[PATCH bpf-next 0/3] bpf: Fix builds broken by fatal resolve_btfids warnings

[Sasha Levin]

Commit 201a454df948 ("resolve_btfids: Fix the --fatal_warnings exit
status") makes resolve_btfids warnings fail the build again with
CONFIG_WERROR=y. That exposed BTF ID references to functions some
configs don't build. KernelCI has been seeing i386
i386_defconfig+kselftest builds fail on linux-next since next-20261015:

  WARN: resolve_btfids: unresolved symbol bpf_arena_reserve_pages
  WARN: resolve_btfids: unresolved symbol bpf_arena_free_pages
  WARN: resolve_btfids: unresolved symbol bpf_arena_alloc_pages
  Failed to generate BTF for vmlinux
  Try to disable CONFIG_DEBUG_INFO_BTF

https://files.kernelci.org/kbuild-gcc-14-i386-kselftest-6ad2315ca3f195e1aa930c8a/build.log.gz

Patch 1 drops three special_kfunc_list entries that have no users,
bpf_arena_reserve_pages among them. Patch 2 makes the remaining arena
entries depend on the condition arena.o is built with. Patch 3 fixes the
same problem for bpf_lsm_socket_sendmsg in bpf_ksock.c, which breaks
x86_64 builds with CONFIG_BPF_LSM=y and CONFIG_SECURITY_NETWORK=n.

The entries left in special_kfunc_list resolve to the same IDs as
before, and the IDs that become BTF_ID_UNUSED were already zero.

Tested by building vmlinux with CONFIG_DEBUG_INFO_BTF=y and
CONFIG_WERROR=y for i386, x86_64, and x86_64 with CONFIG_BPF_LSM=y and
both CONFIG_SECURITY_NETWORK=n and =y, and comparing special_kfunc_list
and bpf_lsm_socket_sendmsg_id before and after the series.

Sasha Levin (3):
  bpf: Drop unused entries from special_kfunc_list again
  bpf: Don't reference arena kfuncs when arena isn't built
  bpf: Fix ksock build with BPF_LSM=y and SECURITY_NETWORK=n

 kernel/bpf/verifier.c | 11 +++++------
 net/core/bpf_ksock.c  |  7 ++++++-
 2 files changed, 11 insertions(+), 7 deletions(-)


base-commit: 25bb03f0a47b622b9025a1558bf2095ec1f55d26
-- 
2.53.0