1 What: /sys/bus/coreboot 1 What: /sys/bus/coreboot
2 Date: August 2022 2 Date: August 2022
3 Contact: Jack Rosenthal <jrosenth@chromi 3 Contact: Jack Rosenthal <jrosenth@chromium.org>
4 Description: 4 Description:
5 The coreboot bus provides a va 5 The coreboot bus provides a variety of virtual devices used to
6 access data structures created 6 access data structures created by the Coreboot BIOS.
7 7
8 What: /sys/bus/coreboot/devices/cbme 8 What: /sys/bus/coreboot/devices/cbmem-<id>
9 Date: August 2022 9 Date: August 2022
10 Contact: Jack Rosenthal <jrosenth@chromi 10 Contact: Jack Rosenthal <jrosenth@chromium.org>
11 Description: 11 Description:
12 CBMEM is a downwards-growing m 12 CBMEM is a downwards-growing memory region created by Coreboot,
13 and contains tagged data struc 13 and contains tagged data structures to be shared with payloads
14 in the boot process and the OS 14 in the boot process and the OS. Each CBMEM entry is given a
15 directory in /sys/bus/coreboot 15 directory in /sys/bus/coreboot/devices based on its id.
16 A list of ids known to Coreboo 16 A list of ids known to Coreboot can be found in the coreboot
17 source tree at 17 source tree at
18 ``src/commonlib/bsd/include/co 18 ``src/commonlib/bsd/include/commonlib/bsd/cbmem_id.h``.
19 19
20 What: /sys/bus/coreboot/devices/cbme 20 What: /sys/bus/coreboot/devices/cbmem-<id>/address
21 Date: August 2022 21 Date: August 2022
22 Contact: Jack Rosenthal <jrosenth@chromi 22 Contact: Jack Rosenthal <jrosenth@chromium.org>
23 Description: 23 Description:
24 This is the physical memory ad 24 This is the physical memory address that the CBMEM entry's data
25 begins at, in hexadecimal (e.g 25 begins at, in hexadecimal (e.g., ``0x76ffe000``).
26 26
27 What: /sys/bus/coreboot/devices/cbme 27 What: /sys/bus/coreboot/devices/cbmem-<id>/size
28 Date: August 2022 28 Date: August 2022
29 Contact: Jack Rosenthal <jrosenth@chromi 29 Contact: Jack Rosenthal <jrosenth@chromium.org>
30 Description: 30 Description:
31 This is the size of the CBMEM 31 This is the size of the CBMEM entry's data, in hexadecimal
32 (e.g., ``0x1234``). 32 (e.g., ``0x1234``).
33 33
34 What: /sys/bus/coreboot/devices/cbme 34 What: /sys/bus/coreboot/devices/cbmem-<id>/mem
35 Date: August 2022 35 Date: August 2022
36 Contact: Jack Rosenthal <jrosenth@chromi 36 Contact: Jack Rosenthal <jrosenth@chromium.org>
37 Description: 37 Description:
38 A file exposing read/write acc 38 A file exposing read/write access to the entry's data. Note
39 that this file does not suppor 39 that this file does not support mmap(), as coreboot
40 does not guarantee that the da 40 does not guarantee that the data will be page-aligned.
41 41
42 The mode of this file is 0600. 42 The mode of this file is 0600. While there shouldn't be
43 anything security-sensitive co 43 anything security-sensitive contained in CBMEM, read access
44 requires root privileges given 44 requires root privileges given this is exposing a small subset
45 of physical memory. 45 of physical memory.
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