kfree(data);
+ return rc;
+}
+
+static ssize_t update_write(struct file *filep, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf, loff_t off,
+ size_t count)
+{
+ int rc;
+
+ pr_debug("count is %ld\n", count);
+ rc = secvar_ops->set(kobj->name, strlen(kobj->name) + 1, buf, count);
+ if (rc) {
+ pr_err("Error setting the %s variable %d\n", kobj->name, rc);
+ return rc;
+ }
+
+ return count;
+}
+
+static struct kobj_attribute format_attr = __ATTR_RO(format);
+
+static struct kobj_attribute size_attr = __ATTR_RO(size);
+
+static struct bin_attribute data_attr = __BIN_ATTR_RO(data, 0);
+
+static struct bin_attribute update_attr = __BIN_ATTR_WO(update, 0);
+
+static struct bin_attribute *secvar_bin_attrs[] = {
+ &data_attr,
+ &update_attr,
+ NULL,
+};
+
+static struct attribute *secvar_attrs[] = {
+ &size_attr.attr,
+ NULL,
+};
+
+static const struct attribute_group secvar_attr_group = {
+ .attrs = secvar_attrs,
+ .bin_attrs = secvar_bin_attrs,
+};
+__ATTRIBUTE_GROUPS(secvar_attr);
+
+static struct kobj_type secvar_ktype = {
+ .sysfs_ops = &kobj_sysfs_ops,
+ .default_groups = secvar_attr_groups,
+};
+
+static int update_kobj_size(void)
+{
+
+ struct device_node *node;
+ u64 varsize;
+ int rc = 0;
+
+ node = of_find_compatible_node(NULL, NULL, "ibm,secvar-backend");
+ if (!of_device_is_available(node)) {
+ rc = -ENODEV;
+ goto out;
+ }
+
+ rc = of_property_read_u64(node, "max-var-size", &varsize);
+ if (rc)
+ goto out;
+
+ data_attr.size = varsize;
+ update_attr.size = varsize;
+
+out:
+ of_node_put(node);
+
+ return rc;
+}
+
+static int secvar_sysfs_load(void)
+{
+ char *name;
+ uint64_t namesize = 0;
+ struct kobject *kobj;
+ int rc;
+
+ name = kzalloc(NAME_MAX_SIZE, GFP_KERNEL);
+ if (!name)
+ return -ENOMEM;
+
+ do {
+ rc = secvar_ops->get_next(name, &namesize, NAME_MAX_SIZE);
+ if (rc) {
+ if (rc != -ENOENT)
+ pr_err("error getting secvar from firmware %d\n",
+ rc);
+ break;
+ }
+
+ kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
+ if (!kobj) {
+ rc = -ENOMEM;
+ break;
+ }
+
+ kobject_init(kobj, &secvar_ktype);
+
+ rc = kobject_add(kobj, &secvar_kset->kobj, "%s", name);
+ if (rc) {
+ pr_warn("kobject_add error %d for attribute: %s\n", rc,
+ name);
+ kobject_put(kobj);
+ kobj = NULL;
+ }
+
+ if (kobj)
+ kobject_uevent(kobj, KOBJ_ADD);
+
+ } while (!rc);
+
+ kfree(name);
+ return rc;
+}
+
+static int secvar_sysfs_init(void)
+{
+ int rc;
+
+ if (!secvar_ops) {
+ pr_warn("secvar: failed to retrieve secvar operations.\n");
+ return -ENODEV;
+ }
+
+ secvar_kobj = kobject_create_and_add("secvar", firmware_kobj);
+ if (!secvar_kobj) {
+ pr_err("secvar: Failed to create firmware kobj\n");
+ return -ENOMEM;
+ }
+
+ rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
+ if (rc) {
+ kobject_put(secvar_kobj);
+ return -ENOMEM;
+ }
+
+ secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
+ if (!secvar_kset) {
+ pr_err("secvar: sysfs kobject registration failed.\n");
+ kobject_put(secvar_kobj);
+ return -ENOMEM;
+ }
+
+ rc = update_kobj_size();
+ if (rc) {
+ pr_err("Cannot read the size of the attribute\n");
+ return rc;
+ }
+
+ secvar_sysfs_load();
+
+ return 0;
+}
+
+late_initcall(secvar_sysfs_init);
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