* [PATCH v9 4/4] firmware: coreboot: Add CFR firmware attributes driver
2026-07-27 19:51 [PATCH v9 0/4] firmware: Add coreboot CFR firmware attributes driver Sean Rhodes
` (2 preceding siblings ...)
2026-07-27 19:51 ` [PATCH v9 3/4] firmware: Rename google firmware directory to coreboot Sean Rhodes
@ 2026-07-27 19:51 ` Sean Rhodes
3 siblings, 0 replies; 5+ messages in thread
From: Sean Rhodes @ 2026-07-27 19:51 UTC (permalink / raw)
To: tzungbi
Cc: Corentin Chary, Luke D. Jones, Denis Benato, Hans de Goede,
Ilpo Järvinen, Prasanth Ksr, Jorge Lopez, Mark Pearson,
Derek J. Clark, Joshua Grisham, platform-driver-x86, linux-kernel,
Dell.Client.Kernel, Sean Rhodes, Michael S. Tsirkin,
Florian Fainelli, Huacai Chen, Chen-Yu Tsai, Brian Norris,
Julius Werner, Thomas Zimmermann, Javier Martinez Canillas,
Takashi Sakamoto, Bjorn Helgaas, Danilo Krummrich,
Uwe Kleine-König (The Capable Hub),
Titouan Ameline de Cadeville, Kees Cook, chrome-platform
coreboot can publish a CFR tree in its coreboot table to describe
firmware setup options. Add a firmware-attributes driver for that table
entry under the coreboot firmware driver directory.
The driver exposes runtime EFI variable-backed boolean, enum and integer
settings through the firmware-attributes ABI. It only registers settings
with readable runtime EFI variables, skips suppressed, volatile,
dependency-gated and non-runtime options, and keeps read-only or inactive
options read-only in sysfs.
For settings with an APM_CNT runtime-apply record, write the EFI variable
and ask firmware to apply the setting immediately on x86. If firmware
reports a failure, restore the old EFI variable value. Settings without a
runtime apply hook, or non-x86 builds, keep the EFI variable update and
set pending_reboot.
Tested on a Star Labs Byte with firmware 26.07 and the driver built as a
module against Linux 6.17: runtime APM_CNT apply was verified with
power_led, and reboot-needed behavior was verified with debug_level.
Link: https://doc.coreboot.org/drivers/cfr.html
Link: https://doc.coreboot.org/drivers/cfr_internal.html
Signed-off-by: Sean Rhodes <sean@starlabs.systems>
---
MAINTAINERS | 6 +
drivers/firmware/coreboot/Kconfig | 14 +
drivers/firmware/coreboot/Makefile | 1 +
drivers/firmware/coreboot/coreboot-cfr.c | 1193 ++++++++++++++++++++++
4 files changed, 1214 insertions(+)
create mode 100644 drivers/firmware/coreboot/coreboot-cfr.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 8c2634a8dc13..a32e4405d20e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6666,6 +6666,12 @@ F: tools/testing/selftests/cgroup/test_hugetlb_memcg.c
F: tools/testing/selftests/cgroup/test_kmem.c
F: tools/testing/selftests/cgroup/test_memcontrol.c
+COREBOOT CFR FIRMWARE ATTRIBUTES DRIVER
+M: Sean Rhodes <sean@starlabs.systems>
+L: chrome-platform@lists.linux.dev
+S: Maintained
+F: drivers/firmware/coreboot/coreboot-cfr.c
+
CORETEMP HARDWARE MONITORING DRIVER
L: linux-hwmon@vger.kernel.org
S: Orphan
diff --git a/drivers/firmware/coreboot/Kconfig b/drivers/firmware/coreboot/Kconfig
index b248bafe8b6b..5c37bdc9c9fd 100644
--- a/drivers/firmware/coreboot/Kconfig
+++ b/drivers/firmware/coreboot/Kconfig
@@ -44,6 +44,20 @@ config GOOGLE_COREBOOT_TABLE
device tree node /firmware/coreboot.
If unsure say N.
+config COREBOOT_CFR
+ tristate "coreboot CFR firmware attributes"
+ depends on EFI
+ depends on GOOGLE_COREBOOT_TABLE
+ select CRC32
+ select FW_ATTR_CLASS
+ help
+ This driver parses the coreboot CFR table and exposes runtime EFI
+ variable-backed options through the firmware-attributes sysfs
+ interface.
+
+ If you have a system running coreboot with CFR runtime
+ configuration support, say Y or M here.
+
config GOOGLE_MEMCONSOLE
tristate
depends on GOOGLE_MEMCONSOLE_X86_LEGACY || GOOGLE_MEMCONSOLE_COREBOOT
diff --git a/drivers/firmware/coreboot/Makefile b/drivers/firmware/coreboot/Makefile
index 8151e323cc43..1b9d0c0e7593 100644
--- a/drivers/firmware/coreboot/Makefile
+++ b/drivers/firmware/coreboot/Makefile
@@ -2,6 +2,7 @@
obj-$(CONFIG_GOOGLE_SMI) += gsmi.o
obj-$(CONFIG_GOOGLE_COREBOOT_TABLE) += coreboot_table.o
+obj-$(CONFIG_COREBOOT_CFR) += coreboot-cfr.o
obj-$(CONFIG_GOOGLE_FRAMEBUFFER_COREBOOT) += framebuffer-coreboot.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE) += memconsole.o
obj-$(CONFIG_GOOGLE_MEMCONSOLE_COREBOOT) += memconsole-coreboot.o
diff --git a/drivers/firmware/coreboot/coreboot-cfr.c b/drivers/firmware/coreboot/coreboot-cfr.c
new file mode 100644
index 000000000000..21b06aa36311
--- /dev/null
+++ b/drivers/firmware/coreboot/coreboot-cfr.c
@@ -0,0 +1,1193 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * coreboot CFR firmware attributes driver.
