[PATCH v3] firmware: google: Implement cbmem in sysfs driver
From: Jack Rosenthal
Date: Fri Jul 29 2022 - 15:31:47 EST
cbmem entries can be read from coreboot table
0x31 (LB_TAG_CBMEM_ENTRY). This commit exports access to cbmem
entries in sysfs under /sys/firmware/coreboot/cbmem-*.
Link: https://issuetracker.google.com/239604743
Cc: Stephen Boyd <swboyd@xxxxxxxxxxxx>
Cc: Guenter Roeck <groeck@xxxxxxxxxxxx>
Cc: Julius Werner <jwerner@xxxxxxxxxxxx>
Tested-by: Jack Rosenthal <jrosenth@xxxxxxxxxxxx>
Signed-off-by: Jack Rosenthal <jrosenth@xxxxxxxxxxxx>
---
.../ABI/testing/sysfs-firmware-coreboot | 16 +
drivers/firmware/google/Kconfig | 8 +
drivers/firmware/google/Makefile | 3 +
drivers/firmware/google/cbmem.c | 408 ++++++++++++++++++
drivers/firmware/google/coreboot_table.h | 11 +
5 files changed, 446 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-firmware-coreboot
create mode 100644 drivers/firmware/google/cbmem.c
diff --git a/Documentation/ABI/testing/sysfs-firmware-coreboot b/Documentation/ABI/testing/sysfs-firmware-coreboot
new file mode 100644
index 000000000000..c66ef96647e9
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-coreboot
@@ -0,0 +1,16 @@
+What: /sys/firmware/coreboot/
+Date: July 2022
+Contact: Jack Rosenthal <jrosenth@xxxxxxxxxxxx>
+Description:
+ Coreboot-based BIOS firmware provides a variety of information
+ in CBMEM. Each CBMEM entry can be found via Coreboot tables.
+ For each CBMEM entry, the following are exposed:
+
+ address: A hexidecimal value of the memory address the data for
+ the entry begins at.
+ size: The size of the data stored.
+ id: The id corresponding to the entry. A list of ids known to
+ coreboot can be found in the coreboot tree at
+ src/commonlib/bsd/include/commonlib/bsd/cbmem_id.h
+ alias: A common name for the id of the entry.
+ mem: A file exposing the raw memory for the entry.
diff --git a/drivers/firmware/google/Kconfig b/drivers/firmware/google/Kconfig
index 983e07dc022e..bf8316d1cb31 100644
--- a/drivers/firmware/google/Kconfig
+++ b/drivers/firmware/google/Kconfig
@@ -19,6 +19,14 @@ config GOOGLE_SMI
driver provides an interface for reading and writing NVRAM
variables.
+config GOOGLE_CBMEM
+ tristate "CBMEM entries in sysfs"
+ depends on GOOGLE_COREBOOT_TABLE
+ help
+ This option enables the kernel to search for Coreboot CBMEM
+ entries, and expose the memory for each entry in sysfs under
+ /sys/firmware/coreboot.
+
config GOOGLE_COREBOOT_TABLE
tristate "Coreboot Table Access"
depends on HAS_IOMEM && (ACPI || OF)
diff --git a/drivers/firmware/google/Makefile b/drivers/firmware/google/Makefile
index d17caded5d88..8151e323cc43 100644
--- a/drivers/firmware/google/Makefile
+++ b/drivers/firmware/google/Makefile
@@ -7,5 +7,8 @@ obj-$(CONFIG_GOOGLE_MEMCONSOLE) += memconsole.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE_COREBOOT) += memconsole-coreboot.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE_X86_LEGACY) += memconsole-x86-legacy.o
+# Must come after coreboot_table.o, as this driver depends on that bus type.
+obj-$(CONFIG_GOOGLE_CBMEM) += cbmem.o
+
vpd-sysfs-y := vpd.o vpd_decode.o
obj-$(CONFIG_GOOGLE_VPD) += vpd-sysfs.o
diff --git a/drivers/firmware/google/cbmem.c b/drivers/firmware/google/cbmem.c
new file mode 100644
index 000000000000..71c5de17e243
--- /dev/null
+++ b/drivers/firmware/google/cbmem.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * cbmem.c
+ *
+ * Driver for exporting cbmem entries in sysfs.
