firmware: Google VPD sysfs driver

This patch introduces the Google Vital Product Data driver.

This driver reads Vital Product Data from coreboot tables and then
creates the corresponding sysfs entries under /sys/firmware/vpd to
provide easy access for userspace programs (does not require flashrom).

The sysfs is structured as follow:

 /sys/firmware/vpd
 |-- ro
 |   |-- key1
 |   `-- key2
 |-- ro_raw
 |-- rw
 |   `-- key1
 `-- rw_raw

Where ro_raw and rw_raw contain the raw VPD partition. The files under
ro and rw correspond to the key name in the VPD and the the file content
is the value for the key.
Signed-off-by: Wei-Ning Huang <wnhuang@google.com>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/firmware/google/Kconfig

@@ -64,4 +64,11 @@ config GOOGLE_MEMCONSOLE_COREBOOT
 	  the coreboot table.  If found, this log is exported to userland
 	  in the file /sys/firmware/log.
 
+config GOOGLE_VPD
+	tristate "Vital Product Data"
+	depends on GOOGLE_COREBOOT_TABLE
+	help
+	  This option enables the kernel to expose the content of Google VPD
+	  under /sys/firmware/vpd.
+
 endif # GOOGLE_FIRMWARE

drivers/firmware/google/Makefile

@@ -6,3 +6,6 @@ obj-$(CONFIG_GOOGLE_COREBOOT_TABLE_OF)     += coreboot_table-of.o
 obj-$(CONFIG_GOOGLE_MEMCONSOLE)            += memconsole.o
 obj-$(CONFIG_GOOGLE_MEMCONSOLE_COREBOOT)   += memconsole-coreboot.o
 obj-$(CONFIG_GOOGLE_MEMCONSOLE_X86_LEGACY) += memconsole-x86-legacy.o
+
+vpd-sysfs-y := vpd.o vpd_decode.o
+obj-$(CONFIG_GOOGLE_VPD)		+= vpd-sysfs.o

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);
+	info->key = kzalloc(key_len + 1, GFP_KERNEL);
+	if (!info->key)
+		return -ENOMEM;
+
+	memcpy(info->key, key, key_len);
+
+	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);
+	list_add_tail(&info->list, &sec->attribs);
+
+	ret = sysfs_create_bin_file(sec->kobj, &info->bin_attr);
+	if (ret) {
+		kfree(info->key);
+		return ret;
+	}
+
+	return 0;
+}
+
+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) {
+		kfree(info->key);
+		sysfs_remove_bin_file(sec->kobj, &info->bin_attr);
+		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 ret;
+	int raw_len;
+
+	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 */
+	raw_len = strlen(name) + 5;
+	sec->raw_name = kzalloc(raw_len, GFP_KERNEL);
+	strncpy(sec->raw_name, name, raw_len);
+	strncat(sec->raw_name, "_raw", raw_len);
+
+	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;
+
+	ret = sysfs_create_bin_file(vpd_kobj, &sec->bin_attr);
+	if (ret)
+		goto free_sec;
+
+	sec->kobj = kobject_create_and_add(name, vpd_kobj);
+	if (!sec->kobj) {
+		ret = -EINVAL;
+		goto sysfs_remove;
+	}
+
+	INIT_LIST_HEAD(&sec->attribs);
+	vpd_section_create_attribs(sec);
+
+	sec->enabled = true;
+
+	return 0;
+
+sysfs_remove:
+	sysfs_remove_bin_file(vpd_kobj, &sec->bin_attr);
+
+free_sec:
+	kfree(sec->raw_name);
+	iounmap(sec->baseaddr);
+
+	return ret;
+}
+
+static int vpd_section_destroy(struct vpd_section *sec)
+{
+	if (sec->enabled) {
+		vpd_section_attrib_destroy(sec);
+		kobject_del(sec->kobj);
+		sysfs_remove_bin_file(vpd_kobj, &sec->bin_attr);
+		kfree(sec->raw_name);
+		iounmap(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));
+	iounmap(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;
+
+	return vpd_sections_init(entry.cbmem_addr);
+}
+
+static struct platform_driver vpd_driver = {
+	.probe = vpd_probe,
+	.driver = {
+		.name = "vpd",
+	},
+};
+
+static int __init vpd_platform_init(void)
+{
+	struct platform_device *pdev;
+
+	pdev = platform_device_register_simple("vpd", -1, NULL, 0);
+	if (!pdev)
+		return -ENODEV;
+
+	vpd_kobj = kobject_create_and_add("vpd", firmware_kobj);
+	if (!vpd_kobj)
+		return -ENOMEM;
+
+	memset(&ro_vpd, 0, sizeof(ro_vpd));
+	memset(&rw_vpd, 0, sizeof(rw_vpd));
+
+	platform_driver_register(&vpd_driver);
+
+	return 0;
+}
+
+static void __exit vpd_platform_exit(void)
+{
+	vpd_section_destroy(&ro_vpd);
+	vpd_section_destroy(&rw_vpd);
+	kobject_del(vpd_kobj);
+}
+
+module_init(vpd_platform_init);
+module_exit(vpd_platform_exit);
+
+MODULE_AUTHOR("Google, Inc.");
+MODULE_LICENSE("GPL");