vm/Native.c - platform/dalvik - 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.
  */
 /*
  * 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(void)
 {
     gDvm.nativeLibs = dvmHashTableCreate(4, freeSharedLibEntry);
     if (gDvm.nativeLibs == NULL)
         return false;

     return true;
 }

 /*
  * Free up our tables.
  */
 void dvmNativeShutdown(void)
 {
     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.
  *
  * Initializes method's class if necessary.
  *
  * An exception is thrown on resolution failure.
  */
 void dvmResolveNativeMethod(const u4* args, JValue* pResult,
     const Method* method, Thread* self)
 {
     ClassObject* clazz = method->clazz;
     void* func;

     /*
      * 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 */
     func = dvmLookupInternalNativeMethod(method);
     if (func != 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\n",
                 clazz->descriptor, method->name, desc);
             free(desc);
         }
         if (dvmIsSynchronizedMethod(method)) {
             LOGE("ERROR: internal-native can't be declared 'synchronized'\n");
             LOGE("Failing on %s.%s\n", method->clazz->descriptor, method->name);
             dvmAbort();     // harsh, but this is VM-internal problem
         }
         DalvikBridgeFunc dfunc = (DalvikBridgeFunc) func;
         dvmSetNativeFunc(method, dfunc, NULL);
         assert(method->insns == NULL);
         dfunc(args, pResult, method, self);
         return;
     }

     /* now scan any DLLs we have loaded for JNI signatures */
     func = lookupSharedLibMethod(method);
     if (func != NULL) {
         if (dvmIsSynchronizedMethod(method))
             dvmSetNativeFunc(method, dvmCallSynchronizedJNIMethod, func);
         else
             dvmSetNativeFunc(method, dvmCallJNIMethod, func);
         dvmCallJNIMethod(args, pResult, method, self);
         return;
     }

     IF_LOGW() {
         char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
         LOGW("No implementation found for native %s.%s %s\n",
             clazz->descriptor, method->name, desc);
         free(desc);
     }

     dvmThrowException("Ljava/lang/UnsatisfiedLinkError;", method->name);
 }


 /*
  * ===========================================================================
  *      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.)

 /*
  * We add one of these to the hash table for every library we load.  The
  * hash is on the "pathName" field.
  */
 typedef struct SharedLib {
     char*       pathName;       /* absolute path to library */
     void*       handle;         /* from dlopen */
     Object*     classLoader;    /* ClassLoader we are associated with */
 } SharedLib;

 /*
  * (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.
  */
 static int hashcmpSharedLib(const void* ventry, const void* vnewEntry)
 {
     const SharedLib* pLib = (const SharedLib*) ventry;
     const SharedLib* pNewLib = (const SharedLib*) vnewEntry;

     LOGD("--- comparing %p '%s' %p '%s'\n",
         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 const SharedLib* findSharedLibEntry(const char* pathName)
 {
     u4 hash = dvmComputeUtf8Hash(pathName);
     void* ent;

     ent = dvmHashTableLookup(gDvm.nativeLibs, hash, (void*)pathName,
                 hashcmpNameStr, false);
     return ent;
 }

 /*
  * Add the new entry to the table.
  *
  * Returns "true" on success, "false" if the entry already exists.
  */
 static bool addSharedLibEntry(SharedLib* pLib)
 {
     u4 hash = dvmComputeUtf8Hash(pLib->pathName);
     void* ent;

     /*
      * 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.
      */
     ent = dvmHashTableLookup(gDvm.nativeLibs, hash, pLib, hashcmpSharedLib,
                 true);
     return (ent == pLib);
 }

 /*
  * 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);
 }


 #if 0
 /*
  * Find a library, given the lib's system-dependent name (e.g. "libjpeg.so").
  *
  * We need to search through the path defined by the java.library.path
  * property.
  *
  * Returns NULL if the library was not found.
  */
 static char* findLibrary(const char* libSysName)
 {
     char* javaLibraryPath = NULL;
     char* testName = NULL;
     char* start;
     char* cp;
     bool done;

     javaLibraryPath = dvmGetProperty("java.library.path");
     if (javaLibraryPath == NULL)
         goto bail;

