f80442a4cd
There are currently unused section descriptions in the btf_header. Those sections are here to support future BTF use cases. For example, the func section (func_off) is to support function signature (e.g. the BPF prog function signature). Instead of spelling out all potential sections up-front in the btf_header. This patch makes changes to btf_header such that extending it (e.g. adding a section) is possible later. The unused ones can be removed for now and they can be added back later. This patch: 1. adds a hdr_len to the btf_header. It will allow adding sections (and other info like parent_label and parent_name) later. The check is similar to the existing bpf_attr. If a user passes in a longer hdr_len, the kernel ensures the extra tailing bytes are 0. 2. allows the section order in the BTF object to be different from its sec_off order in btf_header. 3. each sec_off is followed by a sec_len. It must not have gap or overlapping among sections. The string section is ensured to be at the end due to the 4 bytes alignment requirement of the type section. The above changes will allow enough flexibility to add new sections (and other info) to the btf_header later. This patch also removes an unnecessary !err check at the end of btf_parse(). Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.