src/java_lang_System.cc - LeafOS-Project/android_art - Gitiles

 /*
  * 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 "jni_internal.h"
 #include "object.h"

 #include "JniConstants.h" // Last to avoid problems with LOG redefinition.

 /*
  * 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.
  */
 #ifdef __BIONIC__
 #define HAVE_MEMMOVE_WORDS
 #endif

 #ifdef HAVE_MEMMOVE_WORDS
 extern "C" void _memmove_words(void* dst, const void* src, size_t n);
 #define move16 _memmove_words
 #define move32 _memmove_words
 #else
 static void move16(void* dst, const void* src, size_t n) {
   DCHECK((((uintptr_t) dst | (uintptr_t) src | n) & 0x01) == 0);

   uint16_t* d = reinterpret_cast<uint16_t*>(dst);
   const uint16_t* s = reinterpret_cast<const uint16_t*>(src);

   n /= sizeof(uint16_t);

   if (d < s) {
     // Copy forwards.
     while (n--) {
       *d++ = *s++;
     }
   } else {
     // Copy backwards.
     d += n;
     s += n;
     while (n--) {
       *--d = *--s;
     }
   }
 }

 static void move32(void* dst, const void* src, size_t n) {
   DCHECK((((uintptr_t) dst | (uintptr_t) src | n) & 0x03) == 0);

   uint32_t* d = reinterpret_cast<uint32_t*>(dst);
   const uint32_t* s = reinterpret_cast<const uint32_t*>(src);

   n /= sizeof(uint32_t);

   if (d < s) {
     // Copy forwards.
     while (n--) {
       *d++ = *s++;
     }
   } else {
     // Copy backwards.
     d += n;
     s += n;
     while (n--) {
       *--d = *--s;
     }
   }
 }
 #endif // HAVE_MEMMOVE_WORDS

 namespace art {

 namespace {

 void ThrowArrayStoreException_NotAnArray(const char* identifier, Object* array) {
   std::string actualType(PrettyTypeOf(array));
   Thread::Current()->ThrowNewException("Ljava/lang/ArrayStoreException;", "%s is not an array: %s", identifier, actualType.c_str());
 }

 void System_arraycopy(JNIEnv* env, jclass, jobject javaSrc, jint srcPos, jobject javaDst, jint dstPos, jint length) {
   Thread* self = Thread::Current();

   // Null pointer checks.
   if (javaSrc == NULL) {
     self->ThrowNewException("Ljava/lang/NullPointerException;", "src == null");
     return;
   }
   if (javaDst == NULL) {
     self->ThrowNewException("Ljava/lang/NullPointerException;", "dst == null");
     return;
   }

   // Make sure source and destination are both arrays.
   Object* srcObject = Decode<Object*>(env, javaSrc);
   Object* dstObject = Decode<Object*>(env, javaDst);
   if (!srcObject->IsArrayInstance()) {
     ThrowArrayStoreException_NotAnArray("src", srcObject);
     return;
   }
   if (!dstObject->IsArrayInstance()) {
     ThrowArrayStoreException_NotAnArray("dst", dstObject);
     return;
   }
   Array* srcArray = srcObject->AsArray();
   Array* dstArray = dstObject->AsArray();
   Class* srcComponentType = srcArray->GetClass()->GetComponentType();
   Class* dstComponentType = dstArray->GetClass()->GetComponentType();

   // Bounds checking.
   if (srcPos < 0 || dstPos < 0 || length < 0 || srcPos > srcArray->GetLength() - length || dstPos > dstArray->GetLength() - length) {
     self->ThrowNewException("Ljava/lang/ArrayIndexOutOfBoundsException;",
         "src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
         srcArray->GetLength(), srcPos, dstArray->GetLength(), dstPos, length);
     return;
   }

   uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData());
   const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData());

   // 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 (srcComponentType->IsPrimitive() != dstComponentType->IsPrimitive() || srcComponentType != dstComponentType) {
       std::string srcType(PrettyTypeOf(srcArray));
       std::string dstType(PrettyTypeOf(dstArray));
       self->ThrowNewException("Ljava/lang/ArrayStoreException;",
           "Incompatible types: src=%s, dst=%s", srcType.c_str(), dstType.c_str());
       return;
     }

     switch (srcArray->GetClass()->GetComponentSize()) {
     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(Object*);
   if (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);
     Heap::WriteBarrier(dstArray);
     return;
   }

   // The arrays are not trivially compatible.  However, we
   // may still be able to do this if the destination object is
   // compatible (e.g. copy Object[] to String[], but the Object
   // being copied is actually a String).  We need to copy elements
   // one by one until something goes wrong.
   //
   // Because of overlapping moves, what we really want to do
   // is compare the types and count up how many we can move,
   // then call move32() to shift the actual data.  If we just
   // start from the front we could do a smear rather than a move.

