tools/testing/selftests/perf_events/sigtrap_threads.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Test for perf events with SIGTRAP across all threads.
   4  *
   5  * Copyright (C) 2021, Google LLC.
   6  */
   7
   8 #define _GNU_SOURCE
   9
  10 /* We need the latest siginfo from the kernel repo. */
  11 #include <sys/types.h>
  12 #include <asm/siginfo.h>
  13 #define __have_siginfo_t 1
  14 #define __have_sigval_t 1
  15 #define __have_sigevent_t 1
  16 #define __siginfo_t_defined
  17 #define __sigval_t_defined
  18 #define __sigevent_t_defined
  19 #define _BITS_SIGINFO_CONSTS_H 1
  20 #define _BITS_SIGEVENT_CONSTS_H 1
  21
  22 #include <stdbool.h>
  23 #include <stddef.h>
  24 #include <stdint.h>
  25 #include <stdio.h>
  26 #include <linux/hw_breakpoint.h>
  27 #include <linux/perf_event.h>
  28 #include <pthread.h>
  29 #include <signal.h>
  30 #include <sys/ioctl.h>
  31 #include <sys/syscall.h>
  32 #include <unistd.h>
  33
  34 #include "../kselftest_harness.h"
  35
  36 #define NUM_THREADS 5
  37
  38 /* Data shared between test body, threads, and signal handler. */
  39 static struct {
  40         int tids_want_signal;           /* Which threads still want a signal. */
  41         int signal_count;               /* Sanity check number of signals received. */
  42         volatile int iterate_on;        /* Variable to set breakpoint on. */
  43         siginfo_t first_siginfo;        /* First observed siginfo_t. */
  44 } ctx;
  45
  46 /* Unique value to check si_perf_data is correctly set from perf_event_attr::sig_data. */
  47 #define TEST_SIG_DATA(addr, id) (~(unsigned long)(addr) + id)
  48
  49 static struct perf_event_attr make_event_attr(bool enabled, volatile void *addr,
  50                                               unsigned long id)
  51 {
  52         struct perf_event_attr attr = {
  53                 .type           = PERF_TYPE_BREAKPOINT,
  54                 .size           = sizeof(attr),
  55                 .sample_period  = 1,
  56                 .disabled       = !enabled,
  57                 .bp_addr        = (unsigned long)addr,
  58                 .bp_type        = HW_BREAKPOINT_RW,
  59                 .bp_len         = HW_BREAKPOINT_LEN_1,
  60                 .inherit        = 1, /* Children inherit events ... */
  61                 .inherit_thread = 1, /* ... but only cloned with CLONE_THREAD. */
  62                 .remove_on_exec = 1, /* Required by sigtrap. */
  63                 .sigtrap        = 1, /* Request synchronous SIGTRAP on event. */
  64                 .sig_data       = TEST_SIG_DATA(addr, id),
  65         };
  66         return attr;
  67 }
  68
  69 static void sigtrap_handler(int signum, siginfo_t *info, void *ucontext)
  70 {
  71         if (info->si_code != TRAP_PERF) {
  72                 fprintf(stderr, "%s: unexpected si_code %d\n", __func__, info->si_code);
  73                 return;
  74         }
  75
  76         /*
  77          * The data in siginfo_t we're interested in should all be the same
  78          * across threads.