+ *
+ * Parses LB_TAG_CFR_ROOT records from the coreboot table and exposes
+ * runtime EFI variable-backed options through the firmware-attributes class.
+ */
+
+#include <linux/array_size.h>
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/compiler_attributes.h>
+#include <linux/container_of.h>
+#include <linux/crc32.h>
+#include <linux/ctype.h>
+#include <linux/device.h>
+#include <linux/device-id/coreboot.h>
+#include <linux/efi.h>
+#include <linux/err.h>
+#include <linux/firmware_attributes.h>
+#include <linux/io.h>
+#include <linux/kdev_t.h>
+#include <linux/kobject.h>
+#include <linux/kstrtox.h>
+#include <linux/limits.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/types.h>
+
+#include "coreboot_table.h"
+
+#define DRIVER_NAME "coreboot-cfr"
+
+#define LB_TAG_CFR_ROOT 0x47
+#define CFR_VERSION 0
+
+enum cfr_tags {
+ CFR_TAG_OPTION_FORM = 1,
+ CFR_TAG_ENUM_VALUE = 2,
+ CFR_TAG_OPTION_ENUM = 3,
+ CFR_TAG_OPTION_NUMBER = 4,
+ CFR_TAG_OPTION_BOOL = 5,
+ CFR_TAG_VARCHAR_OPT_NAME = 7,
+ CFR_TAG_VARCHAR_UI_NAME = 8,
+ CFR_TAG_RUNTIME_APPLY = 13,
+};
+
+enum cfr_option_flags {
+ CFR_OPTFLAG_READONLY = BIT(0),
+ CFR_OPTFLAG_INACTIVE = BIT(1),
+ CFR_OPTFLAG_SUPPRESS = BIT(2),
+ CFR_OPTFLAG_VOLATILE = BIT(3),
+ CFR_OPTFLAG_RUNTIME = BIT(4),
+};
+
+enum cfr_runtime_apply_method {
+ CFR_RUNTIME_APPLY_NONE = 0,
+ CFR_RUNTIME_APPLY_APM_CNT = 1,
+};
+
+struct lb_cfr {
+ u32 tag;
+ u32 size;
+ u32 version;
+ u32 checksum;
+} __packed;
+
+struct lb_cfr_varbinary {
+ u32 tag;
+ u32 size;
+ u32 data_length;
+} __packed;
+
+struct lb_cfr_enum_value {
+ u32 tag;
+ u32 size;
+ u32 value;
+} __packed;
+
+struct lb_cfr_runtime_apply {
+ u32 tag;
+ u32 size;
+ u32 method;
+ u32 id;
+} __packed;
+
+struct lb_cfr_numeric_option {
+ u32 tag;
+ u32 size;
+ cb_u64 object_id;
+ cb_u64 dependency_id;
+ u32 flags;
+ u32 default_value;
+ u32 min;
+ u32 max;
+ u32 step;
+ u32 display_flags;
+} __packed;
+
+struct lb_cfr_option_form {
+ u32 tag;
+ u32 size;
+ cb_u64 object_id;
+ cb_u64 dependency_id;
+ u32 flags;
+} __packed;
+
+#define COREBOOT_CFR_OPT_SKIP_FLAGS \
+ (CFR_OPTFLAG_SUPPRESS | CFR_OPTFLAG_VOLATILE)
+
+#define COREBOOT_CFR_OPT_READ_ONLY_FLAGS \
+ (CFR_OPTFLAG_READONLY | CFR_OPTFLAG_INACTIVE)
+
+#define COREBOOT_CFR_EFI_ATTRS \
+ (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS | \
+ EFI_VARIABLE_RUNTIME_ACCESS)
+
+#define COREBOOT_CFR_APM_CNT_PORT 0xb2
+#define COREBOOT_CFR_APM_STS_PORT 0xb3
+#define COREBOOT_CFR_APM_APPLY_CMD 0xe3
+#define COREBOOT_CFR_MAX_FORM_DEPTH 16
+
+static efi_guid_t coreboot_cfr_guid = EFI_GUID(0xceae4c1d, 0x335b, 0x4685,
+ 0xa4, 0xa0, 0xfc, 0x4a,
+ 0x94, 0xee, 0xa0, 0x85);
+
+enum coreboot_cfr_setting_type {
+ COREBOOT_CFR_SETTING_ENUM,
+ COREBOOT_CFR_SETTING_NUMBER,
+ COREBOOT_CFR_SETTING_BOOL,
+};
+
+struct coreboot_cfr_enum {
+ char *label;
+ u32 value;
+};
+
+struct coreboot_cfr_setting {
+ struct kobject kobj;
+ struct list_head node;
+ struct coreboot_cfr_drvdata *drvdata;
+ enum coreboot_cfr_setting_type type;
+ char *name;
+ char *display_name;
+ struct coreboot_cfr_enum *values;
+ unsigned int n_values;
+ u32 default_value;
+ u32 min;
+ u32 max;
+ u32 step;
+ u32 runtime_apply_method;
+ u32 runtime_apply_id;
+ bool read_only;
+};
+
+struct coreboot_cfr_drvdata {
+ struct device *class_dev;
+ struct kset *attrs_kset;
+ struct list_head settings;
+ /* Serializes EFI variable writes and the matching runtime apply hook. */
+ struct mutex lock;
+ bool efi_writes_supported;
+ bool pending_reboot;
+};
+
+struct coreboot_cfr_iterator {
+ const u8 *cursor;
+ size_t remaining;
+};
+
+static struct coreboot_cfr_setting *to_coreboot_cfr_setting(struct kobject *kobj)
+{
+ return container_of(kobj, struct coreboot_cfr_setting, kobj);
+}
+
+static bool coreboot_cfr_string_is_valid_name(const char *name)
+{
+ return name && name[0] && !strchr(name, '/');