     LOGVV("+++ path is '%s'\n", javaLibraryPath);

     start = cp = javaLibraryPath;
     while (cp != NULL) {
         char pathBuf[256];
         int len;

         cp = strchr(start, ':');
         if (cp != NULL)
             *cp = '\0';

         len = snprintf(pathBuf, sizeof(pathBuf), "%s/%s", start, libSysName);
         if (len >= (int) sizeof(pathBuf)) {
             LOGW("Path overflowed %d bytes: '%s' / '%s'\n",
                 len, start, libSysName);
             /* keep going, next one might fit */
         } else {
             LOGVV("+++  trying '%s'\n", pathBuf);
             if (access(pathBuf, R_OK) == 0) {
                 testName = strdup(pathBuf);
                 break;
             }
         }

         start = cp +1;
     }

 bail:
     free(javaLibraryPath);
     return testName;
 }

 /*
  * Load a native shared library, given the system-independent piece of
  * the library name.
  *
  * Throws an exception on failure.
  */
 void dvmLoadNativeLibrary(StringObject* libNameObj, Object* classLoader)
 {
     char* libName = NULL;
     char* libSysName = NULL;
     char* libPath = NULL;

     /*
      * If "classLoader" isn't NULL, call the class loader's "findLibrary"
      * method with the lib name.  If it returns a non-NULL result, we use
      * that as the pathname.
      */
     if (classLoader != NULL) {
         Method* findLibrary;
         Object* findLibResult;

         findLibrary = dvmFindVirtualMethodByDescriptor(classLoader->clazz,
             "findLibrary", "(Ljava/lang/String;)Ljava/lang/String;");
         if (findLibrary == NULL) {
             LOGW("Could not find findLibrary() in %s\n",
                 classLoader->clazz->name);
             dvmThrowException("Ljava/lang/UnsatisfiedLinkError;",
                 "findLibrary");
             goto bail;
         }

         findLibResult = (Object*)(u4) dvmCallMethod(findLibrary, classLoader,
                                             libNameObj);
         if (dvmCheckException()) {
             LOGV("returning early on exception\n");
             goto bail;
         }
         if (findLibResult != NULL) {
             /* success! */
             libPath = dvmCreateCstrFromString(libNameObj);
             LOGI("Found library through CL: '%s'\n", libPath);
             dvmLoadNativeCode(libPath, classLoader);
             goto bail;
         }
     }

     libName = dvmCreateCstrFromString(libNameObj);
     if (libName == NULL)
         goto bail;
     libSysName = dvmCreateSystemLibraryName(libName);
     if (libSysName == NULL)
         goto bail;

     libPath = findLibrary(libSysName);
     if (libPath != NULL) {
         LOGD("Found library through path: '%s'\n", libPath);
         dvmLoadNativeCode(libPath, classLoader);
     } else {
         LOGW("Unable to locate shared lib matching '%s'\n", libSysName);
         dvmThrowException("Ljava/lang/UnsatisfiedLinkError;", libName);
     }

 bail:
     free(libName);
     free(libSysName);
     free(libPath);
 }
 #endif

 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.
  */
 bool dvmLoadNativeCode(const char* pathName, Object* classLoader)
 {
     const SharedLib* pEntry;
     void* handle;

     LOGD("Trying to load lib %s %p\n", pathName, classLoader);

     /*
      * 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) {
             LOGW("Shared lib '%s' already opened by CL %p; can't open in %p\n",
                 pathName, pEntry->classLoader, classLoader);
             return false;
         }
         LOGD("Shared lib '%s' already loaded in same CL %p\n",
             pathName, classLoader);
         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.
      *
      * The current android-arm dynamic linker implementation tends to
      * return "Cannot find library" from dlerror() regardless of the actual
      * problem.  A more useful diagnostic may be sent to stdout/stderr,
      * but often that's not visible.  Some things to try:
      *   - 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
      *   - 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, this is a good one to check)
      */
     handle = dlopen(pathName, RTLD_LAZY);
     if (handle == NULL) {
         LOGI("Unable to dlopen(%s): %s\n", pathName, dlerror());
         return false;
     }

     SharedLib* pNewEntry;
     pNewEntry = (SharedLib*) malloc(sizeof(SharedLib));
     pNewEntry->pathName = strdup(pathName);
     pNewEntry->handle = handle;
     pNewEntry->classLoader = classLoader;
     if (!addSharedLibEntry(pNewEntry)) {
         LOGI("WOW: we lost a race to add a shared lib (%s %p)\n",
             pathName, classLoader);
         /* free up our entry, and just return happy that one exists */
         freeSharedLibEntry(pNewEntry);
     } else {
         LOGD("Added shared lib %s %p\n", pathName, classLoader);

         void* vonLoad;
         int version;

         vonLoad = dlsym(handle, "JNI_OnLoad");
         if (vonLoad == NULL) {
             LOGD("No JNI_OnLoad found in %s %p\n", 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().
              */
             OnLoadFunc func = vonLoad;
             Thread* self = dvmThreadSelf();
             Object* prevOverride = self->classLoaderOverride;

             self->classLoaderOverride = classLoader;
             dvmChangeStatus(NULL, THREAD_NATIVE);
             version = (*func)(gDvm.vmList, NULL);
             dvmChangeStatus(NULL, THREAD_RUNNING);
             self->classLoaderOverride = prevOverride;

             if (version != JNI_VERSION_1_2 && version != JNI_VERSION_1_4 &&
                 version != JNI_VERSION_1_6)
             {
                 LOGW("JNI_OnLoad returned bad version (%d) in %s %p\n",
                     version, pathName, classLoader);
                 // TODO: dlclose, remove hash table entry
                 return false;
             }
         }
     }

     return true;
 }


 /*
  * ===========================================================================
  *      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 = 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)
 {
     u2* utf16 = NULL;
     char* mangle = NULL;
     int charLen;

