diff --git a/emulator/qtools/callstack.h b/emulator/qtools/callstack.h
index b73efea..8982330 100644
--- a/emulator/qtools/callstack.h
+++ b/emulator/qtools/callstack.h
@@ -32,7 +32,9 @@
     typedef SYM symbol_type;
     static const uint32_t kCausedException = 0x01;
     static const uint32_t kInterpreted     = 0x02;
-    static const uint32_t kPopBarrier      = (kCausedException | kInterpreted);
+    static const uint32_t kStartNative     = 0x04;
+    static const uint32_t kPopBarrier      = (kCausedException | kInterpreted
+        | kStartNative);
 
     symbol_type *function;      // the symbol for the function we entered
     uint32_t    addr;           // return address when this function returns
@@ -43,7 +45,7 @@
 
 template <class FRAME, class BASE = CallStackBase>
 class CallStack : public BASE {
-  public:
+public:
     typedef FRAME frame_type;
     typedef typename FRAME::symbol_type symbol_type;
     typedef typename FRAME::symbol_type::region_type region_type;
@@ -57,7 +59,7 @@
     void    threadStart(uint64_t time);
     void    threadStop(uint64_t time);
 
-    // Set to true if you don't want to see any Java methods
+    // Set to true if you don't want to see any Java methods ever
     void    setNativeOnly(bool nativeOnly) {
         mNativeOnly = nativeOnly;
     }
@@ -66,38 +68,36 @@
 
     uint64_t    getGlobalTime(uint64_t time) { return time + mSkippedTime; }
     void        showStack(FILE *stream);
-    void        showSnapshotStack(FILE *stream);
 
     int         mNumFrames;
     FRAME       *mFrames;
     int         mTop;           // index of the next stack frame to write
 
-  private:
-    enum Action { NONE, PUSH, POP };
+private:
+    enum Action { NONE, PUSH, POP, NATIVE_PUSH };
 
     Action      getAction(BBEvent *event, symbol_type *function);
-    Action      getMethodAction(BBEvent *event, symbol_type *function);
+    void        doMethodAction(BBEvent *event, symbol_type *function);
+    void        doMethodPop(BBEvent *event, uint32_t addr, const uint32_t flags);
     void        doSimplePush(symbol_type *function, uint32_t addr,
-                             uint64_t time);
+                             uint64_t time, int flags);
     void        doSimplePop(uint64_t time);
     void        doPush(BBEvent *event, symbol_type *function);
     void        doPop(BBEvent *event, symbol_type *function, Action methodAction);
 
-    void        transitionToJava();
-    void        transitionFromJava(uint64_t time);
-
     TraceReaderType *mTrace;
+
+    // This is a global switch that disables Java methods from appearing
+    // on the stack.
     bool        mNativeOnly;
+  
+    // This keeps track of whether native frames are currently allowed on the
+    // stack.
+    bool        mAllowNativeFrames;
 
     symbol_type mDummyFunction;
     region_type mDummyRegion;
 
-    int         mJavaTop;
-
-    int         mSnapshotNumFrames;
-    FRAME       *mSnapshotFrames;
-    int         mSnapshotTop;   // index of the next stack frame to write
-
     symbol_type *mPrevFunction;
     BBEvent     mPrevEvent;
 
@@ -125,10 +125,7 @@
     mNumFrames = numFrames;
     mFrames = new FRAME[mNumFrames];
     mTop = 0;
-
-    mSnapshotNumFrames = numFrames;
-    mSnapshotFrames = new FRAME[mSnapshotNumFrames];
-    mSnapshotTop = 0;
+    mAllowNativeFrames = true;
 
     memset(&mDummyFunction, 0, sizeof(symbol_type));
     memset(&mDummyRegion, 0, sizeof(region_type));
@@ -139,7 +136,6 @@
     memset(&mUserEvent, 0, sizeof(BBEvent));
     mSkippedTime = 0;
     mLastRunTime = 0;
-    mJavaTop = 0;
 
     // Read the first two methods from the trace if we haven't already read
     // from the method trace yet.
@@ -169,11 +165,29 @@
         // instead.
         if (function->vm_sym != NULL)
             function = function->vm_sym;
+    } else {
+        doMethodAction(event, function);
     }
 
