/*
* 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.
*/
/*
* Resolve classes, methods, fields, and strings.
*
* According to the VM spec (v2 5.5), classes may be initialized by use
* of the "new", "getstatic", "putstatic", or "invokestatic" instructions.
* If we are resolving a static method or static field, we make the
* initialization check here.
*
* (NOTE: the verifier has its own resolve functions, which can be invoked
* if a class isn't pre-verified. Those functions must not update the
* "resolved stuff" tables for static fields and methods, because they do
* not perform initialization.)
*/
#include "Dalvik.h"
#include <stdlib.h>
/*
* Find the class corresponding to "classIdx", which maps to a class name
* string. It might be in the same DEX file as "referrer", in a different
* DEX file, generated by a class loader, or generated by the VM (e.g.
* array classes).
*
* Because the DexTypeId is associated with the referring class' DEX file,
* we may have to resolve the same class more than once if it's referred
* to from classes in multiple DEX files. This is a necessary property for
* DEX files associated with different class loaders.
*
* We cache a copy of the lookup in the DexFile's "resolved class" table,
* so future references to "classIdx" are faster.
*
* Note that "referrer" may be in the process of being linked.
*
* Traditional VMs might do access checks here, but in Dalvik the class
* "constant pool" is shared between all classes in the DEX file. We rely
* on the verifier to do the checks for us.
*
* Does not initialize the class.
*
* "fromUnverifiedConstant" should only be set if this call is the direct
* result of executing a "const-class" or "instance-of" instruction, which
* use class constants not resolved by the bytecode verifier.
*
* Returns NULL with an exception raised on failure.
*/
ClassObject* dvmResolveClass(const ClassObject* referrer, u4 classIdx,
bool fromUnverifiedConstant)
{
DvmDex* pDvmDex = referrer->pDvmDex;
ClassObject* resClass;
const char* className;
/*
* Check the table first -- this gets called from the other "resolve"
* methods.
*/
resClass = dvmDexGetResolvedClass(pDvmDex, classIdx);
if (resClass != NULL)
return resClass;
LOGVV("--- resolving class %u (referrer=%s cl=%p)",
classIdx, referrer->descriptor, referrer->classLoader);
/*
* Class hasn't been loaded yet, or is in the process of being loaded
* and initialized now. Try to get a copy. If we find one, put the
* pointer in the DexTypeId. There isn't a race condition here --
* 32-bit writes are guaranteed atomic on all target platforms. Worst
* case we have two threads storing the same value.
*
* If this is an array class, we'll generate it here.
*/
className = dexStringByTypeIdx(pDvmDex->pDexFile, classIdx);
if (className[0] != '\0' && className[1] == '\0') {
/* primitive type */
resClass = dvmFindPrimitiveClass(className[0]);
} else {
resClass = dvmFindClassNoInit(className, referrer->classLoader);
}
if (resClass != NULL) {
/*
* If the referrer was pre-verified, the resolved class must come
* from the same DEX or from a bootstrap class. The pre-verifier
* makes assumptions that could be invalidated by a wacky class
* loader. (See the notes at the top of oo/Class.c.)
*
* The verifier does *not* fail a class for using a const-class
* or instance-of instruction referring to an unresolveable class,
* because the result of the instruction is simply a Class object
* or boolean -- there's no need to resolve the class object during
* verification. Instance field and virtual method accesses can
* break dangerously if we get the wrong class, but const-class and
* instance-of are only interesting at execution time. So, if we
* we got here as part of executing one of the "unverified class"
* instructions, we skip the additional check.
*
* Ditto for class references from annotations and exception
* handler lists.
*/
if (!fromUnverifiedConstant &&
IS_CLASS_FLAG_SET(referrer, CLASS_ISPREVERIFIED))
{
ClassObject* resClassCheck = resClass;
if (dvmIsArrayClass(resClassCheck))
resClassCheck = resClassCheck->elementClass;
if (referrer->pDvmDex != resClassCheck->pDvmDex &&
resClassCheck->classLoader != NULL)
{
ALOGW("Class resolved by unexpected DEX:"
" %s(%p):%p ref [%s] %s(%p):%p",
referrer->descriptor, referrer->classLoader,
referrer->pDvmDex,
resClass->descriptor, resClassCheck->descriptor,
resClassCheck->classLoader, resClassCheck->pDvmDex);
ALOGW("(%s had used a different %s during pre-verification)",
referrer->descriptor, resClass->descriptor);
dvmThrowIllegalAccessError(
"Class ref in pre-verified class resolved to unexpected "
"implementation");
return NULL;
}
}
LOGVV("##### +ResolveClass(%s): referrer=%s dex=%p ldr=%p ref=%d",
resClass->descriptor, referrer->descriptor, referrer->pDvmDex,
referrer->classLoader, classIdx);
/*
* Add what we found to the list so we can skip the class search
* next time through.
