@@ -67,6 +67,14 @@ config GOOGLE_MEMCONSOLE_COREBOOT
the coreboot table. If found, this log is exported to userland
in the file /sys/firmware/log.
+config GOOGLE_VBOOT_SYSFS
+ tristate "Verified Boot in sysfs"
+ depends on GOOGLE_COREBOOT_TABLE
+ help
+ This option enables the kernel to search for the Verified Boot
+ workbuf coreboot table. If found, the workbuf is exported
+ to userland in /sys/firmware/vboot.
+
config GOOGLE_VPD
tristate "Vital Product Data"
depends on GOOGLE_COREBOOT_TABLE
@@ -6,6 +6,7 @@ obj-$(CONFIG_GOOGLE_FRAMEBUFFER_COREBOOT) += framebuffer-coreboot.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE) += memconsole.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE_COREBOOT) += memconsole-coreboot.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE_X86_LEGACY) += memconsole-x86-legacy.o
+obj-$(CONFIG_GOOGLE_VBOOT_SYSFS) += vboot.o
vpd-sysfs-y := vpd.o vpd_decode.o
obj-$(CONFIG_GOOGLE_VPD) += vpd-sysfs.o
new file mode 100644
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * vboot.c
+ *
+ * Driver for exporting the vboot workbuf to sysfs.
+ *
+ * Copyright 2022 Google Inc.
+ */
+
+#include <linux/capability.h>
+#include <linux/ctype.h>
+#include <linux/dev_printk.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+
+#include "coreboot_table.h"
+
+#define LB_TAG_VBOOT_WORKBUF 0x34
+
+/* "V2SD" = vb2_shared_data.magic */
+#define VB2_SHARED_DATA_MAGIC 0x44533256
+#define VB2_CONTEXT_MAX_SIZE_V2 192
+#define VB2_CONTEXT_MAX_SIZE_V3 384
+
+struct workbuf {
+ u32 magic;
+ u16 version_major;
+ u16 version_minor;
+ union {
+ /*
+ * V1 not supported as workbuf and vboot context
+ * located separately.
+ */
+ struct {
+ u8 context_padding[VB2_CONTEXT_MAX_SIZE_V2];
+ u32 workbuf_size;
+ } v2;
+ struct {
+ u8 context_padding[VB2_CONTEXT_MAX_SIZE_V3];
+ u32 workbuf_size;
+ } v3;
+ };
+} __packed;
+
+static struct kobject *vboot_kobj;
+
+static struct {
+ u8 *buf;
+ u32 size;
+ struct bin_attribute bin_attr;
+} workbuf_info;
+
+static ssize_t workbuf_read(struct file *filp, struct kobject *kobp,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t pos, size_t count)
+{
+ return memory_read_from_buffer(buf, count, &pos, workbuf_info.buf,
+ workbuf_info.size);
+}
+
+static ssize_t workbuf_write(struct file *filp, struct kobject *kobp,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t pos, size_t count)
+{
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ if (pos < 0 || pos >= workbuf_info.size)
+ return -EINVAL;
+ if (count > workbuf_info.size - pos)
+ count = workbuf_info.size - pos;
+
+ memcpy(workbuf_info.buf + pos, buf, count);
+ return count;
+}
+
+/*
+ * This function should only be called during initialization -- prior
+ * to workbuf being added to sysfs. The workbuf can be manipulated
+ * via sysfs, and thus, we should not trust the size in the workbuf
+ * after we've given the user write access to the buffer.
+ */
+static int get_workbuf_size(struct coreboot_device *dev, u32 *size_out)
+{
+ int ret = 0;
+ struct workbuf *workbuf;
+
+ workbuf = memremap(dev->cbmem_ref.cbmem_addr, sizeof(struct workbuf),
+ MEMREMAP_WB);
+
+ if (workbuf->magic != VB2_SHARED_DATA_MAGIC) {
+ dev_err(&dev->dev, "%s: workbuf has invalid magic number\n",
+ __func__);
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ switch (workbuf->version_major) {
+ case 2:
+ *size_out = workbuf->v2.workbuf_size;
+ break;
+ case 3:
+ *size_out = workbuf->v3.workbuf_size;
+ break;
+ default:
+ dev_err(&dev->dev, "%s: workbuf v%hu.%hu not supported",
+ __func__, workbuf->version_major,
+ workbuf->version_minor);
+ ret = -EINVAL;
+ goto exit;
+ }
+
+exit:
+ memunmap(workbuf);
+ return ret;
+}
+
+static int vboot_probe(struct coreboot_device *dev)
+{
+ int ret;
+
+ vboot_kobj = kobject_create_and_add("vboot", firmware_kobj);
+ if (!vboot_kobj)
+ return -ENOMEM;
+
+ ret = get_workbuf_size(dev, &workbuf_info.size);
+ if (ret)
+ goto exit;
+
+ workbuf_info.buf = memremap(dev->cbmem_ref.cbmem_addr,
+ workbuf_info.size, MEMREMAP_WB);
+
+ sysfs_bin_attr_init(&workbuf_info.bin_attr);
+ workbuf_info.bin_attr.attr.name = "workbuf";
+ workbuf_info.bin_attr.attr.mode = 0666;
+ workbuf_info.bin_attr.size = workbuf_info.size;
+ workbuf_info.bin_attr.read = workbuf_read;
+ workbuf_info.bin_attr.write = workbuf_write;
+
+ ret = sysfs_create_bin_file(vboot_kobj, &workbuf_info.bin_attr);
+
+exit:
+ if (ret) {
+ kobject_put(vboot_kobj);
+ return ret;
+ }
+
+ return 0;
+}
+
+static void vboot_remove(struct coreboot_device *dev)
+{
+ sysfs_remove_bin_file(vboot_kobj, &workbuf_info.bin_attr);
+ kobject_put(vboot_kobj);
+ memunmap(&workbuf_info.buf);
+}
+
+static struct coreboot_driver vboot_driver = {
+ .probe = vboot_probe,
+ .remove = vboot_remove,
+ .drv = {
+ .name = "vboot",
+ },
+ .tag = LB_TAG_VBOOT_WORKBUF,
+};
+module_coreboot_driver(vboot_driver);
+
+MODULE_AUTHOR("Google, Inc.");
+MODULE_LICENSE("GPL");