     Action action = getAction(event, function);
-    Action methodAction = getMethodAction(event, function);
 
+    // Allow native frames if we are executing in the kernel.
+    if (!mAllowNativeFrames
+        && (function->region->flags & region_type::kIsKernelRegion) == 0) {
+        action = NONE;
+    }
+
+    if (function->vm_sym != NULL) {
+        function = function->vm_sym;
+        function->vm_sym = NULL;
+    }
+    if (action == PUSH) {
+        doPush(event, function);
+    } else if (action == POP) {
+        doPop(event, function, NONE);
+    }
+
+#if 0
     // Pop off native functions before pushing or popping Java methods.
     if (action == POP && mPrevFunction->vm_sym == NULL) {
         // Pop off the previous function first.
@@ -198,11 +212,16 @@
             doPush(event, function);
         }
     }
+#endif
 
     // If the stack is now empty, then push the current function.
     if (mTop == 0) {
         uint64_t time = event->time - mSkippedTime;
-        doSimplePush(function, 0, time);
+        int flags = 0;
+        if (function->vm_sym != NULL) {
+            flags = FRAME::kInterpreted;
+        }
+        doSimplePush(function, 0, time, 0);
     }
 
     mPrevFunction = function;
@@ -465,12 +484,19 @@
     if ((function->flags & symbol_type::kIsVectorStart) && mTop > 0)
         mFrames[mTop - 1].flags |= FRAME::kCausedException;
 
-    doSimplePush(function, retAddr, time);
+    // If the function being pushed is a Java method, then mark it on
+    // the stack so that we don't pop it off until we get a matching
+    // trace record from the method trace file.
+    int flags = 0;
+    if (function->vm_sym != NULL) {
+        flags = FRAME::kInterpreted;
+    }
+    doSimplePush(function, retAddr, time, flags);
 }
 
 template<class FRAME, class BASE>
-void CallStack<FRAME, BASE>::doSimplePush(symbol_type *function,
-                                          uint32_t addr, uint64_t time)
+void CallStack<FRAME, BASE>::doSimplePush(symbol_type *function, uint32_t addr,
+                                          uint64_t time, int flags)
 {
     // Check for stack overflow
     if (mTop >= mNumFrames) {
@@ -479,30 +505,12 @@
         exit(1);
     }
 
-    // Keep track of the number of Java methods we push on the stack.
-    if (!mNativeOnly && function->vm_sym != NULL) {
-        // If we are pushing the first Java method on the stack, then
-        // save a snapshot of the stack so that we can clean things up
-        // later when we pop off the last Java stack frame.
-        if (mJavaTop == 0) {
-            transitionToJava();
-        }
-        mJavaTop += 1;
-    }
-
     mFrames[mTop].addr = addr;
     mFrames[mTop].function = function;
-    mFrames[mTop].flags = 0;
+    mFrames[mTop].flags = flags;
     mFrames[mTop].time = time;
     mFrames[mTop].global_time = time + mSkippedTime;
 
-    // If the function being pushed is a Java method, then mark it on
-    // the stack so that we don't pop it off until we get a matching
-    // trace record from the method trace file.
-    if (function->vm_sym != NULL) {
-        mFrames[mTop].flags = FRAME::kInterpreted;
-    }
-
     mFrames[mTop].push(mTop, time, this);
     mTop += 1;
 }
@@ -517,17 +525,25 @@
     mTop -= 1;
     mFrames[mTop].pop(mTop, time, this);
 
-    // Keep track of the number of Java methods we have on the stack.
-    symbol_type *function = mFrames[mTop].function;
-    if (!mNativeOnly && function->vm_sym != NULL) {
-        mJavaTop -= 1;
+    if (mNativeOnly)
+        return;
 
