[bpf,v1,0/2] bpf: Fix linker optimization removing kfuncs

Message

Tony Ambardar June 3, 2024, 12:16 p.m. UTC

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.


Tony Ambardar (2):
  Compiler Attributes: Add __retain macro
  bpf: Harden __bpf_kfunc tag against linker kfunc removal

 include/linux/btf.h                 |  2 +-
 include/linux/compiler_attributes.h | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)