drivers/firmware/google/vpd.c

/*
 * vpd.c
 *
 * Driver for exporting VPD content to sysfs.
 *
 * Copyright 2017 Google Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License v2.0 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/ctype.h>
#include <linux/init.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/kobject.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

#include "coreboot_table.h"
#include "vpd_decode.h"

#define CB_TAG_VPD      0x2c
#define VPD_CBMEM_MAGIC 0x43524f53

static struct kobject *vpd_kobj;

struct vpd_cbmem {
	u32 magic;
	u32 version;
	u32 ro_size;
	u32 rw_size;
	u8  blob[0];
};

struct vpd_section {
	bool enabled;
	const char *name;
	char *raw_name;                /* the string name_raw */
	struct kobject *kobj;          /* vpd/name directory */
	char *baseaddr;
	struct bin_attribute bin_attr; /* vpd/name_raw bin_attribute */
	struct list_head attribs;      /* key/value in vpd_attrib_info list */
};

struct vpd_attrib_info {
	char *key;
	const char *value;
	struct bin_attribute bin_attr;
	struct list_head list;
};

static struct vpd_section ro_vpd;
static struct vpd_section rw_vpd;

static ssize_t vpd_attrib_read(struct file *filp, struct kobject *kobp,
			       struct bin_attribute *bin_attr, char *buf,
			       loff_t pos, size_t count)
{
	struct vpd_attrib_info *info = bin_attr->private;

	return memory_read_from_buffer(buf, count, &pos, info->value,
				       info->bin_attr.size);
}

/*
 * vpd_section_check_key_name()
 *
 * The VPD specification supports only [a-zA-Z0-9_]+ characters in key names but
 * old firmware versions may have entries like "S/N" which are problematic when
 * exporting them as sysfs attributes. These keys present in old firmwares are
 * ignored.
 *
 * Returns VPD_OK for a valid key name, VPD_FAIL otherwise.
 *
 * @key: The key name to check
 * @key_len: key name length
 */
static int vpd_section_check_key_name(const u8 *key, s32 key_len)
{
	int c;

	while (key_len-- > 0) {
		c = *key++;

		if (!isalnum(c) && c != '_')
			return VPD_FAIL;
	}

	return VPD_OK;
}

static int vpd_section_attrib_add(const u8 *key, s32 key_len,
				  const u8 *value, s32 value_len,
				  void *arg)
{
	int ret;
	struct vpd_section *sec = arg;
	struct vpd_attrib_info *info;

	/*
	 * Return VPD_OK immediately to decode next entry if the current key
	 * name contains invalid characters.
	 */
	if (vpd_section_check_key_name(key, key_len) != VPD_OK)
		return VPD_OK;

	info = kzalloc(sizeof(*info), GFP_KERNEL);
	if (!info)
		return -ENOMEM;

	info->key = kstrndup(key, key_len, GFP_KERNEL);
	if (!info->key) {
		ret = -ENOMEM;
		goto free_info;
	}

	sysfs_bin_attr_init(&info->bin_attr);
	info->bin_attr.attr.name = info->key;
	info->bin_attr.attr.mode = 0444;
	info->bin_attr.size = value_len;
	info->bin_attr.read = vpd_attrib_read;
	info->bin_attr.private = info;

	info->value = value;

	INIT_LIST_HEAD(&info->list);

	ret = sysfs_create_bin_file(sec->kobj, &info->bin_attr);
	if (ret)
		goto free_info_key;

	list_add_tail(&info->list, &sec->attribs);
	return 0;

free_info_key:
	kfree(info->key);
free_info:
	kfree(info);

	return ret;
}

static void vpd_section_attrib_destroy(struct vpd_section *sec)
{
	struct vpd_attrib_info *info;
	struct vpd_attrib_info *temp;

	list_for_each_entry_safe(info, temp, &sec->attribs, list) {
		sysfs_remove_bin_file(sec->kobj, &info->bin_attr);
		kfree(info->key);
		kfree(info);
	}
}

static ssize_t vpd_section_read(struct file *filp, struct kobject *kobp,
				struct bin_attribute *bin_attr, char *buf,
				loff_t pos, size_t count)
{
	struct vpd_section *sec = bin_attr->private;

	return memory_read_from_buffer(buf, count, &pos, sec->baseaddr,
				       sec->bin_attr.size);
}

static int vpd_section_create_attribs(struct vpd_section *sec)
{
	s32 consumed;
	int ret;

	consumed = 0;
	do {
		ret = vpd_decode_string(sec->bin_attr.size, sec->baseaddr,
					&consumed, vpd_section_attrib_add, sec);
	} while (ret == VPD_OK);

	return 0;
}

static int vpd_section_init(const char *name, struct vpd_section *sec,
			    phys_addr_t physaddr, size_t size)
{
	int err;

	sec->baseaddr = memremap(physaddr, size, MEMREMAP_WB);
	if (!sec->baseaddr)
		return -ENOMEM;

	sec->name = name;

