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While building on a wide range of distros and clang versions it was
noticed that at least version 12.0.1 (noticed on Alpine 3.15 with
"Alpine clang version 12.0.1") is needed to not fail with BTF generation
errors such as:
Debian:10
Debian clang version 11.0.1-2~deb10u1:
CLANG /tmp/build/perf/util/bpf_skel/.tmp/sample_filter.bpf.o
<SNIP>
GENSKEL /tmp/build/perf/util/bpf_skel/sample_filter.skel.h
libbpf: failed to find BTF for extern 'bpf_cast_to_kern_ctx' [21] section: -2
Error: failed to open BPF object file: No such file or directory
make[2]: *** [Makefile.perf:1121: /tmp/build/perf/util/bpf_skel/sample_filter.skel.h] Error 254
make[2]: *** Deleting file '/tmp/build/perf/util/bpf_skel/sample_filter.skel.h'
Amazon Linux 2:
clang version 11.1.0 (Amazon Linux 2 11.1.0-1.amzn2.0.2)
GENSKEL /tmp/build/perf/util/bpf_skel/sample_filter.skel.h
libbpf: elf: skipping unrecognized data section(18) .eh_frame
libbpf: elf: skipping relo section(19) .rel.eh_frame for section(18) .eh_frame
libbpf: failed to find BTF for extern 'bpf_cast_to_kern_ctx' [21] section: -2
Error: failed to open BPF object file: No such file or directory
make[2]: *** [/tmp/build/perf/util/bpf_skel/sample_filter.skel.h] Error 254
make[2]: *** Deleting file `/tmp/build/perf/util/bpf_skel/sample_filter.skel.h'
Ubuntu 20.04:
clang version 10.0.0-4ubuntu1
CLANG /tmp/build/perf/util/bpf_skel/.tmp/augmented_raw_syscalls.bpf.o
GENSKEL /tmp/build/perf/util/bpf_skel/bench_uprobe.skel.h
GENSKEL /tmp/build/perf/util/bpf_skel/bperf_leader.skel.h
libbpf: sec '.reluprobe': corrupted symbol #27 pointing to invalid section #65522 for relo #0
GENSKEL /tmp/build/perf/util/bpf_skel/bperf_follower.skel.h
Error: failed to open BPF object file: BPF object format invalid
make[2]: *** [Makefile.perf:1121: /tmp/build/perf/util/bpf_skel/bench_uprobe.skel.h] Error 95
make[2]: *** Deleting file '/tmp/build/perf/util/bpf_skel/bench_uprobe.skel.h'
So check if the version is at least 12.0.1 otherwise disable building
BPF skels and provide a message about it, continuing the build.
The message, when running on amazonlinux:2:
Makefile.config:698: Warning: Disabled BPF skeletons as reliable BTF generation needs at least clang version 12.0.1
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/ZTvGx/Ou6BVnYBqi@kernel.org
Signed-off-by: Namhyung Kim <namhyung@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.