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/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Indirect reference table management.
*/
#include "Dalvik.h"
static void abortMaybe() {
// If CheckJNI is on, it'll give a more detailed error before aborting.
// Otherwise, we want to abort rather than hand back a bad reference.
if (!gDvmJni.useCheckJni) {
dvmAbort();
}
}
bool IndirectRefTable::init(size_t initialCount,
size_t maxCount, IndirectRefKind desiredKind)
{
assert(initialCount > 0);
assert(initialCount <= maxCount);
assert(desiredKind != kIndirectKindInvalid);
table_ = (IndirectRefSlot*) malloc(initialCount * sizeof(IndirectRefSlot));
if (table_ == NULL) {
return false;
}
memset(table_, 0xd1, initialCount * sizeof(IndirectRefSlot));
segmentState.all = IRT_FIRST_SEGMENT;
alloc_entries_ = initialCount;
max_entries_ = maxCount;
kind_ = desiredKind;
return true;
}
/*
* Clears out the contents of a IndirectRefTable, freeing allocated storage.
*/
void IndirectRefTable::destroy()
{
free(table_);
table_ = NULL;
alloc_entries_ = max_entries_ = -1;
}
IndirectRef IndirectRefTable::add(u4 cookie, Object* obj)
{
IRTSegmentState prevState;
prevState.all = cookie;
size_t topIndex = segmentState.parts.topIndex;
assert(obj != NULL);
assert(dvmIsHeapAddress(obj));
assert(table_ != NULL);
assert(alloc_entries_ <= max_entries_);
assert(segmentState.parts.numHoles >= prevState.parts.numHoles);
/*
* We know there's enough room in the table. Now we just need to find
* the right spot. If there's a hole, find it and fill it; otherwise,
* add to the end of the list.
*/
IndirectRef result;
IndirectRefSlot* slot;
int numHoles = segmentState.parts.numHoles - prevState.parts.numHoles;
if (numHoles > 0) {
assert(topIndex > 1);
/* find the first hole; likely to be near the end of the list,
* we know the item at the topIndex is not a hole */
slot = &table_[topIndex - 1];
assert(slot->obj != NULL);
while ((--slot)->obj != NULL) {
assert(slot >= table_ + prevState.parts.topIndex);
}
segmentState.parts.numHoles--;
} else {
/* add to the end, grow if needed */
if (topIndex == alloc_entries_) {
/* reached end of allocated space; did we hit buffer max? */
if (topIndex == max_entries_) {
ALOGE("JNI ERROR (app bug): %s reference table overflow (max=%d)",
indirectRefKindToString(kind_), max_entries_);
return NULL;
}
size_t newSize = alloc_entries_ * 2;
if (newSize > max_entries_) {
newSize = max_entries_;
}
assert(newSize > alloc_entries_);
IndirectRefSlot* newTable =
(IndirectRefSlot*) realloc(table_, newSize * sizeof(IndirectRefSlot));
if (table_ == NULL) {
ALOGE("JNI ERROR (app bug): unable to expand %s reference table "
"(from %d to %d, max=%d)",
indirectRefKindToString(kind_),
alloc_entries_, newSize, max_entries_);
return NULL;
}
memset(newTable + alloc_entries_, 0xd1,
(newSize - alloc_entries_) * sizeof(IndirectRefSlot));
alloc_entries_ = newSize;
table_ = newTable;
}
slot = &table_[topIndex++];
segmentState.parts.topIndex = topIndex;
}
slot->obj = obj;
slot->serial = nextSerial(slot->serial);
result = toIndirectRef(slot - table_, slot->serial, kind_);
assert(result != NULL);
return result;
}
/*
* Get the referent of an indirect ref from the table.
*
* Returns kInvalidIndirectRefObject if iref is invalid.
*/
Object* IndirectRefTable::get(IndirectRef iref) const {
IndirectRefKind kind = indirectRefKind(iref);
if (kind != kind_) {
if (iref == NULL) {
ALOGW("Attempt to look up NULL %s reference", indirectRefKindToString(kind_));
return kInvalidIndirectRefObject;
}
if (kind == kIndirectKindInvalid) {
ALOGE("JNI ERROR (app bug): invalid %s reference %p",
indirectRefKindToString(kind_), iref);
abortMaybe();
return kInvalidIndirectRefObject;
}
// References of the requested kind cannot appear within this table.
