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Ilya Leoshkevich says: ==================== Some BPF programs compiled on s390 fail to load, because s390 arch-specific linux headers contain float and double types. Introduce support for such types by representing them using the new BTF_KIND_FLOAT. This series deals with libbpf, bpftool, in-kernel BTF parser as well as selftests and documentation. There are also pahole and LLVM parts: * https://github.com/iii-i/dwarves/commit/btf-kind-float-v2 * https://reviews.llvm.org/D83289 but they should go in after the libbpf part is integrated. --- v0: https://lore.kernel.org/bpf/20210210030317.78820-1-iii@linux.ibm.com/ v0 -> v1: Per Andrii's suggestion, remove the unnecessary trailing u32. v1: https://lore.kernel.org/bpf/20210216011216.3168-1-iii@linux.ibm.com/ v1 -> v2: John noticed that sanitization corrupts BTF, because new and old sizes don't match. Per Yonghong's suggestion, use a modifier type (which has the same size as the float type) as a replacement. Per Yonghong's suggestion, add size and alignment checks to the kernel BTF parser. v2: https://lore.kernel.org/bpf/20210219022543.20893-1-iii@linux.ibm.com/ v2 -> v3: Based on Yonghong's suggestions: Use BTF_KIND_CONST instead of BTF_KIND_TYPEDEF and make sure that the C code generated from the sanitized BTF is well-formed; fix size calculation in tests and use NAME_TBD everywhere; limit allowed sizes to 2, 4, 8, 12 and 16 (this should also fix m68k and nds32le builds). v3: https://lore.kernel.org/bpf/20210220034959.27006-1-iii@linux.ibm.com/ v3 -> v4: More fixes for the Yonghong's findings: fix the outdated comment in bpf_object__sanitize_btf() and add the error handling there (I've decided to check uint_id and uchar_id too in order to simplify debugging); add bpftool output example; use div64_u64_rem() instead of % in order to fix the linker error. Also fix the "invalid BTF_INFO" test (new commit, #4). v4: https://lore.kernel.org/bpf/20210222214917.83629-1-iii@linux.ibm.com/ v4 -> v5: Fixes for the Andrii's findings: Use BTF_KIND_STRUCT instead of BTF_KIND_TYPEDEF for sanitization; check byte_sz in libbpf; move btf__add_float; remove relo support; add a dedup test (new commit, #7). v5: https://lore.kernel.org/bpf/20210223231459.99664-1-iii@linux.ibm.com/ v5 -> v6: Fixes for further findings by Andrii: split whitespace issue fix into a separate patch; add 12-byte float to "float test #1, well-formed". v6: https://lore.kernel.org/bpf/20210224234535.106970-1-iii@linux.ibm.com/ v6 -> v7: John suggested to add a comment explaining why sanitization does not preserve the type name, as well as what effect it has on running the code on the older kernels. Yonghong has asked to add a comment explaining why we are not checking the alignment very precisely in the kernel. John suggested to add a bpf_core_field_size test (commit #9). Based on Alexei's feedback [1] I'm proceeding with the BTF_KIND_FLOAT approach. [1] https://lore.kernel.org/bpf/CAADnVQKWPODWZ2RSJ5FJhfYpxkuV0cvSAL1O+FSr9oP1ercoBg@mail.gmail.com/ ==================== 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.