[bpf-next,v2,0/3] selftests/bpf: Improve building with extra

Message

Viktor Malik Oct. 18, 2024, 6:48 a.m. UTC

When trying to build BPF selftests with additional compiler and linker
flags, we're running into multiple problems. This series addresses all
of them:

- CFLAGS are not passed to sub-makes of bpftool and libbpf. This is a
  problem when compiling with PIE as libbpf.a ends up being non-PIE and
  cannot be linked with other binaries (patch #1).

- bpftool Makefile runs `llvm-config --cflags` and appends the result to
  CFLAGS. The result typically contains `-D_GNU_SOURCE` which may be
  already set in CFLAGS. That causes a compilation error (patch #2).

- Some GCC flags are not supported by Clang but there are binaries which
  are always built with Clang but reuse user-defined CFLAGS. When CFLAGS
  contain such flags, compilation fails (patch #3).

Changelog:
----------
v1 -> v2:
- cover forgotten case in patch#1 (noted by Eduard)
- remove -D_GNU_SOURCE unconditionally in patch#2 (suggested by Andrii)
- rewrite patch#3 to just add -Wno-unused-command-line-argument
  (suggested by Andrii)

Viktor Malik (3):
  selftests/bpf: Allow building with extra flags
  bpftool: Prevent setting duplicate _GNU_SOURCE in Makefile
  selftests/bpf: Disable warnings on unused flags for Clang builds

 tools/bpf/bpftool/Makefile           |  6 +++++-
 tools/testing/selftests/bpf/Makefile | 28 +++++++++++++++++++---------
 2 files changed, 24 insertions(+), 10 deletions(-)

Comments

[e-mail] Oct. 22, 2024, midnight UTC | #1

Hello:

This series was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <[e-mail]>:

On Fri, 18 Oct 2024 08:48:58 +0200 you wrote:
> When trying to build BPF selftests with additional compiler and linker
> flags, we're running into multiple problems. This series addresses all
> of them:
> 
> - CFLAGS are not passed to sub-makes of bpftool and libbpf. This is a
>   problem when compiling with PIE as libbpf.a ends up being non-PIE and
>   cannot be linked with other binaries (patch #1).
> 
> [...]

Here is the summary with links:
  - [bpf-next,v2,1/3] selftests/bpf: Allow building with extra flags
    https://git.kernel.org/bpf/bpf-next/c/7b164c648ee2
  - [bpf-next,v2,2/3] bpftool: Prevent setting duplicate _GNU_SOURCE in Makefile
    https://git.kernel.org/bpf/bpf-next/c/a89cf33e4e30
  - [bpf-next,v2,3/3] selftests/bpf: Disable warnings on unused flags for Clang builds
    https://git.kernel.org/bpf/bpf-next/c/832c03d644ba

You are awesome, thank you!