jni_env_ext.cc revision da0a69edb24122d3d35ce1483c5ab94de919d714 
1/*
2 * Copyright (C) 2011 The Android Open Source Project
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 "jni_env_ext.h"
18
19#include <algorithm>
20#include <vector>
21
22#include "check_jni.h"
23#include "indirect_reference_table.h"
24#include "java_vm_ext.h"
25#include "jni_internal.h"
26#include "lock_word.h"
27#include "mirror/object-inl.h"
28#include "nth_caller_visitor.h"
29#include "thread-inl.h"
30
31namespace art {
32
33static constexpr size_t kMonitorsInitial = 32;  // Arbitrary.
34static constexpr size_t kMonitorsMax = 4096;  // Arbitrary sanity check.
35
36// Checking "locals" requires the mutator lock, but at creation time we're really only interested
37// in validity, which isn't changing. To avoid grabbing the mutator lock, factored out and tagged
38// with NO_THREAD_SAFETY_ANALYSIS.
39static bool CheckLocalsValid(JNIEnvExt* in) NO_THREAD_SAFETY_ANALYSIS {
40  if (in == nullptr) {
41    return false;
42  }
43  return in->locals.IsValid();
44}
45
46jint JNIEnvExt::GetEnvHandler(JavaVMExt* vm, /*out*/void** env, jint version) {
47  UNUSED(vm);
48  // GetEnv always returns a JNIEnv* for the most current supported JNI version,
49  // and unlike other calls that take a JNI version doesn't care if you supply
50  // JNI_VERSION_1_1, which we don't otherwise support.
51  if (JavaVMExt::IsBadJniVersion(version) && version != JNI_VERSION_1_1) {
52    return JNI_EVERSION;
53  }
54  Thread* thread = Thread::Current();
55  CHECK(thread != nullptr);
56  *env = thread->GetJniEnv();
57  return JNI_OK;
58}
59
60JNIEnvExt* JNIEnvExt::Create(Thread* self_in, JavaVMExt* vm_in, std::string* error_msg) {
61  std::unique_ptr<JNIEnvExt> ret(new JNIEnvExt(self_in, vm_in, error_msg));
62  if (CheckLocalsValid(ret.get())) {
63    return ret.release();
64  }
65  return nullptr;
66}
67
68JNIEnvExt::JNIEnvExt(Thread* self_in, JavaVMExt* vm_in, std::string* error_msg)
69    : self(self_in),
70      vm(vm_in),
71      local_ref_cookie(IRT_FIRST_SEGMENT),
72      locals(kLocalsInitial, kLocal, error_msg),
73      check_jni(false),
74      runtime_deleted(false),
75      critical(0),
76      monitors("monitors", kMonitorsInitial, kMonitorsMax) {
77  functions = unchecked_functions = GetJniNativeInterface();
78  if (vm->IsCheckJniEnabled()) {
79    SetCheckJniEnabled(true);
80  }
81}
82
83void JNIEnvExt::SetFunctionsToRuntimeShutdownFunctions() {
84  functions = GetRuntimeShutdownNativeInterface();
85  runtime_deleted = true;
86}
87
88JNIEnvExt::~JNIEnvExt() {
89}
90
91jobject JNIEnvExt::NewLocalRef(mirror::Object* obj) {
92  if (obj == nullptr) {
93    return nullptr;
94  }
95  return reinterpret_cast<jobject>(locals.Add(local_ref_cookie, obj));
96}
97
98void JNIEnvExt::DeleteLocalRef(jobject obj) {
99  if (obj != nullptr) {
100    locals.Remove(local_ref_cookie, reinterpret_cast<IndirectRef>(obj));
101  }
102}
103
104void JNIEnvExt::SetCheckJniEnabled(bool enabled) {
105  check_jni = enabled;
106  functions = enabled ? GetCheckJniNativeInterface() : GetJniNativeInterface();
107}
108
109void JNIEnvExt::DumpReferenceTables(std::ostream& os) {
110  locals.Dump(os);
111  monitors.Dump(os);
112}
113
114void JNIEnvExt::PushFrame(int capacity ATTRIBUTE_UNUSED) {
115  // TODO: take 'capacity' into account.
