1 /*
  2  * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.
  8  *
  9  * This code is distributed in the hope that it will be useful, but WITHOUT
 10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 12  * version 2 for more details (a copy is included in the LICENSE file that
 13  * accompanied this code).
 14  *
 15  * You should have received a copy of the GNU General Public License version
 16  * 2 along with this work; if not, write to the Free Software Foundation,
 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 18  *
 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 20  * or visit www.oracle.com if you need additional information or have any
 21  * questions.
 22  *
 23  */
 24 
 25 #include "precompiled.hpp"
 26 #include "interpreter/interpreter.hpp"
 27 #include "jvmtifiles/jvmtiEnv.hpp"
 28 #include "memory/resourceArea.hpp"
 29 #include "prims/jvmtiEnvThreadState.hpp"
 30 #include "prims/jvmtiEventController.inline.hpp"
 31 #include "prims/jvmtiImpl.hpp"
 32 #include "runtime/handles.hpp"
 33 #include "runtime/handles.inline.hpp"
 34 #include "runtime/interfaceSupport.inline.hpp"
 35 #include "runtime/javaCalls.hpp"
 36 #include "runtime/signature.hpp"
 37 #include "runtime/thread.inline.hpp"
 38 #include "runtime/vframe.hpp"
 39 #include "runtime/vmOperations.hpp"
 40 
 41 
 42 ///////////////////////////////////////////////////////////////
 43 //
 44 // class JvmtiFramePop
 45 //
 46 
 47 #ifndef PRODUCT
 48 void JvmtiFramePop::print() {
 49   tty->print_cr("_frame_number=%d", _frame_number);
 50 }
 51 #endif
 52 
 53 
 54 ///////////////////////////////////////////////////////////////
 55 //
 56 // class JvmtiFramePops - private methods
 57 //
 58 
 59 void
 60 JvmtiFramePops::set(JvmtiFramePop& fp) {
 61   if (_pops->find(fp.frame_number()) < 0) {
 62     _pops->append(fp.frame_number());
 63   }
 64 }
 65 
 66 
 67 void
 68 JvmtiFramePops::clear(JvmtiFramePop& fp) {
 69   assert(_pops->length() > 0, "No more frame pops");
 70 
 71   _pops->remove(fp.frame_number());
 72 }
 73 
 74 
 75 int
 76 JvmtiFramePops::clear_to(JvmtiFramePop& fp) {
 77   int cleared = 0;
 78   int index = 0;
 79   while (index < _pops->length()) {
 80     JvmtiFramePop pop = JvmtiFramePop(_pops->at(index));
 81     if (pop.above_on_stack(fp)) {
 82       _pops->remove_at(index);
 83       ++cleared;
 84     } else {
 85       ++index;
 86     }
 87   }
 88   return cleared;
 89 }
 90 
 91 
 92 ///////////////////////////////////////////////////////////////
 93 //
 94 // class JvmtiFramePops - public methods
 95 //
 96 
 97 JvmtiFramePops::JvmtiFramePops() {
 98   _pops = new (ResourceObj::C_HEAP, mtServiceability) GrowableArray<int> (2, mtServiceability);
 99 }
100 
101 JvmtiFramePops::~JvmtiFramePops() {
102   // return memory to c_heap.
103   delete _pops;
104 }
105 
106 
107 #ifndef PRODUCT
108 void JvmtiFramePops::print() {
109   ResourceMark rm;
110 
111   int n = _pops->length();
112   for (int i=0; i<n; i++) {
113     JvmtiFramePop fp = JvmtiFramePop(_pops->at(i));
114     tty->print("%d: ", i);
115     fp.print();
116     tty->cr();
117   }
118 }
119 #endif
120 
121 ///////////////////////////////////////////////////////////////
122 //
123 // class JvmtiEnvThreadState
124 //
125 // Instances of JvmtiEnvThreadState hang off of each JvmtiThreadState,
126 // one per JvmtiEnv.