+}
+
+static char *coreboot_cfr_string_dup(const struct lb_cfr_varbinary *str)
+{
+ const char *data = (const char *)(str + 1);
+ size_t len = str->data_length;
+
+ if (len && !data[len - 1])
+ len--;
+
+ return kmemdup_nul(data, len, GFP_KERNEL);
+}
+
+static const struct coreboot_table_entry *
+coreboot_cfr_next_entry(struct coreboot_cfr_iterator *iterator)
+{
+ const struct coreboot_table_entry *entry;
+
+ if (!iterator->remaining)
+ return NULL;
+
+ if (iterator->remaining < sizeof(*entry))
+ return ERR_PTR(-EINVAL);
+
+ entry = (const struct coreboot_table_entry *)iterator->cursor;
+ if (entry->size < sizeof(*entry) || entry->size > iterator->remaining)
+ return ERR_PTR(-EINVAL);
+
+ iterator->cursor += entry->size;
+ iterator->remaining -= entry->size;
+
+ return entry;
+}
+
+static const struct coreboot_table_entry *
+coreboot_cfr_child_entry(const void *base, size_t len, u32 tag)
+{
+ struct coreboot_cfr_iterator iterator = {
+ .cursor = base,
+ .remaining = len,
+ };
+ const struct coreboot_table_entry *entry;
+
+ for (;;) {
+ entry = coreboot_cfr_next_entry(&iterator);
+ if (!entry || IS_ERR(entry))
+ return entry;
+
+ if (entry->tag == tag)
+ return entry;
+ }
+}
+
+static const struct lb_cfr_varbinary *
+coreboot_cfr_child_string(const void *base, size_t len, u32 tag)
+{
+ const struct lb_cfr_varbinary *str;
+ const struct coreboot_table_entry *entry;
+
+ entry = coreboot_cfr_child_entry(base, len, tag);
+ if (IS_ERR(entry))
+ return ERR_CAST(entry);
+ if (!entry)
+ return NULL;
+
+ if (entry->size < sizeof(*str))
+ return ERR_PTR(-EINVAL);
+
+ str = (const struct lb_cfr_varbinary *)entry;
+ if (str->data_length > entry->size - sizeof(*str))
+ return ERR_PTR(-EINVAL);
+
+ return str;
+}
+
+static const struct lb_cfr_runtime_apply *
+coreboot_cfr_child_runtime_apply(const void *base, size_t len)
+{
+ const struct lb_cfr_runtime_apply *runtime_apply;
+ const struct coreboot_table_entry *entry;
+
+ entry = coreboot_cfr_child_entry(base, len, CFR_TAG_RUNTIME_APPLY);
+ if (IS_ERR(entry))
+ return ERR_CAST(entry);
+ if (!entry)
+ return NULL;
+
+ if (entry->size < sizeof(*runtime_apply))
+ return ERR_PTR(-EINVAL);
+
+ runtime_apply = (const struct lb_cfr_runtime_apply *)entry;
+ if (runtime_apply->method == CFR_RUNTIME_APPLY_APM_CNT &&
+ runtime_apply->id > U8_MAX)
+ return ERR_PTR(-EINVAL);
+
+ return runtime_apply;
+}
+
+static efi_char16_t *coreboot_cfr_efi_name(const char *name)
+{
+ size_t len, i;
+
+ len = strlen(name);
+ if (len >= EFI_VAR_NAME_LEN)
+ return ERR_PTR(-ENAMETOOLONG);
+
+ efi_char16_t *efi_name __free(kfree) =
+ kcalloc(len + 1, sizeof(*efi_name), GFP_KERNEL);
+ if (!efi_name)
+ return ERR_PTR(-ENOMEM);
+
+ for (i = 0; i < len; i++) {
+ if (!isascii(name[i]))
+ return ERR_PTR(-EINVAL);
+ efi_name[i] = name[i];
+ }
+
+ return no_free_ptr(efi_name);
+}
+
+/* Caller must hold the efivar lock. */
+static int coreboot_cfr_read_efi_value(efi_char16_t *efi_name, u32 *value,
+ u32 *attrs)
+{
+ unsigned long size = sizeof(__le32);
+ efi_status_t status;
+ __le32 data;
+ u32 attr;
+
+ status = efivar_get_variable(efi_name, &coreboot_cfr_guid, &attr,
+ &size, &data);
+ if (status != EFI_SUCCESS)
+ return efi_status_to_err(status);
+
+ if (size != sizeof(data))
+ return -EINVAL;
+
+ if (!(attr & EFI_VARIABLE_RUNTIME_ACCESS))
+ return -EOPNOTSUPP;
+
+ *value = le32_to_cpu(data);
+ if (attrs)
+ *attrs = attr;
+
+ return 0;
+}
+
+static int coreboot_cfr_read_value(const struct coreboot_cfr_setting *setting,
+ u32 *value, u32 *attrs)
+{
+ efi_char16_t *efi_name __free(kfree) =
+ coreboot_cfr_efi_name(setting->name);
+ int ret;
+
+ if (IS_ERR(efi_name))
+ return PTR_ERR(no_free_ptr(efi_name));
+
+ ret = efivar_lock();
+ if (ret)
+ return ret;
+
+ ret = coreboot_cfr_read_efi_value(efi_name, value, attrs);
+ efivar_unlock();
+
+ return ret;
