Implement nacl_irt_futex for non-sfi mode.

components/nacl/loader/nonsfi/irt_futex.cc

+// Copyright 2014 The Chromium 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 <errno.h>
+#include <linux/futex.h>
+#include <sys/syscall.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "components/nacl/loader/nonsfi/irt_interfaces.h"
+#include "native_client/src/trusted/service_runtime/include/sys/time.h"
+
+namespace nacl {
+namespace nonsfi {
+namespace {
+
+// Converts a pair of NaCl's timespec of absolute time and host's timespec of
+// the current time to host's timespec of the relative time between them.
+// Note that assuming tv_nsec for the both input structs are non-negative,
+// the returned reltime's tv_nsec is also always non-negative.
+// (I.e., for -0.1 sec, {tv_sec: -1, tv_nsec: 900000000} will be returned).
+void NaClAbsTimeToRelTime(const struct nacl_abi_timespec& nacl_abstime,
+                          const struct timespec& now,
+                          struct timespec* reltime) {
+  reltime->tv_sec = nacl_abstime.tv_sec - now.tv_sec;
+  reltime->tv_nsec = nacl_abstime.tv_nsec - now.tv_nsec;
+  if (reltime->tv_nsec < 0) {
+    reltime->tv_sec -= 1;
+    reltime->tv_nsec += 1000000000;
+  }
+}
+
+int IrtFutexWaitAbs(volatile int* addr, int value,
+                    const struct nacl_abi_timespec* abstime) {
+  struct timespec timeout;
+  struct timespec* timeout_ptr = NULL;
+  if (abstime) {
+    // futex syscall takes relative timeout, but the ABI for IRT's
+    // futex_wait_abs is absolute timeout. So, here we convert it.
+    struct timespec now;
+    if (clock_gettime(CLOCK_REALTIME, &now))
+      return errno;
+    NaClAbsTimeToRelTime(*abstime, now, &timeout);
+
+    // Linux's FUTEX_WAIT returns EINVAL for negative timeout, but an absolute
+    // time that is in the past is a valid argument to irt_futex_wait_abs(),
+    // and a caller expects ETIMEDOUT.
+    // Here check only tv_sec since we assume time_t is signed. See also
+    // the comment for NaClAbsTimeToRelTime.
+    if (timeout.tv_sec < 0)
+      return ETIMEDOUT;
+    timeout_ptr = &timeout;
+  }
+  if (syscall(SYS_futex, addr, FUTEX_WAIT_PRIVATE, value, timeout_ptr, 0, 0))
+    return errno;
+
+  return 0;
+}
+
+int IrtFutexWake(volatile int* addr, int nwake, int* count) {
+  int result = syscall(SYS_futex, addr, FUTEX_WAKE_PRIVATE, nwake, 0, 0, 0);
+  if (result < 0)
+    return errno;
+
+  *count = result;
+  return 0;
+}
+
+}  // namespace
+
+// For futex_wait_abs, the argument type should be nacl_abi_timespec. However,
+// the definition uses its host type, struct timespec. So, here we need to cast
+// it.
+const nacl_irt_futex kIrtFutex = {
+  reinterpret_cast<int(*)(volatile int*, int, const struct timespec*)>(
+      IrtFutexWaitAbs),
+  IrtFutexWake,
+};
+
+}  // namespace nonsfi
+}  // namespace nacl