From 8482941f09067da42f9c3362e15bfb3f3c19d610 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Tue, 14 Jan 2020 19:50:02 -0800 Subject: [PATCH 1/2] bpf: Add bpf_send_signal_thread() helper Commit 8b401f9ed244 ("bpf: implement bpf_send_signal() helper") added helper bpf_send_signal() which permits bpf program to send a signal to the current process. The signal may be delivered to any threads in the process. We found a use case where sending the signal to the current thread is more preferable. - A bpf program will collect the stack trace and then send signal to the user application. - The user application will add some thread specific information to the just collected stack trace for later analysis. If bpf_send_signal() is used, user application will need to check whether the thread receiving the signal matches the thread collecting the stack by checking thread id. If not, it will need to send signal to another thread through pthread_kill(). This patch proposed a new helper bpf_send_signal_thread(), which sends the signal to the thread corresponding to the current kernel task. This way, user space is guaranteed that bpf_program execution context and user space signal handling context are the same thread. Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200115035002.602336-1-yhs@fb.com --- include/uapi/linux/bpf.h | 19 +++++++++++++++++-- kernel/trace/bpf_trace.c | 27 ++++++++++++++++++++++++--- tools/include/uapi/linux/bpf.h | 19 +++++++++++++++++-- 3 files changed, 58 insertions(+), 7 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 52966e758fe5..a88837d4dd18 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2714,7 +2714,8 @@ union bpf_attr { * * int bpf_send_signal(u32 sig) * Description - * Send signal *sig* to the current task. + * Send signal *sig* to the process of the current task. + * The signal may be delivered to any of this process's threads. * Return * 0 on success or successfully queued. * @@ -2850,6 +2851,19 @@ union bpf_attr { * Return * 0 on success, or a negative error in case of failure. * + * int bpf_send_signal_thread(u32 sig) + * Description + * Send signal *sig* to the thread corresponding to the current task. + * Return + * 0 on success or successfully queued. + * + * **-EBUSY** if work queue under nmi is full. + * + * **-EINVAL** if *sig* is invalid. + * + * **-EPERM** if no permission to send the *sig*. + * + * **-EAGAIN** if bpf program can try again. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -2968,7 +2982,8 @@ union bpf_attr { FN(probe_read_kernel), \ FN(probe_read_user_str), \ FN(probe_read_kernel_str), \ - FN(tcp_send_ack), + FN(tcp_send_ack), \ + FN(send_signal_thread), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index e5ef4ae9edb5..19e793aa441a 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -703,6 +703,7 @@ struct send_signal_irq_work { struct irq_work irq_work; struct task_struct *task; u32 sig; + enum pid_type type; }; static DEFINE_PER_CPU(struct send_signal_irq_work, send_signal_work); @@ -712,10 +713,10 @@ static void do_bpf_send_signal(struct irq_work *entry) struct send_signal_irq_work *work; work = container_of(entry, struct send_signal_irq_work, irq_work); - group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, PIDTYPE_TGID); + group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type); } -BPF_CALL_1(bpf_send_signal, u32, sig) +static int bpf_send_signal_common(u32 sig, enum pid_type type) { struct send_signal_irq_work *work = NULL; @@ -748,11 +749,17 @@ BPF_CALL_1(bpf_send_signal, u32, sig) */ work->task = current; work->sig = sig; + work->type = type; irq_work_queue(&work->irq_work); return 0; } - return