     //LOGI("mangling '%s' %d\n", str, len);

     assert(str[len] == '\0');

     charLen = dvmUtf8Len(str);
     utf16 = (u2*) malloc(sizeof(u2) * charLen);
     if (utf16 == NULL)
         goto bail;

     dvmConvertUtf8ToUtf16(utf16, str);

     /*
      * Compute the length of the mangled string.
      */
     int i, mangleLen = 0;

     for (i = 0; i < charLen; i++) {
         u2 ch = utf16[i];

         if (ch > 127) {
             mangleLen += 6;
         } else {
             switch (ch) {
             case '_':
             case ';':
             case '[':
                 mangleLen += 2;
                 break;
             default:
                 mangleLen++;
                 break;
             }
         }
     }

     char* cp;

     mangle = (char*) malloc(mangleLen +1);
     if (mangle == NULL)
         goto bail;

     for (i = 0, cp = mangle; i < charLen; i++) {
         u2 ch = utf16[i];

         if (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';

 bail:
     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.
  */
 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) {
         LOGD("+++ not scanning '%s' for '%s' (wrong CL)\n",
             pLib->pathName, meth->name);
         return 0;
     } else
         LOGV("+++ scanning '%s' for '%s'\n", 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;

     LOGV("+++ calling dlsym(%s)\n", 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);

         LOGV("+++ calling dlsym(%s)\n", mangleCMSig);
         func = dlsym(pLib->handle, mangleCMSig);
         if (func != NULL) {
             LOGV("Found '%s' with dlsym\n", mangleCMSig);
         }
     } else {
         LOGV("Found '%s' with dlsym\n", 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) {
         LOGE("Unexpected init state: nativeLibs not ready\n");
         dvmAbort();
     }
     return (void*) dvmHashForeach(gDvm.nativeLibs, findMethodInLib,
         (void*) method);
 }
	/*
	* 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(void)
	{
	gDvm.nativeLibs = dvmHashTableCreate(4, freeSharedLibEntry);
	if (gDvm.nativeLibs == NULL)
	return false;

	return true;
	}

	/*
	* Free up our tables.
	*/
	void dvmNativeShutdown(void)
	{
	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.
	*
	* Initializes method's class if necessary.
	*
	* An exception is thrown on resolution failure.
	*/
	void dvmResolveNativeMethod(const u4* args, JValue* pResult,
	const Method* method, Thread* self)
	{
	ClassObject* clazz = method->clazz;
	void* func;

	/*
	* 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 */
	func = dvmLookupInternalNativeMethod(method);
	if (func != 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\n",
	clazz->descriptor, method->name, desc);
	free(desc);
	}
	if (dvmIsSynchronizedMethod(method)) {
	LOGE("ERROR: internal-native can't be declared 'synchronized'\n");
	LOGE("Failing on %s.%s\n", method->clazz->descriptor, method->name);
	dvmAbort(); // harsh, but this is VM-internal problem
	}
	DalvikBridgeFunc dfunc = (DalvikBridgeFunc) func;
	dvmSetNativeFunc(method, dfunc, NULL);
	assert(method->insns == NULL);
	dfunc(args, pResult, method, self);
	return;
	}

	/* now scan any DLLs we have loaded for JNI signatures */
	func = lookupSharedLibMethod(method);
	if (func != NULL) {
	if (dvmIsSynchronizedMethod(method))
	dvmSetNativeFunc(method, dvmCallSynchronizedJNIMethod, func);
	else
	dvmSetNativeFunc(method, dvmCallJNIMethod, func);
	dvmCallJNIMethod(args, pResult, method, self);
	return;
	}

	IF_LOGW() {
	char* desc = dexProtoCopyMethodDescriptor(&method->prototype);
	LOGW("No implementation found for native %s.%s %s\n",
	clazz->descriptor, method->name, desc);
	free(desc);
	}

	dvmThrowException("Ljava/lang/UnsatisfiedLinkError;", method->name);
	}


	/*
	* ===========================================================================
	* 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.)

