1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include <errno.h>
6#include <linux/futex.h>
7#include <sys/syscall.h>
8#include <sys/time.h>
9#include <unistd.h>
10
11#include "components/nacl/loader/nonsfi/irt_interfaces.h"
12#include "components/nacl/loader/nonsfi/irt_util.h"
13#include "native_client/src/trusted/service_runtime/include/sys/time.h"
14
15namespace nacl {
16namespace nonsfi {
17namespace {
18
19// Converts a pair of NaCl's timespec of absolute time and host's timespec of
20// the current time to host's timespec of the relative time between them.
21// Note that assuming tv_nsec for the both input structs are non-negative,
22// the returned reltime's tv_nsec is also always non-negative.
23// (I.e., for -0.1 sec, {tv_sec: -1, tv_nsec: 900000000} will be returned).
24void NaClAbsTimeToRelTime(const struct nacl_abi_timespec& nacl_abstime,
25                          const struct timespec& now,
26                          struct timespec* reltime) {
27  reltime->tv_sec = nacl_abstime.tv_sec - now.tv_sec;
28  reltime->tv_nsec = nacl_abstime.tv_nsec - now.tv_nsec;
29  if (reltime->tv_nsec < 0) {
30    reltime->tv_sec -= 1;
31    reltime->tv_nsec += 1000000000;
32  }
33}
34
35int IrtFutexWaitAbs(volatile int* addr, int value,
36                    const struct nacl_abi_timespec* abstime) {
37  struct timespec timeout;
38  struct timespec* timeout_ptr = NULL;
39  if (abstime) {
40    // futex syscall takes relative timeout, but the ABI for IRT's
41    // futex_wait_abs is absolute timeout. So, here we convert it.
42    struct timespec now;
43    if (clock_gettime(CLOCK_REALTIME, &now))
44      return errno;
45    NaClAbsTimeToRelTime(*abstime, now, &timeout);
46
47    // Linux's FUTEX_WAIT returns EINVAL for negative timeout, but an absolute
48    // time that is in the past is a valid argument to irt_futex_wait_abs(),
49    // and a caller expects ETIMEDOUT.
50    // Here check only tv_sec since we assume time_t is signed. See also
51    // the comment for NaClAbsTimeToRelTime.
52    if (timeout.tv_sec < 0)
53      return ETIMEDOUT;
54    timeout_ptr = &timeout;
55  }
56  return CheckError(
57      syscall(SYS_futex, addr, FUTEX_WAIT_PRIVATE, value, timeout_ptr, 0, 0));
58}
59
60int IrtFutexWake(volatile int* addr, int nwake, int* count) {
61  return CheckErrorWithResult(
62      syscall(SYS_futex, addr, FUTEX_WAKE_PRIVATE, nwake, 0, 0, 0), count);
63}
64
65}  // namespace
66
67// For futex_wait_abs, the argument type should be nacl_abi_timespec. However,
68// the definition uses its host type, struct timespec. So, here we need to cast
69// it.
70const nacl_irt_futex kIrtFutex = {
71  reinterpret_cast<int(*)(volatile int*, int, const struct timespec*)>(
72      IrtFutexWaitAbs),
73  IrtFutexWake,
74};
75
76}  // namespace nonsfi
77}  // namespace nacl
78