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Date: Thu, 23 May 2024 16:08:46 -0700 Message-Id: <20240523230848.2022072-7-thinker.li@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240523230848.2022072-1-thinker.li@gmail.com> References: <20240523230848.2022072-1-thinker.li@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Not only a user space program can detach a struct_ops link, the subsystem managing a link can also detach the link. This patch adds a kfunc to simulate detaching a link by the subsystem managing it and makes sure user space programs get notified through epoll. Signed-off-by: Kui-Feng Lee --- .../selftests/bpf/bpf_testmod/bpf_testmod.c | 42 ++++++++++++ .../bpf/bpf_testmod/bpf_testmod_kfunc.h | 1 + .../bpf/prog_tests/test_struct_ops_module.c | 67 +++++++++++++++++++ .../selftests/bpf/progs/struct_ops_detach.c | 7 ++ 4 files changed, 117 insertions(+) diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c index 0a09732cde4b..2b3a89609b7e 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c @@ -744,6 +744,38 @@ __bpf_kfunc int bpf_kfunc_call_kernel_getpeername(struct addr_args *args) return err; } +static DEFINE_SPINLOCK(detach_lock); +static struct bpf_link *link_to_detach; + +__bpf_kfunc int bpf_dummy_do_link_detach(void) +{ + struct bpf_link *link; + int ret = -ENOENT; + + /* A subsystem must ensure that a link is valid when detaching the + * link. In order to achieve that, the subsystem may need to obtain + * a lock to safeguard a table that holds the pointer to the link + * being detached. However, the subsystem cannot invoke + * link->ops->detach() while holding the lock because other tasks + * may be in the process of unregistering, which could lead to + * acquiring the same lock and causing a deadlock. This is why + * bpf_link_inc_not_zero() is used to maintain the link's validity. + */ + spin_lock(&detach_lock); + link = link_to_detach; + /* Make sure the link is still valid by increasing its refcnt */ + if (link && IS_ERR(bpf_link_inc_not_zero(link))) + link = NULL; + spin_unlock(&detach_lock); + + if (link) { + ret = link->ops->detach(link); + bpf_link_put(link); + } + + return ret; +} + BTF_KFUNCS_START(bpf_testmod_check_kfunc_ids) BTF_ID_FLAGS(func, bpf_testmod_test_mod_kfunc) BTF_ID_FLAGS(func, bpf_kfunc_call_test1) @@ -780,6 +812,7 @@ BTF_ID_FLAGS(func, bpf_kfunc_call_kernel_sendmsg, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_kfunc_call_sock_sendmsg, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_kfunc_call_kernel_getsockname, KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_kfunc_call_kernel_getpeername, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_dummy_do_link_detach) BTF_KFUNCS_END(bpf_testmod_check_kfunc_ids) static int bpf_testmod_ops_init(struct btf *btf) @@ -832,11 +865,20 @@ static int bpf_dummy_reg(void *kdata, struct bpf_link *link) if (ops->test_2) ops->test_2(4, ops->data); + spin_lock(&detach_lock); + if (!link_to_detach) + link_to_detach = link; + spin_unlock(&detach_lock); + return 0; } static void bpf_dummy_unreg(void *kdata, struct bpf_link *link) { + spin_lock(&detach_lock); + if (link == link_to_detach) + link_to_detach = NULL; + spin_unlock(&detach_lock); } static int bpf_testmod_test_1(void) diff --git a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h index b0d586a6751f..19131baf4a9e 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod_kfunc.h @@ -121,6 +121,7 @@ void