1  # ABI data consumption
 2  
 3  This text describes the ABI coreboot presents to downstream users. Such
 4  users are payloads and/or operating systems. Therefore, this text serves
 5  at what can be relied on for downstream consumption. Anything not explicitly
 6  listed as consumable is subject to change without notice.
 7  
 8  ## Background and Usage
 9  
10  coreboot passes information to downstream users using coreboot tables. These
11  table definitions can be found in
12  `./src/commonlib/include/commonlib/coreboot_tables.h` and
13  `./payloads/libpayload/include/coreboot_tables.h` respectively within coreboot
14  and libpayload. One of the most vital and important pieces of information
15  found within these tables is the memory map of the system indicating
16  available and reserved memory.
17  
18  In 2009 cbmem was added to coreboot. The "CBMEM high table memory manager"
19  serves a way for coreboot to bookkeep its own internal data. While some
20  of this data may be exposed through the coreboot tables the data structures
21  used to manage the data within the cbmem area is subject to change.
22  
23  Provided the above, if one needs a piece of data exposed to the OS
24  or payload it should reside within the coreboot tables. If it isn't there
25  then a code change will be required to add it to the coreboot tables.