   // TODO: this idea is flawed. a malicious caller could exploit the check-use
   // race by modifying the source array after we check but before we copy,
   // and cause us to copy incompatible elements.

   Object* const * srcObj = reinterpret_cast<Object* const *>(srcBytes + srcPos * width);
   Class* dstClass = dstArray->GetClass()->GetComponentType();

   Class* initialElementClass = NULL;
   if (length > 0 && srcObj[0] != NULL) {
     initialElementClass = srcObj[0]->GetClass();
     if (!dstClass->IsAssignableFrom(initialElementClass)) {
       initialElementClass = NULL;
     }
   }

   int copyCount;
   for (copyCount = 0; copyCount < length; copyCount++) {
     if (srcObj[copyCount] != NULL && srcObj[copyCount]->GetClass() != initialElementClass && !dstClass->IsAssignableFrom(srcObj[copyCount]->GetClass())) {
       // Can't put this element into the array.
       // We'll copy up to this point, then throw.
       break;
     }
   }

   move32(dstBytes + dstPos * width, srcBytes + srcPos * width, copyCount * width);
   Heap::WriteBarrier(dstArray);
   if (copyCount != length) {
     std::string actualSrcType(PrettyTypeOf(srcObj[copyCount]));
     std::string dstType(PrettyTypeOf(dstArray));
     self->ThrowNewException("Ljava/lang/ArrayStoreException;",
         "source[%d] of type %s cannot be stored in destination array of type %s",
         srcPos + copyCount, actualSrcType.c_str(), dstType.c_str());
     return;
   }
 }

 jint System_identityHashCode(JNIEnv* env, jclass, jobject javaObject) {
   Object* o = Decode<Object*>(env, javaObject);
   return static_cast<jint>(reinterpret_cast<uintptr_t>(o));
 }

 JNINativeMethod gMethods[] = {
   NATIVE_METHOD(System, arraycopy, "(Ljava/lang/Object;ILjava/lang/Object;II)V"),
   NATIVE_METHOD(System, identityHashCode, "(Ljava/lang/Object;)I"),
 };

 }  // namespace

 void register_java_lang_System(JNIEnv* env) {
     jniRegisterNativeMethods(env, "java/lang/System", gMethods, NELEM(gMethods));
 }

 }  // namespace art
	/*
	* 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 "jni_internal.h"
	#include "object.h"

	#include "JniConstants.h" // Last to avoid problems with LOG redefinition.

	/*
	* 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.
	*/
	#ifdef __BIONIC__
	#define HAVE_MEMMOVE_WORDS
	#endif

	#ifdef HAVE_MEMMOVE_WORDS
	extern "C" void _memmove_words(void* dst, const void* src, size_t n);
	#define move16 _memmove_words
	#define move32 _memmove_words
	#else
	static void move16(void* dst, const void* src, size_t n) {
	DCHECK((((uintptr_t) dst \| (uintptr_t) src \| n) & 0x01) == 0);

	uint16_t* d = reinterpret_cast<uint16_t*>(dst);
	const uint16_t* s = reinterpret_cast<const uint16_t*>(src);

	n /= sizeof(uint16_t);

	if (d < s) {
	// Copy forwards.
	while (n--) {
	d++ = s++;
	}
	} else {
	// Copy backwards.
	d += n;
	s += n;
	while (n--) {
	--d = --s;
	}
	}
	}

	static void move32(void* dst, const void* src, size_t n) {
	DCHECK((((uintptr_t) dst \| (uintptr_t) src \| n) & 0x03) == 0);

	uint32_t* d = reinterpret_cast<uint32_t*>(dst);
	const uint32_t* s = reinterpret_cast<const uint32_t*>(src);

	n /= sizeof(uint32_t);

	if (d < s) {
	// Copy forwards.
	while (n--) {
	d++ = s++;
	}
	} else {
	// Copy backwards.
	d += n;
	s += n;
	while (n--) {
	--d = --s;
	}
	}
	}
	#endif // HAVE_MEMMOVE_WORDS

	namespace art {

	namespace {

	void ThrowArrayStoreException_NotAnArray(const char* identifier, Object* array) {
	std::string actualType(PrettyTypeOf(array));
	Thread::Current()->ThrowNewException("Ljava/lang/ArrayStoreException;", "%s is not an array: %s", identifier, actualType.c_str());
	}

	void System_arraycopy(JNIEnv* env, jclass, jobject javaSrc, jint srcPos, jobject javaDst, jint dstPos, jint length) {
	Thread* self = Thread::Current();

	// Null pointer checks.
	if (javaSrc == NULL) {
	self->ThrowNewException("Ljava/lang/NullPointerException;", "src == null");
	return;
	}
	if (javaDst == NULL) {
	self->ThrowNewException("Ljava/lang/NullPointerException;", "dst == null");
	return;
	}