+}
+
+/* Caller must hold the efivar lock. */
+static int coreboot_cfr_write_efi_value(efi_char16_t *efi_name, u32 value,
+ u32 attrs)
+{
+ efi_status_t status;
+ __le32 data;
+
+ if (!efivar_supports_writes())
+ return -EROFS;
+
+ data = cpu_to_le32(value);
+ status = efivar_set_variable_locked(efi_name, &coreboot_cfr_guid, attrs,
+ sizeof(data), &data, false);
+ if (status != EFI_SUCCESS)
+ return efi_status_to_err(status);
+
+ return 0;
+}
+
+static int coreboot_cfr_apply_runtime(struct coreboot_cfr_setting *setting)
+{
+#ifdef CONFIG_X86
+ u8 status;
+
+ if (setting->runtime_apply_method != CFR_RUNTIME_APPLY_APM_CNT)
+ return -EOPNOTSUPP;
+
+ outb((u8)setting->runtime_apply_id, COREBOOT_CFR_APM_STS_PORT);
+ outb(COREBOOT_CFR_APM_APPLY_CMD, COREBOOT_CFR_APM_CNT_PORT);
+ status = inb(COREBOOT_CFR_APM_STS_PORT);
+ if (status)
+ return -EIO;
+
+ return 0;
+#else
+ return -EOPNOTSUPP;
+#endif
+}
+
+static int coreboot_cfr_write_value(struct coreboot_cfr_setting *setting,
+ u32 value)
+{
+ efi_char16_t *efi_name __free(kfree) = NULL;
+ u32 attrs;
+ u32 old;
+ int restore_ret;
+ int ret;
+
+ if (setting->read_only)
+ return -EACCES;
+
+ efi_name = coreboot_cfr_efi_name(setting->name);
+ if (IS_ERR(efi_name))
+ return PTR_ERR(no_free_ptr(efi_name));
+
+ guard(mutex)(&setting->drvdata->lock);
+
+ ret = efivar_lock();
+ if (ret)
+ return ret;
+
+ ret = coreboot_cfr_read_efi_value(efi_name, &old, &attrs);
+ if (ret)
+ goto out_unlock_efi;
+
+ if ((attrs & COREBOOT_CFR_EFI_ATTRS) != COREBOOT_CFR_EFI_ATTRS) {
+ ret = -EOPNOTSUPP;
+ goto out_unlock_efi;
+ }
+
+ if (old == value)
+ goto out_unlock_efi;
+
+ ret = coreboot_cfr_write_efi_value(efi_name, value, attrs);
+ if (ret)
+ goto out_unlock_efi;
+
+ ret = coreboot_cfr_apply_runtime(setting);
+ if (ret == -EOPNOTSUPP) {
+ /* EFI changed; firmware will consume it after reboot. */
+ setting->drvdata->pending_reboot = true;
+ ret = 0;
+ } else if (ret) {
+ restore_ret = coreboot_cfr_write_efi_value(efi_name, old, attrs);
+ if (restore_ret) {
+ setting->drvdata->pending_reboot = true;
+ ret = restore_ret;
+ } else {
+ goto out_unlock_efi;
+ }
+ }
+
+ efivar_unlock();
+ kobject_uevent(&setting->drvdata->class_dev->kobj, KOBJ_CHANGE);
+ return ret;
+
+out_unlock_efi:
+ efivar_unlock();
+ return ret;
+}
+
+static const char *
+coreboot_cfr_label_from_value(const struct coreboot_cfr_setting *setting,
+ u32 value)
+{
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ if (setting->values[i].value == value)
+ return setting->values[i].label;
+ }
+
+ return NULL;
+}
+
+static int coreboot_cfr_parse_value(struct coreboot_cfr_setting *setting,
+ const char *label, u32 *value_out)
+{
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ if (!sysfs_streq(label, setting->values[i].label))
+ continue;
+
+ *value_out = setting->values[i].value;
+ return 0;
+ }
+
+ return kstrtou32(label, 0, value_out);
+}
+
+static bool coreboot_cfr_value_is_valid(struct coreboot_cfr_setting *setting,
+ u32 value)
+{
+ u32 delta;
+
+ if (setting->type != COREBOOT_CFR_SETTING_NUMBER) {
+ /* Enum and bool values are valid only if they have a label. */
+ return coreboot_cfr_label_from_value(setting, value);
+ }
+
+ if (value < setting->min || value > setting->max)
+ return false;
+
+ if (!setting->step)
+ return true;
+
+ delta = value - setting->min;
+ return delta % setting->step == 0;
+}
+
+static ssize_t type_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER)
+ return sysfs_emit(buf, "integer\n");
+
+ return sysfs_emit(buf, "enumeration\n");
+}
+
+static ssize_t display_name_language_code_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return sysfs_emit(buf, "en_US.UTF-8\n");
+}
+
+static ssize_t display_name_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%s\n", setting->display_name);
+}
+
