jni_env_ext.cc revision 46ee31b67d7ee1bd085fbc240502053caa3cf8fa 
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 "android-base/stringprintf.h"
23
24#include "check_jni.h"
25#include "indirect_reference_table.h"
26#include "java_vm_ext.h"
27#include "jni_internal.h"
28#include "lock_word.h"
29#include "mirror/object-inl.h"
30#include "nth_caller_visitor.h"
31#include "thread-inl.h"
32
33namespace art {
34
35using android::base::StringPrintf;
36
37static constexpr size_t kMonitorsInitial = 32;  // Arbitrary.
38static constexpr size_t kMonitorsMax = 4096;  // Arbitrary sanity check.
39
40// Checking "locals" requires the mutator lock, but at creation time we're really only interested
41// in validity, which isn't changing. To avoid grabbing the mutator lock, factored out and tagged
42// with NO_THREAD_SAFETY_ANALYSIS.
43static bool CheckLocalsValid(JNIEnvExt* in) NO_THREAD_SAFETY_ANALYSIS {
44  if (in == nullptr) {
45    return false;
46  }
47  return in->locals.IsValid();
48}
49
50jint JNIEnvExt::GetEnvHandler(JavaVMExt* vm, /*out*/void** env, jint version) {
51  UNUSED(vm);
52  // GetEnv always returns a JNIEnv* for the most current supported JNI version,
53  // and unlike other calls that take a JNI version doesn't care if you supply
54  // JNI_VERSION_1_1, which we don't otherwise support.
55  if (JavaVMExt::IsBadJniVersion(version) && version != JNI_VERSION_1_1) {
56    return JNI_EVERSION;
57  }
58  Thread* thread = Thread::Current();
59  CHECK(thread != nullptr);
60  *env = thread->GetJniEnv();
61  return JNI_OK;
62}
63
64JNIEnvExt* JNIEnvExt::Create(Thread* self_in, JavaVMExt* vm_in, std::string* error_msg) {
65  std::unique_ptr<JNIEnvExt> ret(new JNIEnvExt(self_in, vm_in, error_msg));
66  if (CheckLocalsValid(ret.get())) {
67    return ret.release();
68  }
69  return nullptr;
70}
71
72JNIEnvExt::JNIEnvExt(Thread* self_in, JavaVMExt* vm_in, std::string* error_msg)
73    : self(self_in),
74      vm(vm_in),
75      local_ref_cookie(kIRTFirstSegment),
76      locals(kLocalsInitial, kLocal, IndirectReferenceTable::ResizableCapacity::kYes, error_msg),
77      check_jni(false),
78      runtime_deleted(false),
79      critical(0),
80      monitors("monitors", kMonitorsInitial, kMonitorsMax) {
81  functions = unchecked_functions = GetJniNativeInterface();
82  if (vm->IsCheckJniEnabled()) {
83    SetCheckJniEnabled(true);
84  }
85}
86
87void JNIEnvExt::SetFunctionsToRuntimeShutdownFunctions() {
88  functions = GetRuntimeShutdownNativeInterface();
89  runtime_deleted = true;
90}
91
92JNIEnvExt::~JNIEnvExt() {
93}
94
95jobject JNIEnvExt::NewLocalRef(mirror::Object* obj) {
96  if (obj == nullptr) {
97    return nullptr;
98  }
99  return reinterpret_cast<jobject>(locals.Add(local_ref_cookie, obj));
100}
101
102void JNIEnvExt::DeleteLocalRef(jobject obj) {
103  if (obj != nullptr) {
104    locals.Remove(local_ref_cookie, reinterpret_cast<IndirectRef>(obj));
105  }
106}
107
108void JNIEnvExt::SetCheckJniEnabled(bool enabled) {
109  check_jni = enabled;
110  functions = enabled ? GetCheckJniNativeInterface() : GetJniNativeInterface();
111}
112
113void JNIEnvExt::DumpReferenceTables(std::ostream& os) {
114  locals.Dump(os);
115  monitors.Dump(os);
116}
117
118void JNIEnvExt::PushFrame(int capacity ATTRIBUTE_UNUSED) {
119  // TODO: take 'capacity' into account.
