| 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. |