116  stacked_local_ref_cookies.push_back(local_ref_cookie);
117  local_ref_cookie = locals.GetSegmentState();
118}
119
120void JNIEnvExt::PopFrame() {
121  locals.SetSegmentState(local_ref_cookie);
122  local_ref_cookie = stacked_local_ref_cookies.back();
123  stacked_local_ref_cookies.pop_back();
124}
125
126// Note: the offset code is brittle, as we can't use OFFSETOF_MEMBER or offsetof easily. Thus, there
127//       are tests in jni_internal_test to match the results against the actual values.
128
129// This is encoding the knowledge of the structure and layout of JNIEnv fields.
130static size_t JNIEnvSize(size_t pointer_size) {
131  // A single pointer.
132  return pointer_size;
133}
134
135Offset JNIEnvExt::SegmentStateOffset(size_t pointer_size) {
136  size_t locals_offset = JNIEnvSize(pointer_size) +
137                         2 * pointer_size +          // Thread* self + JavaVMExt* vm.
138                         4 +                         // local_ref_cookie.
139                         (pointer_size - 4);         // Padding.
140  size_t irt_segment_state_offset =
141      IndirectReferenceTable::SegmentStateOffset(pointer_size).Int32Value();
142  return Offset(locals_offset + irt_segment_state_offset);
143}
144
145Offset JNIEnvExt::LocalRefCookieOffset(size_t pointer_size) {
146  return Offset(JNIEnvSize(pointer_size) +
147                2 * pointer_size);          // Thread* self + JavaVMExt* vm
148}
149
150Offset JNIEnvExt::SelfOffset(size_t pointer_size) {
151  return Offset(JNIEnvSize(pointer_size));
152}
153
154// Use some defining part of the caller's frame as the identifying mark for the JNI segment.
155static uintptr_t GetJavaCallFrame(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_) {
156  NthCallerVisitor zeroth_caller(self, 0, false);
157  zeroth_caller.WalkStack();
158  if (zeroth_caller.caller == nullptr) {
159    // No Java code, must be from pure native code.
160    return 0;
161  } else if (zeroth_caller.GetCurrentQuickFrame() == nullptr) {
162    // Shadow frame = interpreter. Use the actual shadow frame's address.
163    DCHECK(zeroth_caller.GetCurrentShadowFrame() != nullptr);
164    return reinterpret_cast<uintptr_t>(zeroth_caller.GetCurrentShadowFrame());
165  } else {
166    // Quick frame = compiled code. Use the bottom of the frame.
167    return reinterpret_cast<uintptr_t>(zeroth_caller.GetCurrentQuickFrame());
168  }
169}
170
171void JNIEnvExt::RecordMonitorEnter(jobject obj) {
172  locked_objects_.push_back(std::make_pair(GetJavaCallFrame(self), obj));
173}
174
175static std::string ComputeMonitorDescription(Thread* self,
176                                             jobject obj) REQUIRES_SHARED(Locks::mutator_lock_) {
177  ObjPtr<mirror::Object> o = self->DecodeJObject(obj);
178  if ((o->GetLockWord(false).GetState() == LockWord::kThinLocked) &&
179      Locks::mutator_lock_->IsExclusiveHeld(self)) {
180    // Getting the identity hashcode here would result in lock inflation and suspension of the
181    // current thread, which isn't safe if this is the only runnable thread.
182    return StringPrintf("<@addr=0x%" PRIxPTR "> (a %s)",
183                        reinterpret_cast<intptr_t>(o.Ptr()),
184                        PrettyTypeOf(o).c_str());
185  } else {
186    // IdentityHashCode can cause thread suspension, which would invalidate o if it moved. So
187    // we get the pretty type before we call IdentityHashCode.
