UKUUG Linux 2001 — Linux Developers' Conference 29 June - 1 July 2001, Renold Building, UMIST, Manchester

Richard J Moore

Generalised Kernel Hooks Interface - A High Speed Call-back Mechanism for the Linux Kernel

Generalised Kernel Hooks Interface (GKHI) is a generalised facility for placing hooks in arbitrary kernel (or kernel module) locations. A hook a location in the kernel that calls out of the kernel to a kernel module routine - a hook exit. It enables many kernel enhancements, which are otherwise self-contained, to become loadable kernel modules and retain a substantial degree of independence from the kernel source. This affords advantages for maintenance and co-existence with other kernel enhancements.

The hooks are implemented as fast and slim-line insertions to kernel code when not active, with practically no overhead to the kernel.

The hook interface allows multiple kernel modules to register their exits for a given hook, in order to receive control at that given hook location.

A particularly interesting application of GKHI is in dynamic assertion checking and First Failure System Technology (FFST).

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