f7c0bbf27e
Andrii Nakryiko says: ==================== This patch set introduces an alternative and complimentary to existing libbpf API interface for working with BPF objects, maps, programs, and global data from userspace side. This approach is relying on code generation. bpftool produces a struct (a.k.a. skeleton) tailored and specific to provided BPF object file. It includes hard-coded fields and data structures for every map, program, link, and global data present. Altogether this approach significantly reduces amount of userspace boilerplate code required to open, load, attach, and work with BPF objects. It improves attach/detach story, by providing pre-allocated space for bpf_links, and ensuring they are properly detached on shutdown. It allows to do away with by name/title lookups of maps and programs, because libbpf's skeleton API, in conjunction with generated code from bpftool, is filling in hard-coded fields with actual pointers to corresponding struct bpf_map/bpf_program/bpf_link. Also, thanks to BPF array mmap() support, working with global data (variables) from userspace is now as natural as it is from BPF side: each variable is just a struct field inside skeleton struct. Furthermore, this allows to have a natural way for userspace to pre-initialize global data (including previously impossible to initialize .rodata) by just assigning values to the same per-variable fields. Libbpf will carefully take into account this initialization image, will use it to pre-populate BPF maps at creation time, and will re-mmap() BPF map's contents at exactly the same userspace memory address such that it can continue working with all the same pointers without any interruptions. If kernel doesn't support mmap(), global data will still be successfully initialized, but after map creation global data structures inside skeleton will be NULL-ed out. This allows userspace application to gracefully handle lack of mmap() support, if necessary. A bunch of selftests are also converted to using skeletons, demonstrating significant simplification of userspace part of test and reduction in amount of code necessary. v3->v4: - add OPTS_VALID check to btf_dump__emit_type_decl (Alexei); - expose skeleton as LIBBPF_API functions (Alexei); - copyright clean up, update internal map init refactor (Alexei); v2->v3: - make skeleton part of public API; - expose btf_dump__emit_type_decl and btf__align_of APIs; - move LIBBPF_API and DECLARE_LIBBPF_OPTS into libbpf_common.h for reuse; v1->v2: - checkpatch.pl and reverse Christmas tree styling (Jakub); - sanitize variable names to accomodate in-function static vars; rfc->v1: - runqslower moved out into separate patch set waiting for vmlinux.h improvements; - skeleton generation code deals with unknown internal maps more gracefully. ==================== Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.