group_send_sig_info(sig, SEND_SIG_PRIV, current, PIDTYPE_TGID); + return group_send_sig_info(sig, SEND_SIG_PRIV, current, type); +} + +BPF_CALL_1(bpf_send_signal, u32, sig) +{ + return bpf_send_signal_common(sig, PIDTYPE_TGID); } static const struct bpf_func_proto bpf_send_signal_proto = { @@ -762,6 +769,18 @@ static const struct bpf_func_proto bpf_send_signal_proto = { .arg1_type = ARG_ANYTHING, }; +BPF_CALL_1(bpf_send_signal_thread, u32, sig) +{ + return bpf_send_signal_common(sig, PIDTYPE_PID); +} + +static const struct bpf_func_proto bpf_send_signal_thread_proto = { + .func = bpf_send_signal_thread, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_ANYTHING, +}; + static const struct bpf_func_proto * tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) { @@ -822,6 +841,8 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) #endif case BPF_FUNC_send_signal: return &bpf_send_signal_proto; + case BPF_FUNC_send_signal_thread: + return &bpf_send_signal_thread_proto; default: return NULL; } diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 52966e758fe5..a88837d4dd18 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2714,7 +2714,8 @@ union bpf_attr { * * int bpf_send_signal(u32 sig) * Description - * Send signal *sig* to the current task. + * Send signal *sig* to the process of the current task. + * The signal may be delivered to any of this process's threads. * Return * 0 on success or successfully queued. * @@ -2850,6 +2851,19 @@ union bpf_attr { * Return * 0 on success, or a negative error in case of failure. * + * int bpf_send_signal_thread(u32 sig) + * Description + * Send signal *sig* to the thread corresponding to the current task. + * Return + * 0 on success or successfully queued. + * + * **-EBUSY** if work queue under nmi is full. + * + * **-EINVAL** if *sig* is invalid. + * + * **-EPERM** if no permission to send the *sig*. + * + * **-EAGAIN** if bpf program can try again. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -2968,7 +2982,8 @@ union bpf_attr { FN(probe_read_kernel), \ FN(probe_read_user_str), \ FN(probe_read_kernel_str), \ - FN(tcp_send_ack), + FN(tcp_send_ack), \ + FN(send_signal_thread), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call From ab8b7f0cb3585ecb40e3305850f28658a1b8940e Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Tue, 14 Jan 2020 19:50:03 -0800 Subject: [PATCH 2/2] tools/bpf: Add self tests for bpf_send_signal_thread() The test_progs send_signal() is amended to test bpf_send_signal_thread() as well. $ ./test_progs -n 40 #40/1 send_signal_tracepoint:OK #40/2 send_signal_perf:OK #40/3 send_signal_nmi:OK #40/4 send_signal_tracepoint_thread:OK #40/5 send_signal_perf_thread:OK #40/6 send_signal_nmi_thread:OK #40 send_signal:OK Summary: 1/6 PASSED, 0 SKIPPED, 0 FAILED Also took this opportunity to rewrite the send_signal test using skeleton framework and array mmap to make code simpler and more readable. Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Link: https://lore.kernel.org/bpf/20200115035003.602425-1-yhs@fb.com --- .../selftests/bpf/prog_tests/send_signal.c | 130 +++++++----------- .../bpf/progs/test_send_signal_kern.c | 49 +++---- 2 files changed, 73 insertions(+), 106 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c b/tools/testing/selftests/bpf/prog_tests/send_signal.c index b607112c64e7..d4cedd86c424 100644 --- a/tools/testing/selftests/bpf/prog_tests/send_signal.c +++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 #include +#include "test_send_signal_kern.skel.h" static volatile int sigusr1_received = 0; @@ -9,17 +10,15 @@ static void sigusr1_handler(int signum) } static void