*
* TODO: should we be doing this when fromUnverifiedConstant==true?
* (see comments at top of oo/Class.c)
*/
dvmDexSetResolvedClass(pDvmDex, classIdx, resClass);
} else {
/* not found, exception should be raised */
LOGVV("Class not found: %s",
dexStringByTypeIdx(pDvmDex->pDexFile, classIdx));
assert(dvmCheckException(dvmThreadSelf()));
}
return resClass;
}
/*
* Find the method corresponding to "methodRef".
*
* We use "referrer" to find the DexFile with the constant pool that
* "methodRef" is an index into. We also use its class loader. The method
* being resolved may very well be in a different DEX file.
*
* If this is a static method, we ensure that the method's class is
* initialized.
*/
Method* dvmResolveMethod(const ClassObject* referrer, u4 methodIdx,
MethodType methodType)
{
DvmDex* pDvmDex = referrer->pDvmDex;
ClassObject* resClass;
const DexMethodId* pMethodId;
Method* resMethod;
assert(methodType != METHOD_INTERFACE);
LOGVV("--- resolving method %u (referrer=%s)", methodIdx,
referrer->descriptor);
pMethodId = dexGetMethodId(pDvmDex->pDexFile, methodIdx);
resClass = dvmResolveClass(referrer, pMethodId->classIdx, false);
if (resClass == NULL) {
/* can't find the class that the method is a part of */
assert(dvmCheckException(dvmThreadSelf()));
return NULL;
}
if (dvmIsInterfaceClass(resClass)) {
/* method is part of an interface */
dvmThrowIncompatibleClassChangeErrorWithClassMessage(
resClass->descriptor);
return NULL;
}
const char* name = dexStringById(pDvmDex->pDexFile, pMethodId->nameIdx);
DexProto proto;
dexProtoSetFromMethodId(&proto, pDvmDex->pDexFile, pMethodId);
/*
* We need to chase up the class hierarchy to find methods defined
* in super-classes. (We only want to check the current class
* if we're looking for a constructor; since DIRECT calls are only
* for constructors and private methods, we don't want to walk up.)
*/
if (methodType == METHOD_DIRECT) {
resMethod = dvmFindDirectMethod(resClass, name, &proto);
} else if (methodType == METHOD_STATIC) {
resMethod = dvmFindDirectMethodHier(resClass, name, &proto);
} else {
resMethod = dvmFindVirtualMethodHier(resClass, name, &proto);
}
if (resMethod == NULL) {
dvmThrowNoSuchMethodError(name);
return NULL;
}
LOGVV("--- found method %d (%s.%s)",
methodIdx, resClass->descriptor, resMethod->name);
/* see if this is a pure-abstract method */
if (dvmIsAbstractMethod(resMethod) && !dvmIsAbstractClass(resClass)) {
dvmThrowAbstractMethodError(name);
return NULL;
}
/*
* If we're the first to resolve this class, we need to initialize
* it now. Only necessary for METHOD_STATIC.
*/
if (methodType == METHOD_STATIC) {
if (!dvmIsClassInitialized(resMethod->clazz) &&
!dvmInitClass(resMethod->clazz))
{
assert(dvmCheckException(dvmThreadSelf()));
return NULL;
} else {
assert(!dvmCheckException(dvmThreadSelf()));
}
} else {
/*
* Edge case: if the <clinit> for a class creates an instance
* of itself, we will call <init> on a class that is still being
* initialized by us.
*/
assert(dvmIsClassInitialized(resMethod->clazz) ||
dvmIsClassInitializing(resMethod->clazz));
}
/*
* If the class has been initialized, add a pointer to our data structure
* so we don't have to jump through the hoops again. If this is a
* static method and the defining class is still initializing (i.e. this
* thread is executing <clinit>), don't do the store, otherwise other
* threads could call the method without waiting for class init to finish.
*/
if (methodType == METHOD_STATIC && !dvmIsClassInitialized(resMethod->clazz))
{
LOGVV("--- not caching resolved method %s.%s (class init=%d/%d)",
resMethod->clazz->descriptor, resMethod->name,
dvmIsClassInitializing(resMethod->clazz),
dvmIsClassInitialized(resMethod->clazz));
} else {
dvmDexSetResolvedMethod(pDvmDex, methodIdx, resMethod);
}
return resMethod;
}
/*
* Resolve an interface method reference.
*
* Returns NULL with an exception raised on failure.