127 //
128 
129 JvmtiEnvThreadState::JvmtiEnvThreadState(JavaThread *thread, JvmtiEnvBase *env) :
130   _event_enable() {
131   _thread                 = thread;
132   _env                    = (JvmtiEnv*)env;
133   _next                   = NULL;
134   _frame_pops             = NULL;
135   _current_bci            = 0;
136   _current_method_id      = NULL;
137   _breakpoint_posted      = false;
138   _single_stepping_posted = false;
139   _agent_thread_local_storage_data = NULL;
140 }
141 
142 JvmtiEnvThreadState::~JvmtiEnvThreadState()   {
143   delete _frame_pops;
144   _frame_pops = NULL;
145 }
146 
147 // Given that a new (potential) event has come in,
148 // maintain the current JVMTI location on a per-thread per-env basis
149 // and use it to filter out duplicate events:
150 // - instruction rewrites
151 // - breakpoint followed by single step
152 // - single step at a breakpoint
153 void JvmtiEnvThreadState::compare_and_set_current_location(Method* new_method,
154                                                            address new_location, jvmtiEvent event) {
155 
156   int new_bci = new_location - new_method->code_base();
157 
158   // The method is identified and stored as a jmethodID which is safe in this
159   // case because the class cannot be unloaded while a method is executing.
160   jmethodID new_method_id = new_method->jmethod_id();
161 
162   // the last breakpoint or single step was at this same location
163   if (_current_bci == new_bci && _current_method_id == new_method_id) {
164     switch (event) {
165     case JVMTI_EVENT_BREAKPOINT:
166       // Repeat breakpoint is complicated. If we previously posted a breakpoint
167       // event at this location and if we also single stepped at this location
168       // then we skip the duplicate breakpoint.
169       _breakpoint_posted = _breakpoint_posted && _single_stepping_posted;
170       break;
171     case JVMTI_EVENT_SINGLE_STEP:
172       // Repeat single step is easy: just don't post it again.
173       // If step is pending for popframe then it may not be
174       // a repeat step. The new_bci and method_id is same as current_bci
175       // and current method_id after pop and step for recursive calls.
176       // This has been handled by clearing the location
177       _single_stepping_posted = true;
178       break;
179     default:
180       assert(false, "invalid event value passed");
181       break;
182     }
183     return;
184   }
185 
186   set_current_location(new_method_id, new_bci);
187   _breakpoint_posted = false;
188   _single_stepping_posted = false;
189 }
190 
191 
192 JvmtiFramePops* JvmtiEnvThreadState::get_frame_pops() {
193 #ifdef ASSERT
194   Thread *current = Thread::current();
195 #endif
196   assert(get_thread()->is_handshake_safe_for(current),
197          "frame pop data only accessible from same thread or direct handshake");
198   if (_frame_pops == NULL) {
199     _frame_pops = new JvmtiFramePops();
200     assert(_frame_pops != NULL, "_frame_pops != NULL");
201   }
202   return _frame_pops;
203 }
204 
205 
206 bool JvmtiEnvThreadState::has_frame_pops() {
207   return _frame_pops == NULL? false : (_frame_pops->length() > 0);
208 }
209 
210 void JvmtiEnvThreadState::set_frame_pop(int frame_number) {
211 #ifdef ASSERT
212   Thread *current = Thread::current();
213 #endif
214   assert(get_thread()->is_handshake_safe_for(current),
215          "frame pop data only accessible from same thread or direct handshake");
216   JvmtiFramePop fpop(frame_number);
217   JvmtiEventController::set_frame_pop(this, fpop);
218 }
219 
220 
221 void JvmtiEnvThreadState::clear_frame_pop(int frame_number) {
222 #ifdef ASSERT
223   Thread *current = Thread::current();
224 #endif
225   assert(get_thread()->is_handshake_safe_for(current),
226          "frame pop data only accessible from same thread or direct handshake");
227   JvmtiFramePop fpop(frame_number);
228   JvmtiEventController::clear_frame_pop(this, fpop);
229 }
230 
231 
232 bool JvmtiEnvThreadState::is_frame_pop(int cur_frame_number) {
233 #ifdef ASSERT
234   Thread *current = Thread::current();
235 #endif
236   assert(get_thread()->is_handshake_safe_for(current),
237          "frame pop data only accessible from same thread or direct handshake");
238   if (!get_thread()->is_interp_only_mode() || _frame_pops == NULL) {
239     return false;
240   }
241   JvmtiFramePop fp(cur_frame_number);
242   return get_frame_pops()->contains(fp);
243 }
244 
245 
246 class GetCurrentLocationClosure : public HandshakeClosure {
247  private:
248    jmethodID _method_id;
249    int _bci;
250    bool _completed;
251  public:
252   GetCurrentLocationClosure()
253     : HandshakeClosure("GetCurrentLocation"),
254       _method_id(NULL),
255       _bci(0),
256       _completed(false) {}
257   void do_thread(Thread *target) {
258     JavaThread *jt = JavaThread::cast(target);
259     ResourceMark rmark; // jt != Thread::current()
260     RegisterMap rm(jt, false);
261     // There can be a race condition between a handshake
262     // and the target thread exiting from Java execution.
