1/*
2 * Copyright (c) Facebook, Inc. and its affiliates.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <folly/ClockGettimeWrappers.h>
18#include <folly/CPortability.h>
19#include <folly/Likely.h>
20#include <folly/portability/Time.h>
21
22#include <chrono>
23
24#include <ctime>
25
26#ifndef _WIN32
27#define _GNU_SOURCE 1
28#include <dlfcn.h>
29#endif
30
31namespace folly {
32namespace chrono {
33
34static int64_t clock_gettime_ns_fallback(clockid_t clock) {
35 struct timespec ts;
36 int r = clock_gettime(clock, &ts);
37 if (UNLIKELY(r != 0)) {
38 // Mimic what __clock_gettime_ns does (even though this can be a legit
39 // value).
40 return -1;
41 }
42 std::chrono::nanoseconds result =
43 std::chrono::seconds(ts.tv_sec) + std::chrono::nanoseconds(ts.tv_nsec);
44 return result.count();
45}
46
47// Initialize with default behavior, which we might override on Linux hosts
48// with VDSO support.
49int (*clock_gettime)(clockid_t, timespec* ts) = &::clock_gettime;
50int64_t (*clock_gettime_ns)(clockid_t) = &clock_gettime_ns_fallback;
51
52// In MSAN mode use glibc's versions as they are intercepted by the MSAN
53// runtime which properly tracks memory initialization.
54#if defined(FOLLY_HAVE_LINUX_VDSO) && !defined(FOLLY_SANITIZE_MEMORY)
55
56namespace {
57
58struct VdsoInitializer {
59 VdsoInitializer() {
60 m_handle = dlopen("linux-vdso.so.1", RTLD_LAZY | RTLD_LOCAL | RTLD_NOLOAD);
61 if (!m_handle) {
62 return;
63 }
64
65 void* p = dlsym(m_handle, "__vdso_clock_gettime");
66 if (p) {
67 folly::chrono::clock_gettime = (int (*)(clockid_t, timespec*))p;
68 }
69 p = dlsym(m_handle, "__vdso_clock_gettime_ns");
70 if (p) {
71 folly::chrono::clock_gettime_ns = (int64_t(*)(clockid_t))p;
72 }
73 }
74
75 ~VdsoInitializer() {
76 if (m_handle) {
77 clock_gettime = &::clock_gettime;
78 clock_gettime_ns = &clock_gettime_ns_fallback;
79 dlclose(m_handle);
80 }
81 }
82
83 private:
84 void* m_handle;
85};
86
87const VdsoInitializer vdso_initializer;
88} // namespace
89
90#endif
91} // namespace chrono
92} // namespace folly
93