+ *
+ * Copyright 2022 Google Inc.
+ */
+
+#include <linux/capability.h>
+#include <linux/ctype.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_CBMEM_ENTRY 0x31
+
+/*
+ * This list should be kept in sync with
+ * src/commonlib/bsd/include/commonlib/bsd/cbmem_id.h from coreboot.
+ */
+static const struct {
+ const char *alias;
+ u32 id;
+} cbmem_aliases[] = {
+ { "acpi", 0x41435049 },
+ { "acpi-bert", 0x42455254 },
+ { "acpi-cnvs", 0x434e5653 },
+ { "acpi-gnvs", 0x474e5653 },
+ { "acpi-hest", 0x48455354 },
+ { "acpi-ucsi", 0x55435349 },
+ { "after-car", 0xc4787a93 },
+ { "agesa-runtime", 0x41474553 },
+ { "agesa-mtrr", 0xf08b4b9d },
+ { "amdmct-meminfo", 0x494d454e },
+ { "car-globals", 0xcac4e6a3 },
+ { "cbtable", 0x43425442 },
+ { "cbtable-fwd", 0x43425443 },
+ { "cb-early-dram", 0x4544524d },
+ { "console", 0x434f4e53 },
+ { "cpu-crashlog", 0x4350555f },
+ { "coverage", 0x47434f56 },
+ { "cse-update", 0x43534555 },
+ { "ehci-debug", 0xe4c1deb9 },
+ { "elog", 0x454c4f47 },
+ { "freespace", 0x46524545 },
+ { "fsp-reserved-memory", 0x46535052 },
+ { "fsp-runtime", 0x52505346 },
+ { "gdt", 0x4c474454 },
+ { "hob-pointer", 0x484f4221 },
+ { "igd-opregion", 0x4f444749 },
+ { "imd-root", 0xff4017ff },
+ { "imd-small", 0x53a11439 },
+ { "mdata-hash", 0x6873484d },
+ { "meminfo", 0x494d454d },
+ { "mma-data", 0x4d4d4144 },
+ { "mmc-status", 0x4d4d4353 },
+ { "mptable", 0x534d5054 },
+ { "mrcdata", 0x4d524344 },
+ { "pmc-crashlog", 0x504d435f },
+ { "var-mrcdata", 0x4d524345 },
+ { "mtc", 0xcb31d31c },
+ { "none", 0x00000000 },
+ { "pirq", 0x49525154 },
+ { "power-state", 0x50535454 },
+ { "ram-oops", 0x05430095 },
+ { "ramstage", 0x9a357a9e },
+ { "ramstage-cache", 0x9a3ca54e },
+ { "refcode", 0x04efc0de },
+ { "refcode-cache", 0x4efc0de5 },
+ { "resume", 0x5245534d },
+ { "resume-scratch", 0x52455343 },
+ { "romstage-info", 0x47545352 },
+ { "romstage-ram-stack", 0x90357ac4 },
+ { "root", 0xff4007ff },
+ { "smbios", 0x534d4254 },
+ { "smm-save-space", 0x07e9acee },
+ { "stagex-meta", 0x57a9e000 },
+ { "stagex-cache", 0x57a9e100 },
+ { "stagex-mem", 0x57a9e200 },
+ { "storage-data", 0x53746f72 },
+ { "tcpa-log", 0x54435041 },
+ { "tcpa-tcg-log", 0x54445041 },
+ { "timestamp", 0x54494d45 },
+ { "tpm2-tcg-log", 0x54504d32 },
+ { "tpm-ppi", 0x54505049 },
+ { "vboot-handoff", 0x780074f0 },
+ { "vboot-sel-reg", 0x780074f1 },
+ { "vboot-workbuf", 0x78007343 },
+ { "vpd", 0x56504420 },
+ { "wifi-calibration", 0x57494649 },
+ { "ec-hostevent", 0x63ccbbc3 },
+ { "ext-vbt", 0x69866684 },
+ { "vga-rom0", 0x524f4d30 },
+ { "vga-rom1", 0x524f4d31 },
+ { "vga-rom2", 0x524f4d32 },
+ { "vga-rom3", 0x524f4d33 },
+ { "fmap", 0x464d4150 },
+ { "cbfs-ro-mcache", 0x524d5346 },
+ { "cbfs-rw-mcache", 0x574d5346 },
+ { "fsp-logo", 0x4c4f474f },
+ { "smm-combuffer", 0x53534d32 },
+ { "type-c-info", 0x54595045 },
