[PATCH bpf-next 6/8] selftests/bpf: Add a test to verify kprobe_write_ctx compatibility enforcement
From: Leon Hwang <hidden>
Date: 2026-02-24 15:42:48
Also in:
bpf, linux-kselftest, lkml
Subsystem:
bpf [general] (safe dynamic programs and tools), bpf [selftests] (test runners & infrastructure), kernel selftest framework, the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Shuah Khan, Linus Torvalds
Add prog_array coverage for kprobe programs with and without kprobe_write_ctx requirements. The test verifies one-way enforcement: !kprobe_write_ctx programs cannot tail-call kprobe_write_ctx programs. Assisted-by: Codex:gpt-5.3-codex Signed-off-by: Leon Hwang <redacted> --- .../selftests/bpf/prog_tests/attach_probe.c | 44 +++++++++++++++++++ .../selftests/bpf/progs/kprobe_write_ctx.c | 6 +++ 2 files changed, 50 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
index 9e77e5da7097..a9444db92246 100644
--- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
+++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c@@ -220,11 +220,53 @@ static void test_attach_kprobe_write_ctx(void) kprobe_write_ctx__destroy(skel); } + +static void test_kprobe_write_ctx_prog_array_compat(void) +{ + __u32 key = 0, read_prog_fd, write_prog_fd; + struct kprobe_write_ctx *skel = NULL; + int map_fd = -1, err; + + skel = kprobe_write_ctx__open_and_load(); + if (!ASSERT_OK_PTR(skel, "kprobe_write_ctx__open_and_load")) + return; + + map_fd = bpf_map_create(BPF_MAP_TYPE_PROG_ARRAY, NULL, sizeof(key), + sizeof(__u32), 1, NULL); + if (!ASSERT_GE(map_fd, 0, "bpf_map_create")) + goto cleanup; + + read_prog_fd = bpf_program__fd(skel->progs.kprobe_read_ctx); + write_prog_fd = bpf_program__fd(skel->progs.kprobe_write_ctx); + if (!ASSERT_GE(read_prog_fd, 0, "read_prog_fd")) + goto cleanup; + if (!ASSERT_GE(write_prog_fd, 0, "write_prog_fd")) + goto cleanup; + + err = bpf_map_update_elem(map_fd, &key, &read_prog_fd, BPF_ANY); + if (!ASSERT_OK(err, "bpf_map_update_elem success")) + goto cleanup; + + err = bpf_map_update_elem(map_fd, &key, &write_prog_fd, BPF_ANY); + if (!ASSERT_ERR(err, "bpf_map_update_elem failure")) + goto cleanup; + ASSERT_EQ(errno, EINVAL, "bpf_map_update_elem errno"); + +cleanup: + if (map_fd >= 0) + close(map_fd); + kprobe_write_ctx__destroy(skel); +} #else static void test_attach_kprobe_write_ctx(void) { test__skip(); } + +static void test_kprobe_write_ctx_prog_array_compat(void) +{ + test__skip(); +} #endif static void test_attach_probe_auto(struct test_attach_probe *skel)
@@ -434,6 +476,8 @@ void test_attach_probe(void) test_attach_kprobe_long_event_name(); if (test__start_subtest("kprobe-write-ctx")) test_attach_kprobe_write_ctx(); + if (test__start_subtest("kprobe-write-ctx-prog-array-compat")) + test_kprobe_write_ctx_prog_array_compat(); cleanup: test_attach_probe__destroy(skel);
diff --git a/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c b/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c
index f77aef0474d3..09e0c487bde5 100644
--- a/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c
+++ b/tools/testing/selftests/bpf/progs/kprobe_write_ctx.c@@ -13,6 +13,12 @@ int kprobe_write_ctx(struct pt_regs *ctx) return 0; } +SEC("kprobe") +int kprobe_read_ctx(struct pt_regs *ctx) +{ + return 0; +} + SEC("kprobe.multi") int kprobe_multi_write_ctx(struct pt_regs *ctx) {
--
2.52.0