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Add selftest with few subtests testing proper bpf_cookie usage. Kprobe and uprobe subtests are pretty straightforward and just validate that the same BPF program attached with different bpf_cookie will be triggered with those different bpf_cookie values. Tracepoint subtest is a bit more interesting, as it is the only perf_event-based BPF hook that shares bpf_prog_array between multiple perf_events internally. This means that the same BPF program can't be attached to the same tracepoint multiple times. So we have 3 identical copies. This arrangement allows to test bpf_prog_array_copy()'s handling of bpf_prog_array list manipulation logic when programs are attached and detached. The test validates that bpf_cookie isn't mixed up and isn't lost during such list manipulations. Perf_event subtest validates that two BPF links can be created against the same perf_event (but not at the same time, only one BPF program can be attached to perf_event itself), and that for each we can specify different bpf_cookie value. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/20210815070609.987780-15-andrii@kernel.org
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.