lwn.git/tools/testing/selftests/bpf/test_kmods, branch master

selftests/bpf: Add syscall ctx variable offset tests

2026-04-06T22:27:26+00:00

Add various tests to exercise fixed and variable offsets on PTR_TO_CTX for syscall programs, and cover disallowed cases for other program types lacking convert_ctx_access callback. Load verifier_ctx with CAP_SYS_ADMIN so that kfunc related logic can be tested. While at it, convert assembly tests to C. Unfortunately, ctx_pointer_to_helper_2's unpriv case conflicts with usage of kfuncs in the file and cannot be run. Reviewed-by: Emil Tsalapatis Acked-by: Puranjay Mohan Acked-by: Mykyta Yatsenko Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260406194403.1649608-5-memxor@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: move trampoline_count to dedicated bpf_testmod target

2026-03-24T20:39:32+00:00

trampoline_count fills all trampoline attachment slots for a single target function and verifies that one extra attach fails with -E2BIG. It currently targets bpf_modify_return_test, which is also used by other selftests such as modify_return, get_func_ip_test, and get_func_args_test. When such tests run in parallel, they can contend for the same per-function trampoline quota and cause unexpected attach failures. This issue is currently masked by harness serialization. Move trampoline_count to a dedicated bpf_testmod target and register it for fmod_ret attachment. Also route the final trigger through trigger_module_test_read(), so the execution path exercises the same dedicated target. This keeps the test semantics unchanged while isolating it from other selftests, so it no longer needs to run in serial mode. Remove the TODO comment as well. Tested: ./test_progs -t trampoline_count -vv ./test_progs -j$(nproc) -t trampoline_count -vv ./test_progs -j$(nproc) -t \ trampoline_count,modify_return,get_func_ip_test,get_func_args_test -vv 20 runs of: ./test_progs -j$(nproc) -t \ trampoline_count,modify_return,get_func_ip_test,get_func_args_test Signed-off-by: Sun Jian Acked-by: Jiri Olsa Link: https://lore.kernel.org/r/20260324044949.869801-1-sun.jian.kdev@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Add test for struct_ops __ref argument in any position

2026-03-24T15:51:23+00:00

Add a selftest to verify that the verifier correctly identifies refcounted arguments in struct_ops programs, even when they are not the first argument. This ensures that the restriction on tail calls for programs with __ref arguments is properly enforced regardless of which argument they appear in. This test verifies the fix for check_struct_ops_btf_id() proposed by Keisuke Nishimura [0], which corrected a bug where only the first argument was checked for the refcounted flag. The test includes: - An update to bpf_testmod to add 'test_refcounted_multi', an operator with three arguments where the third is tagged with "__ref". - A BPF program 'test_refcounted_multi' that attempts a tail call. - A test runner that asserts the verifier rejects the program with "program with __ref argument cannot tail call". [0]: https://lore.kernel.org/bpf/20260320130219.63711-1-keisuke.nishimura@inria.fr/ Signed-off-by: Varun R Mallya Link: https://lore.kernel.org/r/20260321214038.80479-1-varunrmallya@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Improve test coverage for kfunc call

2026-03-13T14:13:35+00:00

On powerpc, immediate load instructions are sign extended. In case of unsigned types, arguments should be explicitly zero-extended by the caller. For kfunc call, this needs to be handled in the JIT code. In bpf_kfunc_call_test4(), that tests for sign-extension of signed argument types in kfunc calls, add some additional failure checks. And add bpf_kfunc_call_test5() to test zero-extension of unsigned argument types in kfunc calls. Signed-off-by: Hari Bathini Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20260312080113.843408-1-hbathini@linux.ibm.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Fix map_kptr grace period wait

2026-02-13T22:14:27+00:00

Commit c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast") broke map_kptr selftest since it removed the function we were kprobing. Use a new kfunc that invokes call_rcu_tasks_trace and sets a program provided pointer to an integer to 1. Technically this can be unsafe if the memory being written to from the callback disappears, but this is just for usage in a test where we ensure we spin until we see the value to be set to 1, so it's ok. Reported-by: Shung-Hsi Yu Fixes: c27cea4416a3 ("rcu: Re-implement RCU Tasks Trace in terms of SRCU-fast") Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260211185747.3630539-1-memxor@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Add tests for execution context helpers