  79          */
  80         if (!__atomic_fetch_add(&ctx.signal_count, 1, __ATOMIC_RELAXED))
  81                 ctx.first_siginfo = *info;
  82         __atomic_fetch_sub(&ctx.tids_want_signal, syscall(__NR_gettid), __ATOMIC_RELAXED);
  83 }
  84
  85 static void *test_thread(void *arg)
  86 {
  87         pthread_barrier_t *barrier = (pthread_barrier_t *)arg;
  88         pid_t tid = syscall(__NR_gettid);
  89         int iter;
  90         int i;
  91
  92         pthread_barrier_wait(barrier);
  93
  94         __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
  95         iter = ctx.iterate_on; /* read */
  96         for (i = 0; i < iter - 1; i++) {
  97                 __atomic_fetch_add(&ctx.tids_want_signal, tid, __ATOMIC_RELAXED);
  98                 ctx.iterate_on = iter; /* idempotent write */
  99         }
 100
 101         return NULL;
 102 }
 103
 104 FIXTURE(sigtrap_threads)
 105 {
 106         struct sigaction oldact;
 107         pthread_t threads[NUM_THREADS];
 108         pthread_barrier_t barrier;
 109         int fd;
 110 };
 111
 112 FIXTURE_SETUP(sigtrap_threads)
 113 {
 114         struct perf_event_attr attr = make_event_attr(false, &ctx.iterate_on, 0);
 115         struct sigaction action = {};
 116         int i;
 117
 118         memset(&ctx, 0, sizeof(ctx));
 119
 120         /* Initialize sigtrap handler. */
 121         action.sa_flags = SA_SIGINFO | SA_NODEFER;
 122         action.sa_sigaction = sigtrap_handler;
 123         sigemptyset(&action.sa_mask);
 124         ASSERT_EQ(sigaction(SIGTRAP, &action, &self->oldact), 0);
 125
 126         /* Initialize perf event. */
 127         self->fd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
 128         ASSERT_NE(self->fd, -1);
 129
 130         /* Spawn threads inheriting perf event. */
 131         pthread_barrier_init(&self->barrier, NULL, NUM_THREADS + 1);
 132         for (i = 0; i < NUM_THREADS; i++)
 133                 ASSERT_EQ(pthread_create(&self->threads[i], NULL, test_thread, &self->barrier), 0);
 134 }
 135
 136 FIXTURE_TEARDOWN(sigtrap_threads)
 137 {
 138         pthread_barrier_destroy(&self->barrier);
 139         close(self->fd);
 140         sigaction(SIGTRAP, &self->oldact, NULL);
 141 }
 142
 143 static void run_test_threads(struct __test_metadata *_metadata,
 144                              FIXTURE_DATA(sigtrap_threads) *self)
 145 {
 146         int i;
 147
 148         pthread_barrier_wait(&self->barrier);
 149         for (i = 0; i < NUM_THREADS; i++)
 150                 ASSERT_EQ(pthread_join(self->threads[i], NULL), 0);
 151 }
 152
 153 TEST_F(sigtrap_threads, remain_disabled)
 154 {
 155         run_test_threads(_metadata, self);
 156         EXPECT_EQ(ctx.signal_count, 0);
 157         EXPECT_NE(ctx.tids_want_signal, 0);
 158 }
 159
 160 TEST_F(sigtrap_threads, enable_event)
 161 {
 162         EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
 163         run_test_threads(_metadata, self);
 164
 165         EXPECT_EQ(ctx.signal_count, NUM_THREADS);
 166         EXPECT_EQ(ctx.tids_want_signal, 0);
 167         EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
 168         EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
 169         EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 0));
 170
 171         /* Check enabled for parent. */
 172         ctx.iterate_on = 0;
 173         EXPECT_EQ(ctx.signal_count, NUM_THREADS + 1);
 174 }
 175
 176 /* Test that modification propagates to all inherited events. */
 177 TEST_F(sigtrap_threads, modify_and_enable_event)
 178 {
 179         struct perf_event_attr new_attr = make_event_attr(true, &ctx.iterate_on, 42);
 180
 181         EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_MODIFY_ATTRIBUTES, &new_attr), 0);
 182         run_test_threads(_metadata, self);
 183
 184         EXPECT_EQ(ctx.signal_count, NUM_THREADS);
 185         EXPECT_EQ(ctx.tids_want_signal, 0);
 186         EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
 187         EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
 188         EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 42));
 189
 190         /* Check enabled for parent. */
 191         ctx.iterate_on = 0;
 192         EXPECT_EQ(ctx.signal_count, NUM_THREADS + 1);
 193 }
 194
 195 /* Stress test event + signal handling. */
 196 TEST_F(sigtrap_threads, signal_stress)
 197 {
 198         ctx.iterate_on = 3000;
 199
 200         EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_ENABLE, 0), 0);
 201         run_test_threads(_metadata, self);
 202         EXPECT_EQ(ioctl(self->fd, PERF_EVENT_IOC_DISABLE, 0), 0);
 203
 204         EXPECT_EQ(ctx.signal_count, NUM_THREADS * ctx.iterate_on);
 205         EXPECT_EQ(ctx.tids_want_signal, 0);
 206         EXPECT_EQ(ctx.first_siginfo.si_addr, &ctx.iterate_on);
 207         EXPECT_EQ(ctx.first_siginfo.si_perf_type, PERF_TYPE_BREAKPOINT);
 208         EXPECT_EQ(ctx.first_siginfo.si_perf_data, TEST_SIG_DATA(&ctx.iterate_on, 0));
 209 }
 210
 211 TEST_HARNESS_MAIN