From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- tools/perf/tests/sigtrap.c | 275 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 275 insertions(+) create mode 100644 tools/perf/tests/sigtrap.c (limited to 'tools/perf/tests/sigtrap.c') diff --git a/tools/perf/tests/sigtrap.c b/tools/perf/tests/sigtrap.c new file mode 100644 index 000000000..a67c756f9 --- /dev/null +++ b/tools/perf/tests/sigtrap.c @@ -0,0 +1,275 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Basic test for sigtrap support. + * + * Copyright (C) 2021, Google LLC. + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include "cloexec.h" +#include "debug.h" +#include "event.h" +#include "tests.h" +#include "../perf-sys.h" + +#define NUM_THREADS 5 + +static struct { + int tids_want_signal; /* Which threads still want a signal. */ + int signal_count; /* Sanity check number of signals received. */ + volatile int iterate_on; /* Variable to set breakpoint on. */ + siginfo_t first_siginfo; /* First observed siginfo_t. */ +} ctx; + +#define TEST_SIG_DATA (~(unsigned long)(&ctx.iterate_on)) + +static struct perf_event_attr make_event_attr(void) +{ + struct perf_event_attr attr = { + .type = PERF_TYPE_BREAKPOINT, + .size = sizeof(attr), + .sample_period = 1, + .disabled = 1, + .bp_addr = (unsigned long)&ctx.iterate_on, + .bp_type = HW_BREAKPOINT_RW, + .bp_len = HW_BREAKPOINT_LEN_1, + .inherit = 1, /* Children inherit events ... */ + .inherit_thread = 1, /* ... but only cloned with CLONE_THREAD. */ + .remove_on_exec = 1, /* Required by sigtrap. */ + .sigtrap = 1, /* Request synchronous SIGTRAP on event. */ + .sig_data = TEST_SIG_DATA, + .exclude_kernel = 1, /* To allow */ + .exclude_hv = 1, /* running as !root */ + }; + return attr; +} + +#ifdef HAVE_BPF_SKEL +#include +#include + +static struct btf *btf; + +static bool btf__available(void) +{ + if (btf == NULL) + btf = btf__load_vmlinux_btf(); + + return btf != NULL; +} + +static void btf__exit(void) +{ + btf__free(btf); + btf = NULL; +} + +static bool attr_has_sigtrap(void) +{ + int id; + + if (!btf__available()) { + /* should be an old kernel */ + return false; + } + + id = btf__find_by_name_kind(btf, "perf_event_attr", BTF_KIND_STRUCT); + if (id < 0) + return false; + + return __btf_type__find_member_by_name(btf, id, "sigtrap") != NULL; +} + +static bool kernel_with_sleepable_spinlocks(void) +{ + const struct btf_member *member; + const struct btf_type *type; + const char *type_name; + int id; + + if (!btf__available()) + return false; + + id = btf__find_by_name_kind(btf, "spinlock", BTF_KIND_STRUCT); + if (id < 0) + return false; + + // Only RT has a "lock" member for "struct spinlock" + member = __btf_type__find_member_by_name(btf, id, "lock"); + if (member == NULL) + return false; + + // But check its type as well + type = btf__type_by_id(btf, member->type); + if (!type || !btf_is_struct(type)) + return false; + + type_name = btf__name_by_offset(btf, type->name_off); + return type_name && !strcmp(type_name, "rt_mutex_base"); +} +#else /* !HAVE_BPF_SKEL */ +static bool attr_has_sigtrap(void) +{ + struct perf_event_attr attr = { + .type = PERF_TYPE_SOFTWARE, + .config = PERF_COUNT_SW_DUMMY, + .size = sizeof(attr), + .remove_on_exec = 1, /* Required by sigtrap. */ + .sigtrap = 1, /* Request synchronous SIGTRAP on event. */ + }; + int fd; + bool ret = false; + + fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag()); + if (fd >= 0) { + ret = true; + close(fd); + } + + return ret; +} + +static bool kernel_with_sleepable_spinlocks(void) +{ + return false; +} + +static void btf__exit(void) +{ +} +#endif /* HAVE_BPF_SKEL */ + +static void +sigtrap_handler(int signum __maybe_unused, siginfo_t *info, void *ucontext __maybe_unused) +{ + if (!