263     // We must recheck that the last Java frame still exists.
264     if (!jt->is_exiting() && jt->has_last_Java_frame()) {
265       javaVFrame* vf = jt->last_java_vframe(&rm);
266       if (vf != NULL) {
267         Method* method = vf->method();
268         _method_id = method->jmethod_id();
269         _bci = vf->bci();
270       }
271     }
272     _completed = true;
273   }
274   void get_current_location(jmethodID *method_id, int *bci) {
275     *method_id = _method_id;
276     *bci = _bci;
277   }
278   bool completed() {
279     return _completed;
280   }
281 };
282 
283 void JvmtiEnvThreadState::reset_current_location(jvmtiEvent event_type, bool enabled) {
284   assert(event_type == JVMTI_EVENT_SINGLE_STEP || event_type == JVMTI_EVENT_BREAKPOINT,
285          "must be single-step or breakpoint event");
286 
287   // Current location is used to detect the following:
288   // 1) a breakpoint event followed by single-stepping to the same bci
289   // 2) single-step to a bytecode that will be transformed to a fast version
290   // We skip to avoid posting the duplicate single-stepping event.
291 
292   // If single-stepping is disabled, clear current location so that
293   // single-stepping to the same method and bcp at a later time will be
294   // detected if single-stepping is enabled at that time (see 4388912).
295 
296   // If single-stepping is enabled, set the current location to the
297   // current method and bcp. This covers the following type of case,
298   // e.g., the debugger stepi command:
299   // - bytecode single stepped
300   // - SINGLE_STEP event posted and SINGLE_STEP event disabled
301   // - SINGLE_STEP event reenabled
302   // - bytecode rewritten to fast version
303 
304   // If breakpoint event is disabled, clear current location only if
305   // single-stepping is not enabled.  Otherwise, keep the thread location
306   // to detect any duplicate events.
307 
308   if (enabled) {
309     // If enabling breakpoint, no need to reset.
310     // Can't do anything if empty stack.
311     if (event_type == JVMTI_EVENT_SINGLE_STEP && _thread->has_last_Java_frame()) {
312       jmethodID method_id;
313       int bci;
314       // The java thread stack may not be walkable for a running thread
315       // so get current location with direct handshake.
316       GetCurrentLocationClosure op;
317       Thread *current = Thread::current();
318       if (_thread->is_handshake_safe_for(current)) {
319         op.do_thread(_thread);
320       } else {
321         Handshake::execute(&op, _thread);
322         guarantee(op.completed(), "Handshake failed. Target thread is not alive?");
323       }
324       op.get_current_location(&method_id, &bci);
325       set_current_location(method_id, bci);
326     }
327   } else if (event_type == JVMTI_EVENT_SINGLE_STEP || !is_enabled(JVMTI_EVENT_SINGLE_STEP)) {
328     // If this is to disable breakpoint, also check if single-step is not enabled
329     clear_current_location();
330   }
331 }