From ffed24eff9e0e52d8e74df1c18db8ed43b4666e6 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Wed, 6 Dec 2023 09:30:41 +0100 Subject: selftests/bpf: Add test for early update in prog_array_map_poke_run Adding test that tries to trigger the BUG_IN during early map update in prog_array_map_poke_run function. The idea is to share prog array map between thread that constantly updates it and another one loading a program that uses that prog array. Eventually we will hit a place where the program is ok to be updated (poke->tailcall_target_stable check) but the address is still not registered in kallsyms, so the bpf_arch_text_poke returns -EINVAL and cause imbalance for the next tail call update check, which will fail with -EBUSY in bpf_arch_text_poke as described in previous fix. Signed-off-by: Jiri Olsa Signed-off-by: Daniel Borkmann Acked-by: Ilya Leoshkevich Link: https://lore.kernel.org/bpf/20231206083041.1306660-3-jolsa@kernel.org --- tools/testing/selftests/bpf/prog_tests/tailcalls.c | 84 ++++++++++++++++++++++ tools/testing/selftests/bpf/progs/tailcall_poke.c | 32 +++++++++ 2 files changed, 116 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/tailcall_poke.c (limited to 'tools') diff --git a/tools/testing/selftests/bpf/prog_tests/tailcalls.c b/tools/testing/selftests/bpf/prog_tests/tailcalls.c index fc6b2954e8f5..59993fc9c0d7 100644 --- a/tools/testing/selftests/bpf/prog_tests/tailcalls.c +++ b/tools/testing/selftests/bpf/prog_tests/tailcalls.c @@ -1,6 +1,9 @@ // SPDX-License-Identifier: GPL-2.0 +#include #include #include +#include "tailcall_poke.skel.h" + /* test_tailcall_1 checks basic functionality by patching multiple locations * in a single program for a single tail call slot with nop->jmp, jmp->nop @@ -1105,6 +1108,85 @@ out: bpf_object__close(tgt_obj); } +#define JMP_TABLE "/sys/fs/bpf/jmp_table" + +static int poke_thread_exit; + +static void *poke_update(void *arg) +{ + __u32 zero = 0, prog1_fd, prog2_fd, map_fd; + struct tailcall_poke *call = arg; + + map_fd = bpf_map__fd(call->maps.jmp_table); + prog1_fd = bpf_program__fd(call->progs.call1); + prog2_fd = bpf_program__fd(call->progs.call2); + + while (!poke_thread_exit) { + bpf_map_update_elem(map_fd, &zero, &prog1_fd, BPF_ANY); + bpf_map_update_elem(map_fd, &zero, &prog2_fd, BPF_ANY); + } + + return NULL; +} + +/* + * We are trying to hit prog array update during another program load + * that shares the same prog array map. + * + * For that we share the jmp_table map between two skeleton instances + * by pinning the jmp_table to same path. Then first skeleton instance + * periodically updates jmp_table in 'poke update' thread while we load + * the second skeleton instance in the main thread. + */ +static void test_tailcall_poke(void) +{ + struct tailcall_poke *call, *test; + int err, cnt = 10; + pthread_t thread; + + unlink(JMP_TABLE); + + call = tailcall_poke__open_and_load(); + if (!ASSERT_OK_PTR(call, "tailcall_poke__open")) + return; + + err = bpf_map__pin(call->maps.jmp_table, JMP_TABLE); + if (!ASSERT_OK(err, "bpf_map__pin")) + goto out; + + err = pthread_create(&thread, NULL, poke_update, call); + if (!ASSERT_OK(err, "new toggler")) + goto out; + + while (cnt--) { + test = tailcall_poke__open(); + if (!ASSERT_OK_PTR(test, "tailcall_poke__open")) + break; + + err = bpf_map__set_pin_path(test->maps.jmp_table, JMP_TABLE); + if (!ASSERT_OK(err, "bpf_map__pin")) { + tailcall_poke__destroy(test); + break; + } + + bpf_program__set_autoload(test->progs.test, true); + bpf_program__set_autoload(test->progs.call1, false); + bpf_program__set_autoload(test->progs.call2, false); + + err = tailcall_poke__load(test); + tailcall_poke__destroy(test); + if (!ASSERT_OK(err, "tailcall_poke__load")) + break; + } + + poke_thread_exit = 1; + ASSERT_OK(pthread_join(thread, NULL), "pthread_join"); + +out: + bpf_map__unpin(call->maps.jmp_table, JMP_TABLE); + tailcall_poke__destroy(call); +} + void test_tailcalls(void) { if (test__start_subtest("tailcall_1")) @@ -1139,4 +1221,6 @@ void test_tailcalls(void) test_tailcall_bpf2bpf_fentry_fexit(); if (test__start_subtest("tailcall_bpf2bpf_fentry_entry")) test_tailcall_bpf2bpf_fentry_entry(); + if (test__start_subtest("tailcall_poke")) + test_tailcall_poke(); } diff --git a/tools/testing/selftests/bpf/progs/tailcall_poke.c b/tools/testing/selftests/bpf/progs/tailcall_poke.c new file mode 100644 index 000000000000..c78b94b75e83 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/tailcall_poke.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include + +char _license[] SEC("license") = "GPL"; + +struct { + __uint(type, BPF_MAP_TYPE_PROG_ARRAY); + __uint(max_entries, 1); + __uint(key_size, sizeof(__u32)); + __uint(value_size, sizeof(__u32)); +} jmp_table SEC(".maps"); + +SEC("?fentry/bpf_fentry_test1") +int BPF_PROG(test, int a) +{ + bpf_tail_call_static(ctx, &jmp_table, 0); + return 0; +} + +SEC("fentry/bpf_fentry_test1") +int BPF_PROG(call1, int a) +{ + return 0; +} + +SEC("fentry/bpf_fentry_test1") +int BPF_PROG(call2, int a) +{ + return 0; +} -- cgit