__atomic_fetch_add(&ctx.signal_count, 1, __ATOMIC_RELAXED)) + ctx.first_siginfo = *info; + __atomic_fetch_sub(&ctx.tids_want_signal, syscall(SYS_gettid), __ATOMIC_RELAXED); +} + +static void *test_thread(void *arg) +{ + pthread_barrier_t *barrier = (pthread_barrier_t *)arg; + pid_t tid = syscall(SYS_gettid); + int i; + + pthread_barrier_wait(barrier); + + __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED); + for (i = 0; i < ctx.iterate_on - 1; i++) + __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED); + + return NULL; +} + +static int run_test_threads(pthread_t *threads, pthread_barrier_t *barrier) +{ + int i; + + pthread_barrier_wait(barrier); + for (i = 0; i < NUM_THREADS; i++) + TEST_ASSERT_EQUAL("pthread_join() failed", pthread_join(threads[i], NULL), 0); + + return TEST_OK; +} + +static int run_stress_test(int fd, pthread_t *threads, pthread_barrier_t *barrier) +{ + int ret, expected_sigtraps; + + ctx.iterate_on = 3000; + + TEST_ASSERT_EQUAL("misfired signal?", ctx.signal_count, 0); + TEST_ASSERT_EQUAL("enable failed", ioctl(fd, PERF_EVENT_IOC_ENABLE, 0), 0); + ret = run_test_threads(threads, barrier); + TEST_ASSERT_EQUAL("disable failed", ioctl(fd, PERF_EVENT_IOC_DISABLE, 0), 0); + + expected_sigtraps = NUM_THREADS * ctx.iterate_on; + + if (ctx.signal_count < expected_sigtraps && kernel_with_sleepable_spinlocks()) { + pr_debug("Expected %d sigtraps, got %d, running on a kernel with sleepable spinlocks.\n", + expected_sigtraps, ctx.signal_count); + pr_debug("See https://lore.kernel.org/all/e368f2c848d77fbc8d259f44e2055fe469c219cf.camel@gmx.de/\n"); + return TEST_SKIP; + } else + TEST_ASSERT_EQUAL("unexpected sigtraps", ctx.signal_count, expected_sigtraps); + + TEST_ASSERT_EQUAL("missing signals or incorrectly delivered", ctx.tids_want_signal, 0); + TEST_ASSERT_VAL("unexpected si_addr", ctx.first_siginfo.si_addr == &ctx.iterate_on); +#if 0 /* FIXME: enable when libc's signal.h has si_perf_{type,data} */ + TEST_ASSERT_EQUAL("unexpected si_perf_type", ctx.first_siginfo.si_perf_type, + PERF_TYPE_BREAKPOINT); + TEST_ASSERT_EQUAL("unexpected si_perf_data", ctx.first_siginfo.si_perf_data, + TEST_SIG_DATA); +#endif + + return ret; +} + +static int test__sigtrap(struct test_suite *test __maybe_unused, int subtest __maybe_unused) +{ + struct perf_event_attr attr = make_event_attr(); + struct sigaction action = {}; + struct sigaction oldact; + pthread_t threads[NUM_THREADS]; + pthread_barrier_t barrier; + char sbuf[STRERR_BUFSIZE]; + int i, fd, ret = TEST_FAIL; + + if (!BP_SIGNAL_IS_SUPPORTED) { + pr_debug("Test not supported on this architecture"); + return TEST_SKIP; + } + + pthread_barrier_init(&barrier, NULL, NUM_THREADS + 1); + + action.sa_flags = SA_SIGINFO | SA_NODEFER; + action.sa_sigaction = sigtrap_handler; + sigemptyset(&action.sa_mask); + if (sigaction(SIGTRAP, &action, &oldact)) { + pr_debug("FAILED sigaction(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf))); + goto out; + } + + fd = sys_perf_event_open(&attr, 0, -1, -1, perf_event_open_cloexec_flag()); + if (fd < 0) { + if (attr_has_sigtrap()) { + pr_debug("FAILED sys_perf_event_open(): %s\n", + str_error_r(errno, sbuf, sizeof(sbuf))); + } else { + pr_debug("perf_event_attr doesn't have sigtrap\n"); + ret = TEST_SKIP; + } + goto out_restore_sigaction; + } + + for (i = 0; i < NUM_THREADS; i++) { + if (pthread_create(&threads[i], NULL, test_thread, &barrier)) { + pr_debug("FAILED pthread_create(): %s\n", str_error_r(errno, sbuf, sizeof(sbuf))); + goto out_close_perf_event; + } + } + + ret = run_stress_test(fd, threads, &barrier); + +out_close_perf_event: + close(fd); +out_restore_sigaction: + sigaction(SIGTRAP, &oldact, NULL); +out: + pthread_barrier_destroy(&barrier); + btf__exit(); + return ret; +} + +DEFINE_SUITE("Sigtrap", sigtrap); -- cgit v1.3.1