/*
* Copyright (C) 2008 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.
*/
#include "common_throws.h"
#include "gc/accounting/card_table-inl.h"
#include "jni_internal.h"
#include "mirror/array.h"
#include "mirror/class.h"
#include "mirror/class-inl.h"
#include "mirror/object-inl.h"
#include "mirror/object_array-inl.h"
#include "scoped_thread_state_change.h"
/*
* We make guarantees about the atomicity of accesses to primitive
* variables. These guarantees also apply to elements of arrays.
* In particular, 8-bit, 16-bit, and 32-bit accesses must be atomic and
* must not cause "word tearing". Accesses to 64-bit array elements must
* either be atomic or treated as two 32-bit operations. References are
* always read and written atomically, regardless of the number of bits
* used to represent them.
*
* We can't rely on standard libc functions like memcpy(3) and memmove(3)
* in our implementation of System.arraycopy, because they may copy
* byte-by-byte (either for the full run or for "unaligned" parts at the
* start or end). We need to use functions that guarantee 16-bit or 32-bit
* atomicity as appropriate.
*
* System.arraycopy() is heavily used, so having an efficient implementation
* is important. The bionic libc provides a platform-optimized memory move
* function that should be used when possible. If it's not available,
* the trivial "reference implementation" versions below can be used until
* a proper version can be written.
*
* For these functions, The caller must guarantee that dst/src are aligned
* appropriately for the element type, and that n is a multiple of the
* element size.
*/
/*
* Works like memmove(), except:
* - if all arguments are at least 32-bit aligned, we guarantee that we
* will use operations that preserve atomicity of 32-bit values
* - if not, we guarantee atomicity of 16-bit values
*
* If all three arguments are not at least 16-bit aligned, the behavior
* of this function is undefined. (We could remove this restriction by
* testing for unaligned values and punting to memmove(), but that's
* not currently useful.)
*
* TODO: add loop for 64-bit alignment
* TODO: use __builtin_prefetch
* TODO: write ARM/MIPS/x86 optimized versions
*/
void MemmoveWords(void* dst, const void* src, size_t n) {
DCHECK_EQ((((uintptr_t) dst | (uintptr_t) src | n) & 0x01), 0U);
char* d = reinterpret_cast<char*>(dst);
const char* s = reinterpret_cast<const char*>(src);
size_t copyCount;
// If the source and destination pointers are the same, this is
// an expensive no-op. Testing for an empty move now allows us
// to skip a check later.
if (n == 0 || d == s) {
return;
}
// Determine if the source and destination buffers will overlap if
// we copy data forward (i.e. *dst++ = *src++).
//
// It's okay if the destination buffer starts before the source and
// there is some overlap, because the reader is always ahead of the
// writer.
if (LIKELY((d < s) || ((size_t)(d - s) >= n))) {
// Copy forward. We prefer 32-bit loads and stores even for 16-bit
// data, so sort that out.
if (((reinterpret_cast<uintptr_t>(d) | reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
// Not 32-bit aligned. Two possibilities:
// (1) Congruent, we can align to 32-bit by copying one 16-bit val
// (2) Non-congruent, we can do one of:
// a. copy whole buffer as a series of 16-bit values
// b. load/store 32 bits, using shifts to ensure alignment
// c. just copy the as 32-bit values and assume the CPU
// will do a reasonable job
//
// We're currently using (a), which is suboptimal.
if (((reinterpret_cast<uintptr_t>(d) ^ reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
copyCount = n;
} else {
copyCount = 2;
}
n -= copyCount;
copyCount /= sizeof(uint16_t);
while (copyCount--) {
*reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
d += sizeof(uint16_t);
s += sizeof(uint16_t);
}
}
// Copy 32-bit aligned words.
copyCount = n / sizeof(uint32_t);
while (copyCount--) {
*reinterpret_cast<uint32_t*>(d) = *reinterpret_cast<const uint32_t*>(s);
d += sizeof(uint32_t);
s += sizeof(uint32_t);
}
// Check for leftovers. Either we finished exactly, or we have one remaining 16-bit chunk.