+static ssize_t possible_values_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ ssize_t len = 0;
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ len += sysfs_emit_at(buf, len, "%s%s", i ? ";" : "",
+ setting->values[i].label);
+ }
+
+ len += sysfs_emit_at(buf, len, "\n");
+ return len;
+}
+
+static ssize_t min_value_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%u\n", setting->min);
+}
+
+static ssize_t max_value_show(struct kobject *kobj, struct kobj_attribute *attr,
+ char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%u\n", setting->max);
+}
+
+static ssize_t scalar_increment_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ return sysfs_emit(buf, "%u\n", setting->step);
+}
+
+static ssize_t default_value_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ const char *label;
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER)
+ return sysfs_emit(buf, "%u\n", setting->default_value);
+
+ label = coreboot_cfr_label_from_value(setting, setting->default_value);
+ if (!label)
+ return sysfs_emit(buf, "%u\n", setting->default_value);
+
+ return sysfs_emit(buf, "%s\n", label);
+}
+
+static ssize_t current_value_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ const char *label;
+ u32 value;
+ int ret;
+
+ ret = coreboot_cfr_read_value(setting, &value, NULL);
+ if (ret)
+ return ret;
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER)
+ return sysfs_emit(buf, "%u\n", value);
+
+ label = coreboot_cfr_label_from_value(setting, value);
+ if (!label)
+ return -EINVAL;
+
+ return sysfs_emit(buf, "%s\n", label);
+}
+
+static ssize_t current_value_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+ u32 value;
+ int ret;
+
+ ret = coreboot_cfr_parse_value(setting, buf, &value);
+ if (ret)
+ return ret;
+
+ if (!coreboot_cfr_value_is_valid(setting, value))
+ return -EINVAL;
+
+ ret = coreboot_cfr_write_value(setting, value);
+ if (ret)
+ return ret;
+
+ return count;
+}
+
+static struct kobj_attribute type_attr = __ATTR_RO(type);
+static struct kobj_attribute display_name_language_code_attr =
+ __ATTR_RO(display_name_language_code);
+static struct kobj_attribute display_name_attr = __ATTR_RO(display_name);
+static struct kobj_attribute possible_values_attr = __ATTR_RO(possible_values);
+static struct kobj_attribute min_value_attr = __ATTR_RO(min_value);
+static struct kobj_attribute max_value_attr = __ATTR_RO(max_value);
+static struct kobj_attribute scalar_increment_attr = __ATTR_RO(scalar_increment);
+static struct kobj_attribute default_value_attr = __ATTR_RO(default_value);
+static struct kobj_attribute current_value_attr = __ATTR_RW(current_value);
+
+static struct attribute *coreboot_cfr_setting_attrs[] = {
+ &type_attr.attr,
+ &display_name_language_code_attr.attr,
+ &display_name_attr.attr,
+ &possible_values_attr.attr,
+ &min_value_attr.attr,
+ &max_value_attr.attr,
+ &scalar_increment_attr.attr,
+ &default_value_attr.attr,
+ ¤t_value_attr.attr,
+ NULL,
+};
+
+static umode_t coreboot_cfr_attr_is_visible(struct kobject *kobj,
+ struct attribute *attr, int n)
+{
+ struct coreboot_cfr_setting *setting = to_coreboot_cfr_setting(kobj);
+
+ if (setting->type == COREBOOT_CFR_SETTING_NUMBER &&
+ attr == &possible_values_attr.attr)
+ return 0;
+
+ if (setting->type != COREBOOT_CFR_SETTING_NUMBER &&
+ (attr == &min_value_attr.attr || attr == &max_value_attr.attr ||
+ attr == &scalar_increment_attr.attr))
+ return 0;
+
+ if (setting->read_only && attr == ¤t_value_attr.attr)
+ return 0444;
+
+ return attr->mode;
+}
+
+static const struct attribute_group coreboot_cfr_setting_group = {
+ .attrs = coreboot_cfr_setting_attrs,
+ .is_visible = coreboot_cfr_attr_is_visible,
+};
+
+static void coreboot_cfr_free_setting(struct coreboot_cfr_setting *setting)
+{
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++)
+ kfree(setting->values[i].label);
+
+ kfree(setting->values);
