Verify the fact that an fentry prog could be attached to another one, building up an attachment chain of limited size. Use existing bpf_testmod as a start of the chain. Note, that currently it's not possible to: * form a cycle within an attachment chain * splice two attachment chains Those limitations are coming from the fact that attach_prog_fd is specified at the prog load (thus making it impossible to attach to a program loaded after it in this way), as well as tracing progs not implementing link_detach. This is the reason there is only one test for the chain length. Signed-off-by: Dmitrii Dolgov <9erthalion6@xxxxxxxxx> --- .../bpf/prog_tests/recursive_attach.c | 85 +++++++++++++++++++ .../selftests/bpf/progs/fentry_recursive.c | 19 +++++ .../bpf/progs/fentry_recursive_target.c | 20 +++++ 3 files changed, 124 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/recursive_attach.c create mode 100644 tools/testing/selftests/bpf/progs/fentry_recursive.c create mode 100644 tools/testing/selftests/bpf/progs/fentry_recursive_target.c diff --git a/tools/testing/selftests/bpf/prog_tests/recursive_attach.c b/tools/testing/selftests/bpf/prog_tests/recursive_attach.c new file mode 100644 index 000000000000..9c422dd92c4e --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/recursive_attach.c @@ -0,0 +1,85 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023 Red Hat, Inc. */ +#include <test_progs.h> +#include "fentry_recursive.skel.h" +#include "fentry_recursive_target.skel.h" +#include <bpf/btf.h> +#include "bpf/libbpf_internal.h" + +#define ATTACH_DEPTH 33 + +/* + * Test following scenarios: + * - one can attach fentry progs recursively, one fentry to another one + * - an attachment chain generated this way is limited, after 32 attachment no + * more progs could be added + */ +void test_recursive_fentry_attach(void) +{ + struct fentry_recursive_target *target_skel = NULL; + struct fentry_recursive *tracing_chain[ATTACH_DEPTH + 1] = {}; + struct bpf_program *prog; + int prev_fd, err; + + target_skel = fentry_recursive_target__open_and_load(); + if (!ASSERT_OK_PTR(target_skel, "fentry_recursive_target__open_and_load")) + goto close_prog; + + /* This is going to be the start of the chain */ + tracing_chain[0] = fentry_recursive__open(); + if (!ASSERT_OK_PTR(tracing_chain[0], "fentry_recursive__open")) + goto close_prog; + + prog = tracing_chain[0]->progs.recursive_attach; + prev_fd = bpf_program__fd(target_skel->progs.test1); + err = bpf_program__set_attach_target(prog, prev_fd, "test1"); + if (!ASSERT_OK(err, "bpf_program__set_attach_target")) + goto close_prog; + + err = fentry_recursive__load(tracing_chain[0]); + if (!ASSERT_OK(err, "fentry_recursive__load")) + goto close_prog; + + /* Create an attachment chain to exhaust the limit */ + for (int i = 1; i < ATTACH_DEPTH; i++) { + tracing_chain[i] = fentry_recursive__open(); + if (!ASSERT_OK_PTR(tracing_chain[i], "fentry_recursive__open")) + goto close_prog; + + prog = tracing_chain[i]->progs.recursive_attach; + prev_fd = bpf_program__fd(tracing_chain[i-1]->progs.recursive_attach); + err = bpf_program__set_attach_target(prog, prev_fd, "recursive_attach"); + if (!ASSERT_OK(err, "bpf_program__set_attach_target")) + goto close_prog; + + err = fentry_recursive__load(tracing_chain[i]); + if (!ASSERT_OK(err, "fentry_recursive__load")) + goto close_prog; + + err = fentry_recursive__attach(tracing_chain[i]); + if (!ASSERT_OK(err, "fentry_recursive__attach")) + goto close_prog; + } + + /* The next attachment would fail */ + tracing_chain[ATTACH_DEPTH] = fentry_recursive__open(); + if (!ASSERT_OK_PTR(tracing_chain[ATTACH_DEPTH], "last fentry_recursive__open")) + goto close_prog; + + prog = tracing_chain[ATTACH_DEPTH]->progs.recursive_attach; + prev_fd = bpf_program__fd(tracing_chain[ATTACH_DEPTH - 1]->progs.recursive_attach); + err = bpf_program__set_attach_target(prog, prev_fd, "recursive_attach"); + if (!ASSERT_OK(err, "last bpf_program__set_attach_target")) + goto close_prog; + + err = fentry_recursive__load(tracing_chain[ATTACH_DEPTH]); + if (!ASSERT_ERR(err, "last fentry_recursive__load")) + goto close_prog; + +close_prog: + fentry_recursive_target__destroy(target_skel); + for (int i = 1; i < ATTACH_DEPTH + 1; i++) { + if (tracing_chain[i]) + fentry_recursive__destroy(tracing_chain[i]); + } +} diff --git a/tools/testing/selftests/bpf/progs/fentry_recursive.c b/tools/testing/selftests/bpf/progs/fentry_recursive.c new file mode 100644 index 000000000000..1df490230344 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/fentry_recursive.c @@ -0,0 +1,19 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023 Red Hat, Inc. */ +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +char _license[] SEC("license") = "GPL"; + +__u64 test1_result = 0; + +/* + * Dummy fentry bpf prog for testing fentry attachment chains + */ +SEC("fentry/XXX") +int BPF_PROG(recursive_attach, int a) +{ + test1_result = a == 1; + return 0; +} diff --git a/tools/testing/selftests/bpf/progs/fentry_recursive_target.c b/tools/testing/selftests/bpf/progs/fentry_recursive_target.c new file mode 100644 index 000000000000..b6fb8ebd598d --- /dev/null +++ b/tools/testing/selftests/bpf/progs/fentry_recursive_target.c @@ -0,0 +1,20 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023 Red Hat, Inc. */ +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +char _license[] SEC("license") = "GPL"; + +__u64 test1_result = 0; + +/* + * Dummy fentry bpf prog for testing fentry attachment chains. It's going to be + * a start of the chain. + */ +SEC("fentry/bpf_testmod_fentry_test1") +int BPF_PROG(test1, int a) +{ + test1_result = a == 1; + return 0; +} -- 2.41.0