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/*
* 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.
*/
/*
* Native method resolution.
*
* Currently the "Dalvik native" methods are only used for internal methods.
* Someday we may want to export the interface as a faster but riskier
* alternative to JNI.
*/
#include "Dalvik.h"
#include <stdlib.h>
#include <dlfcn.h>
static void freeSharedLibEntry(void* ptr);
static void* lookupSharedLibMethod(const Method* method);
/*
* Initialize the native code loader.
*/
bool dvmNativeStartup()
{
gDvm.nativeLibs = dvmHashTableCreate(4, freeSharedLibEntry);
if (gDvm.nativeLibs == NULL)
return false;
return true;
}
/*
* Free up our tables.
*/
void dvmNativeShutdown()
{
dvmHashTableFree(gDvm.nativeLibs);
gDvm.nativeLibs = NULL;
}
/*
* Resolve a native method and invoke it.
*
* This is executed as if it were a native bridge or function. If the
* resolution succeeds, method->insns is replaced, and we don't go through
* here again unless the method is unregistered.
*
* Initializes method's class if necessary.
*
* An exception is thrown on resolution failure.
*
* (This should not be taking "const Method*", because it modifies the
* structure, but the declaration needs to match the DalvikBridgeFunc
* type definition.)
*/
void dvmResolveNativeMethod(const u4* args, JValue* pResult,
const Method* method, Thread* self)
{
ClassObject* clazz = method->clazz;
/*
* If this is a static method, it could be called before the class
* has been initialized.
*/
if (dvmIsStaticMethod(method)) {
if (!dvmIsClassInitialized(clazz) && !dvmInitClass(clazz)) {
assert(dvmCheckException(dvmThreadSelf()));
return;
}
} else {
assert(dvmIsClassInitialized(clazz) ||
dvmIsClassInitializing(clazz));
}
/* start with our internal-native methods */
DalvikNativeFunc infunc = dvmLookupInternalNativeMethod(method);
if (infunc != NULL) {
/* resolution always gets the same answer, so no race here */
IF_LOGVV() {
char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
LOGVV("+++ resolved native %s.%s %s, invoking",
clazz->descriptor, method->name, desc);
free(desc);
}
if (dvmIsSynchronizedMethod(method)) {
ALOGE("ERROR: internal-native can't be declared 'synchronized'");
ALOGE("Failing on %s.%s", method->clazz->descriptor, method->name);
dvmAbort(); // harsh, but this is VM-internal problem
}
DalvikBridgeFunc dfunc = (DalvikBridgeFunc) infunc;
dvmSetNativeFunc((Method*) method, dfunc, NULL);
dfunc(args, pResult, method, self);
return;
}
/* now scan any DLLs we have loaded for JNI signatures */
void* func = lookupSharedLibMethod(method);
if (func != NULL) {
/* found it, point it at the JNI bridge and then call it */
dvmUseJNIBridge((Method*) method, func);
(*method->nativeFunc)(args, pResult, method, self);
return;
}
IF_ALOGW() {
char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
ALOGW("No implementation found for native %s.%s:%s",
clazz->descriptor, method->name, desc);
free(desc);
}
dvmThrowUnsatisfiedLinkError("Native method not found", method);
}
/*
* ===========================================================================
* Native shared library support
* ===========================================================================
*/
// TODO? if a ClassLoader is unloaded, we need to unload all DLLs that
// are associated with it. (Or not -- can't determine if native code
// is still using parts of it.)
enum OnLoadState {
kOnLoadPending = 0, /* initial state, must be zero */
kOnLoadFailed,
kOnLoadOkay,
};
/*
* We add one of these to the hash table for every library we load. The
* hash is on the "pathName" field.
*/
struct SharedLib {
char* pathName; /* absolute path to library */
void* handle; /* from dlopen */
Object* classLoader; /* ClassLoader we are associated with */
pthread_mutex_t onLoadLock; /* guards remaining items */
pthread_cond_t onLoadCond; /* wait for JNI_OnLoad in other thread */
u4 onLoadThreadId; /* recursive invocation guard */
OnLoadState onLoadResult; /* result of earlier JNI_OnLoad */
};
/*
* (This is a dvmHashTableLookup callback.)
*
* Find an entry that matches the string.
*/
static int hashcmpNameStr(const void* ventry, const void* vname)
{
const SharedLib* pLib = (const SharedLib*) ventry;
const char* name = (const char*) vname;
return strcmp(pLib->pathName, name);
}
/*
* (This is a dvmHashTableLookup callback.)