+ kfree(setting->display_name);
+ kfree(setting->name);
+ kfree(setting);
+}
+
+static void coreboot_cfr_setting_release(struct kobject *kobj)
+{
+ coreboot_cfr_free_setting(to_coreboot_cfr_setting(kobj));
+}
+
+static const struct kobj_type coreboot_cfr_setting_ktype = {
+ .release = coreboot_cfr_setting_release,
+ .sysfs_ops = &kobj_sysfs_ops,
+};
+
+static ssize_t pending_reboot_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct device *dev = kobj_to_dev(kobj->parent);
+ struct coreboot_cfr_drvdata *data;
+
+ data = dev_get_drvdata(dev);
+
+ return sysfs_emit(buf, "%d\n", data->pending_reboot);
+}
+
+static struct kobj_attribute pending_reboot_attr = __ATTR_RO(pending_reboot);
+
+static int coreboot_cfr_copy_bool_values(struct coreboot_cfr_setting *setting)
+{
+ static const struct coreboot_cfr_enum bool_values[] = {
+ { .label = "Disabled", .value = 0 },
+ { .label = "Enabled", .value = 1 },
+ };
+ unsigned int i;
+
+ setting->values = kcalloc(ARRAY_SIZE(bool_values), sizeof(*setting->values),
+ GFP_KERNEL);
+ if (!setting->values)
+ return -ENOMEM;
+
+ for (i = 0; i < ARRAY_SIZE(bool_values); i++) {
+ setting->values[i].label = kstrdup(bool_values[i].label,
+ GFP_KERNEL);
+ if (!setting->values[i].label)
+ return -ENOMEM;
+ setting->values[i].value = bool_values[i].value;
+ setting->n_values++;
+ }
+
+ return 0;
+}
+
+static int coreboot_cfr_count_enum_values(const void *base, size_t len)
+{
+ struct coreboot_cfr_iterator iterator = {
+ .cursor = base,
+ .remaining = len,
+ };
+ const struct coreboot_table_entry *entry;
+ int count = 0;
+
+ for (;;) {
+ entry = coreboot_cfr_next_entry(&iterator);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+ if (!entry)
+ return count;
+
+ if (entry->tag == CFR_TAG_ENUM_VALUE)
+ count++;
+ }
+}
+
+static int coreboot_cfr_copy_enum_values(struct coreboot_cfr_setting *setting,
+ const void *base, size_t len)
+{
+ struct coreboot_cfr_iterator iterator = {
+ .cursor = base,
+ .remaining = len,
+ };
+ const struct lb_cfr_enum_value *enum_value;
+ const struct lb_cfr_varbinary *label;
+ const struct coreboot_table_entry *entry;
+ struct coreboot_cfr_enum *value;
+ int count;
+
+ count = coreboot_cfr_count_enum_values(base, len);
+ if (count <= 0)
+ return count ?: -EINVAL;
+
+ setting->values = kcalloc(count, sizeof(*setting->values), GFP_KERNEL);
+ if (!setting->values)
+ return -ENOMEM;
+
+ for (;;) {
+ entry = coreboot_cfr_next_entry(&iterator);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+ if (!entry)
+ return 0;
+
+ if (entry->tag != CFR_TAG_ENUM_VALUE)
+ continue;
+
+ if (entry->size < sizeof(*enum_value))
+ return -EINVAL;
+
+ enum_value = (const struct lb_cfr_enum_value *)entry;
+ label = coreboot_cfr_child_string(enum_value + 1,
+ enum_value->size - sizeof(*enum_value),
+ CFR_TAG_VARCHAR_UI_NAME);
+ if (IS_ERR(label))
+ return PTR_ERR(label);
+ if (!label)
+ return -EINVAL;
+
+ value = &setting->values[setting->n_values];
+ value->label = coreboot_cfr_string_dup(label);
+ if (!value->label)
+ return -ENOMEM;
+
+ value->value = enum_value->value;
+ setting->n_values++;
+ }
+}
+
+static bool
+coreboot_cfr_possible_values_fit(const struct coreboot_cfr_setting *setting)
+{
+ size_t len = 1; /* Trailing newline. */
+ size_t label_len;
+ unsigned int i;
+
+ for (i = 0; i < setting->n_values; i++) {
+ if (len >= PAGE_SIZE)
+ return false;
+
+ if (i)
+ len++;
+
+ label_len = strlen(setting->values[i].label);
+ if (label_len >= PAGE_SIZE - len)
+ return false;
+
+ len += label_len;
+ }
+
+ return true;
+}
+
+static int coreboot_cfr_setting_is_usable(struct coreboot_cfr_setting *setting)
+{
+ u32 value;
+ int ret;
+
+ ret = coreboot_cfr_read_value(setting, &value, NULL);
+ if (ret)
+ return ret;
+
+ if (!coreboot_cfr_value_is_valid(setting, value))
+ return -EINVAL;
+
+ return 0;
+}
+
