selftests/bpf: Keep int return type for tailcall subprogs

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LLVM23 ([1]) supports 'true' function signature in BTF. The return type
of the caller of a tailcall must be an 'int'. Otherwise, verification will
fail (see check_btf_func() in check_btf.c). So with llvm23, it is possible
that the compiler may change the caller's return type from 'int' to 'void'.
To prevent this, barrier_var() and __sink() are used to avoid returning
a constant prone to be optimized.

  [1] https://github.com/llvm/llvm-project/pull/198426

Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260609233407.2711577-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Yonghong Song 2026-06-09 16:34:07 -07:00 • committed by Alexei Starovoitov

parent c15261b1bb

commit be1d838b88

6 changed files with 57 additions and 20 deletions

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tools/testing/selftests/bpf/progs/tailcall_bpf2bpf2.c

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tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy1.c

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tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy2.c

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tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy3.c

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tools/testing/selftests/bpf/progs/tailcall_bpf2bpf_hierarchy_fentry.c

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tools/testing/selftests/bpf/progs/verifier_sock.c

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