if ((n & 0x02) != 0) {
*reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
}
} else {
// Copy backward, starting at the end.
d += n;
s += n;
if (((reinterpret_cast<uintptr_t>(d) | reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
// try for 32-bit alignment.
if (((reinterpret_cast<uintptr_t>(d) ^ reinterpret_cast<uintptr_t>(s)) & 0x03) != 0) {
copyCount = n;
} else {
copyCount = 2;
}
n -= copyCount;
copyCount /= sizeof(uint16_t);
while (copyCount--) {
d -= sizeof(uint16_t);
s -= sizeof(uint16_t);
*reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
}
}
// Copy 32-bit aligned words.
copyCount = n / sizeof(uint32_t);
while (copyCount--) {
d -= sizeof(uint32_t);
s -= sizeof(uint32_t);
*reinterpret_cast<uint32_t*>(d) = *reinterpret_cast<const uint32_t*>(s);
}
// Copy leftovers.
if ((n & 0x02) != 0) {
d -= sizeof(uint16_t);
s -= sizeof(uint16_t);
*reinterpret_cast<uint16_t*>(d) = *reinterpret_cast<const uint16_t*>(s);
}
}
}
#define move16 MemmoveWords
#define move32 MemmoveWords
namespace art {
static void ThrowArrayStoreException_NotAnArray(const char* identifier, mirror::Object* array)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
std::string actualType(PrettyTypeOf(array));
Thread* self = Thread::Current();
ThrowLocation throw_location = self->GetCurrentLocationForThrow();
self->ThrowNewExceptionF(throw_location, "Ljava/lang/ArrayStoreException;",
"%s of type %s is not an array", identifier, actualType.c_str());
}
static void System_arraycopy(JNIEnv* env, jclass, jobject javaSrc, jint srcPos, jobject javaDst, jint dstPos, jint length) {
ScopedObjectAccess soa(env);
// Null pointer checks.
if (UNLIKELY(javaSrc == NULL)) {
ThrowNullPointerException(NULL, "src == null");
return;
}
if (UNLIKELY(javaDst == NULL)) {
ThrowNullPointerException(NULL, "dst == null");
return;
}
// Make sure source and destination are both arrays.
mirror::Object* srcObject = soa.Decode<mirror::Object*>(javaSrc);
mirror::Object* dstObject = soa.Decode<mirror::Object*>(javaDst);
if (UNLIKELY(!srcObject->IsArrayInstance())) {
ThrowArrayStoreException_NotAnArray("source", srcObject);
return;
}
if (UNLIKELY(!dstObject->IsArrayInstance())) {
ThrowArrayStoreException_NotAnArray("destination", dstObject);
return;
}
mirror::Array* srcArray = srcObject->AsArray();
mirror::Array* dstArray = dstObject->AsArray();
mirror::Class* srcComponentType = srcArray->GetClass()->GetComponentType();
mirror::Class* dstComponentType = dstArray->GetClass()->GetComponentType();
// Bounds checking.
if (UNLIKELY(srcPos < 0 || dstPos < 0 || length < 0 || srcPos > srcArray->GetLength() - length || dstPos > dstArray->GetLength() - length)) {
ThrowLocation throw_location = soa.Self()->GetCurrentLocationForThrow();
soa.Self()->ThrowNewExceptionF(throw_location, "Ljava/lang/ArrayIndexOutOfBoundsException;",
"src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
srcArray->GetLength(), srcPos, dstArray->GetLength(), dstPos, length);
return;
}
// Handle primitive arrays.
if (srcComponentType->IsPrimitive() || dstComponentType->IsPrimitive()) {
// If one of the arrays holds a primitive type the other array must hold the exact same type.
