0c991ebc8c
Add new operation (LINK_UPDATE), which allows to replace active bpf_prog from under given bpf_link. Currently this is only supported for bpf_cgroup_link, but will be extended to other kinds of bpf_links in follow-up patches. For bpf_cgroup_link, implemented functionality matches existing semantics for direct bpf_prog attachment (including BPF_F_REPLACE flag). User can either unconditionally set new bpf_prog regardless of which bpf_prog is currently active under given bpf_link, or, optionally, can specify expected active bpf_prog. If active bpf_prog doesn't match expected one, no changes are performed, old bpf_link stays intact and attached, operation returns a failure. cgroup_bpf_replace() operation is resolving race between auto-detachment and bpf_prog update in the same fashion as it's done for bpf_link detachment, except in this case update has no way of succeeding because of target cgroup marked as dying. So in this case error is returned. Signed-off-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200330030001.2312810-3-andriin@fb.com
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.