1 files changed, 293 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/secvar-sysfs.c b/arch/powerpc/kernel/secvar-sysfs.c
new file mode 100644
index 000000000..eb3c053f3
--- /dev/null
+++ b/arch/powerpc/kernel/secvar-sysfs.c
@@ -0,0 +1,293 @@
+// 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)
+{
+	char tmp[32];
+	ssize_t len = secvar_ops->format(tmp, sizeof(tmp));
+
+	if (len > 0)
+		return sysfs_emit(buf, "%s\n", tmp);
+	else if (len < 0)
+		pr_err("Error %zd reading format string\n", len);
+	else
+		pr_err("Got empty format string from backend\n");
+
+	return -EIO;
+}
+
+
+static ssize_t size_show(struct kobject *kobj, struct kobj_attribute *attr,
+			 char *buf)
+{
+	u64 dsize;
+	int rc;
+
+	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
+	if (rc) {
+		if (rc != -ENOENT)
+			pr_err("Error retrieving %s variable size %d\n", kobj->name, rc);
+		return rc;
+	}
+
+	return sysfs_emit(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)
+{
+	char *data;
+	u64 dsize;
+	int rc;
+
+	rc = secvar_ops->get(kobj->name, strlen(kobj->name) + 1, NULL, &dsize);
+	if (rc) {
+		if (rc != -ENOENT)
+			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)
+{
+
+	u64 varsize;
+	int rc = secvar_ops->max_size(&varsize);
+
+	if (rc)
+		return rc;
+
+	data_attr.size = varsize;
+	update_attr.size = varsize;
+
+	return 0;
+}
+
+static int secvar_sysfs_config(struct kobject *kobj)
+{
+	struct attribute_group config_group = {
+		.name = "config",
+		.attrs = (struct attribute **)secvar_ops->config_attrs,
+	};
+
+	if (secvar_ops->config_attrs)
+		return sysfs_create_group(kobj, &config_group);
+
+	return 0;
+}
+
+static int add_var(const char *name)
+{
+	struct kobject *kobj;
+	int rc;
+
+	kobj = kzalloc(sizeof(*kobj), GFP_KERNEL);
+	if (!kobj)
+		return -ENOMEM;
+
+	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);
+		return rc;
+	}
+
+	kobject_uevent(kobj, KOBJ_ADD);
+	return 0;
+}
+
+static int secvar_sysfs_load(void)
+{
+	u64 namesize = 0;
+	char *name;
+	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);
+			else
+				rc = 0;
+
+			break;
+		}
+
+		rc = add_var(name);
+	} while (!rc);
+
+	kfree(name);
+	return rc;
+}
+
+static int secvar_sysfs_load_static(void)
+{
+	const char * const *name_ptr = secvar_ops->var_names;
+	int rc;
+
+	while (*name_ptr) {
+		rc = add_var(*name_ptr);
+		if (rc)
+			return rc;
+		name_ptr++;
+	}
+
+	return 0;
+}
+
+static int secvar_sysfs_init(void)
+{
+	u64 max_size;
+	int rc;
+
+	if (!secvar_ops) {
+		pr_warn("Failed to retrieve secvar operations\n");
+		return -ENODEV;
+	}
+
+	secvar_kobj = kobject_create_and_add("secvar", firmware_kobj);
+	if (!secvar_kobj) {
+		pr_err("Failed to create firmware kobj\n");
+		return -ENOMEM;
+	}
+
+	rc = sysfs_create_file(secvar_kobj, &format_attr.attr);
+	if (rc) {
+		pr_err("Failed to create format object\n");
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	secvar_kset = kset_create_and_add("vars", NULL, secvar_kobj);
+	if (!secvar_kset) {
+		pr_err("sysfs kobject registration failed\n");
+		rc = -ENOMEM;
+		goto err;
+	}
+
+	rc = update_kobj_size();
+	if (rc) {
+		pr_err("Cannot read the size of the attribute\n");
+		goto err;
+	}
+
+	rc = secvar_sysfs_config(secvar_kobj);
+	if (rc) {
+		pr_err("Failed to create config directory\n");
+		goto err;
+	}
+
+	if (secvar_ops->get_next)
+		rc = secvar_sysfs_load();
+	else
+		rc = secvar_sysfs_load_static();
+
+	if (rc) {
+		pr_err("Failed to create variable attributes\n");
+		goto err;
+	}
+
+	// Due to sysfs limitations, we will only ever get a write buffer of
+	// up to 1 page in size. Print a warning if this is potentially going
+	// to cause problems, so that the user is aware.
+	secvar_ops->max_size(&max_size);
+	if (max_size > PAGE_SIZE)
+		pr_warn_ratelimited("PAGE_SIZE (%lu) is smaller than maximum object size (%llu), writes are limited to PAGE_SIZE\n",
+				    PAGE_SIZE, max_size);
+
+	return 0;
+err:
+	kobject_put(secvar_kobj);
+	return rc;
+}
+
+late_initcall(secvar_sysfs_init);