NOTICE
This directory contains include header files needed to compile BPF programs.
The files are either copied from the kernel source (in subdir linux/) or "shadow" files that contain useful defines that are often used in kernel headers.
For example bpf/compiler.h contains practical compile macros
like READ_ONCE and WRITE_ONCE with verifier workarounds via
bpf_barrier(). And the likely() + unlikely() annotations.
The include file linux/bpf.h is the most central file that all
BPF (kernel-side) programs include. It is maintained in this directory,
because this project knows what BPF features it uses, which makes the update
cycle tied to the project itself. We prefer not to depend on the OS distro
kernel headers version of this file. (Hint, due to the use of enum instead of
define the usual macro C-preprocessor define detection will not work. This is
done on purpose to discourage userspace from detecting features via header file
defines.).