2026-01-25T16:20:50+00:00

Add a new selftest suite `exe_ctx` to verify the accuracy of the bpf_in_task(), bpf_in_hardirq(), and bpf_in_serving_softirq() helpers introduced in bpf_experimental.h. Testing these execution contexts deterministically requires crossing context boundaries within a single CPU. To achieve this, the test implements a "Trigger-Observer" pattern using bpf_testmod: 1. Trigger: A BPF syscall program calls a new bpf_testmod kfunc bpf_kfunc_trigger_ctx_check(). 2. Task to HardIRQ: The kfunc uses irq_work_queue() to trigger a self-IPI on the local CPU. 3. HardIRQ to SoftIRQ: The irq_work handler calls a dummy function (observed by BPF fentry) and then schedules a tasklet to transition into SoftIRQ context. The user-space runner ensures determinism by pinning itself to CPU 0 before execution, forcing the entire interrupt chain to remain on a single core. Dummy noinline functions with compiler barriers are added to bpf_testmod.c to serve as stable attachment points for fentry programs. A retry loop is used in user-space to wait for the asynchronous SoftIRQ to complete. Note that testing on s390x is avoided because supporting those helpers purely in BPF on s390x is not possible at this point. Reviewed-by: Alexei Starovoitov Signed-off-by: Changwoo Min Link: https://lore.kernel.org/r/20260125115413.117502-3-changwoo@igalia.com Signed-off-by: Alexei Starovoitov

selftests/bpf: test bpf_get_func_arg() for tp_btf

2026-01-21T17:31:35+00:00

Test bpf_get_func_arg() and bpf_get_func_arg_cnt() for tp_btf. The code is most copied from test1 and test2. Signed-off-by: Menglong Dong Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20260121044348.113201-3-dongml2@chinatelecom.cn Signed-off-by: Alexei Starovoitov

selftests/bpf: update verifier test for default trusted pointer semantics

2026-01-21T01:11:24+00:00

Replace the verifier test for default trusted pointer semantics, which previously relied on BPF kfunc bpf_get_root_mem_cgroup(), with a new test utilizing dedicated BPF kfuncs defined within the bpf_testmod. bpf_get_root_mem_cgroup() was modified such that it again relies on KF_ACQUIRE semantics, therefore no longer making it a suitable candidate to test BPF verifier default trusted pointer semantics against. Link: https://lore.kernel.org/bpf/20260113083949.2502978-2-mattbobrowski@google.com Signed-off-by: Matt Bobrowski Link: https://lore.kernel.org/r/20260120091630.3420452-1-mattbobrowski@google.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Migrate struct_ops_assoc test to KF_IMPLICIT_ARGS

2026-01-21T00:22:38+00:00

A test kfunc named bpf_kfunc_multi_st_ops_test_1_impl() is a user of __prog suffix. Subsequent patch removes __prog support in favor of KF_IMPLICIT_ARGS, so migrate this kfunc to use implicit argument. Signed-off-by: Ihor Solodrai Link: https://lore.kernel.org/r/20260120222638.3976562-12-ihor.solodrai@linux.dev Signed-off-by: Alexei Starovoitov

selftests/bpf: Add tests for KF_IMPLICIT_ARGS

2026-01-21T00:15:57+00:00

Add trivial end-to-end tests to validate that KF_IMPLICIT_ARGS flag is properly handled by both resolve_btfids and the verifier. Declare kfuncs in bpf_testmod. Check that bpf_prog_aux pointer is set in the kfunc implementation. Verify that calls with implicit args and a legacy case all work. Acked-by: Eduard Zingerman Signed-off-by: Ihor Solodrai Link: https://lore.kernel.org/r/20260120222638.3976562-7-ihor.solodrai@linux.dev Signed-off-by: Alexei Starovoitov