[PATCH 1/2] firmware: coreboot: Export the binary FMAP

patrick.rudolph
2019-10-08T11:54:04Z

From: Patrick Rudolph <patrick.rudolph@9elements.com>

Expose coreboot's binary FMAP[1] to /sys/firmware/fmap.

coreboot copies the FMAP to a CBMEM buffer at boot since CB:35377[2],
allowing an architecture independ way of exposing the FMAP to userspace.

Will be used by fwupd[3] to determine the current firmware layout.

[1]: https://doc.coreboot.org/lib/flashmap.html
[2]: https://review.coreboot.org/c/coreboot/+/35377
[3]: https://fwupd.org/

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
drivers/firmware/google/Kconfig | 8 ++
drivers/firmware/google/Makefile | 1 +
drivers/firmware/google/fmap-coreboot.c | 156 ++++++++++++++++++++++
drivers/firmware/google/fmap-coreboot.h | 13 ++
drivers/firmware/google/fmap_serialized.h | 59 ++++++++
5 files changed, 237 insertions(+)
create mode 100644 drivers/firmware/google/fmap-coreboot.c
create mode 100644 drivers/firmware/google/fmap-coreboot.h
create mode 100644 drivers/firmware/google/fmap_serialized.h

diff --git a/drivers/firmware/google/Kconfig b/drivers/firmware/google/Kconfig
index a3a6ca659ffa..5fbbd7b8fef6 100644
--- a/drivers/firmware/google/Kconfig
+++ b/drivers/firmware/google/Kconfig
@@ -74,4 +74,12 @@ config GOOGLE_VPD
This option enables the kernel to expose the content of Google VPD
under /sys/firmware/vpd.

+config GOOGLE_FMAP
+ tristate "Coreboot FMAP access"
+ depends on GOOGLE_COREBOOT_TABLE
+ help
+ This option enables the kernel to search for a Google FMAP in
+ the coreboot table. If found, this binary file is exported to userland
+ in the file /sys/firmware/fmap.
+
endif # GOOGLE_FIRMWARE
diff --git a/drivers/firmware/google/Makefile b/drivers/firmware/google/Makefile
index d17caded5d88..6d31fe167700 100644
--- a/drivers/firmware/google/Makefile
+++ b/drivers/firmware/google/Makefile
@@ -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_FMAP) += fmap-coreboot.o