if (UNLIKELY(srcComponentType != dstComponentType)) {
std::string srcType(PrettyTypeOf(srcArray));
std::string dstType(PrettyTypeOf(dstArray));
ThrowLocation throw_location = soa.Self()->GetCurrentLocationForThrow();
soa.Self()->ThrowNewExceptionF(throw_location, "Ljava/lang/ArrayStoreException;",
"Incompatible types: src=%s, dst=%s",
srcType.c_str(), dstType.c_str());
return;
}
size_t width = srcArray->GetClass()->GetComponentSize();
uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData(width));
const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData(width));
switch (width) {
case 1:
memmove(dstBytes + dstPos, srcBytes + srcPos, length);
break;
case 2:
move16(dstBytes + dstPos * 2, srcBytes + srcPos * 2, length * 2);
break;
case 4:
move32(dstBytes + dstPos * 4, srcBytes + srcPos * 4, length * 4);
break;
case 8:
// We don't need to guarantee atomicity of the entire 64-bit word.
move32(dstBytes + dstPos * 8, srcBytes + srcPos * 8, length * 8);
break;
default:
LOG(FATAL) << "Unknown primitive array type: " << PrettyTypeOf(srcArray);
}
return;
}
// Neither class is primitive. Are the types trivially compatible?
const size_t width = sizeof(mirror::Object*);
uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData(width));
const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData(width));
if (dstArray == srcArray || dstComponentType->IsAssignableFrom(srcComponentType)) {
// Yes. Bulk copy.
COMPILE_ASSERT(sizeof(width) == sizeof(uint32_t), move32_assumes_Object_references_are_32_bit);
move32(dstBytes + dstPos * width, srcBytes + srcPos * width, length * width);
Runtime::Current()->GetHeap()->WriteBarrierArray(dstArray, dstPos, length);
return;
}
// The arrays are not trivially compatible. However, we may still be able to copy some or all of
// the elements if the source objects are compatible (for example, copying an Object[] to
// String[], the Objects being copied might actually be Strings).
// We can't do a bulk move because that would introduce a check-use race condition, so we copy
// elements one by one.
// We already dealt with overlapping copies, so we don't need to cope with that case below.
CHECK_NE(dstArray, srcArray);
mirror::Object* const * srcObjects =
reinterpret_cast<mirror::Object* const *>(srcBytes + srcPos * width);
mirror::Object** dstObjects = reinterpret_cast<mirror::Object**>(dstBytes + dstPos * width);
mirror::Class* dstClass = dstArray->GetClass()->GetComponentType();
// We want to avoid redundant IsAssignableFrom checks where possible, so we cache a class that
// we know is assignable to the destination array's component type.
mirror::Class* lastAssignableElementClass = dstClass;
mirror::Object* o = NULL;
int i = 0;
for (; i < length; ++i) {
o = srcObjects[i];
if (o != NULL) {
mirror::Class* oClass = o->GetClass();
if (lastAssignableElementClass == oClass) {
dstObjects[i] = o;
} else if (dstClass->IsAssignableFrom(oClass)) {
lastAssignableElementClass = oClass;
dstObjects[i] = o;
} else {
// Can't put this element into the array.
break;
}
} else {
dstObjects[i] = NULL;
}
}
Runtime::Current()->GetHeap()->WriteBarrierArray(dstArray, dstPos, length);
if (UNLIKELY(i != length)) {
std::string actualSrcType(PrettyTypeOf(o));
std::string dstType(PrettyTypeOf(dstArray));
ThrowLocation throw_location = soa.Self()->GetCurrentLocationForThrow();
soa.Self()->ThrowNewExceptionF(throw_location, "Ljava/lang/ArrayStoreException;",
"source[%d] of type %s cannot be stored in destination array of type %s",
srcPos + i, actualSrcType.c_str(), dstType.c_str());
return;
}
}
static jint System_identityHashCode(JNIEnv* env, jclass, jobject javaObject) {
ScopedObjectAccess soa(env);
mirror::Object* o = soa.Decode<mirror::Object*>(javaObject);
return static_cast<jint>(o->IdentityHashCode());
}
static JNINativeMethod gMethods[] = {
NATIVE_METHOD(System, arraycopy, "(Ljava/lang/Object;ILjava/lang/Object;II)V"),
NATIVE_METHOD(System, identityHashCode, "(Ljava/lang/Object;)I"),
};
void register_java_lang_System(JNIEnv* env) {
REGISTER_NATIVE_METHODS("java/lang/System");
}
} // namespace art