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Martin KaFai says: ==================== This series adds support to allow bpf program calling kernel function. The use case included in this set is to allow bpf-tcp-cc to directly call some tcp-cc helper functions (e.g. "tcp_cong_avoid_ai()"). Those functions have already been used by some kernel tcp-cc implementations. This set will also allow the bpf-tcp-cc program to directly call the kernel tcp-cc implementation, For example, a bpf_dctcp may only want to implement its own dctcp_cwnd_event() and reuse other dctcp_*() directly from the kernel tcp_dctcp.c instead of reimplementing (or copy-and-pasting) them. The tcp-cc kernel functions mentioned above will be white listed for the struct_ops bpf-tcp-cc programs to use in a later patch. The white listed functions are not bounded to a fixed ABI contract. Those functions have already been used by the existing kernel tcp-cc. If any of them has changed, both in-tree and out-of-tree kernel tcp-cc implementations have to be changed. The same goes for the struct_ops bpf-tcp-cc programs which have to be adjusted accordingly. Please see individual patch for details. v2: - Patch 2 in v1 is removed. No need to support extern func in kernel. Changed libbpf to adjust the .ksyms datasec for extern func in patch 11. (Andrii) - Name change: btf_check_func_arg_match() and btf_check_subprog_arg_match() in patch 2. (Andrii) - Always set unreliable on any error in patch 2 since it does not matter. (Andrii) - s/kern_func/kfunc/ and s/descriptor/desc/ in this set. (Andrii) - Remove some unnecessary changes in disasm.h and disasm.c in patch 3. In particular, no need to change the function signature in bpf_insn_revmap_call_t. Also, removed the changes in print_bpf_insn(). - Fixed an issue in check_kfunc_call() when the calling kernel function returns a pointer in patch 3. Added a selftest. - Adjusted the verifier selftests due to the changes in the verifier log in patch 3. - Fixed a comparison issue in kfunc_desc_cmp_by_imm() in patch 3. (Andrii) - Name change: is_ldimm64_insn(), new helper: is_call_insn() in patch 10 (Andrii) - Move btf_func_linkage() from btf.h to libbpf.c in patch 11. (Andrii) - Fixed the linker error when CONFIG_BPF_SYSCALL is not defined. Moved the check_kfunc_call from filter.c to test_run.c in patch 14. (kernel test robot) ==================== Signed-off-by: Alexei Starovoitov <ast@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.