[PATCH bpf-next v3 0/2] bpf: Allow void return type for global subprogs

[Emil Tsalapatis <emil@etsalapatis.com>]

Global subprogs are currently not allowed to return void. Adjust
verifier logic to allow global functions with a void return type.
Exception callbacks are excluded from this change, and still require
a scalar return type.

Also adjust existing selftests that were ensuring that global subprogs
with void return types fail to verify. These tests should now load
successfully.

v2 -> v3
(https://lore.kernel.org/bpf/20260210183257.217285-1-emil@etsalapatis.com/)
- Allow freplace for global programs that return void and add selftests (Kumar)

v1 -> v2
(https://lore.kernel.org/bpf/20260127231414.359283-1-emil@etsalapatis.com/)

- Only mark R0 as valid for non-void global functions (AI)
- Rename subprog_is_void to subprog_returns_void (Kumar)
- Add test that R0 is invalid after calling a void global (Alexei)
- Add check to ensure exception callbacks do not return void
and associated selftest

Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Emil Tsalapatis (2):
  bpf: Allow void global functions in the verifier
  selftests: bpf: Add tests for void global subprogs

 kernel/bpf/btf.c                              |  7 ++-
 kernel/bpf/verifier.c                         | 59 +++++++++++++++++--
 .../selftests/bpf/prog_tests/fexit_bpf2bpf.c  | 24 ++++++++
 .../bpf/prog_tests/test_global_funcs.c        |  2 +
 .../selftests/bpf/progs/exceptions_fail.c     | 19 +++++-
 .../bpf/progs/freplace_int_with_void.c        | 14 +++++
 .../selftests/bpf/progs/freplace_void.c       | 14 +++++
 .../selftests/bpf/progs/test_global_func18.c  | 23 ++++++++
 .../selftests/bpf/progs/test_global_func7.c   |  2 +-
 9 files changed, 151 insertions(+), 13 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/progs/freplace_int_with_void.c
 create mode 100644 tools/testing/selftests/bpf/progs/freplace_void.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_global_func18.c

-- 
2.49.0