+ { "mem-chip-info", 0x5048434d },
+};
+
+static const char *get_alias(u32 cbmem_id)
+{
+ for (int i = 0; i < ARRAY_SIZE(cbmem_aliases); i++) {
+ if (cbmem_id == cbmem_aliases[i].id)
+ return cbmem_aliases[i].alias;
+ }
+
+ return NULL;
+}
+
+static struct kobject *coreboot_kobj;
+
+struct cbmem_entry;
+struct cbmem_entry_attr {
+ struct kobj_attribute kobj_attr;
+ struct cbmem_entry *entry;
+};
+
+struct cbmem_entry {
+ char *kobj_name;
+ struct kobject *kobj;
+ struct coreboot_device *dev;
+ struct bin_attribute mem_file;
+ char *mem_file_buf;
+ struct cbmem_entry_attr address_file;
+ struct cbmem_entry_attr size_file;
+ struct cbmem_entry_attr id_file;
+ const char *alias;
+ struct cbmem_entry_attr alias_name_file;
+ char *alias_link_name;
+};
+
+static struct cbmem_entry_attr *to_cbmem_entry_attr(struct kobj_attribute *a)
+{
+ return container_of(a, struct cbmem_entry_attr, kobj_attr);
+}
+
+static ssize_t cbmem_entry_mem_read(struct file *filp, struct kobject *kobp,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t pos, size_t count)
+{
+ struct cbmem_entry *entry = bin_attr->private;
+
+ return memory_read_from_buffer(buf, count, &pos, entry->mem_file_buf,
+ bin_attr->size);
+}
+
+static ssize_t cbmem_entry_mem_write(struct file *filp, struct kobject *kobp,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t pos, size_t count)
+{
+ struct cbmem_entry *entry = bin_attr->private;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ if (pos < 0 || pos >= bin_attr->size)
+ return -EINVAL;
+ if (count > bin_attr->size - pos)
+ count = bin_attr->size - pos;
+
+ memcpy(entry->mem_file_buf + pos, buf, count);
+ return count;
+}
+
+static ssize_t cbmem_entry_alias_name_show(struct kobject *kobj,
+ struct kobj_attribute *a, char *buf)
+{
+ struct cbmem_entry_attr *entry_attr = to_cbmem_entry_attr(a);
+
+ return sysfs_emit(buf, "%s\n", entry_attr->entry->alias);
+}
+
+static int cbmem_entry_setup_alias(struct cbmem_entry *entry)
+{
+ int ret;
+
+ entry->alias = get_alias(entry->dev->cbmem_entry.id);
+ if (!entry->alias)
+ return 0;
+
+ sysfs_attr_init(&entry->alias_name_file.kobj_attr.attr);
+ entry->alias_name_file.kobj_attr.attr.name = "alias";
+ entry->alias_name_file.kobj_attr.attr.mode = 0444;
+ entry->alias_name_file.kobj_attr.show = cbmem_entry_alias_name_show;
+ entry->alias_name_file.entry = entry;
+ ret = sysfs_create_file(entry->kobj,
+ &entry->alias_name_file.kobj_attr.attr);
+ if (ret)
+ return ret;
+
+ entry->alias_link_name =
+ kasprintf(GFP_KERNEL, "cbmem-%s", entry->alias);
+ if (!entry->alias_link_name) {
+ ret = -ENOMEM;
+ goto free_alias_name_file;
+ }
+
+ ret = sysfs_create_link(coreboot_kobj, entry->kobj,
+ entry->alias_link_name);
+ if (ret)
+ goto free_alias_link_name;
+
+ return 0;
+
+free_alias_link_name:
+ kfree(entry->alias_link_name);
+free_alias_name_file:
+ sysfs_remove_file(entry->kobj, &entry->alias_name_file.kobj_attr.attr);
+
+ return ret;
+}
+
+static ssize_t cbmem_entry_address_show(struct kobject *kobj,
+ struct kobj_attribute *a, char *buf)
+{
+ struct cbmem_entry_attr *entry_attr = to_cbmem_entry_attr(a);
+
+ return sysfs_emit(buf, "0x%llx\n",
+ entry_attr->entry->dev->cbmem_entry.address);
+}
+
+static ssize_t cbmem_entry_size_show(struct kobject *kobj,
+ struct kobj_attribute *a, char *buf)
+{
+ struct cbmem_entry_attr *entry_attr = to_cbmem_entry_attr(a);
+
+ return sysfs_emit(buf, "0x%x\n",
+ entry_attr->entry->dev->cbmem_entry.entry_size);
+}
+
+static ssize_t cbmem_entry_id_show(struct kobject *kobj,
+ struct kobj_attribute *a, char *buf)
+{
+ struct cbmem_entry_attr *entry_attr = to_cbmem_entry_attr(a);
+
+ return sysfs_emit(buf, "0x%x\n",
+ entry_attr->entry->dev->cbmem_entry.id);
+}
+
+static int cbmem_entry_setup(struct cbmem_entry *entry)
+{
+ int ret;
+
+ entry->mem_file_buf = memremap(entry->dev->cbmem_entry.address,
+ entry->dev->cbmem_entry.entry_size,
+ MEMREMAP_WB);
+ if (!entry->mem_file_buf)
+ return -ENOMEM;
+
+ entry->kobj_name =
+ kasprintf(GFP_KERNEL, "cbmem-%08x", entry->dev->cbmem_entry.id);
+ if (!entry->kobj_name) {
+ ret = -ENOMEM;
+ goto memunmap;
+ }
+
+ entry->kobj = kobject_create_and_add(entry->kobj_name, coreboot_kobj);
+ if (!entry->kobj) {
+ ret = -ENOMEM;
+ goto free_name;
+ }
+
+ sysfs_bin_attr_init(&entry->mem_file);
+ entry->mem_file.attr.name = "mem";
+ entry->mem_file.attr.mode = 0664;
+ entry->mem_file.size = entry->dev->cbmem_entry.entry_size;
+ entry->mem_file.read = cbmem_entry_mem_read;
+ entry->mem_file.write = cbmem_entry_mem_write;
+ entry->mem_file.private = entry;
+ ret = sysfs_create_bin_file(entry->kobj, &entry->mem_file);
+ if (ret)
+ goto free_kobj;
+
+ sysfs_attr_init(&entry->address_file.kobj_attr.attr);
+ entry->address_file.kobj_attr.attr.name = "address";
+ entry->address_file.kobj_attr.attr.mode = 0444;
+ entry->address_file.kobj_attr.show = cbmem_entry_address_show;
+ entry->address_file.entry = entry;
+ ret = sysfs_create_file(entry->kobj,
+ &entry->address_file.kobj_attr.attr);
+ if (ret)
+ goto free_mem_file;
+
+ sysfs_attr_init(&entry->size_file.kobj_attr.attr);
+ entry->size_file.kobj_attr.attr.name = "size";
+ entry->size_file.kobj_attr.attr.mode = 0444;
+ entry->size_file.kobj_attr.show = cbmem_entry_size_show;
+ entry->size_file.entry = entry;
+ ret = sysfs_create_file(entry->kobj, &entry->size_file.kobj_attr.attr);
+ if (ret)
+ goto free_address_file;
+
+ sysfs_attr_init(&entry->id_file.kobj_attr.attr);
+ entry->id_file.kobj_attr.attr.name = "id";
+ entry->id_file.kobj_attr.attr.mode = 0444;
+ entry->id_file.kobj_attr.show = cbmem_entry_id_show;
+ entry->id_file.entry = entry;
+ ret = sysfs_create_file(entry->kobj, &entry->id_file.kobj_attr.attr);
+ if (ret)
+ goto free_size_file;