*
* Find an entry that matches the new entry.
*
* We don't compare the class loader here, because you're not allowed to
* have the same shared library associated with more than one CL.
*/
static int hashcmpSharedLib(const void* ventry, const void* vnewEntry)
{
const SharedLib* pLib = (const SharedLib*) ventry;
const SharedLib* pNewLib = (const SharedLib*) vnewEntry;
ALOGD("--- comparing %p '%s' %p '%s'",
pLib, pLib->pathName, pNewLib, pNewLib->pathName);
return strcmp(pLib->pathName, pNewLib->pathName);
}
/*
* Check to see if an entry with the same pathname already exists.
*/
static SharedLib* findSharedLibEntry(const char* pathName)
{
u4 hash = dvmComputeUtf8Hash(pathName);
void* ent;
ent = dvmHashTableLookup(gDvm.nativeLibs, hash, (void*)pathName,
hashcmpNameStr, false);
return (SharedLib*)ent;
}
/*
* Add the new entry to the table.
*
* Returns the table entry, which will not be the same as "pLib" if the
* entry already exists.
*/
static SharedLib* addSharedLibEntry(SharedLib* pLib)
{
u4 hash = dvmComputeUtf8Hash(pLib->pathName);
/*
* Do the lookup with the "add" flag set. If we add it, we will get
* our own pointer back. If somebody beat us to the punch, we'll get
* their pointer back instead.
*/
return (SharedLib*)dvmHashTableLookup(gDvm.nativeLibs, hash, pLib,
hashcmpSharedLib, true);
}
/*
* Free up an entry. (This is a dvmHashTableFree callback.)
*/
static void freeSharedLibEntry(void* ptr)
{
SharedLib* pLib = (SharedLib*) ptr;
/*
* Calling dlclose() here is somewhat dangerous, because it's possible
* that a thread outside the VM is still accessing the code we loaded.
*/
if (false)
dlclose(pLib->handle);
free(pLib->pathName);
free(pLib);
}
/*
* Convert library name to system-dependent form, e.g. "jpeg" becomes
* "libjpeg.so".
*
* (Should we have this take buffer+len and avoid the alloc? It gets
* called very rarely.)
*/
char* dvmCreateSystemLibraryName(char* libName)
{
char buf[256];
int len;
len = snprintf(buf, sizeof(buf), OS_SHARED_LIB_FORMAT_STR, libName);
if (len >= (int) sizeof(buf))
return NULL;
else
return strdup(buf);
}
/*
* Check the result of an earlier call to JNI_OnLoad on this library. If
* the call has not yet finished in another thread, wait for it.
*/
static bool checkOnLoadResult(SharedLib* pEntry)
{
Thread* self = dvmThreadSelf();
if (pEntry->onLoadThreadId == self->threadId) {
/*
* Check this so we don't end up waiting for ourselves. We need
* to return "true" so the caller can continue.
*/
ALOGI("threadid=%d: recursive native library load attempt (%s)",
self->threadId, pEntry->pathName);
return true;
}
ALOGV("+++ retrieving %s OnLoad status", pEntry->pathName);
bool result;
dvmLockMutex(&pEntry->onLoadLock);
while (pEntry->onLoadResult == kOnLoadPending) {
ALOGD("threadid=%d: waiting for %s OnLoad status",
self->threadId, pEntry->pathName);
ThreadStatus oldStatus = dvmChangeStatus(self, THREAD_VMWAIT);
pthread_cond_wait(&pEntry->onLoadCond, &pEntry->onLoadLock);
dvmChangeStatus(self, oldStatus);
}
if (pEntry->onLoadResult == kOnLoadOkay) {
ALOGV("+++ earlier OnLoad(%s) okay", pEntry->pathName);
result = true;
} else {
ALOGV("+++ earlier OnLoad(%s) failed", pEntry->pathName);
result = false;
}
dvmUnlockMutex(&pEntry->onLoadLock);
return result;
}
typedef int (*OnLoadFunc)(JavaVM*, void*);
/*
* Load native code from the specified absolute pathname. Per the spec,
* if we've already loaded a library with the specified pathname, we
* return without doing anything.
*
* TODO? for better results we should absolutify the pathname. For fully
* correct results we should stat to get the inode and compare that. The
* existing implementation is fine so long as everybody is using
* System.loadLibrary.
*
* The library will be associated with the specified class loader. The JNI
* spec says we can't load the same library into more than one class loader.