test_send_signal_common(struct perf_event_attr *attr, - int prog_type, + bool signal_thread, const char *test_name) { - int err = -1, pmu_fd, prog_fd, info_map_fd, status_map_fd; - const char *file = "./test_send_signal_kern.o"; - struct bpf_object *obj = NULL; + struct test_send_signal_kern *skel; int pipe_c2p[2], pipe_p2c[2]; - __u32 key = 0, duration = 0; + int err = -1, pmu_fd = -1; + __u32 duration = 0; char buf[256]; pid_t pid; - __u64 val; if (CHECK(pipe(pipe_c2p), test_name, "pipe pipe_c2p error: %s\n", strerror(errno))) @@ -73,45 +72,42 @@ static void test_send_signal_common(struct perf_event_attr *attr, close(pipe_c2p[1]); /* close write */ close(pipe_p2c[0]); /* close read */ - err = bpf_prog_load(file, prog_type, &obj, &prog_fd); - if (CHECK(err < 0, test_name, "bpf_prog_load error: %s\n", - strerror(errno))) - goto prog_load_failure; + skel = test_send_signal_kern__open_and_load(); + if (CHECK(!skel, "skel_open_and_load", "skeleton open_and_load failed\n")) + goto skel_open_load_failure; - pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1, - -1 /* group id */, 0 /* flags */); - if (CHECK(pmu_fd < 0, test_name, "perf_event_open error: %s\n", - strerror(errno))) { - err = -1; - goto close_prog; + /* add a delay for child thread to ramp up */ + usleep(100); + + if (!attr) { + err = test_send_signal_kern__attach(skel); + if (CHECK(err, "skel_attach", "skeleton attach failed\n")) { + err = -1; + goto destroy_skel; + } + } else { + pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1, + -1 /* group id */, 0 /* flags */); + if (CHECK(pmu_fd < 0, test_name, "perf_event_open error: %s\n", + strerror(errno))) { + err = -1; + goto destroy_skel; + } + + skel->links.send_signal_perf = + bpf_program__attach_perf_event(skel->progs.send_signal_perf, pmu_fd); + if (CHECK(IS_ERR(skel->links.send_signal_perf), "attach_perf_event", + "err %ld\n", PTR_ERR(skel->links.send_signal_perf))) + goto disable_pmu; } - err = ioctl(pmu_fd, PERF_EVENT_IOC_ENABLE, 0); - if (CHECK(err < 0, test_name, "ioctl perf_event_ioc_enable error: %s\n", - strerror(errno))) - goto disable_pmu; - - err = ioctl(pmu_fd, PERF_EVENT_IOC_SET_BPF, prog_fd); - if (CHECK(err < 0, test_name, "ioctl perf_event_ioc_set_bpf error: %s\n", - strerror(errno))) - goto disable_pmu; - - err = -1; - info_map_fd = bpf_object__find_map_fd_by_name(obj, "info_map"); - if (CHECK(info_map_fd < 0, test_name, "find map %s error\n", "info_map")) - goto disable_pmu; - - status_map_fd = bpf_object__find_map_fd_by_name(obj, "status_map"); - if (CHECK(status_map_fd < 0, test_name, "find map %s error\n", "status_map")) - goto disable_pmu; - /* wait until child signal handler installed */ read(pipe_c2p[0], buf, 1); /* trigger the bpf send_signal */ - key = 0; - val = (((__u64)(SIGUSR1)) << 32) | pid; - bpf_map_update_elem(info_map_fd, &key, &val, 0); + skel->bss->pid = pid; + skel->bss->sig = SIGUSR1; + skel->bss->signal_thread = signal_thread; /* notify child that bpf program can send_signal now */ write(pipe_p2c[1], buf, 1); @@ -132,46 +128,20 @@ static void test_send_signal_common(struct perf_event_attr *attr, disable_pmu: close(pmu_fd); -close_prog: - bpf_object__close(obj); -prog_load_failure: +destroy_skel: + test_send_signal_kern__destroy(skel); +skel_open_load_failure: close(pipe_c2p[0]); close(pipe_p2c[1]); wait(NULL); } -static void test_send_signal_tracepoint(void) +static void test_send_signal_tracepoint(bool signal_thread) { - const char *id_path = "/sys/kernel/debug/tracing/events/syscalls/sys_enter_nanosleep/id"; - struct perf_event_attr attr = { - .type = PERF_TYPE_TRACEPOINT, - .sample_type = PERF_SAMPLE_RAW | PERF_SAMPLE_CALLCHAIN, - .sample_period = 1, - .wakeup_events = 1, - }; - __u32 duration = 0; - int bytes, efd; - char buf[256]; - - efd = open(id_path, O_RDONLY, 0); - if (CHECK(efd < 0, "tracepoint", - "open syscalls/sys_enter_nanosleep/id failure: %s\n", - strerror(errno))) - return; - - bytes = read(efd, buf, sizeof(buf)); - close(efd); - if (CHECK(bytes <= 0 || bytes >= sizeof(buf), "tracepoint", - "read syscalls/sys_enter_nanosleep/id failure: %s\n", - strerror(errno))) - return; - - attr.config = strtol(buf, NULL, 0); - - test_send_signal_common(&attr, BPF_PROG_TYPE_TRACEPOINT, "tracepoint"); + test_send_signal_common(NULL, signal_thread, "tracepoint"); } -static void test_send_signal_perf(void) +static void test_send_signal_perf(bool signal_thread) { struct perf_event_attr attr = { .sample_period = 1, @@ -179,11 +149,10 @@ static void test_send_signal_perf(void) .config = PERF_COUNT_SW_CPU_CLOCK, }; - test_send_signal_common(&attr, BPF_PROG_TYPE_PERF_EVENT, - "perf_sw_event"); + test_send_signal_common(&attr, signal_thread, "perf_sw_event"); } -static void test_send_signal_nmi(void) +static void test_send_signal_nmi(bool signal_thread) { struct perf_event_attr attr = { .sample_freq = 50, @@ -210,16 +179,21 @@ static void test_send_signal_nmi(void) close(pmu_fd); } - test_send_signal_common(&attr, BPF_PROG_TYPE_PERF_EVENT, - "perf_hw_event"); + test_send_signal_common(&attr, signal_thread, "perf_hw_event"); } void test_send_signal(void) { if (test__start_subtest("send_signal_tracepoint")) - test_send_signal_tracepoint(); + test_send_signal_tracepoint(false); if (test__start_subtest("send_signal_perf")) - test_send_signal_perf(); + test_send_signal_perf(false); if (test__start_subtest("send_signal_nmi")) - test_send_signal_nmi(); + test_send_signal_nmi(false); + if (test__start_subtest("send_signal_tracepoint_thread")) + test_send_signal_tracepoint(true); + if (test__start_subtest("send_signal_perf_thread")) + test_send_signal_perf(true); + if (test__start_subtest("send_signal_nmi_thread")) + test_send_signal_nmi(true); } diff --git a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c index 0e6be01157e6..726733f9f20b 100644 --- a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c +++ b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c @@ -4,44 +4,37 @@ #include #include "bpf_helpers.h" -struct { - __uint(type, BPF_MAP_TYPE_ARRAY); - __uint(max_entries, 1); - __type(key, __u32); - __type(value, __u64); -} info_map SEC(".maps"); +__u32 sig = 0, pid = 0, status = 0, signal_thread = 0; -struct { - __uint(type, BPF_MAP_TYPE_ARRAY); - __uint(max_entries, 1); - __type(key, __u32); - __type(value, __u64); -} status_map SEC(".maps"); - -SEC("send_signal_demo") -int bpf_send_signal_test(void *ctx) +static __always_inline int bpf_send_signal_test(void *ctx) { - __u64 *info_val, *status_val; - __u32 key = 0, pid, sig; int ret; - status_val = bpf_map_lookup_elem(&status_map, &key); - if (!status_val || *status_val != 0) + if (status != 0 || sig == 0 || pid == 0) return 0; - info_val = bpf_map_lookup_elem(&info_map, &key); - if (!info_val || *info_val == 0) - return 0; - - sig = *info_val >> 32; - pid = *info_val & 0xffffFFFF; - if ((bpf_get_current_pid_tgid() >> 32) == pid) { - ret = bpf_send_signal(sig); + if (signal_thread) + ret = bpf_send_signal_thread(sig); + else + ret = bpf_send_signal(sig); if (ret == 0) - *status_val = 1; + status = 1; } return 0; } + +SEC("tracepoint/syscalls/sys_enter_nanosleep") +int send_signal_tp(void *ctx) +{ + return bpf_send_signal_test(ctx); +} + +SEC("perf_event") +int send_signal_perf(void *ctx) +{ + return bpf_send_signal_test(ctx); +} + char __license[] SEC("license") = "GPL";