+
+ ret = cbmem_entry_setup_alias(entry);
+ if (ret)
+ goto free_id_file;
+
+ return 0;
+
+free_id_file:
+ sysfs_remove_file(entry->kobj, &entry->id_file.kobj_attr.attr);
+free_size_file:
+ sysfs_remove_file(entry->kobj, &entry->size_file.kobj_attr.attr);
+free_address_file:
+ sysfs_remove_file(entry->kobj, &entry->address_file.kobj_attr.attr);
+free_mem_file:
+ sysfs_remove_bin_file(entry->kobj, &entry->mem_file);
+free_kobj:
+ kobject_put(entry->kobj);
+free_name:
+ kfree(entry->kobj_name);
+memunmap:
+ memunmap(entry->mem_file_buf);
+ return ret;
+}
+
+static int cbmem_entry_probe(struct coreboot_device *dev)
+{
+ int ret;
+ struct cbmem_entry *entry;
+
+ entry = kzalloc(sizeof(*entry), GFP_KERNEL);
+ if (!entry)
+ return -ENOMEM;
+
+ dev_set_drvdata(&dev->dev, entry);
+ entry->dev = dev;
+ ret = cbmem_entry_setup(entry);
+ if (ret) {
+ kfree(entry);
+ return ret;
+ }
+
+ return 0;
+}
+
+static void cbmem_entry_remove(struct coreboot_device *dev)
+{
+ struct cbmem_entry *entry = dev_get_drvdata(&dev->dev);
+
+ sysfs_remove_file(entry->kobj, &entry->alias_name_file.kobj_attr.attr);
+ sysfs_remove_bin_file(entry->kobj, &entry->mem_file);
+ if (entry->alias)
+ sysfs_remove_link(entry->kobj, entry->alias_link_name);
+ kfree(entry->alias_link_name);
+ memunmap(entry->mem_file_buf);
+ kobject_put(entry->kobj);
+ kfree(entry->kobj_name);
+ kfree(entry);
+}
+
+static struct coreboot_driver cbmem_entry_driver = {
+ .probe = cbmem_entry_probe,
+ .remove = cbmem_entry_remove,
+ .drv = {
+ .name = "cbmem",
+ },
+ .tag = LB_TAG_CBMEM_ENTRY,
+};
+
+static int __init cbmem_init(void)
+{
+ int ret;
+
+ coreboot_kobj = kobject_create_and_add("coreboot", firmware_kobj);
+ if (!coreboot_kobj)
+ return -ENOMEM;
+
+ ret = coreboot_driver_register(&cbmem_entry_driver);
+ if (ret) {
+ kobject_put(coreboot_kobj);
+ return ret;
+ }
+
+ return 0;
+}
+module_init(cbmem_init);
+
+static void __exit cbmem_exit(void)
+{
+ kobject_put(coreboot_kobj);
+ coreboot_driver_unregister(&cbmem_entry_driver);
+}
+module_exit(cbmem_exit);
+
+MODULE_AUTHOR("Google, Inc.");
+MODULE_LICENSE("GPL");
diff --git a/drivers/firmware/google/coreboot_table.h b/drivers/firmware/google/coreboot_table.h
index beb778674acd..6c03a8852d1b 100644
--- a/drivers/firmware/google/coreboot_table.h
+++ b/drivers/firmware/google/coreboot_table.h
@@ -39,6 +39,16 @@ struct lb_cbmem_ref {
u64 cbmem_addr;
};
+/* Corresponds to LB_TAG_CBMEM_ENTRY. */
+struct lb_cbmem_entry {
+ u32 tag;
+ u32 size;
+
+ u64 address;
+ u32 entry_size;
+ u32 id;
+};
+
/* Describes framebuffer setup by coreboot */
struct lb_framebuffer {
u32 tag;
@@ -65,6 +75,7 @@ struct coreboot_device {
union {
struct coreboot_table_entry entry;
struct lb_cbmem_ref cbmem_ref;
+ struct lb_cbmem_entry cbmem_entry;
struct lb_framebuffer framebuffer;
};
};
--
2.37.1.455.g008518b4e5-goog