-        // When there are no more Java stack frames, then clean up
-        // the client's stack.  We need to do this because the client
-        // doesn't see the changes to the native stack underlying the
-        // fake Java stack until the last Java method is popped off.
-        if (mJavaTop == 0) {
-            transitionFromJava(time);
+    // If the stack is empty, then allow more native frames.
+    // Otherwise, if we are transitioning from Java to native, then allow
+    // more native frames.
+    // Otherwise, if we are transitioning from native to Java, then disallow
+    // more native frames.
+    if (mTop == 0) {
+        mAllowNativeFrames = true;
+    } else {
+        bool newerIsJava = (mFrames[mTop].flags & FRAME::kInterpreted) != 0;
+        bool olderIsJava = (mFrames[mTop - 1].flags & FRAME::kInterpreted) != 0;
+        if (newerIsJava && !olderIsJava) {
+            // We are transitioning from Java to native
+            mAllowNativeFrames = true;
+        } else if (!newerIsJava && olderIsJava) {
+            // We are transitioning from native to Java
+            mAllowNativeFrames = false;
         }
     }
 }
@@ -671,20 +687,45 @@
 }
 
 template<class FRAME, class BASE>
-typename CallStack<FRAME, BASE>::Action
-CallStack<FRAME, BASE>::getMethodAction(BBEvent *event, symbol_type *function)
+void CallStack<FRAME, BASE>::doMethodPop(BBEvent *event, uint32_t addr,
+                                         const uint32_t flags)
 {
-    if (function->vm_sym == NULL && mPrevFunction->vm_sym == NULL) {
-        return NONE;
+    uint64_t time = event->time - mSkippedTime;
+
+    // Search the stack from the top down for a frame that contains a
+    // matching method.
+    int stackLevel;
+    for (stackLevel = mTop - 1; stackLevel >= 0; --stackLevel) {
+        if (mFrames[stackLevel].flags & flags) {
+            // If we are searching for a native method, then don't bother trying
+            // to match the address.
+            if (flags == FRAME::kStartNative)
+                break;
+            symbol_type *func = mFrames[stackLevel].function;
+            uint32_t methodAddr = func->region->base_addr + func->addr;
+            if (methodAddr == addr) {
+                break;
+            }
+        }
     }
 
-    Action action = NONE;
-    uint32_t prevAddr = mPrevFunction->addr + mPrevFunction->region->base_addr;
-    uint32_t addr = function->addr + function->region->base_addr;
+    // If we found a matching frame then pop the stack up to and including
+    // that frame.
+    if (stackLevel >= 0) {
+        // Pop the stack frames
+        for (int ii = mTop - 1; ii >= stackLevel; --ii)
+            doSimplePop(time);
+    }
+}
 
+template<class FRAME, class BASE>
+void CallStack<FRAME, BASE>::doMethodAction(BBEvent *event, symbol_type *function)
+{
     // If the events get ahead of the method trace, then read ahead until we
     // sync up again.  This can happen if there is a pop of a method in the
-    // method trace for which we don't have a previous push.
+    // method trace for which we don't have a previous push.  Such an unmatched
+    // pop can happen because the user can start tracing at any time and so
+    // there might already be a stack when we start tracing.
     while (event->time >= sNextMethod.time) {
         sCurrentMethod = sNextMethod;
         if (mTrace->ReadMethod(&sNextMethod)) {
@@ -693,59 +734,26 @@
     }
 
     if (event->time >= sCurrentMethod.time && event->pid == sCurrentMethod.pid) {
-        if (addr == sCurrentMethod.addr || prevAddr == sCurrentMethod.addr) {
-            action = (sCurrentMethod.flags == 0) ? PUSH : POP;
-            // We found a match, so read the next record.
-            sCurrentMethod = sNextMethod;
-            if (sNextMethod.time != ~0ull && mTrace->ReadMethod(&sNextMethod)) {
-                sNextMethod.time = ~0ull;
-            }
-        }
-    }
-    return action;
-}
-
-// When the first Java method is pushed on the stack, this method is
-// called to save a snapshot of the current native stack so that the
-// client's view of the native stack can be patched up later when the
-// Java stack is empty.
-template<class FRAME, class BASE>
-void CallStack<FRAME, BASE>::transitionToJava()
-{
-    mSnapshotTop = mTop;
-    for (int ii = 0; ii < mTop; ++ii) {
-        mSnapshotFrames[ii] = mFrames[ii];
-    }
-}
-
-// When the Java stack becomes empty, the native stack becomes
-// visible.  This method is called when the Java stack becomes empty
-// to patch up the client's view of the native stack, which may have
-// changed underneath the Java stack.  The stack snapshot is used to
-// create a sequence of pops and pushes to make the client's view of
-// the native stack match the current native stack.
-template<class FRAME, class BASE>
-void CallStack<FRAME, BASE>::transitionFromJava(uint64_t time)
-{
-    int top = mTop;
-    if (top > mSnapshotTop) {
-        top = mSnapshotTop;
-    }
-    for (int ii = 0; ii < top; ++ii) {
-        if (mSnapshotFrames[ii].function->addr == mFrames[ii].function->addr) {
-            continue;
+        uint64_t time = event->time - mSkippedTime;
+        int flags = sCurrentMethod.flags;
+        if (flags == kMethodEnter) {
+            doSimplePush(function, 0, time, FRAME::kInterpreted);
+            mAllowNativeFrames = false;
+        } else if (flags == kNativeEnter) {
+            doSimplePush(function, 0, time, FRAME::kStartNative);
+            mAllowNativeFrames = true;
+        } else if (flags == kMethodExit || flags == kMethodException) {
+            doMethodPop(event, sCurrentMethod.addr, FRAME::kInterpreted);
+        } else if (flags == kNativeExit || flags == kNativeException) {
+            doMethodPop(event, sCurrentMethod.addr, FRAME::kStartNative);
         }
 