*/
Method* dvmResolveInterfaceMethod(const ClassObject* referrer, u4 methodIdx)
{
DvmDex* pDvmDex = referrer->pDvmDex;
ClassObject* resClass;
const DexMethodId* pMethodId;
Method* resMethod;
LOGVV("--- resolving interface method %d (referrer=%s)",
methodIdx, referrer->descriptor);
pMethodId = dexGetMethodId(pDvmDex->pDexFile, methodIdx);
resClass = dvmResolveClass(referrer, pMethodId->classIdx, false);
if (resClass == NULL) {
/* can't find the class that the method is a part of */
assert(dvmCheckException(dvmThreadSelf()));
return NULL;
}
if (!dvmIsInterfaceClass(resClass)) {
/* whoops */
dvmThrowIncompatibleClassChangeErrorWithClassMessage(
resClass->descriptor);
return NULL;
}
/*
* This is the first time the method has been resolved. Set it in our
* resolved-method structure. It always resolves to the same thing,
* so looking it up and storing it doesn't create a race condition.
*
* If we scan into the interface's superclass -- which is always
* java/lang/Object -- we will catch things like:
* interface I ...
* I myobj = (something that implements I)
* myobj.hashCode()
* However, the Method->methodIndex will be an offset into clazz->vtable,
* rather than an offset into clazz->iftable. The invoke-interface
* code can test to see if the method returned is abstract or concrete,
* and use methodIndex accordingly. I'm not doing this yet because
* (a) we waste time in an unusual case, and (b) we're probably going
* to fix it in the DEX optimizer.
*
* We do need to scan the superinterfaces, in case we're invoking a
* superinterface method on an interface reference. The class in the
* DexTypeId is for the static type of the object, not the class in
* which the method is first defined. We have the full, flattened
* list in "iftable".
*/
const char* methodName =
dexStringById(pDvmDex->pDexFile, pMethodId->nameIdx);
DexProto proto;
dexProtoSetFromMethodId(&proto, pDvmDex->pDexFile, pMethodId);
LOGVV("+++ looking for '%s' '%s' in resClass='%s'",
methodName, methodSig, resClass->descriptor);
resMethod = dvmFindInterfaceMethodHier(resClass, methodName, &proto);
if (resMethod == NULL) {
dvmThrowNoSuchMethodError(methodName);
return NULL;
}
LOGVV("--- found interface method %d (%s.%s)",
methodIdx, resClass->descriptor, resMethod->name);
/* we're expecting this to be abstract */
assert(dvmIsAbstractMethod(resMethod));
/* interface methods are always public; no need to check access */
/*
* The interface class *may* be initialized. According to VM spec
* v2 2.17.4, the interfaces a class refers to "need not" be initialized
* when the class is initialized.
*
* It isn't necessary for an interface class to be initialized before
* we resolve methods on that interface.
*
* We choose not to do the initialization now.
*/
//assert(dvmIsClassInitialized(resMethod->clazz));
/*
* Add a pointer to our data structure so we don't have to jump
* through the hoops again.
*
* As noted above, no need to worry about whether the interface that
* defines the method has been or is currently executing <clinit>.
*/
dvmDexSetResolvedMethod(pDvmDex, methodIdx, resMethod);
return resMethod;
}
/*
* Resolve an instance field reference.
*
* Returns NULL and throws an exception on error (no such field, illegal
* access).
*/
InstField* dvmResolveInstField(const ClassObject* referrer, u4 ifieldIdx)
{
DvmDex* pDvmDex = referrer->pDvmDex;
ClassObject* resClass;
const DexFieldId* pFieldId;
InstField* resField;
LOGVV("--- resolving field %u (referrer=%s cl=%p)",
ifieldIdx, referrer->descriptor, referrer->classLoader);
pFieldId = dexGetFieldId(pDvmDex->pDexFile, ifieldIdx);
/*
* Find the field's class.
*/
resClass = dvmResolveClass(referrer, pFieldId->classIdx, false);
if (resClass == NULL) {
assert(dvmCheckException(dvmThreadSelf()));
return NULL;
}
resField = dvmFindInstanceFieldHier(resClass,
dexStringById(pDvmDex->pDexFile, pFieldId->nameIdx),
dexStringByTypeIdx(pDvmDex->pDexFile, pFieldId->typeIdx));
if (resField == NULL) {
dvmThrowNoSuchFieldError(
dexStringById(pDvmDex->pDexFile, pFieldId->nameIdx));
return NULL;
}
/*
* Class must be initialized by now (unless verifier is buggy). We
* could still be in the process of initializing it if the field
* access is from a static initializer.
*/
assert(dvmIsClassInitialized(resField->clazz) ||
dvmIsClassInitializing(resField->clazz));
/*
* The class is initialized (or initializing), the field has been
* found. Add a pointer to our data structure so we don't have to
* jump through the hoops again.
*
* Anything that uses the resolved table entry must have an instance
* of the class, so any class init activity has already happened (or
* been deliberately bypassed when <clinit> created an instance).
