1 /*
2 * Copyright 2018 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "sdk/android/src/jni/jvm.h"
12
13 #include <asm/unistd.h>
14 #include <pthread.h>
15 #include <sys/prctl.h>
16 #include <sys/syscall.h>
17 #include <unistd.h>
18
19 #include <string>
20
21 #include "rtc_base/checks.h"
22
23 namespace webrtc {
24 namespace jni {
25
26 static JavaVM* g_jvm = nullptr;
27
28 static pthread_once_t g_jni_ptr_once = PTHREAD_ONCE_INIT;
29
30 // Key for per-thread JNIEnv* data. Non-NULL in threads attached to |g_jvm| by
31 // AttachCurrentThreadIfNeeded(), NULL in unattached threads and threads that
32 // were attached by the JVM because of a Java->native call.
33 static pthread_key_t g_jni_ptr;
34
GetJVM()35 JavaVM* GetJVM() {
36 RTC_CHECK(g_jvm) << "JNI_OnLoad failed to run?";
37 return g_jvm;
38 }
39
40 // Return a |JNIEnv*| usable on this thread or NULL if this thread is detached.
GetEnv()41 JNIEnv* GetEnv() {
42 void* env = nullptr;
43 jint status = g_jvm->GetEnv(&env, JNI_VERSION_1_6);
44 RTC_CHECK(((env != nullptr) && (status == JNI_OK)) ||
45 ((env == nullptr) && (status == JNI_EDETACHED)))
46 << "Unexpected GetEnv return: " << status << ":" << env;
47 return reinterpret_cast<JNIEnv*>(env);
48 }
49
ThreadDestructor(void * prev_jni_ptr)50 static void ThreadDestructor(void* prev_jni_ptr) {
51 // This function only runs on threads where |g_jni_ptr| is non-NULL, meaning
52 // we were responsible for originally attaching the thread, so are responsible
53 // for detaching it now. However, because some JVM implementations (notably
54 // Oracle's http://goo.gl/eHApYT) also use the pthread_key_create mechanism,
55 // the JVMs accounting info for this thread may already be wiped out by the
56 // time this is called. Thus it may appear we are already detached even though
57 // it was our responsibility to detach! Oh well.
58 if (!GetEnv())
59 return;
60
61 RTC_CHECK(GetEnv() == prev_jni_ptr)
62 << "Detaching from another thread: " << prev_jni_ptr << ":" << GetEnv();
63 jint status = g_jvm->DetachCurrentThread();
64 RTC_CHECK(status == JNI_OK) << "Failed to detach thread: " << status;
65 RTC_CHECK(!GetEnv()) << "Detaching was a successful no-op???";
66 }
67
CreateJNIPtrKey()68 static void CreateJNIPtrKey() {
69 RTC_CHECK(!pthread_key_create(&g_jni_ptr, &ThreadDestructor))
70 << "pthread_key_create";
71 }
72
InitGlobalJniVariables(JavaVM * jvm)73 jint InitGlobalJniVariables(JavaVM* jvm) {
74 RTC_CHECK(!g_jvm) << "InitGlobalJniVariables!";
75 g_jvm = jvm;
76 RTC_CHECK(g_jvm) << "InitGlobalJniVariables handed NULL?";
77
78 RTC_CHECK(!pthread_once(&g_jni_ptr_once, &CreateJNIPtrKey)) << "pthread_once";
79
80 JNIEnv* jni = nullptr;
81 if (jvm->GetEnv(reinterpret_cast<void**>(&jni), JNI_VERSION_1_6) != JNI_OK)
82 return -1;
83
84 return JNI_VERSION_1_6;
85 }
86
87 // Return thread ID as a string.
GetThreadId()88 static std::string GetThreadId() {
89 char buf[21]; // Big enough to hold a kuint64max plus terminating NULL.
90 RTC_CHECK_LT(snprintf(buf, sizeof(buf), "%ld",
91 static_cast<long>(syscall(__NR_gettid))),
92 sizeof(buf))
93 << "Thread id is bigger than uint64??";
94 return std::string(buf);
95 }
96
97 // Return the current thread's name.
GetThreadName()98 static std::string GetThreadName() {
99 char name[17] = {0};
100 if (prctl(PR_GET_NAME, name) != 0)
101 return std::string("<noname>");
102 return std::string(name);
103 }
104
105 // Return a |JNIEnv*| usable on this thread. Attaches to |g_jvm| if necessary.
AttachCurrentThreadIfNeeded()106 JNIEnv* AttachCurrentThreadIfNeeded() {
107 JNIEnv* jni = GetEnv();
108 if (jni)
109 return jni;
110 RTC_CHECK(!pthread_getspecific(g_jni_ptr))
111 << "TLS has a JNIEnv* but not attached?";
112
113 std::string name(GetThreadName() + " - " + GetThreadId());
114 JavaVMAttachArgs args;
115 args.version = JNI_VERSION_1_6;
116 args.name = &name[0];
117 args.group = nullptr;
118 // Deal with difference in signatures between Oracle's jni.h and Android's.
119 #ifdef _JAVASOFT_JNI_H_ // Oracle's jni.h violates the JNI spec!
120 void* env = nullptr;
121 #else
122 JNIEnv* env = nullptr;
123 #endif
124 RTC_CHECK(!g_jvm->AttachCurrentThread(&env, &args))
125 << "Failed to attach thread";
126 RTC_CHECK(env) << "AttachCurrentThread handed back NULL!";
127 jni = reinterpret_cast<JNIEnv*>(env);
128 RTC_CHECK(!pthread_setspecific(g_jni_ptr, jni)) << "pthread_setspecific";
129 return jni;
130 }
131
132 } // namespace jni
133 } // namespace webrtc
134