linux.git/tools/testing/selftests/bpf/progs/tailcall_callback.c, branch master Linux kernel source tree selftests/bpf: Test direct tail calls from callbacks 2026-09-03T16:44:51+00:00 Kumar Kartikeya Dwivedi memxor@gmail.com 2026-09-03T14:44:22+00:00 d9ae3e4c7fb5bfaccc9ca295692d54130862f3b2 tailcall_callback tests a tail call one static subprogram below a callback. That reaches the later stack-depth rejection, but it does not exercise the tail-call helper while the current frame is itself a callback. Add a callback that calls bpf_tail_call directly and expect the existing "cannot tail call within callback" diagnostic. On an affected kernel, the load instead reaches the "callback unexpected regs" verifier bug, so the expected message is absent and the test fails. The existing ordinary subprogram case remains a success control for legitimate tail calls. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20260903144433.1716731-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> 
tailcall_callback tests a tail call one static subprogram below a callback.
That reaches the later stack-depth rejection, but it does not exercise the
tail-call helper while the current frame is itself a callback.

Add a callback that calls bpf_tail_call directly and expect the existing
"cannot tail call within callback" diagnostic. On an affected kernel, the
load instead reaches the "callback unexpected regs" verifier bug, so the
expected message is absent and the test fails. The existing ordinary
subprogram case remains a success control for legitimate tail calls.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260903144433.1716731-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
selftests/bpf: Add testcases for callback with tailcall 2026-07-17T00:46:25+00:00 Pu Lehui pulehui@huawei.com 2026-07-16T12:01:57+00:00 42bfd21a8b70143e68ae6d017752abb3f04738f5 Add 2 testcases for callback with tailcall: 1. failure case: callback->subprog->tailcall. 2. success case: subprog with tailcall do not affect no-tailcall callback. Signed-off-by: Pu Lehui <pulehui@huawei.com> Link: https://patch.msgid.link/20260716120157.835937-4-pulehui@huaweicloud.com Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> 
Add 2 testcases for callback with tailcall:
1. failure case: callback->subprog->tailcall.
2. success case: subprog with tailcall do not affect
   no-tailcall callback.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
Link: https://patch.msgid.link/20260716120157.835937-4-pulehui@huaweicloud.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>