	/* We want to export the raw partion with name ${name}_raw */
	sec->raw_name = kasprintf(GFP_KERNEL, "%s_raw", name);
	if (!sec->raw_name) {
		err = -ENOMEM;
		goto err_memunmap;
	}

	sysfs_bin_attr_init(&sec->bin_attr);
	sec->bin_attr.attr.name = sec->raw_name;
	sec->bin_attr.attr.mode = 0444;
	sec->bin_attr.size = size;
	sec->bin_attr.read = vpd_section_read;
	sec->bin_attr.private = sec;

	err = sysfs_create_bin_file(vpd_kobj, &sec->bin_attr);
	if (err)
		goto err_free_raw_name;

	sec->kobj = kobject_create_and_add(name, vpd_kobj);
	if (!sec->kobj) {
		err = -EINVAL;
		goto err_sysfs_remove;
	}

	INIT_LIST_HEAD(&sec->attribs);
	vpd_section_create_attribs(sec);

	sec->enabled = true;

	return 0;

err_sysfs_remove:
	sysfs_remove_bin_file(vpd_kobj, &sec->bin_attr);
err_free_raw_name:
	kfree(sec->raw_name);
err_memunmap:
	memunmap(sec->baseaddr);
	return err;
}

static int vpd_section_destroy(struct vpd_section *sec)
{
	if (sec->enabled) {
		vpd_section_attrib_destroy(sec);
		kobject_put(sec->kobj);
		sysfs_remove_bin_file(vpd_kobj, &sec->bin_attr);
		kfree(sec->raw_name);
		memunmap(sec->baseaddr);
	}

	return 0;
}

static int vpd_sections_init(phys_addr_t physaddr)
{
	struct vpd_cbmem __iomem *temp;
	struct vpd_cbmem header;
	int ret = 0;

	temp = memremap(physaddr, sizeof(struct vpd_cbmem), MEMREMAP_WB);
	if (!temp)
		return -ENOMEM;

	memcpy_fromio(&header, temp, sizeof(struct vpd_cbmem));
	memunmap(temp);

	if (header.magic != VPD_CBMEM_MAGIC)
		return -ENODEV;

	if (header.ro_size) {
		ret = vpd_section_init("ro", &ro_vpd,
				       physaddr + sizeof(struct vpd_cbmem),
				       header.ro_size);
		if (ret)
			return ret;
	}

	if (header.rw_size) {
		ret = vpd_section_init("rw", &rw_vpd,
				       physaddr + sizeof(struct vpd_cbmem) +
				       header.ro_size, header.rw_size);
		if (ret)
			return ret;
	}

	return 0;
}

static int vpd_probe(struct platform_device *pdev)
{
	int ret;
	struct lb_cbmem_ref entry;

	ret = coreboot_table_find(CB_TAG_VPD, &entry, sizeof(entry));
	if (ret)
		return ret;

	vpd_kobj = kobject_create_and_add("vpd", firmware_kobj);
	if (!vpd_kobj)
		return -ENOMEM;

	ret = vpd_sections_init(entry.cbmem_addr);
	if (ret) {
		kobject_put(vpd_kobj);
		return ret;
	}

	return 0;
}

static int vpd_remove(struct platform_device *pdev)
{
	vpd_section_destroy(&ro_vpd);
	vpd_section_destroy(&rw_vpd);

	kobject_put(vpd_kobj);

	return 0;
}

static struct platform_driver vpd_driver = {
	.probe = vpd_probe,
	.remove = vpd_remove,
	.driver = {
		.name = "vpd",
	},
};

static struct platform_device *vpd_pdev;

static int __init vpd_platform_init(void)
{
	int ret;

	ret = platform_driver_register(&vpd_driver);
	if (ret)
		return ret;

	vpd_pdev = platform_device_register_simple("vpd", -1, NULL, 0);
	if (IS_ERR(vpd_pdev)) {
		platform_driver_unregister(&vpd_driver);
		return PTR_ERR(vpd_pdev);
	}

	return 0;
}

static void __exit vpd_platform_exit(void)
{
	platform_device_unregister(vpd_pdev);
	platform_driver_unregister(&vpd_driver);
}

module_init(vpd_platform_init);
module_exit(vpd_platform_exit);

MODULE_AUTHOR("Google, Inc.");
MODULE_LICENSE("GPL");