120  stacked_local_ref_cookies.push_back(local_ref_cookie);
121  local_ref_cookie = locals.GetSegmentState();
122}
123
124void JNIEnvExt::PopFrame() {
125  locals.SetSegmentState(local_ref_cookie);
126  local_ref_cookie = stacked_local_ref_cookies.back();
127  stacked_local_ref_cookies.pop_back();
128}
129
130// Note: the offset code is brittle, as we can't use OFFSETOF_MEMBER or offsetof easily. Thus, there
131//       are tests in jni_internal_test to match the results against the actual values.
132
133// This is encoding the knowledge of the structure and layout of JNIEnv fields.
134static size_t JNIEnvSize(size_t pointer_size) {
135  // A single pointer.
136  return pointer_size;
137}
138
139Offset JNIEnvExt::SegmentStateOffset(size_t pointer_size) {
140  size_t locals_offset = JNIEnvSize(pointer_size) +
141                         2 * pointer_size +          // Thread* self + JavaVMExt* vm.
142                         4 +                         // local_ref_cookie.
143                         (pointer_size - 4);         // Padding.
144  size_t irt_segment_state_offset =
145      IndirectReferenceTable::SegmentStateOffset(pointer_size).Int32Value();
146  return Offset(locals_offset + irt_segment_state_offset);
147}
148
149Offset JNIEnvExt::LocalRefCookieOffset(size_t pointer_size) {
150  return Offset(JNIEnvSize(pointer_size) +
151                2 * pointer_size);          // Thread* self + JavaVMExt* vm
152}
153
154Offset JNIEnvExt::SelfOffset(size_t pointer_size) {
155  return Offset(JNIEnvSize(pointer_size));
156}
157
158// Use some defining part of the caller's frame as the identifying mark for the JNI segment.
159static uintptr_t GetJavaCallFrame(Thread* self) REQUIRES_SHARED(Locks::mutator_lock_) {
160  NthCallerVisitor zeroth_caller(self, 0, false);
161  zeroth_caller.WalkStack();
162  if (zeroth_caller.caller == nullptr) {
163    // No Java code, must be from pure native code.
164    return 0;
165  } else if (zeroth_caller.GetCurrentQuickFrame() == nullptr) {
166    // Shadow frame = interpreter. Use the actual shadow frame's address.
167    DCHECK(zeroth_caller.GetCurrentShadowFrame() != nullptr);
168    return reinterpret_cast<uintptr_t>(zeroth_caller.GetCurrentShadowFrame());
169  } else {
170    // Quick frame = compiled code. Use the bottom of the frame.
171    return reinterpret_cast<uintptr_t>(zeroth_caller.GetCurrentQuickFrame());
172  }
173}
174
175void JNIEnvExt::RecordMonitorEnter(jobject obj) {
176  locked_objects_.push_back(std::make_pair(GetJavaCallFrame(self), obj));
177}
178
179static std::string ComputeMonitorDescription(Thread* self,
180                                             jobject obj) REQUIRES_SHARED(Locks::mutator_lock_) {
181  ObjPtr<mirror::Object> o = self->DecodeJObject(obj);
182  if ((o->GetLockWord(false).GetState() == LockWord::kThinLocked) &&
183      Locks::mutator_lock_->IsExclusiveHeld(self)) {
184    // Getting the identity hashcode here would result in lock inflation and suspension of the
185    // current thread, which isn't safe if this is the only runnable thread.
186    return StringPrintf("<@addr=0x%" PRIxPTR "> (a %s)",
187                        reinterpret_cast<intptr_t>(o.Ptr()),
188                        o->PrettyTypeOf().c_str());
189  } else {
190    // IdentityHashCode can cause thread suspension, which would invalidate o if it moved. So
191    // we get the pretty type before we call IdentityHashCode.