-        // Pop off all the rest of the frames from the snapshot
-        for (int jj = top - 1; jj >= ii; --jj) {
-            mSnapshotFrames[jj].pop(jj, time, this);
+        // We found a match, so read the next record. When we get to the end
+        // of the trace, we set the time to the maximum value (~0).
+        sCurrentMethod = sNextMethod;
+        if (sNextMethod.time != ~0ull && mTrace->ReadMethod(&sNextMethod)) {
+            sNextMethod.time = ~0ull;
         }
-
-        // Push the new frames from the native stack
-        for (int jj = ii; jj < mTop; ++jj) {
-            mFrames[jj].push(jj, time, this);
-        }
-        break;
     }
 }
 
@@ -764,16 +772,4 @@
     }
 }
 
-template<class FRAME, class BASE>
-void CallStack<FRAME, BASE>::showSnapshotStack(FILE *stream)
-{
-    fprintf(stream, "mSnapshotTop: %d\n", mSnapshotTop);
-    for (int ii = 0; ii < mSnapshotTop; ++ii) {
-        fprintf(stream, "  %d: t %d f %x 0x%08x 0x%08x %s\n",
-                ii, mSnapshotFrames[ii].time, mSnapshotFrames[ii].flags,
-                mSnapshotFrames[ii].addr, mSnapshotFrames[ii].function->addr,
-                mSnapshotFrames[ii].function->name);
-    }
-}
-
 #endif /* CALL_STACK_H */
diff --git a/emulator/qtools/hash_table.h b/emulator/qtools/hash_table.h
index 45786ec..4ea9ed5 100644
--- a/emulator/qtools/hash_table.h
+++ b/emulator/qtools/hash_table.h
@@ -21,6 +21,7 @@
     typedef T value_type;
 
     void         Update(const char *key, T value);
+    bool         Remove(const char *key);
     T            Find(const char *key);
     entry_type*  GetFirst();
     entry_type*  GetNext();
@@ -121,6 +122,31 @@
 }
 
 template<class T>
+bool HashTable<T>::Remove(const char *key)
+{
+    // Hash the key to get the table position
+    int len = strlen(key);
+    int pos = HashFunction(key) & mask_;
+
+    // Search the chain for a matching key and keep track of the previous
+    // element in the chain.
+    entry_type *prev = NULL;
+    for (entry_type *ptr = table_[pos]; ptr; prev = ptr, ptr = ptr->next) {
+        if (strcmp(ptr->key, key) == 0) {
+            if (prev == NULL) {
+                table_[pos] = ptr->next;
+            } else {
+                prev->next = ptr->next;
+            }
+            delete ptr->key;
+            delete ptr;
+            return true;
+        }
+    }
+    return false;
+}
+
+template<class T>
 typename HashTable<T>::value_type HashTable<T>::Find(const char *key)
 {
     // Hash the key to get the table position
diff --git a/emulator/qtools/trace_reader.h b/emulator/qtools/trace_reader.h
index f73f17a..b91cb1b 100644
--- a/emulator/qtools/trace_reader.h
+++ b/emulator/qtools/trace_reader.h
@@ -62,6 +62,19 @@
             return NULL;
         }
 