* So it's always okay to update the table.
*/
dvmDexSetResolvedField(pDvmDex, ifieldIdx, (Field*)resField);
LOGVV(" field %u is %s.%s",
ifieldIdx, resField->clazz->descriptor, resField->name);
return resField;
}
/*
* Resolve a static field reference. The DexFile format doesn't distinguish
* between static and instance field references, so the "resolved" pointer
* in the Dex struct will have the wrong type. We trivially cast it here.
*
* Causes the field's class to be initialized.
*/
StaticField* dvmResolveStaticField(const ClassObject* referrer, u4 sfieldIdx)
{
DvmDex* pDvmDex = referrer->pDvmDex;
ClassObject* resClass;
const DexFieldId* pFieldId;
StaticField* resField;
pFieldId = dexGetFieldId(pDvmDex->pDexFile, sfieldIdx);
/*
* Find the field's class.
*/
resClass = dvmResolveClass(referrer, pFieldId->classIdx, false);
if (resClass == NULL) {
assert(dvmCheckException(dvmThreadSelf()));
return NULL;
}
resField = dvmFindStaticFieldHier(resClass,
dexStringById(pDvmDex->pDexFile, pFieldId->nameIdx),
dexStringByTypeIdx(pDvmDex->pDexFile, pFieldId->typeIdx));
if (resField == NULL) {
dvmThrowNoSuchFieldError(
dexStringById(pDvmDex->pDexFile, pFieldId->nameIdx));
return NULL;
}
/*
* If we're the first to resolve the field in which this class resides,
* we need to do it now. Note that, if the field was inherited from
* a superclass, it is not necessarily the same as "resClass".
*/
if (!dvmIsClassInitialized(resField->clazz) &&
!dvmInitClass(resField->clazz))
{
assert(dvmCheckException(dvmThreadSelf()));
return NULL;
}
/*
* If the class has been initialized, add a pointer to our data structure
* so we don't have to jump through the hoops again. If it's still
* initializing (i.e. this thread is executing <clinit>), don't do
* the store, otherwise other threads could use the field without waiting
* for class init to finish.
*/
if (dvmIsClassInitialized(resField->clazz)) {
dvmDexSetResolvedField(pDvmDex, sfieldIdx, (Field*) resField);
} else {
LOGVV("--- not caching resolved field %s.%s (class init=%d/%d)",
resField->clazz->descriptor, resField->name,
dvmIsClassInitializing(resField->clazz),
dvmIsClassInitialized(resField->clazz));
}
return resField;
}
/*
* Resolve a string reference.
*
* Finding the string is easy. We need to return a reference to a
* java/lang/String object, not a bunch of characters, which means the
* first time we get here we need to create an interned string.
*/
StringObject* dvmResolveString(const ClassObject* referrer, u4 stringIdx)
{
DvmDex* pDvmDex = referrer->pDvmDex;
StringObject* strObj;
StringObject* internStrObj;
const char* utf8;
u4 utf16Size;
LOGVV("+++ resolving string, referrer is %s", referrer->descriptor);
/*
* Create a UTF-16 version so we can trivially compare it to what's
* already interned.
*/
utf8 = dexStringAndSizeById(pDvmDex->pDexFile, stringIdx, &utf16Size);
strObj = dvmCreateStringFromCstrAndLength(utf8, utf16Size);
if (strObj == NULL) {
/* ran out of space in GC heap? */
assert(dvmCheckException(dvmThreadSelf()));
goto bail;
}
/*
* Add it to the intern list. The return value is the one in the
* intern list, which (due to race conditions) may or may not be
* the one we just created. The intern list is synchronized, so
* there will be only one "live" version.
*
* By requesting an immortal interned string, we guarantee that
* the returned object will never be collected by the GC.
*
* A NULL return here indicates some sort of hashing failure.
*/
internStrObj = dvmLookupImmortalInternedString(strObj);
dvmReleaseTrackedAlloc((Object*) strObj, NULL);
strObj = internStrObj;
if (strObj == NULL) {
assert(dvmCheckException(dvmThreadSelf()));
goto bail;
}
/* save a reference so we can go straight to the object next time */
dvmDexSetResolvedString(pDvmDex, stringIdx, strObj);
bail:
return strObj;
}
/*
* For debugging: return a string representing the methodType.
*/
const char* dvmMethodTypeStr(MethodType methodType)
{
switch (methodType) {
case METHOD_DIRECT: return "direct";
case METHOD_STATIC: return "static";
case METHOD_VIRTUAL: return "virtual";
case METHOD_INTERFACE: return "interface";
case METHOD_UNKNOWN: return "UNKNOWN";
}
assert(false);
return "BOGUS";
}