Non-SFI mode: Add Linux asynchronous signal support

tests/signal_handler/user_signal_test.cc

+/*
+ * Copyright (c) 2015 The Native Client Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include <pthread.h>
+#include <semaphore.h>
+
+#include "native_client/src/include/nacl/nacl_signal.h"
+#include "native_client/src/include/nacl_assert.h"
+#include "native_client/src/public/nonsfi/irt_signal_handling.h"
+#include "native_client/src/untrusted/irt/irt.h"
+#include "native_client/src/untrusted/nacl/nacl_irt.h"
+#include "native_client/src/untrusted/nacl/nacl_thread.h"
+#include "native_client/src/untrusted/pthread/pthread_types.h"
+
+volatile int g_signal_count;
+volatile int g_futex;
+volatile int g_test_running;
+int g_tid;
+void* g_expected_tls;
+sem_t g_sem;
+
+/*
+ * Check that sending a signal before initializing signal support will result in
+ * an error.
+ */
+void test_send_signal_before_init() {
+  int retval = nacl_signal_send_async_signal(0);
+  ASSERT_EQ(retval, ESRCH);
+}
+
+/*
+ * Check that nacl_tls_get() is signal-async-safe.

[Mark Seaborn, 2015/06/26 18:32:00]

Nit: "async-signal-safe"

[Luis Héctor Chávez, 2015/07/06 23:45:00]

Done.

+ */
+void tls_get_signal_handler(NaClExceptionContext *exc) {
+  if (!g_test_running)
+    return;
+  ASSERT_EQ(nacl_tls_get(), g_expected_tls);
+  g_signal_count++;
+  sem_post(&g_sem);

[Mark Seaborn, 2015/06/26 18:32:00]

Nit: check return value on all calls (sem_post(), pthread_join() etc.)

[Luis Héctor Chávez, 2015/07/06 23:45:00]

Done.

+}
+
+void *tls_get_thread_func(void *arg) {
+  g_expected_tls = nacl_tls_get();
+  sem_post(&g_sem);
+  while (g_test_running) {
+    ASSERT_EQ(nacl_tls_get(), g_expected_tls);
+  }
+  return NULL;
+}
+
+void test_async_safe_tls_get() {
+  nacl_signal_set_handler(tls_get_signal_handler);
+
+  pthread_t tid;
+  g_signal_count = 0;
+  g_test_running = true;
+  int result = pthread_create(&tid, NULL, tls_get_thread_func, NULL);
+  ASSERT_EQ(0, result);
+
+  sem_wait(&g_sem);
+  const int kSignalCount = 1000;
+  for (int i = 0; i < kSignalCount; i++) {
+    nacl_signal_send_async_signal(tid->native_tid);

[Mark Seaborn, 2015/06/26 18:32:00]

Using tid->native_tid here is unfortunate because it requires our libpthread to
support saving the TID, which we don't really need apart from for this test.

Here's an alternative:  In main(), modify __libnacl_irt_thread.thread_create to
point to a wrapper function like this one:

static __thread int native_tid;

int thread_create_wrapper(func, stack, thread_ptr) {
  /* Trick to figure out address of thread-local var in the new thread. */
  uintptr_t var_offset = (uintptr_t) &native_tid - get_tls();
  uintptr_t new_tid_ptr = (uintptr_t) thread_ptr + var_offset;

  return thread_create_v2(func, stack, thread_ptr, new_tid_ptr);
}

[Luis Héctor Chávez, 2015/07/06 23:45:00]

The trick was not needed, since I need to be able to read the native_tid from
the caller thread, not the thread itself.