192    const std::string pretty_type(o->PrettyTypeOf());
193    return StringPrintf("<0x%08x> (a %s)", o->IdentityHashCode(), pretty_type.c_str());
194  }
195}
196
197static void RemoveMonitors(Thread* self,
198                           uintptr_t frame,
199                           ReferenceTable* monitors,
200                           std::vector<std::pair<uintptr_t, jobject>>* locked_objects)
201    REQUIRES_SHARED(Locks::mutator_lock_) {
202  auto kept_end = std::remove_if(
203      locked_objects->begin(),
204      locked_objects->end(),
205      [self, frame, monitors](const std::pair<uintptr_t, jobject>& pair)
206          REQUIRES_SHARED(Locks::mutator_lock_) {
207        if (frame == pair.first) {
208          ObjPtr<mirror::Object> o = self->DecodeJObject(pair.second);
209          monitors->Remove(o);
210          return true;
211        }
212        return false;
213      });
214  locked_objects->erase(kept_end, locked_objects->end());
215}
216
217void JNIEnvExt::CheckMonitorRelease(jobject obj) {
218  uintptr_t current_frame = GetJavaCallFrame(self);
219  std::pair<uintptr_t, jobject> exact_pair = std::make_pair(current_frame, obj);
220  auto it = std::find(locked_objects_.begin(), locked_objects_.end(), exact_pair);
221  bool will_abort = false;
222  if (it != locked_objects_.end()) {
223    locked_objects_.erase(it);
224  } else {
225    // Check whether this monitor was locked in another JNI "session."
226    ObjPtr<mirror::Object> mirror_obj = self->DecodeJObject(obj);
227    for (std::pair<uintptr_t, jobject>& pair : locked_objects_) {
228      if (self->DecodeJObject(pair.second) == mirror_obj) {
229        std::string monitor_descr = ComputeMonitorDescription(self, pair.second);
230        vm->JniAbortF("<JNI MonitorExit>",
231                      "Unlocking monitor that wasn't locked here: %s",
232                      monitor_descr.c_str());
233        will_abort = true;
234        break;
235      }
236    }
237  }
238
239  // When we abort, also make sure that any locks from the current "session" are removed from
240  // the monitors table, otherwise we may visit local objects in GC during abort (which won't be
241  // valid anymore).
242  if (will_abort) {
243    RemoveMonitors(self, current_frame, &monitors, &locked_objects_);
244  }
245}
246
247void JNIEnvExt::CheckNoHeldMonitors() {
248  uintptr_t current_frame = GetJavaCallFrame(self);
249  // The locked_objects_ are grouped by their stack frame component, as this enforces structured
250  // locking, and the groups form a stack. So the current frame entries are at the end. Check
251  // whether the vector is empty, and when there are elements, whether the last element belongs
252  // to this call - this signals that there are unlocked monitors.
253  if (!locked_objects_.empty()) {
254    std::pair<uintptr_t, jobject>& pair = locked_objects_[locked_objects_.size() - 1];
255    if (pair.first == current_frame) {
256      std::string monitor_descr = ComputeMonitorDescription(self, pair.second);
257      vm->JniAbortF("<JNI End>",
258                    "Still holding a locked object on JNI end: %s",
259                    monitor_descr.c_str());
260      // When we abort, also make sure that any locks from the current "session" are removed from
261      // the monitors table, otherwise we may visit local objects in GC during abort.
262      RemoveMonitors(self, current_frame, &monitors, &locked_objects_);
263    } else if (kIsDebugBuild) {
264      // Make sure there are really no other entries and our checking worked as expected.
265      for (std::pair<uintptr_t, jobject>& check_pair : locked_objects_) {
266        CHECK_NE(check_pair.first, current_frame);
267      }
268    }
269  }
270}
271
272}  // namespace art
273