*
* Returns "true" on success. On failure, sets *detail to a
* human-readable description of the error or NULL if no detail is
* available; ownership of the string is transferred to the caller.
*/
bool dvmLoadNativeCode(const char* pathName, Object* classLoader,
char** detail)
{
SharedLib* pEntry;
void* handle;
bool verbose;
/* reduce noise by not chattering about system libraries */
verbose = !!strncmp(pathName, "/system", sizeof("/system")-1);
verbose = verbose && !!strncmp(pathName, "/vendor", sizeof("/vendor")-1);
if (verbose)
ALOGD("Trying to load lib %s %p", pathName, classLoader);
*detail = NULL;
/*
* See if we've already loaded it. If we have, and the class loader
* matches, return successfully without doing anything.
*/
pEntry = findSharedLibEntry(pathName);
if (pEntry != NULL) {
if (pEntry->classLoader != classLoader) {
ALOGW("Shared lib '%s' already opened by CL %p; can't open in %p",
pathName, pEntry->classLoader, classLoader);
return false;
}
if (verbose) {
ALOGD("Shared lib '%s' already loaded in same CL %p",
pathName, classLoader);
}
if (!checkOnLoadResult(pEntry))
return false;
return true;
}
/*
* Open the shared library. Because we're using a full path, the system
* doesn't have to search through LD_LIBRARY_PATH. (It may do so to
* resolve this library's dependencies though.)
*
* Failures here are expected when java.library.path has several entries
* and we have to hunt for the lib.
*
* The current version of the dynamic linker prints detailed information
* about dlopen() failures. Some things to check if the message is
* cryptic:
* - make sure the library exists on the device
* - verify that the right path is being opened (the debug log message
* above can help with that)
* - check to see if the library is valid (e.g. not zero bytes long)
* - check config/prelink-linux-arm.map to ensure that the library
* is listed and is not being overrun by the previous entry (if
* loading suddenly stops working on a prelinked library, this is
* a good one to check)
* - write a trivial app that calls sleep() then dlopen(), attach
* to it with "strace -p <pid>" while it sleeps, and watch for
* attempts to open nonexistent dependent shared libs
*
* This can execute slowly for a large library on a busy system, so we
* want to switch from RUNNING to VMWAIT while it executes. This allows
* the GC to ignore us.
*/
Thread* self = dvmThreadSelf();
ThreadStatus oldStatus = dvmChangeStatus(self, THREAD_VMWAIT);
handle = dlopen(pathName, RTLD_LAZY);
dvmChangeStatus(self, oldStatus);
if (handle == NULL) {
*detail = strdup(dlerror());
ALOGE("dlopen(\"%s\") failed: %s", pathName, *detail);
return false;
}
/* create a new entry */
SharedLib* pNewEntry;
pNewEntry = (SharedLib*) calloc(1, sizeof(SharedLib));
pNewEntry->pathName = strdup(pathName);
pNewEntry->handle = handle;
pNewEntry->classLoader = classLoader;
dvmInitMutex(&pNewEntry->onLoadLock);
pthread_cond_init(&pNewEntry->onLoadCond, NULL);
pNewEntry->onLoadThreadId = self->threadId;
/* try to add it to the list */
SharedLib* pActualEntry = addSharedLibEntry(pNewEntry);
if (pNewEntry != pActualEntry) {
ALOGI("WOW: we lost a race to add a shared lib (%s CL=%p)",
pathName, classLoader);
freeSharedLibEntry(pNewEntry);
return checkOnLoadResult(pActualEntry);
} else {
if (verbose)
ALOGD("Added shared lib %s %p", pathName, classLoader);
bool result = true;
void* vonLoad;
int version;
vonLoad = dlsym(handle, "JNI_OnLoad");
if (vonLoad == NULL) {
ALOGD("No JNI_OnLoad found in %s %p, skipping init",
pathName, classLoader);
} else {
/*
* Call JNI_OnLoad. We have to override the current class
* loader, which will always be "null" since the stuff at the
* top of the stack is around Runtime.loadLibrary(). (See
* the comments in the JNI FindClass function.)
*/
OnLoadFunc func = (OnLoadFunc)vonLoad;
Object* prevOverride = self->classLoaderOverride;
self->classLoaderOverride = classLoader;
oldStatus = dvmChangeStatus(self, THREAD_NATIVE);
if (gDvm.verboseJni) {
ALOGI("[Calling JNI_OnLoad for \"%s\"]", pathName);
}
version = (*func)(gDvmJni.jniVm, NULL);
dvmChangeStatus(self, oldStatus);
self->classLoaderOverride = prevOverride;
if (version != JNI_VERSION_1_2 && version != JNI_VERSION_1_4 &&
version != JNI_VERSION_1_6)
{
ALOGW("JNI_OnLoad returned bad version (%d) in %s %p",
version, pathName, classLoader);
/*
* It's unwise to call dlclose() here, but we can mark it
* as bad and ensure that future load attempts will fail.