bpf_kfunc_call_test_fail1(struct prog_test_fail1 *p); void bpf_kfunc_call_test_fail2(struct prog_test_fail2 *p); void bpf_kfunc_call_test_fail3(struct prog_test_fail3 *p); void bpf_kfunc_call_test_mem_len_fail1(void *mem, int len); +int bpf_dummy_do_link_detach(void) __ksym; void bpf_kfunc_common_test(void) __ksym; diff --git a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c index bbcf12696a6b..f4000bf04752 100644 --- a/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c +++ b/tools/testing/selftests/bpf/prog_tests/test_struct_ops_module.c @@ -2,6 +2,7 @@ /* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */ #include #include +#include #include @@ -297,6 +298,70 @@ static void test_detach_link(void) struct_ops_detach__destroy(skel); } +/* Detach a link from the subsystem that the link was registered to */ +static void test_subsystem_detach(void) +{ + LIBBPF_OPTS(bpf_test_run_opts, topts, + .data_in = &pkt_v4, + .data_size_in = sizeof(pkt_v4)); + struct epoll_event ev, events[2]; + struct struct_ops_detach *skel; + struct bpf_link *link = NULL; + int fd, epollfd = -1, nfds; + int prog_fd; + int err; + + skel = struct_ops_detach__open_and_load(); + if (!ASSERT_OK_PTR(skel, "struct_ops_detach_open_and_load")) + return; + + link = bpf_map__attach_struct_ops(skel->maps.testmod_do_detach); + if (!ASSERT_OK_PTR(link, "attach_struct_ops")) + goto cleanup; + + fd = bpf_link__fd(link); + if (!ASSERT_GE(fd, 0, "link_fd")) + goto cleanup; + + prog_fd = bpf_program__fd(skel->progs.start_detach); + if (!ASSERT_GE(prog_fd, 0, "start_detach_fd")) + goto cleanup; + + /* Do detachment from the registered subsystem */ + err = bpf_prog_test_run_opts(prog_fd, &topts); + if (!ASSERT_OK(err, "start_detach_run")) + goto cleanup; + + if (!ASSERT_EQ(topts.retval, 0, "start_detach_run_retval")) + goto cleanup; + + epollfd = epoll_create1(0); + if (!ASSERT_GE(epollfd, 0, "epoll_create1")) + goto cleanup; + + ev.events = EPOLLHUP; + ev.data.fd = fd; + err = epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &ev); + if (!ASSERT_OK(err, "epoll_ctl")) + goto cleanup; + + /* Wait for EPOLLHUP */ + nfds = epoll_wait(epollfd, events, 2, 5000); + if (!ASSERT_EQ(nfds, 1, "epoll_wait")) + goto cleanup; + + if (!ASSERT_EQ(events[0].data.fd, fd, "epoll_wait_fd")) + goto cleanup; + if (!ASSERT_TRUE(events[0].events & EPOLLHUP, "events[0].events")) + goto cleanup; + +cleanup: + if (epollfd >= 0) + close(epollfd); + bpf_link__destroy(link); + struct_ops_detach__destroy(skel); +} + void serial_test_struct_ops_module(void) { if (test__start_subtest("struct_ops_load")) @@ -311,5 +376,7 @@ void serial_test_struct_ops_module(void) test_struct_ops_forgotten_cb(); if (test__start_subtest("test_detach_link")) test_detach_link(); + if (test__start_subtest("test_subsystem_detach")) + test_subsystem_detach(); } diff --git a/tools/testing/selftests/bpf/progs/struct_ops_detach.c b/tools/testing/selftests/bpf/progs/struct_ops_detach.c index 45eacc2ca657..5c742b0df04d 100644 --- a/tools/testing/selftests/bpf/progs/struct_ops_detach.c +++ b/tools/testing/selftests/bpf/progs/struct_ops_detach.c @@ -2,8 +2,15 @@ /* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */ #include #include "../bpf_testmod/bpf_testmod.h" +#include "../bpf_testmod/bpf_testmod_kfunc.h" char _license[] SEC("license") = "GPL"; SEC(".struct_ops.link") struct bpf_testmod_ops testmod_do_detach; + +SEC("tc") +int start_detach(void *skb) +{ + return bpf_dummy_do_link_detach(); +}