What is Kernel Application Binary Interface (kABI)?

Resolution

• The Kernel Application Binary Interface (kABI) is a set of in-kernel symbols used by drivers and other kernel modules.

• The kernel-abi-stablelists packages contain reference files, /lib/modules/kabi-<MAJOR><MINOR>/kabi_stablelist_<ARCH>, listing interfaces provided by the kernel that are considered to be stable by Red Hat engineering. Such interfaces are safe for long-term use by third-party loadable device drivers, as well as for other purposes.

• With Red Hat Enterprise Linux 7 and 8, the stablelist is valid for the particular major release. This means that once a symbol has been introduced into kABI for a particular major release, it will not be removed, nor will its meaning be changed during that kernel major release complete life cycle.

• With Red Hat Enterprise Linux 9, each minor release will have a unique stablelist that is valid throughout the minor release lifecycle. For more information on this, please refer to the following knowledgebase article;

  • Red Hat Enterprise Linux 9 kABI Policy

• Red Hat recommends recompiling kernel modules against every minor release of Red Hat Enterprise Linux.

• With the introduction of CentOS Stream, it is possible to build out-of-tree kernel modules against the ongoing development of the Red Hat Enterprise Linux kernel.

• The kABI whitelist package name varies with the major release version: kabi-whitelists (Red Hat Enterprise Linux 6), kernel-abi-whitelists (Red Hat Enterprise Linux 7,8) and kernel-abi-stablelists (Red Hat Enterprise Linux 8,9).

  # rpm -ql kernel-abi-stablelists /lib/modules/kabi-current 
  /lib/modules/kabi-rhel84 
  /lib/modules/kabi-rhel84/kabi_stablelist_aarch64 
  /lib/modules/kabi-rhel84/kabi_stablelist_ppc64le 
  /lib/modules/kabi-rhel84/kabi_stablelist_s390x 
  /lib/modules/kabi-rhel84/kabi_stablelist_x86_64 
  

• Please note that, in very rare and special circumstances, a symbol in a kABI stablelist needs to be changed. For example, Red Hat could introduce kABI breakage when a critical security issue cannot be resolved without breaking kABI. Red Hat will inform the partners if such a situation should occur.

Non-stablelist kABI

• Red Hat generally strives not to make changes even to non-stablelist kABI symbols in regular security and errata updates. However, there is no guarantee that the symbols will be compatible within the same minor release.

• When non-stablelist kABI symbols are changed in the kernel updates, it is not considered to be kABI breakage.