+    sem_wait(&g_sem);
+  }
+  g_test_running = false;
+  // Send a last signal to make sure any waiting syscalls get interrupted.
+  nacl_signal_send_async_signal(tid->native_tid);
+  pthread_join(tid, NULL);
+  ASSERT_EQ(g_signal_count, kSignalCount);
+}
+
+/*
+ * Check that both futex_wake() and futex_wait_abs() are signal-async-safe.
+ */
+void futex_signal_handler(NaClExceptionContext *exc) {
+  if (!g_test_running)
+    return;
+  g_signal_count++;
+  sem_post(&g_sem);
+  int count = 0;
+  int retval = __libnacl_irt_futex.futex_wake(&g_futex, 1, &count);
+  ASSERT_EQ(retval, 0);
+  ASSERT_EQ(count, 0);
+}
+
+void *futex_thread_func(void *arg) {
+  sem_post(&g_sem);
+  while (g_test_running) {
+    int retval = __libnacl_irt_futex.futex_wait_abs(&g_futex, 0, NULL);
+    ASSERT_EQ(retval, EINTR);
+  }
+  return NULL;
+}
+
+void test_async_safe_futex() {
+  nacl_signal_set_handler(futex_signal_handler);
+
+  pthread_t tid;
+  g_test_running = true;
+  g_futex = 0;
+  int result = pthread_create(&tid, NULL, futex_thread_func, NULL);
+  ASSERT_EQ(0, result);
+
+  sem_wait(&g_sem);
+  g_signal_count = 0;
+  const int kSignalCount = 1000;
+  for (int i = 0; i < kSignalCount; i++) {
+    nacl_signal_send_async_signal(tid->native_tid);
+    sem_wait(&g_sem);
+  }
+  g_test_running = false;
+  // Send a last signal to make sure any waiting syscalls get interrupted.
+  nacl_signal_send_async_signal(tid->native_tid);
+  pthread_join(tid, NULL);
+  ASSERT_EQ(g_signal_count, kSignalCount);
+}
+
+/*
+ * Check that nacl_signal_send_async_signal() is async-signal-safe.
+ */
+void signal_signal_handler(NaClExceptionContext *exc) {
+  if (!g_test_running)
+    return;
+  if (++g_signal_count % 2 == 1) {
+    nacl_signal_send_async_signal(g_tid);
+    sem_post(&g_sem);
+  }
+}
+
+void *signal_thread_func(void *arg) {
+  sem_post(&g_sem);
+  while (g_test_running) {
+    int retval = sleep(1);
+    ASSERT_EQ(retval, 1);
+    ASSERT_EQ(errno, EINTR);
+  }
+  return NULL;
+}
+
+void test_async_safe_signal() {
+  nacl_signal_set_handler(signal_signal_handler);
+
+  pthread_t tid;
+  g_test_running = true;
+  g_signal_count = 0;
+  int result = pthread_create(&tid, NULL, signal_thread_func, NULL);
+  ASSERT_EQ(0, result);
+  g_tid = tid->native_tid;
+
+  sem_wait(&g_sem);
+  const int kSignalCount = 1000;
+  for (int i = 0; i < kSignalCount; i++) {
+    nacl_signal_send_async_signal(g_tid);
+    sem_wait(&g_sem);
+  }
+  g_test_running = false;
+  // Send a last signal to make sure any waiting syscalls get interrupted.
+  nacl_signal_send_async_signal(g_tid);
+  pthread_join(tid, NULL);
+  ASSERT_EQ(g_signal_count, 2 * kSignalCount);
+}
+
+/*
+ * Check that passing 0 as |tid| to nacl_signal_send_async_signal() works and
+ * sends a signal to the main thread.
+ */
+void main_signal_handler(NaClExceptionContext *exc) {
+  g_signal_count = 1;
+}
+
+void test_main_signal() {
+  nacl_signal_set_handler(main_signal_handler);
+
+  g_signal_count = 0;
+  int retval = nacl_signal_send_async_signal(0);
+  ASSERT_EQ(retval, 0);
+  ASSERT_EQ(g_signal_count, 1);
+}
+
+void run_test(const char *test_name, void (*test_func)(void)) {
+  printf("Running %s...\n", test_name);
+  test_func();
+}
+
+#define RUN_TEST(test_func) (run_test(#test_func, test_func))
+
+int main(void) {
+  RUN_TEST(test_send_signal_before_init);
+
+  nonsfi_initialize_signal_handler();
+  sem_init(&g_sem, 0, 0);
+
+  RUN_TEST(test_async_safe_tls_get);
+  RUN_TEST(test_async_safe_futex);
+  RUN_TEST(test_async_safe_signal);
+  RUN_TEST(test_main_signal);
+
+  return 0;
+}