+        region_entry   *MakePrivateCopy(region_entry *dest) {
+            dest->refs = 0;
+            dest->path = Strdup(path);
+            dest->vstart = vstart;
+            dest->vend = vend;
+            dest->base_addr = base_addr;
+            dest->file_offset = file_offset;
+            dest->flags = flags;
+            dest->nsymbols = nsymbols;
+            dest->symbols = symbols;
+            return dest;
+        }
+
         int             refs;        // reference count
         char            *path;
         uint32_t        vstart;
@@ -100,6 +113,11 @@
         static const int kHasKernelRegion       = 0x08;
         static const int kHasFirstMmap          = 0x10;
 
+        struct methodFrame {
+            uint32_t    addr;
+            bool        isNative;
+        };
+
         ProcessState() {
             cpu_time = 0;
             tgid = 0;
@@ -153,7 +171,7 @@
         }
 
         // Dumps the stack contents to standard output.  For debugging.
-        void            DumpStack();
+        void            DumpStack(FILE *stream);
 
         uint64_t        cpu_time;
         uint64_t        start_time;
@@ -173,7 +191,7 @@
         ProcessState    *addr_manager;   // the address space manager process
         ProcessState    *next;
         int             method_stack_top;
-        uint32_t        method_stack[kMaxMethodStackSize];
+        methodFrame     method_stack[kMaxMethodStackSize];
         symbol_type     *current_method_sym;
     };
 
@@ -184,6 +202,7 @@
     void                CopyKernelRegion(ProcessState *pstate);
     void                ClearRegions(ProcessState *pstate);
     void                CopyRegions(ProcessState *parent, ProcessState *child);
+    void                DumpRegions(FILE *stream, ProcessState *pstate);
     symbol_type         *LookupFunction(int pid, uint32_t addr, uint64_t time);
     symbol_type         *GetSymbols(int *num_syms);
     ProcessState        *GetCurrentProcess()            { return current_; }
@@ -217,6 +236,10 @@
     void                AddRegion(ProcessState *pstate, region_type *region);
     region_type         *FindRegion(uint32_t addr, int nregions,
                                     region_type **regions);
+    int                 FindRegionIndex(uint32_t addr, int nregions,
+                                         region_type **regions);
+    void                FindAndRemoveRegion(ProcessState *pstate,
+                                            uint32_t vstart, uint32_t vend);
     symbol_type         *FindFunction(uint32_t addr, int nsyms,
                                       symbol_type *symbols, bool exact_match);
     symbol_type         *FindCurrentMethod(int pid, uint64_t time);
@@ -926,6 +949,63 @@
 }
 
 template<class T>
+void TraceReader<T>::FindAndRemoveRegion(ProcessState *pstate, uint32_t vstart,
+                                         uint32_t vend)
+{
+    ProcessState *manager = pstate->addr_manager;
+    int nregions = manager->nregions;
+    int index = FindRegionIndex(vstart, nregions, manager->regions);
+    region_type *region = manager->regions[index];
+
+    // If the region does not contain [vstart,vend], then return.
+    if (vstart < region->vstart || vend > region->vend)
+        return;
+
+    // If the existing region exactly matches the address range [vstart,vend]
+    // then remove the whole region.
+    if (vstart == region->vstart && vend == region->vend) {
+        // The regions are reference-counted.
+        if (region->refs == 0) {
+            // Free the region
+            hash_->Remove(region->path);
+            delete region;
+        } else {
+            region->refs -= 1;
+        }
+
+        if (nregions > 1) {
+            // Assign the region at the end of the array to this empty slot
+            manager->regions[index] = manager->regions[nregions - 1];
+
+            // Resort the regions into increasing start address
+            qsort(manager->regions, nregions - 1, sizeof(region_type*),
+                  cmp_region_addr<T>);
+        }
+        manager->nregions = nregions - 1;
+        return;
+    }
+
+    // If the existing region contains the given range and ends at the
+    // end of the given range (a common case for some reason), then
+    // truncate the existing region so that it ends at vstart (because
+    // we are deleting the range [vstart,vend]).
+    if (vstart > region->vstart && vend == region->vend) {
+        region_type *truncated;
+
+        if (region->refs == 0) {
+            // This region is not shared, so truncate it directly
+            truncated = region;
+        } else {
+            // This region is shared, so make a copy that we can truncate
+            region->refs -= 1;
+            truncated = region->MakePrivateCopy(new region_type);
+        }
+        truncated->vend = vstart;
+        manager->regions[index] = truncated;
+    }
+}
+
+template<class T>
 void TraceReader<T>::CopyRegions(ProcessState *parent, ProcessState *child)
 {
     // Copy the parent's address space
@@ -944,6 +1024,20 @@
 }
 
