629b98e2b1
While separate features have been defined to determine which linking flags are required to use libbfd depending on the distribution (libbfd, libbfd-liberty and libbfd-liberty-z), the same has not been done for other features requiring linking to libbfd. For example, disassembler-four-args requires linking to libbfd too, but it should use the right linking flags. If not all the required ones are specified, e.g. -liberty, detection will always fail even if the feature is available. Instead of creating new features, similarly to libbfd, simply retry detection with the different set of flags until detection succeeds (or fails, if the libraries are missing). In this way, feature detection is transparent for the users of this building mechanism (e.g. perf), and those users don't have for example to set an appropriate value for the FEATURE_CHECK_LDFLAGS-disassembler-four-args variable. The number of retries and features for which the retry mechanism is implemented is low enough to make the increase in the complexity of Makefile negligible. Tested with perf and bpftool on Ubuntu 20.04.4 LTS, Fedora 36 and openSUSE Tumbleweed. Committer notes: Do the retry for disassembler-init-styled as well. Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Andres Freund <andres@anarazel.de> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Ingo Molnar <mingo@redhat.com> Cc: John Fastabend <john.fastabend@gmail.com> Cc: KP Singh <kpsingh@kernel.org> Cc: Martin KaFai Lau <martin.lau@linux.dev> Cc: Nathan Chancellor <nathan@kernel.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Nick Terrell <terrelln@fb.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Quentin Monnet <quentin@isovalent.com> Cc: Song Liu <song@kernel.org> Cc: Stanislav Fomichev <sdf@google.com> Cc: bpf@vger.kernel.org Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20220719170555.2576993-1-roberto.sassu@huawei.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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.