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What: /sys/bus/coreboot
Date: August 2022
Contact: Jack Rosenthal <jrosenth@chromium.org>
Description:
The coreboot bus provides a variety of virtual devices used to
access data structures created by the Coreboot BIOS.
What: /sys/bus/coreboot/devices/cbmem-<id>
Date: August 2022
Contact: Jack Rosenthal <jrosenth@chromium.org>
Description:
CBMEM is a downwards-growing memory region created by Coreboot,
and contains tagged data structures to be shared with payloads
in the boot process and the OS. Each CBMEM entry is given a
directory in /sys/bus/coreboot/devices based on its id.
A list of ids known to Coreboot can be found in the coreboot
source tree at
``src/commonlib/bsd/include/commonlib/bsd/cbmem_id.h``.
What: /sys/bus/coreboot/devices/cbmem-<id>/address
Date: August 2022
Contact: Jack Rosenthal <jrosenth@chromium.org>
Description:
This is the physical memory address that the CBMEM entry's data
begins at, in hexadecimal (e.g., ``0x76ffe000``).
What: /sys/bus/coreboot/devices/cbmem-<id>/size
Date: August 2022
Contact: Jack Rosenthal <jrosenth@chromium.org>
Description:
This is the size of the CBMEM entry's data, in hexadecimal
(e.g., ``0x1234``).
What: /sys/bus/coreboot/devices/cbmem-<id>/mem
Date: August 2022
Contact: Jack Rosenthal <jrosenth@chromium.org>
Description:
A file exposing read/write access to the entry's data. Note
that this file does not support mmap(), as coreboot
does not guarantee that the data will be page-aligned.
The mode of this file is 0600. While there shouldn't be
anything security-sensitive contained in CBMEM, read access
requires root privileges given this is exposing a small subset
of physical memory.
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