[PATCH bpf v2 0/2] bpf: Fix linker optimization removing kfuncs

[Tony Ambardar <tony.ambardar@gmail.com>]

This patch series fixes unwanted stripping of kernel kfuncs during linker
optimization, as indicated by build warnings from resolve_btfids e.g.
"WARN: resolve_btfids: unresolved symbol ...". This can happen because the
__bpf_kfunc macro annotating kfunc declarations is ignored during linking.

Patch 1 adds support for the compiler attribute "__retain__", used to
avoid linker garbage cleanup. Patch 2 then updates __bpf_kfunc to use this
attribute when LTO builds are enabled.

Build-tested locally against mips64el with gcc 13.3, and run through
upstream kernel-patches/bpf CI.

Tony Ambardar (2):
  compiler_types.h: Define __retain for __attribute__((__retain__))
  bpf: Harden __bpf_kfunc tag against linker kfunc removal

 include/linux/btf.h            |  2 +-
 include/linux/compiler_types.h | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

-- 

v2:
- move __retain macro to compiler_types.h (Miguel Ojeda)

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2.34.1