return kInvalidIndirectRefObject;
}
u4 topIndex = segmentState.parts.topIndex;
u4 index = extractIndex(iref);
if (index >= topIndex) {
/* bad -- stale reference? */
ALOGE("JNI ERROR (app bug): accessed stale %s reference %p (index %d in a table of size %d)",
indirectRefKindToString(kind_), iref, index, topIndex);
abortMaybe();
return kInvalidIndirectRefObject;
}
Object* obj = table_[index].obj;
if (obj == NULL) {
ALOGI("JNI ERROR (app bug): accessed deleted %s reference %p",
indirectRefKindToString(kind_), iref);
abortMaybe();
return kInvalidIndirectRefObject;
}
u4 serial = extractSerial(iref);
if (serial != table_[index].serial) {
ALOGE("JNI ERROR (app bug): attempt to use stale %s reference %p",
indirectRefKindToString(kind_), iref);
abortMaybe();
return kInvalidIndirectRefObject;
}
return obj;
}
static int findObject(const Object* obj, int bottomIndex, int topIndex,
const IndirectRefSlot* table) {
for (int i = bottomIndex; i < topIndex; ++i) {
if (table[i].obj == obj) {
return i;
}
}
return -1;
}
bool IndirectRefTable::contains(const Object* obj) const {
return findObject(obj, 0, segmentState.parts.topIndex, table_) >= 0;
}
/*
* Remove "obj" from "pRef". We extract the table offset bits from "iref"
* and zap the corresponding entry, leaving a hole if it's not at the top.
*
* If the entry is not between the current top index and the bottom index
* specified by the cookie, we don't remove anything. This is the behavior
* required by JNI's DeleteLocalRef function.
*
* Note this is NOT called when a local frame is popped. This is only used
* for explicit single removals.
*
* Returns "false" if nothing was removed.
*/
bool IndirectRefTable::remove(u4 cookie, IndirectRef iref)
{
IRTSegmentState prevState;
prevState.all = cookie;
u4 topIndex = segmentState.parts.topIndex;
u4 bottomIndex = prevState.parts.topIndex;
assert(table_ != NULL);
assert(alloc_entries_ <= max_entries_);
assert(segmentState.parts.numHoles >= prevState.parts.numHoles);
IndirectRefKind kind = indirectRefKind(iref);
u4 index;
if (kind == kind_) {
index = extractIndex(iref);
if (index < bottomIndex) {
/* wrong segment */
ALOGV("Attempt to remove index outside index area (%ud vs %ud-%ud)",
index, bottomIndex, topIndex);
return false;
}
if (index >= topIndex) {
/* bad -- stale reference? */
ALOGD("Attempt to remove invalid index %ud (bottom=%ud top=%ud)",
index, bottomIndex, topIndex);
return false;
}
if (table_[index].obj == NULL) {
ALOGD("Attempt to remove cleared %s reference %p",
indirectRefKindToString(kind_), iref);
return false;
}
u4 serial = extractSerial(iref);
if (table_[index].serial != serial) {
ALOGD("Attempt to remove stale %s reference %p",
indirectRefKindToString(kind_), iref);
return false;
}
} else if (kind == kIndirectKindInvalid && gDvmJni.workAroundAppJniBugs) {
// reference looks like a pointer, scan the table to find the index
int i = findObject(reinterpret_cast<Object*>(iref), bottomIndex, topIndex, table_);
if (i < 0) {
ALOGW("trying to work around app JNI bugs, but didn't find %p in table!", iref);
return false;
}
index = i;
} else {
// References of the requested kind cannot appear within this table.
return false;
}
if (index == topIndex - 1) {
// Top-most entry. Scan up and consume holes.
int numHoles = segmentState.parts.numHoles - prevState.parts.numHoles;
if (numHoles != 0) {
while (--topIndex > bottomIndex && numHoles != 0) {
ALOGV("+++ checking for hole at %d (cookie=0x%08x) val=%p",
topIndex-1, cookie, table_[topIndex-1].obj);
if (table_[topIndex-1].obj != NULL) {
break;
}
ALOGV("+++ ate hole at %d", topIndex-1);
numHoles--;
}
segmentState.parts.numHoles = numHoles + prevState.parts.numHoles;
segmentState.parts.topIndex = topIndex;
} else {
segmentState.parts.topIndex = topIndex-1;
ALOGV("+++ ate last entry %d", topIndex-1);
}
} else {
/*
* Not the top-most entry. This creates a hole. We NULL out the
* entry to prevent somebody from deleting it twice and screwing up
* the hole count.
*/
table_[index].obj = NULL;
segmentState.parts.numHoles++;
ALOGV("+++ left hole at %d, holes=%d", index, segmentState.parts.numHoles);
}
return true;
}
const char* indirectRefKindToString(IndirectRefKind kind)
{
switch (kind) {
case kIndirectKindInvalid: return "invalid";
case kIndirectKindLocal: return "local";
case kIndirectKindGlobal: return "global";
case kIndirectKindWeakGlobal: return "weak global";
default: return "UNKNOWN";
}
}
void IndirectRefTable::dump(const char* descr) const
{
size_t count = capacity();
Object** copy = new Object*[count];
for (size_t i = 0; i < count; i++) {
copy[i] = table_[i].obj;
}
dvmDumpReferenceTableContents(copy, count, descr);
delete[] copy;
}
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