*
* We don't know how far JNI_OnLoad got, so there could
* be some partially-initialized stuff accessible through
* newly-registered native method calls. We could try to
* unregister them, but that doesn't seem worthwhile.
*/
result = false;
} else {
if (gDvm.verboseJni) {
ALOGI("[Returned from JNI_OnLoad for \"%s\"]", pathName);
}
}
}
if (result)
pNewEntry->onLoadResult = kOnLoadOkay;
else
pNewEntry->onLoadResult = kOnLoadFailed;
pNewEntry->onLoadThreadId = 0;
/*
* Broadcast a wakeup to anybody sleeping on the condition variable.
*/
dvmLockMutex(&pNewEntry->onLoadLock);
pthread_cond_broadcast(&pNewEntry->onLoadCond);
dvmUnlockMutex(&pNewEntry->onLoadLock);
return result;
}
}
/*
* Un-register JNI native methods.
*
* There are two relevant fields in struct Method, "nativeFunc" and
* "insns". The former holds a function pointer to a "bridge" function
* (or, for internal native, the actual implementation). The latter holds
* a pointer to the actual JNI method.
*
* The obvious approach is to reset both fields to their initial state
* (nativeFunc points at dvmResolveNativeMethod, insns holds NULL), but
* that creates some unpleasant race conditions. In particular, if another
* thread is executing inside the call bridge for the method in question,
* and we reset insns to NULL, the VM will crash. (See the comments above
* dvmSetNativeFunc() for additional commentary.)
*
* We can't rely on being able to update two 32-bit fields in one atomic
* operation (e.g. no 64-bit atomic ops on ARMv5TE), so we want to change
* only one field. It turns out we can simply reset nativeFunc to its
* initial state, leaving insns alone, because dvmResolveNativeMethod
* ignores "insns" entirely.
*
* When the method is re-registered, both fields will be updated, but
* dvmSetNativeFunc guarantees that "insns" is updated first. This means
* we shouldn't be in a situation where we have a "live" call bridge and
* a stale implementation pointer.
*/
static void unregisterJNINativeMethods(Method* methods, size_t count)
{
while (count != 0) {
count--;
Method* meth = &methods[count];
if (!dvmIsNativeMethod(meth))
continue;
if (dvmIsAbstractMethod(meth)) /* avoid abstract method stubs */
continue;
/*
* Strictly speaking this ought to test the function pointer against
* the various JNI bridge functions to ensure that we only undo
* methods that were registered through JNI. In practice, any
* native method with a non-NULL "insns" is a registered JNI method.
*
* If we inadvertently unregister an internal-native, it'll get
* re-resolved on the next call; unregistering an unregistered
* JNI method is a no-op. So we don't really need to test for
* anything.
*/
ALOGD("Unregistering JNI method %s.%s:%s",
meth->clazz->descriptor, meth->name, meth->shorty);
dvmSetNativeFunc(meth, dvmResolveNativeMethod, NULL);
}
}
/*
* Un-register all JNI native methods from a class.
*/
void dvmUnregisterJNINativeMethods(ClassObject* clazz)
{
unregisterJNINativeMethods(clazz->directMethods, clazz->directMethodCount);
unregisterJNINativeMethods(clazz->virtualMethods, clazz->virtualMethodCount);
}
/*
* ===========================================================================
* Signature-based method lookup
* ===========================================================================
*/
/*
* Create the pre-mangled form of the class+method string.
*
* Returns a newly-allocated string, and sets "*pLen" to the length.
*/
static char* createJniNameString(const char* classDescriptor,
const char* methodName, int* pLen)
{
char* result;
size_t descriptorLength = strlen(classDescriptor);
*pLen = 4 + descriptorLength + strlen(methodName);
result = (char*)malloc(*pLen +1);
if (result == NULL)
return NULL;
/*
* Add one to classDescriptor to skip the "L", and then replace
* the final ";" with a "/" after the sprintf() call.
*/
sprintf(result, "Java/%s%s", classDescriptor + 1, methodName);
result[5 + (descriptorLength - 2)] = '/';
return result;
}
/*
* Returns a newly-allocated, mangled copy of "str".
