From: Patrick Rudolph patrick.rudolph@9elements.com
Make all CBMEM buffers available to userland. This is useful for tools that are currently using /dev/mem.
Make the id, size and address available, as well as the raw table data.
Tools can easily scan the right CBMEM buffer by reading /sys/bus/coreboot/drivers/cbmem/coreboot*/cbmem_attributes/id The binary table data can then be read from /sys/bus/coreboot/drivers/cbmem/coreboot*/cbmem_attributes/data
Signed-off-by: Patrick Rudolph patrick.rudolph@9elements.com --- drivers/firmware/google/Kconfig | 9 ++ drivers/firmware/google/Makefile | 1 + drivers/firmware/google/cbmem-coreboot.c | 162 +++++++++++++++++++++++ drivers/firmware/google/coreboot_table.h | 13 ++ 4 files changed, 185 insertions(+) create mode 100644 drivers/firmware/google/cbmem-coreboot.c
diff --git a/drivers/firmware/google/Kconfig b/drivers/firmware/google/Kconfig index a3a6ca659ffa..11a67c397ab3 100644 --- a/drivers/firmware/google/Kconfig +++ b/drivers/firmware/google/Kconfig @@ -58,6 +58,15 @@ config GOOGLE_FRAMEBUFFER_COREBOOT This option enables the kernel to search for a framebuffer in the coreboot table. If found, it is registered with simplefb.
+config GOOGLE_CBMEM_COREBOOT + tristate "Coreboot CBMEM access" + depends on GOOGLE_COREBOOT_TABLE + help + This option exposes all available CBMEM buffers to userland. + The CBMEM id, size and address as well as the raw table data + are exported as sysfs attributes of the corresponding coreboot + table. + config GOOGLE_MEMCONSOLE_COREBOOT tristate "Firmware Memory Console" depends on GOOGLE_COREBOOT_TABLE diff --git a/drivers/firmware/google/Makefile b/drivers/firmware/google/Makefile index d17caded5d88..62053cd6d058 100644 --- a/drivers/firmware/google/Makefile +++ b/drivers/firmware/google/Makefile @@ -2,6 +2,7 @@
obj-$(CONFIG_GOOGLE_SMI) += gsmi.o obj-$(CONFIG_GOOGLE_COREBOOT_TABLE) += coreboot_table.o +obj-$(CONFIG_GOOGLE_CBMEM_COREBOOT) += cbmem-coreboot.o obj-$(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/google/cbmem-coreboot.c b/drivers/firmware/google/cbmem-coreboot.c new file mode 100644 index 000000000000..94b93d8351fe --- /dev/null +++ b/drivers/firmware/google/cbmem-coreboot.c @@ -0,0 +1,162 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * fmap-coreboot.c + * + * Exports CBMEM as attributes in sysfs. + * + * Copyright 2012-2013 David Herrmann dh.herrmann@gmail.com + * Copyright 2017 Google Inc. + * Copyright 2019 9elements Agency GmbH + */ + +#include <linux/device.h> +#include <linux/kernel.h> +#include <linux/string.h> +#include <linux/module.h> +#include <linux/io.h> +#include <linux/slab.h> + +#include "coreboot_table.h" + +#define CB_TAG_CBMEM_ENTRY 0x31 + +struct cb_priv { + void __iomem *remap; + struct lb_cbmem_entry entry; +}; + +static ssize_t id_show(struct device *dev, + struct device_attribute *attr, char *buffer) +{ + const struct cb_priv *priv; + + priv = (const struct cb_priv *)dev_get_platdata(dev); + + return sprintf(buffer, "%08x\n", priv->entry.id); +} + +static ssize_t size_show(struct device *dev, + struct device_attribute *attr, char *buffer) +{ + const struct cb_priv *priv; + + priv = (const struct cb_priv *)dev_get_platdata(dev); + + return sprintf(buffer, "%u\n", priv->entry.size); +} + +static ssize_t address_show(struct device *dev, + struct device_attribute *attr, char *buffer) +{ + const struct cb_priv *priv; + + priv = (const struct cb_priv *)dev_get_platdata(dev); + + return sprintf(buffer, "%016llx\n", priv->entry.address); +} + +static DEVICE_ATTR_RO(id); +static DEVICE_ATTR_RO(size); +static DEVICE_ATTR_RO(address); + +static struct attribute *cb_mem_attrs[] = { + &dev_attr_address.attr, + &dev_attr_id.attr, + &dev_attr_size.attr, + NULL +}; + +static ssize_t cbmem_data_read(struct file *filp, struct kobject *kobj, + struct bin_attribute *bin_attr, + char *buffer, loff_t offset, size_t count) +{ + struct device *dev = kobj_to_dev(kobj); + const struct cb_priv *priv; + + priv = (const struct cb_priv *)dev_get_platdata(dev); + + return memory_read_from_buffer(buffer, count, &offset, + priv->remap, priv->entry.size); +} + +static struct bin_attribute coreboot_attr_data = { + .attr = { .name = "data", .mode = 0444 }, + .read = cbmem_data_read, +}; + +static struct bin_attribute *cb_mem_bin_attrs[] = { + &coreboot_attr_data, + NULL +}; + +static struct attribute_group cb_mem_attr_group = { + .name = "cbmem_attributes", + .attrs = cb_mem_attrs, + .bin_attrs = cb_mem_bin_attrs, +}; + +static int cbmem_probe(struct coreboot_device *cdev) +{ + struct device *dev = &cdev->dev; + struct cb_priv *priv; + int err; + + priv = kzalloc(sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + memcpy(&priv->entry, &cdev->cbmem_entry, sizeof(priv->entry)); + + priv->remap = memremap(priv->entry.address, + priv->entry.entry_size, MEMREMAP_WB); + if (!priv->remap) { + err = -ENOMEM; + goto failure; + } + + err = sysfs_create_group(&dev->kobj, &cb_mem_attr_group); + if (err) { + dev_err(dev, "failed to create sysfs attributes: %d\n", err); + memunmap(priv->remap); + goto failure; + } + + dev->platform_data = priv; + + return 0; +failure: + kfree(priv); + return err; +} + +static int cbmem_remove(struct coreboot_device *cdev) +{ + struct device *dev = &cdev->dev; + const struct cb_priv *priv; + + priv = (const struct cb_priv *)dev_get_platdata(dev); + + sysfs_remove_group(&dev->kobj, &cb_mem_attr_group); + + if (priv) + memunmap(priv->remap); + kfree(priv); + + dev->platform_data = NULL; + + return 0; +} + +static struct coreboot_driver cbmem_driver = { + .probe = cbmem_probe, + .remove = cbmem_remove, + .drv = { + .name = "cbmem", + }, + .tag = CB_TAG_CBMEM_ENTRY, +}; + +module_coreboot_driver(cbmem_driver); + +MODULE_AUTHOR("9elements Agency GmbH"); +MODULE_LICENSE("GPL"); diff --git a/drivers/firmware/google/coreboot_table.h b/drivers/firmware/google/coreboot_table.h index 7b7b4a6eedda..506048c724d8 100644 --- a/drivers/firmware/google/coreboot_table.h +++ b/drivers/firmware/google/coreboot_table.h @@ -59,6 +59,18 @@ struct lb_framebuffer { u8 reserved_mask_size; };
+/* There can be more than one of these records as there is one per cbmem entry. + * Describes a buffer in memory containing runtime data. + */ +struct lb_cbmem_entry { + u32 tag; + u32 size; + + u64 address; + u32 entry_size; + u32 id; +}; + /* A device, additionally with information from coreboot. */ struct coreboot_device { struct device dev; @@ -66,6 +78,7 @@ struct coreboot_device { struct coreboot_table_entry entry; struct lb_cbmem_ref cbmem_ref; struct lb_framebuffer framebuffer; + struct lb_cbmem_entry cbmem_entry; }; };