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1What: /sys/bus/coreboot2Date: August 20223Contact: Jack Rosenthal <jrosenth@chromium.org>4Description:5 The coreboot bus provides a variety of virtual devices used to6 access data structures created by the Coreboot BIOS.7 8What: /sys/bus/coreboot/devices/cbmem-<id>9Date: August 202210Contact: Jack Rosenthal <jrosenth@chromium.org>11Description:12 CBMEM is a downwards-growing memory region created by Coreboot,13 and contains tagged data structures to be shared with payloads14 in the boot process and the OS. Each CBMEM entry is given a15 directory in /sys/bus/coreboot/devices based on its id.16 A list of ids known to Coreboot can be found in the coreboot17 source tree at18 ``src/commonlib/bsd/include/commonlib/bsd/cbmem_id.h``.19 20What: /sys/bus/coreboot/devices/cbmem-<id>/address21Date: August 202222Contact: Jack Rosenthal <jrosenth@chromium.org>23Description:24 This is the physical memory address that the CBMEM entry's data25 begins at, in hexadecimal (e.g., ``0x76ffe000``).26 27What: /sys/bus/coreboot/devices/cbmem-<id>/size28Date: August 202229Contact: Jack Rosenthal <jrosenth@chromium.org>30Description:31 This is the size of the CBMEM entry's data, in hexadecimal32 (e.g., ``0x1234``).33 34What: /sys/bus/coreboot/devices/cbmem-<id>/mem35Date: August 202236Contact: Jack Rosenthal <jrosenth@chromium.org>37Description:38 A file exposing read/write access to the entry's data. Note39 that this file does not support mmap(), as coreboot40 does not guarantee that the data will be page-aligned.41 42 The mode of this file is 0600. While there shouldn't be43 anything security-sensitive contained in CBMEM, read access44 requires root privileges given this is exposing a small subset45 of physical memory.46