188    const std::string pretty_type(PrettyTypeOf(o));
189    return StringPrintf("<0x%08x> (a %s)", o->IdentityHashCode(), pretty_type.c_str());
190  }
191}
192
193static void RemoveMonitors(Thread* self,
194                           uintptr_t frame,
195                           ReferenceTable* monitors,
196                           std::vector<std::pair<uintptr_t, jobject>>* locked_objects)
197    REQUIRES_SHARED(Locks::mutator_lock_) {
198  auto kept_end = std::remove_if(
199      locked_objects->begin(),
200      locked_objects->end(),
201      [self, frame, monitors](const std::pair<uintptr_t, jobject>& pair)
202          REQUIRES_SHARED(Locks::mutator_lock_) {
203        if (frame == pair.first) {
204          ObjPtr<mirror::Object> o = self->DecodeJObject(pair.second);
205          monitors->Remove(o);
206          return true;
207        }
208        return false;
209      });
210  locked_objects->erase(kept_end, locked_objects->end());
211}
212
213void JNIEnvExt::CheckMonitorRelease(jobject obj) {
214  uintptr_t current_frame = GetJavaCallFrame(self);
215  std::pair<uintptr_t, jobject> exact_pair = std::make_pair(current_frame, obj);
216  auto it = std::find(locked_objects_.begin(), locked_objects_.end(), exact_pair);
217  bool will_abort = false;
218  if (it != locked_objects_.end()) {
219    locked_objects_.erase(it);
220  } else {
221    // Check whether this monitor was locked in another JNI "session."
222    ObjPtr<mirror::Object> mirror_obj = self->DecodeJObject(obj);
223    for (std::pair<uintptr_t, jobject>& pair : locked_objects_) {
224      if (self->DecodeJObject(pair.second) == mirror_obj) {
225        std::string monitor_descr = ComputeMonitorDescription(self, pair.second);
226        vm->JniAbortF("<JNI MonitorExit>",
227                      "Unlocking monitor that wasn't locked here: %s",
228                      monitor_descr.c_str());
229        will_abort = true;
230        break;
231      }
232    }
233  }
234
235  // When we abort, also make sure that any locks from the current "session" are removed from
236  // the monitors table, otherwise we may visit local objects in GC during abort (which won't be
237  // valid anymore).
238  if (will_abort) {
239    RemoveMonitors(self, current_frame, &monitors, &locked_objects_);
240  }
241}
242
243void JNIEnvExt::CheckNoHeldMonitors() {
244  uintptr_t current_frame = GetJavaCallFrame(self);
245  // The locked_objects_ are grouped by their stack frame component, as this enforces structured
246  // locking, and the groups form a stack. So the current frame entries are at the end. Check
247  // whether the vector is empty, and when there are elements, whether the last element belongs
248  // to this call - this signals that there are unlocked monitors.
249  if (!locked_objects_.empty()) {
250    std::pair<uintptr_t, jobject>& pair = locked_objects_[locked_objects_.size() - 1];
251    if (pair.first == current_frame) {
252      std::string monitor_descr = ComputeMonitorDescription(self, pair.second);
253      vm->JniAbortF("<JNI End>",
254                    "Still holding a locked object on JNI end: %s",
255                    monitor_descr.c_str());
256      // When we abort, also make sure that any locks from the current "session" are removed from
257      // the monitors table, otherwise we may visit local objects in GC during abort.
258      RemoveMonitors(self, current_frame, &monitors, &locked_objects_);
259    } else if (kIsDebugBuild) {
260      // Make sure there are really no other entries and our checking worked as expected.
261      for (std::pair<uintptr_t, jobject>& check_pair : locked_objects_) {
262        CHECK_NE(check_pair.first, current_frame);
263      }
264    }
265  }
266}
267
268}  // namespace art
269