 template<class T>
+void TraceReader<T>::DumpRegions(FILE *stream, ProcessState *pstate) {
+    ProcessState *manager = pstate->addr_manager;
+    for (int ii = 0; ii < manager->nregions; ++ii) {
+        fprintf(stream, "  %08x - %08x offset: %5x  nsyms: %4d refs: %d %s\n",
+                manager->regions[ii]->vstart,
+                manager->regions[ii]->vend,
+                manager->regions[ii]->file_offset,
+                manager->regions[ii]->nsymbols,
+                manager->regions[ii]->refs,
+                manager->regions[ii]->path);
+    }
+}
+
+template<class T>
 typename TraceReader<T>::region_type *
 TraceReader<T>::FindRegion(uint32_t addr, int nregions, region_type **regions)
 {
@@ -968,6 +1062,30 @@
 }
 
 template<class T>
+int TraceReader<T>::FindRegionIndex(uint32_t addr, int nregions,
+                                    region_type **regions)
+{
+    int high = nregions;
+    int low = -1;
+    while (low + 1 < high) {
+        int middle = (high + low) / 2;
+        uint32_t middle_addr = regions[middle]->vstart;
+        if (middle_addr == addr)
+            return middle;
+        if (middle_addr > addr)
+            high = middle;
+        else
+            low = middle;
+    }
+
+    // If we get here then we did not find an exact address match.  So use
+    // the closest region address that is less than the given address.
+    if (low < 0)
+        low = 0;
+    return low;
+}
+
+template<class T>
 typename TraceReader<T>::symbol_type *
 TraceReader<T>::FindFunction(uint32_t addr, int nsyms, symbol_type *symbols,
                              bool exact_match)
@@ -1007,15 +1125,12 @@
             uint32_t sym_addr = addr - cached_func_->region->base_addr;
             if (sym_addr >= cached_func_->addr
                 && sym_addr < (cached_func_ + 1)->addr) {
-                // If this function is the virtual machine interpreter, then
-                // read the method trace to find the "real" method name based
-                // on the current time and pid.
-                if (cached_func_->flags & symbol_type::kIsInterpreter) {
-                    symbol_type *sym = FindCurrentMethod(pid, time);
-                    if (sym != NULL) {
-                        sym->vm_sym = cached_func_;
-                        return sym;
-                    }
+
+                // Check if there is a Java method on the method trace.
+                symbol_type *sym = FindCurrentMethod(pid, time);
+                if (sym != NULL) {
+                    sym->vm_sym = cached_func_;
+                    return sym;
                 }
                 return cached_func_;
             }
@@ -1040,15 +1155,11 @@
     if (cached_func_ != NULL) {
         cached_func_->region = region;
 
-        // If this function is the virtual machine interpreter, then
-        // read the method trace to find the "real" method name based
-        // on the current time and pid.
-        if (cached_func_->flags & symbol_type::kIsInterpreter) {
-            symbol_type *sym = FindCurrentMethod(pid, time);
-            if (sym != NULL) {
-                sym->vm_sym = cached_func_;
-                return sym;
-            }
+        // Check if there is a Java method on the method trace.
+        symbol_type *sym = FindCurrentMethod(pid, time);
+        if (sym != NULL) {
+            sym->vm_sym = cached_func_;
+            return sym;
         }
     }
 