+static int coreboot_cfr_register_setting(struct coreboot_cfr_drvdata *data,
+ struct coreboot_cfr_setting *setting)
+{
+ int ret;
+
+ ret = kobject_init_and_add(&setting->kobj, &coreboot_cfr_setting_ktype,
+ &data->attrs_kset->kobj, "%s", setting->name);
+ if (ret)
+ goto err_put_kobj;
+
+ ret = sysfs_create_group(&setting->kobj, &coreboot_cfr_setting_group);
+ if (ret)
+ goto err_put_kobj;
+
+ list_add_tail(&setting->node, &data->settings);
+ return 0;
+
+err_put_kobj:
+ kobject_put(&setting->kobj);
+ return ret;
+}
+
+static int coreboot_cfr_add_numeric_option(struct coreboot_cfr_drvdata *data,
+ const struct lb_cfr_numeric_option *option,
+ bool parent_read_only)
+{
+ const struct lb_cfr_varbinary *name;
+ const struct lb_cfr_varbinary *display_name;
+ const struct lb_cfr_runtime_apply *runtime_apply;
+ const void *child_base = option + 1;
+ struct coreboot_cfr_setting *setting;
+ size_t child_len = option->size - sizeof(*option);
+ int ret;
+
+ if (!(option->flags & CFR_OPTFLAG_RUNTIME))
+ return 0;
+
+ if (option->flags & COREBOOT_CFR_OPT_SKIP_FLAGS)
+ return 0;
+
+ if (option->dependency_id)
+ return 0;
+
+ setting = kzalloc_obj(*setting, GFP_KERNEL);
+ if (!setting)
+ return -ENOMEM;
+
+ INIT_LIST_HEAD(&setting->node);
+ setting->drvdata = data;
+ setting->default_value = option->default_value;
+ setting->min = option->min;
+ setting->max = option->max;
+ setting->step = option->step ?: 1;
+ setting->read_only =
+ (option->flags & COREBOOT_CFR_OPT_READ_ONLY_FLAGS) ||
+ !data->efi_writes_supported || parent_read_only;
+
+ runtime_apply = coreboot_cfr_child_runtime_apply(child_base, child_len);
+ if (IS_ERR(runtime_apply)) {
+ ret = PTR_ERR(runtime_apply);
+ goto err_put_setting;
+ }
+
+ if (runtime_apply && runtime_apply->method == CFR_RUNTIME_APPLY_APM_CNT) {
+ setting->runtime_apply_method = runtime_apply->method;
+ setting->runtime_apply_id = runtime_apply->id;
+ }
+
+ name = coreboot_cfr_child_string(child_base, child_len,
+ CFR_TAG_VARCHAR_OPT_NAME);
+ if (IS_ERR(name)) {
+ ret = PTR_ERR(name);
+ goto err_put_setting;
+ }
+ if (!name) {
+ ret = -EINVAL;
+ goto err_put_setting;
+ }
+
+ setting->name = coreboot_cfr_string_dup(name);
+ if (!setting->name) {
+ ret = -ENOMEM;
+ goto err_put_setting;
+ }
+
+ if (!coreboot_cfr_string_is_valid_name(setting->name)) {
+ ret = -EINVAL;
+ goto err_put_setting;
+ }
+
+ display_name = coreboot_cfr_child_string(child_base, child_len,
+ CFR_TAG_VARCHAR_UI_NAME);
+ if (IS_ERR(display_name)) {
+ ret = PTR_ERR(display_name);
+ goto err_put_setting;
+ }
+ if (display_name)
+ setting->display_name = coreboot_cfr_string_dup(display_name);
+ else
+ setting->display_name = kstrdup(setting->name, GFP_KERNEL);
+ if (!setting->display_name) {
+ ret = -ENOMEM;
+ goto err_put_setting;
+ }
+
+ switch (option->tag) {
+ case CFR_TAG_OPTION_BOOL:
+ setting->type = COREBOOT_CFR_SETTING_BOOL;
+ setting->min = 0;
+ setting->max = 1;
+ setting->step = 1;
+ ret = coreboot_cfr_copy_bool_values(setting);
+ break;
+ case CFR_TAG_OPTION_ENUM:
+ setting->type = COREBOOT_CFR_SETTING_ENUM;
+ ret = coreboot_cfr_copy_enum_values(setting, child_base,
+ child_len);
+ break;
+ case CFR_TAG_OPTION_NUMBER:
+ setting->type = COREBOOT_CFR_SETTING_NUMBER;
+ if (!setting->min && !setting->max)
+ setting->max = U32_MAX;
+ else if (setting->max < setting->min)
+ setting->max = U32_MAX;
+ ret = 0;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ if (ret)
+ goto err_put_setting;
+ /* possible_values must be returned completely in one sysfs read. */
+ if (setting->type != COREBOOT_CFR_SETTING_NUMBER &&
+ !coreboot_cfr_possible_values_fit(setting)) {
+ ret = 0;
+ goto err_put_setting;
+ }
+
+ ret = coreboot_cfr_setting_is_usable(setting);
+ if (ret) {
+ /*
+ * CFR may describe options without a matching, readable runtime
+ * EFI variable. Skip those, but propagate transient EFI failures.