*
* "str" is a "modified UTF-8" string. We convert it to UTF-16 first to
* make life simpler.
*/
static char* mangleString(const char* str, int len)
{
//ALOGI("mangling '%s' %d", str, len);
assert(str[len] == '\0');
size_t charLen = dvmUtf8Len(str);
u2* utf16 = (u2*) malloc(sizeof(u2) * charLen);
if (utf16 == NULL)
return NULL;
dvmConvertUtf8ToUtf16(utf16, str);
/*
* Compute the length of the mangled string.
*/
size_t mangleLen = 0;
for (size_t i = 0; i < charLen; i++) {
u2 ch = utf16[i];
if (ch == '$' || ch > 127) {
mangleLen += 6;
} else {
switch (ch) {
case '_':
case ';':
case '[':
mangleLen += 2;
break;
default:
mangleLen++;
break;
}
}
}
char* mangle = (char*) malloc(mangleLen +1);
if (mangle == NULL) {
free(utf16);
return NULL;
}
char* cp = mangle;
for (size_t i = 0; i < charLen; i++) {
u2 ch = utf16[i];
if (ch == '$' || ch > 127) {
sprintf(cp, "_0%04x", ch);
cp += 6;
} else {
switch (ch) {
case '_':
*cp++ = '_';
*cp++ = '1';
break;
case ';':
*cp++ = '_';
*cp++ = '2';
break;
case '[':
*cp++ = '_';
*cp++ = '3';
break;
case '/':
*cp++ = '_';
break;
default:
*cp++ = (char) ch;
break;
}
}
}
*cp = '\0';
free(utf16);
return mangle;
}
/*
* Create the mangled form of the parameter types.
*/
static char* createMangledSignature(const DexProto* proto)
{
DexStringCache sigCache;
const char* interim;
char* result;
dexStringCacheInit(&sigCache);
interim = dexProtoGetParameterDescriptors(proto, &sigCache);
result = mangleString(interim, strlen(interim));
dexStringCacheRelease(&sigCache);
return result;
}
/*
* (This is a dvmHashForeach callback.)
*
* Search for a matching method in this shared library.
*
* TODO: we may want to skip libraries for which JNI_OnLoad failed.
*/
static int findMethodInLib(void* vlib, void* vmethod)
{
const SharedLib* pLib = (const SharedLib*) vlib;
const Method* meth = (const Method*) vmethod;
char* preMangleCM = NULL;
char* mangleCM = NULL;
char* mangleSig = NULL;
char* mangleCMSig = NULL;
void* func = NULL;
int len;
if (meth->clazz->classLoader != pLib->classLoader) {
ALOGV("+++ not scanning '%s' for '%s' (wrong CL)",
pLib->pathName, meth->name);
return 0;
} else
ALOGV("+++ scanning '%s' for '%s'", pLib->pathName, meth->name);
/*
* First, we try it without the signature.
*/
preMangleCM =
createJniNameString(meth->clazz->descriptor, meth->name, &len);
if (preMangleCM == NULL)
goto bail;
mangleCM = mangleString(preMangleCM, len);
if (mangleCM == NULL)
goto bail;
ALOGV("+++ calling dlsym(%s)", mangleCM);
func = dlsym(pLib->handle, mangleCM);
if (func == NULL) {
mangleSig =
createMangledSignature(&meth->prototype);
if (mangleSig == NULL)
goto bail;
mangleCMSig = (char*) malloc(strlen(mangleCM) + strlen(mangleSig) +3);
if (mangleCMSig == NULL)
goto bail;
sprintf(mangleCMSig, "%s__%s", mangleCM, mangleSig);
ALOGV("+++ calling dlsym(%s)", mangleCMSig);
func = dlsym(pLib->handle, mangleCMSig);
if (func != NULL) {
ALOGV("Found '%s' with dlsym", mangleCMSig);
}
} else {
ALOGV("Found '%s' with dlsym", mangleCM);
}
bail:
free(preMangleCM);
free(mangleCM);
free(mangleSig);
free(mangleCMSig);
return (int) func;
}
/*
* See if the requested method lives in any of the currently-loaded
* shared libraries. We do this by checking each of them for the expected
* method signature.
*/
static void* lookupSharedLibMethod(const Method* method)
{
if (gDvm.nativeLibs == NULL) {
ALOGE("Unexpected init state: nativeLibs not ready");
dvmAbort();
}
return (void*) dvmHashForeach(gDvm.nativeLibs, findMethodInLib,
(void*) method);
}
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