@@ -1142,11 +1253,17 @@
         current_->exit_val = event->pid;
         current_->flags |= ProcessState::kCalledExit;
         break;
+    case kPidMunmap:
+        FindAndRemoveRegion(current_, event->vstart, event->vend);
+        break;
     case kPidMmap:
         {
             region_type *region;
             region_type *existing_region = hash_->Find(event->path);
-            if (existing_region == NULL || existing_region->vstart != event->vstart) {
+            if (existing_region == NULL
+                || existing_region->vstart != event->vstart
+                || existing_region->vend != event->vend
+                || existing_region->file_offset != event->offset) {
                 // Create a new region and add it to the current process'
                 // address space.
                 region = new region_type;
@@ -1264,10 +1381,12 @@
 }
 
 template <class T>
-void TraceReader<T>::ProcessState::DumpStack()
+void TraceReader<T>::ProcessState::DumpStack(FILE *stream)
 {
+    const char *native;
     for (int ii = 0; ii < method_stack_top; ii++) {
-        printf("%2d: 0x%08x\n", ii, method_stack[ii]);
+        native = method_stack[ii].isNative ? "n" : " ";
+        fprintf(stream, "%2d: %s 0x%08x\n", ii, native, method_stack[ii].addr);
     }
 }
 
@@ -1277,13 +1396,17 @@
 {
     uint32_t addr;
     int top = pstate->method_stack_top;
-    if (method_rec->flags == kMethodEnter) {
+    int flags = method_rec->flags;
+    bool isNative;
+    if (flags == kMethodEnter || flags == kNativeEnter) {
         // Push this method on the stack
         if (top >= pstate->kMaxMethodStackSize) {
             fprintf(stderr, "Stack overflow at time %llu\n", method_rec->time);
             exit(1);
         }
-        pstate->method_stack[top] = method_rec->addr;
+        pstate->method_stack[top].addr = method_rec->addr;
+        isNative = (flags == kNativeEnter);
+        pstate->method_stack[top].isNative = isNative;
         pstate->method_stack_top = top + 1;
         addr = method_rec->addr;
     } else {
@@ -1293,14 +1416,27 @@
             return;
         }
         top -= 1;
-        addr = pstate->method_stack[top];
-        if (addr != method_rec->addr) {
+        addr = pstate->method_stack[top].addr;
+
+        // If this is a non-native method then the address we are popping should
+        // match the top-of-stack address.  Native pops don't always match the
+        // address of the native push for some reason.
+        if (addr != method_rec->addr && !pstate->method_stack[top].isNative) {
             fprintf(stderr,
                     "Stack method (0x%x) at index %d does not match trace record (0x%x) at time %llu\n",
                     addr, top, method_rec->addr, method_rec->time);
-            for (int ii = 0; ii <= top; ii++) {
-                fprintf(stderr, "  %d: 0x%x\n", ii, pstate->method_stack[ii]);
-            }
+            pstate->DumpStack(stderr);
+            exit(1);
+        }
+
+        // If we are popping a native method, then the top-of-stack should also
+        // be a native method.
+        bool poppingNative = (flags == kNativeExit) || (flags == kNativeException);
+        if (poppingNative != pstate->method_stack[top].isNative) {
+            fprintf(stderr,
+                    "Popping native vs. non-native mismatch at index %d time %llu\n",
+                    top, method_rec->time);
+            pstate->DumpStack(stderr);
             exit(1);
         }
 
@@ -1310,8 +1446,17 @@
             pstate->current_method_sym = NULL;
             return;
         }
-        addr = pstate->method_stack[top - 1];
+        addr = pstate->method_stack[top - 1].addr;
+        isNative = pstate->method_stack[top - 1].isNative;
     }
+
+    // If the top-of-stack is a native method, then set the current method
+    // to NULL.
+    if (isNative) {
+        pstate->current_method_sym = NULL;
+        return;
+    }
+
     ProcessState *manager = pstate->addr_manager;
     region_type *region = FindRegion(addr, manager->nregions, manager->regions);
     uint32_t sym_addr = addr - region->base_addr;
@@ -1324,6 +1469,11 @@
     }
 }
 
+// Returns the current top-of-stack Java method, if any, for the given pid
+// at the given time. The "time" parameter must be monotonically increasing
+// across successive calls to this method.
+// If the Java method stack is empty or if a native JNI method is on the
+// top of the stack, then this method returns NULL.
 template <class T>
 typename TraceReader<T>::symbol_type*
 TraceReader<T>::FindCurrentMethod(int pid, uint64_t time)