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* [PATCH bpf-next v4 0/4] bpf: Allow void return type for global subprogs
@ 2026-02-25  3:33 Emil Tsalapatis
  2026-02-25  3:33 ` [PATCH bpf-next v4 1/4] bpf: Factor out program return value calculation Emil Tsalapatis
                   ` (3 more replies)
  0 siblings, 4 replies; 11+ messages in thread
From: Emil Tsalapatis @ 2026-02-25  3:33 UTC (permalink / raw)
  To: bpf
  Cc: andrii, ast, daniel, eddyz87, martin.lau, memxor, song,
	yonghong.song, Emil Tsalapatis

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. 

Adding additional logic for void globals significantly complicates
check_return_code(), mainly because of how the new feature interacts
with bpf_throw(). To avoid complicating the code, refactor the return
value range validation logic into two separate functions, one for
program exits through BPF_EXIT and one for program exits through
bpf_throw(). The changes are non-functional.

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

Patches 1-2 refactor check_return_code into two separate functions, one
for BPF_EXIT and one for bpf_throw(). No functional changes.

Patches 3-4 enable void globals in the verifier and add additional
selftests.

v3 -> v4
(https://lore.kernel.org/bpf/20260223215046.1706110-1-emil@etsalapatis.com/)
- Factor out bpf_throw() return value validation logic into its own
  function (Eduard)
- Validate the range of bpf_throw() return values from void globals (Eduard)
- Move new selftest to verifier_global_subprogs.c (Eduard)
- Remove unnecessary verifier_bug_if() statements (Eduard)
- Add new test to ensure void globals can call bpf_throw

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 (4):
  bpf: Factor out program return value calculation
  bpf: Separate bpf_throw() and bpf_exit() return value validation
  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                         | 372 ++++++++++++------
 .../selftests/bpf/prog_tests/exceptions.c     |   1 +
 .../selftests/bpf/prog_tests/fexit_bpf2bpf.c  |  24 ++
 .../testing/selftests/bpf/progs/exceptions.c  |  14 +
 .../selftests/bpf/progs/exceptions_fail.c     |  35 +-
 .../bpf/progs/freplace_int_with_void.c        |  14 +
 .../selftests/bpf/progs/freplace_void.c       |  12 +
 .../selftests/bpf/progs/test_global_func7.c   |   2 +-
 .../bpf/progs/verifier_global_subprogs.c      |  19 +
 10 files changed, 381 insertions(+), 119 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

-- 
2.49.0


^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2026-02-26 21:17 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-02-25  3:33 [PATCH bpf-next v4 0/4] bpf: Allow void return type for global subprogs Emil Tsalapatis
2026-02-25  3:33 ` [PATCH bpf-next v4 1/4] bpf: Factor out program return value calculation Emil Tsalapatis
2026-02-25 23:31   ` Eduard Zingerman
2026-02-26 21:17     ` Emil Tsalapatis
2026-02-25  3:33 ` [PATCH bpf-next v4 2/4] bpf: Separate bpf_throw() and bpf_exit() return value validation Emil Tsalapatis
2026-02-25  4:23   ` bot+bpf-ci
2026-02-26  1:48     ` Emil Tsalapatis
2026-02-26  4:56   ` Eduard Zingerman
2026-02-26 20:35     ` Emil Tsalapatis
2026-02-25  3:33 ` [PATCH bpf-next v4 3/4] bpf: Allow void global functions in the verifier Emil Tsalapatis
2026-02-25  3:33 ` [PATCH bpf-next v4 4/4] selftests: bpf: Add tests for void global subprogs Emil Tsalapatis

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