	// Make sure source and destination are both arrays.
	Object* srcObject = Decode<Object*>(env, javaSrc);
	Object* dstObject = Decode<Object*>(env, javaDst);
	if (!srcObject->IsArrayInstance()) {
	ThrowArrayStoreException_NotAnArray("src", srcObject);
	return;
	}
	if (!dstObject->IsArrayInstance()) {
	ThrowArrayStoreException_NotAnArray("dst", dstObject);
	return;
	}
	Array* srcArray = srcObject->AsArray();
	Array* dstArray = dstObject->AsArray();
	Class* srcComponentType = srcArray->GetClass()->GetComponentType();
	Class* dstComponentType = dstArray->GetClass()->GetComponentType();

	// Bounds checking.
	if (srcPos < 0 \|\| dstPos < 0 \|\| length < 0 \|\| srcPos > srcArray->GetLength() - length \|\| dstPos > dstArray->GetLength() - length) {
	self->ThrowNewException("Ljava/lang/ArrayIndexOutOfBoundsException;",
	"src.length=%d srcPos=%d dst.length=%d dstPos=%d length=%d",
	srcArray->GetLength(), srcPos, dstArray->GetLength(), dstPos, length);
	return;
	}

	uint8_t* dstBytes = reinterpret_cast<uint8_t*>(dstArray->GetRawData());
	const uint8_t* srcBytes = reinterpret_cast<const uint8_t*>(srcArray->GetRawData());

	// 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 (srcComponentType->IsPrimitive() != dstComponentType->IsPrimitive() \|\| srcComponentType != dstComponentType) {
	std::string srcType(PrettyTypeOf(srcArray));
	std::string dstType(PrettyTypeOf(dstArray));
	self->ThrowNewException("Ljava/lang/ArrayStoreException;",
	"Incompatible types: src=%s, dst=%s", srcType.c_str(), dstType.c_str());
	return;
	}

	switch (srcArray->GetClass()->GetComponentSize()) {
	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(Object*);
	if (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);
	Heap::WriteBarrier(dstArray);
	return;
	}

	// The arrays are not trivially compatible. However, we
	// may still be able to do this if the destination object is
	// compatible (e.g. copy Object[] to String[], but the Object
	// being copied is actually a String). We need to copy elements
	// one by one until something goes wrong.
	//
	// Because of overlapping moves, what we really want to do
	// is compare the types and count up how many we can move,
	// then call move32() to shift the actual data. If we just
	// start from the front we could do a smear rather than a move.

	// TODO: this idea is flawed. a malicious caller could exploit the check-use
	// race by modifying the source array after we check but before we copy,
	// and cause us to copy incompatible elements.

	Object* const * srcObj = reinterpret_cast<Object* const >(srcBytes + srcPos width);
	Class* dstClass = dstArray->GetClass()->GetComponentType();

	Class* initialElementClass = NULL;
	if (length > 0 && srcObj[0] != NULL) {
	initialElementClass = srcObj[0]->GetClass();
	if (!dstClass->IsAssignableFrom(initialElementClass)) {
	initialElementClass = NULL;
	}
	}

	int copyCount;
	for (copyCount = 0; copyCount < length; copyCount++) {
	if (srcObj[copyCount] != NULL && srcObj[copyCount]->GetClass() != initialElementClass && !dstClass->IsAssignableFrom(srcObj[copyCount]->GetClass())) {
	// Can't put this element into the array.
	// We'll copy up to this point, then throw.
	break;
	}
	}

	move32(dstBytes + dstPos * width, srcBytes + srcPos * width, copyCount * width);
	Heap::WriteBarrier(dstArray);
	if (copyCount != length) {
	std::string actualSrcType(PrettyTypeOf(srcObj[copyCount]));
	std::string dstType(PrettyTypeOf(dstArray));
	self->ThrowNewException("Ljava/lang/ArrayStoreException;",
	"source[%d] of type %s cannot be stored in destination array of type %s",
	srcPos + copyCount, actualSrcType.c_str(), dstType.c_str());
	return;
	}
	}

	jint System_identityHashCode(JNIEnv* env, jclass, jobject javaObject) {
	Object* o = Decode<Object*>(env, javaObject);
	return static_cast<jint>(reinterpret_cast<uintptr_t>(o));
	}

	JNINativeMethod gMethods[] = {
	NATIVE_METHOD(System, arraycopy, "(Ljava/lang/Object;ILjava/lang/Object;II)V"),
	NATIVE_METHOD(System, identityHashCode, "(Ljava/lang/Object;)I"),
	};

	} // namespace

	void register_java_lang_System(JNIEnv* env) {
	jniRegisterNativeMethods(env, "java/lang/System", gMethods, NELEM(gMethods));
	}

	} // namespace art