vpd-sysfs-y := vpd.o vpd_decode.o
obj-$(CONFIG_GOOGLE_VPD) += vpd-sysfs.o
diff --git a/drivers/firmware/google/fmap-coreboot.c b/drivers/firmware/google/fmap-coreboot.c
new file mode 100644
index 000000000000..14050030ebc6
--- /dev/null
+++ b/drivers/firmware/google/fmap-coreboot.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * fmap-coreboot.c
+ *
+ * Exports the binary FMAP through coreboot table.
+ *
+ * Copyright 2012-2013 David Herrmann <dh.herrmann@gmail.com>
+ * Copyright 2017 Google Inc.
+ * Copyright 2019 9elements Agency GmbH <patrick.rudolph@9elements.com>
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/string.h>
+#include <linux/io.h>
+
+#include "coreboot_table.h"
+#include "fmap_serialized.h"
+
+#define CB_TAG_FMAP 0x37
+
+static void *fmap;
+static u32 fmap_size;
+
+/*
+ * Convert FMAP region to name.
+ * The caller has to free the string.
+ * Return NULL if no containing region was found.
+ */
+const char *coreboot_fmap_region_to_name(const u32 start, const u32 size)
+{
+ const char *name = NULL;
+ struct fmap *iter;
+ u32 size_old = ~0;
+ int i;
+
+ iter = fmap;
+ /* Find smallest containing region */
+ for (i = 0; i < iter->nareas && fmap; i++) {
+ if (iter->areas[i].offset <= start &&
+ iter->areas[i].size >= size &&
+ iter->areas[i].size <= size_old) {
+ size_old = iter->areas[i].size;
+ name = iter->areas[i].name;
+ }
+ }
+
+ if (name)
+ return kstrdup(name, GFP_KERNEL);
+ return NULL;
+}
+EXPORT_SYMBOL(coreboot_fmap_region_to_name);
+
+static ssize_t fmap_read(struct file *filp, struct kobject *kobp,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t pos, size_t count)
+{
+ if (!fmap)
+ return -ENODEV;
+
+ return memory_read_from_buffer(buf, count, &pos, fmap, fmap_size);
+}
+
+static int fmap_probe(struct coreboot_device *dev)
+{
+ struct lb_cbmem_ref *cbmem_ref = &dev->cbmem_ref;
+ struct fmap *header;
+
+ if (!cbmem_ref)
+ return -ENODEV;
+
+ header = memremap(cbmem_ref->cbmem_addr, sizeof(*header), MEMREMAP_WB);
+ if (!header) {
+ pr_warn("coreboot: Failed to remap FMAP\n");
+ return -ENOMEM;
+ }
+
+ /* Validate FMAP signature */
+ if (memcmp(header->signature, FMAP_SIGNATURE,
+ sizeof(header->signature))) {
+ pr_warn("coreboot: FMAP signature mismatch\n");
+ memunmap(header);
+ return -ENODEV;
+ }
+
+ /* Validate FMAP version */
+ if (header->ver_major != FMAP_VER_MAJOR) {
+ pr_warn("coreboot: FMAP version not supported\n");
+ memunmap(header);
+ return -ENODEV;
+ }
+
+ pr_info("coreboot: Got valid FMAP v%u.%u for 0x%x byte ROM\n",
+ header->ver_major, header->ver_minor, header->size);
+
+ fmap_size = sizeof(*header) + header->nareas * sizeof(struct fmap_area);
+ memunmap(header);
+
+ fmap = devm_memremap(&dev->dev, cbmem_ref->cbmem_addr, fmap_size,
+ MEMREMAP_WB);
+ if (!fmap) {
+ pr_warn("coreboot: Failed to remap FMAP\n");
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static int fmap_remove(struct coreboot_device *dev)
+{
+ struct platform_device *pdev = dev_get_drvdata(&dev->dev);
+
+ platform_device_unregister(pdev);
+
+ return 0;
+}
+
+static struct coreboot_driver fmap_driver = {
+ .probe = fmap_probe,
+ .remove = fmap_remove,
+ .drv = {
+ .name = "fmap",
+ },
+ .tag = CB_TAG_FMAP,
+};
+
+static struct bin_attribute fmap_bin_attr = {
+ .attr = {.name = "fmap", .mode = 0444},
+ .read = fmap_read,
+};
+
+static int __init coreboot_fmap_init(void)
+{
+ int err;
+
+ err = sysfs_create_bin_file(firmware_kobj, &fmap_bin_attr);
+ if (err)
+ return err;
+
+ return coreboot_driver_register(&fmap_driver);
+}
+
+static void coreboot_fmap_exit(void)
+{
+ coreboot_driver_unregister(&fmap_driver);
+ sysfs_remove_bin_file(firmware_kobj, &fmap_bin_attr);
+}
+
+module_init(coreboot_fmap_init);
+module_exit(coreboot_fmap_exit);
+
+MODULE_AUTHOR("9elements Agency GmbH");
+MODULE_LICENSE("GPL");
diff --git a/drivers/firmware/google/fmap-coreboot.h b/drivers/firmware/google/fmap-coreboot.h
new file mode 100644
index 000000000000..7107a01af0e3
--- /dev/null
+++ b/drivers/firmware/google/fmap-coreboot.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * bootmedia-coreboot.h
+ *
+ * Copyright 2019 9elements Agency GmbH <patrick.rudolph@9elements.com>
+ */
+
+#ifndef __FMAP_COREBOOT_H
+#define __FMAP_COREBOOT_H
+
+const char *coreboot_fmap_region_to_name(const u32 start, const u32 size);
+
+#endif /* __FMAP_COREBOOT_H */
diff --git a/drivers/firmware/google/fmap_serialized.h b/drivers/firmware/google/fmap_serialized.h
new file mode 100644
index 000000000000..a001e47fa244
--- /dev/null
+++ b/drivers/firmware/google/fmap_serialized.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2010, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ */
+
+#ifndef FLASHMAP_SERIALIZED_H__
+#define FLASHMAP_SERIALIZED_H__
+
+#define FMAP_SIGNATURE "__FMAP__"
+#define FMAP_VER_MAJOR 1 /* this header's FMAP major version */
+#define FMAP_VER_MINOR 1 /* this header's FMAP minor version */
+#define FMAP_STRLEN 32 /* maximum length for strings,
+ * including null-terminator
+ */
+
+enum fmap_flags {
+ FMAP_AREA_STATIC = 1 << 0,
+ FMAP_AREA_COMPRESSED = 1 << 1,
+ FMAP_AREA_RO = 1 << 2,
+ FMAP_AREA_PRESERVE = 1 << 3,
+};
+
+/* Mapping of volatile and static regions in firmware binary */
+struct fmap_area {
+ u32 offset; /* offset relative to base */
+ u32 size; /* size in bytes */
+ u8 name[FMAP_STRLEN]; /* descriptive name */
+ u16 flags; /* flags for this area */
+} __packed;
+
+struct fmap {
+ u8 signature[8]; /* "__FMAP__" (0x5F5F464D41505F5F) */
+ u8 ver_major; /* major version */
+ u8 ver_minor; /* minor version */
+ u64 base; /* address of the firmware binary */
+ u32 size; /* size of firmware binary in bytes */
+ u8 name[FMAP_STRLEN]; /* name of this firmware binary */
+ u16 nareas; /* number of areas described by
+ * fmap_areas[] below
+ */
+ struct fmap_area areas[];
+} __packed;
+
+#endif /* FLASHMAP_SERIALIZED_H__ */
--
2.21.0