+ */
+ if (ret == -ENOENT || ret == -EINVAL || ret == -EOPNOTSUPP ||
+ ret == -ENAMETOOLONG)
+ ret = 0;
+ goto err_put_setting;
+ }
+
+ /* The kobject release callback owns setting after this call. */
+ return coreboot_cfr_register_setting(data, setting);
+
+err_put_setting:
+ coreboot_cfr_free_setting(setting);
+ return ret;
+}
+
+static int coreboot_cfr_parse_records(struct coreboot_cfr_drvdata *data,
+ const void *base, size_t len,
+ unsigned int depth,
+ bool parent_read_only)
+{
+ struct coreboot_cfr_iterator iterator = {
+ .cursor = base,
+ .remaining = len,
+ };
+ const struct lb_cfr_option_form *form;
+ const struct lb_cfr_numeric_option *option;
+ const struct coreboot_table_entry *entry;
+ const void *child_base;
+ size_t child_len;
+ int ret;
+
+ for (;;) {
+ entry = coreboot_cfr_next_entry(&iterator);
+ if (IS_ERR(entry))
+ return PTR_ERR(entry);
+ if (!entry)
+ return 0;
+
+ switch (entry->tag) {
+ case CFR_TAG_OPTION_FORM:
+ if (entry->size < sizeof(struct lb_cfr_option_form))
+ return -EINVAL;
+
+ form = (const struct lb_cfr_option_form *)entry;
+ if (form->dependency_id ||
+ form->flags & CFR_OPTFLAG_SUPPRESS)
+ break;
+
+ if (depth >= COREBOOT_CFR_MAX_FORM_DEPTH)
+ return -E2BIG;
+
+ child_base = form + 1;
+ child_len = entry->size - sizeof(struct lb_cfr_option_form);
+ ret = coreboot_cfr_parse_records(data, child_base,
+ child_len, depth + 1,
+ parent_read_only ||
+ (form->flags &
+ COREBOOT_CFR_OPT_READ_ONLY_FLAGS));
+ if (ret)
+ return ret;
+ break;
+ case CFR_TAG_OPTION_ENUM:
+ case CFR_TAG_OPTION_NUMBER:
+ case CFR_TAG_OPTION_BOOL:
+ option = (const struct lb_cfr_numeric_option *)entry;
+ if (entry->size < sizeof(*option))
+ return -EINVAL;
+ ret = coreboot_cfr_add_numeric_option(data, option,
+ parent_read_only);
+ if (ret)
+ return ret;
+ break;
+ default:
+ /* Ignore unsupported, child-only and future record types. */
+ break;
+ }
+ }
+}
+
+static void coreboot_cfr_unregister_settings(struct coreboot_cfr_drvdata *data)
+{
+ struct coreboot_cfr_setting *setting, *tmp;
+
+ list_for_each_entry_safe(setting, tmp, &data->settings, node) {
+ sysfs_remove_group(&setting->kobj, &coreboot_cfr_setting_group);
+ list_del(&setting->node);
+ kobject_put(&setting->kobj);
+ }
+}
+
+static int coreboot_cfr_probe(struct coreboot_device *dev)
+{
+ const struct lb_cfr *root = (const struct lb_cfr *)dev->raw;
+ struct coreboot_cfr_drvdata *data;
+ size_t payload_len;
+ int ret;
+
+ if (dev->entry.size < sizeof(*root))
+ return -EINVAL;
+
+ if (root->tag != LB_TAG_CFR_ROOT || root->version != CFR_VERSION)
+ return -EINVAL;
+
+ if (root->size < sizeof(*root) || root->size > dev->entry.size)
+ return -EINVAL;
+
+ payload_len = root->size - sizeof(*root);
+ if (crc32_be(0, root + 1, payload_len) != root->checksum)
+ return -EBADMSG;
+
+ if (!efivar_is_available())
+ return -EPROBE_DEFER;
+
+ data = devm_kzalloc(&dev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ ret = efivar_lock();
+ if (ret)
+ return ret;
+ data->efi_writes_supported = efivar_supports_writes();
+ efivar_unlock();
+
+ INIT_LIST_HEAD(&data->settings);
+ ret = devm_mutex_init(&dev->dev, &data->lock);
+ if (ret)
+ return ret;
+
+ dev_set_drvdata(&dev->dev, data);
+
+ data->class_dev = device_create(&firmware_attributes_class, NULL,
+ MKDEV(0, 0), NULL, DRIVER_NAME);
+ if (IS_ERR(data->class_dev))
+ return PTR_ERR(data->class_dev);
+ dev_set_drvdata(data->class_dev, data);
+
+ data->attrs_kset = kset_create_and_add("attributes", NULL,
+ &data->class_dev->kobj);
+ if (!data->attrs_kset) {
+ ret = -ENOMEM;
+ goto err_unregister_dev;
+ }
+
+ ret = sysfs_create_file(&data->attrs_kset->kobj,
+ &pending_reboot_attr.attr);
+ if (ret)
+ goto err_unregister_attrs;
+
+ ret = coreboot_cfr_parse_records(data, root + 1, payload_len, 0, false);
+ if (ret)
+ goto err_unregister_settings;
+
+ if (list_empty(&data->settings)) {
+ ret = -ENODEV;
+ goto err_unregister_settings;
+ }
+
+ return 0;
+
+err_unregister_settings:
+ coreboot_cfr_unregister_settings(data);
+ sysfs_remove_file(&data->attrs_kset->kobj, &pending_reboot_attr.attr);
+err_unregister_attrs:
+ kset_unregister(data->attrs_kset);
+err_unregister_dev:
+ device_unregister(data->class_dev);
+ return ret;
+}
+
+static void coreboot_cfr_remove(struct coreboot_device *dev)
+{
+ struct coreboot_cfr_drvdata *data = dev_get_drvdata(&dev->dev);
+
+ coreboot_cfr_unregister_settings(data);
+ sysfs_remove_file(&data->attrs_kset->kobj, &pending_reboot_attr.attr);
+ kset_unregister(data->attrs_kset);
+ device_unregister(data->class_dev);
+}
+
+static const struct coreboot_device_id coreboot_cfr_ids[] = {
+ { .tag = LB_TAG_CFR_ROOT },
+ { }
+};
+MODULE_DEVICE_TABLE(coreboot, coreboot_cfr_ids);
+
+static struct coreboot_driver coreboot_cfr_driver = {
+ .probe = coreboot_cfr_probe,
+ .remove = coreboot_cfr_remove,
+ .drv = {
+ .name = DRIVER_NAME,
+ },
+ .id_table = coreboot_cfr_ids,
+};
+module_coreboot_driver(coreboot_cfr_driver);
+
+MODULE_AUTHOR("Sean Rhodes <sean@starlabs.systems>");
+MODULE_DESCRIPTION("coreboot CFR firmware attributes driver");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("EFIVAR");
^ permalink raw reply related [flat|nested] 5+ messages in thread