	/*
	* We add one of these to the hash table for every library we load. The
	* hash is on the "pathName" field.
	*/
	typedef struct SharedLib {
	char* pathName; /* absolute path to library */
	void* handle; /* from dlopen */
	Object* classLoader; /* ClassLoader we are associated with */
	} SharedLib;

	/*
	* (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.
	*/
	static int hashcmpSharedLib(const void* ventry, const void* vnewEntry)
	{
	const SharedLib* pLib = (const SharedLib*) ventry;
	const SharedLib* pNewLib = (const SharedLib*) vnewEntry;

	LOGD("--- comparing %p '%s' %p '%s'\n",
	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 const SharedLib* findSharedLibEntry(const char* pathName)
	{
	u4 hash = dvmComputeUtf8Hash(pathName);
	void* ent;

	ent = dvmHashTableLookup(gDvm.nativeLibs, hash, (void*)pathName,
	hashcmpNameStr, false);
	return ent;
	}

	/*
	* Add the new entry to the table.
	*
	* Returns "true" on success, "false" if the entry already exists.
	*/
	static bool addSharedLibEntry(SharedLib* pLib)
	{
	u4 hash = dvmComputeUtf8Hash(pLib->pathName);
	void* ent;

	/*
	* 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.
	*/
	ent = dvmHashTableLookup(gDvm.nativeLibs, hash, pLib, hashcmpSharedLib,
	true);
	return (ent == pLib);
	}

	/*
	* 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);
	}


	#if 0
	/*
	* Find a library, given the lib's system-dependent name (e.g. "libjpeg.so").
	*
	* We need to search through the path defined by the java.library.path
	* property.
	*
	* Returns NULL if the library was not found.
	*/
	static char* findLibrary(const char* libSysName)
	{
	char* javaLibraryPath = NULL;
	char* testName = NULL;
	char* start;
	char* cp;
	bool done;

	javaLibraryPath = dvmGetProperty("java.library.path");
	if (javaLibraryPath == NULL)
	goto bail;

	LOGVV("+++ path is '%s'\n", javaLibraryPath);

	start = cp = javaLibraryPath;
	while (cp != NULL) {
	char pathBuf[256];
	int len;

	cp = strchr(start, ':');
	if (cp != NULL)
	*cp = '\0';

	len = snprintf(pathBuf, sizeof(pathBuf), "%s/%s", start, libSysName);
	if (len >= (int) sizeof(pathBuf)) {
	LOGW("Path overflowed %d bytes: '%s' / '%s'\n",
	len, start, libSysName);
	/* keep going, next one might fit */
	} else {
	LOGVV("+++ trying '%s'\n", pathBuf);
	if (access(pathBuf, R_OK) == 0) {
	testName = strdup(pathBuf);
	break;
	}
	}

	start = cp +1;
	}

	bail:
	free(javaLibraryPath);
	return testName;
	}

	/*
	* Load a native shared library, given the system-independent piece of
	* the library name.
	*
	* Throws an exception on failure.
	*/
	void dvmLoadNativeLibrary(StringObject* libNameObj, Object* classLoader)
	{
	char* libName = NULL;
	char* libSysName = NULL;
	char* libPath = NULL;

	/*
	* If "classLoader" isn't NULL, call the class loader's "findLibrary"
	* method with the lib name. If it returns a non-NULL result, we use
	* that as the pathname.
	*/
	if (classLoader != NULL) {
	Method* findLibrary;
	Object* findLibResult;

	findLibrary = dvmFindVirtualMethodByDescriptor(classLoader->clazz,
	"findLibrary", "(Ljava/lang/String;)Ljava/lang/String;");
	if (findLibrary == NULL) {
	LOGW("Could not find findLibrary() in %s\n",
	classLoader->clazz->name);
	dvmThrowException("Ljava/lang/UnsatisfiedLinkError;",
	"findLibrary");
	goto bail;
	}

	findLibResult = (Object*)(u4) dvmCallMethod(findLibrary, classLoader,
	libNameObj);
	if (dvmCheckException()) {
	LOGV("returning early on exception\n");
	goto bail;
	}
	if (findLibResult != NULL) {
	/* success! */
	libPath = dvmCreateCstrFromString(libNameObj);
	LOGI("Found library through CL: '%s'\n", libPath);
	dvmLoadNativeCode(libPath, classLoader);
	goto bail;
	}
	}

	libName = dvmCreateCstrFromString(libNameObj);
	if (libName == NULL)
	goto bail;
	libSysName = dvmCreateSystemLibraryName(libName);
	if (libSysName == NULL)
	goto bail;

	libPath = findLibrary(libSysName);
	if (libPath != NULL) {
	LOGD("Found library through path: '%s'\n", libPath);
	dvmLoadNativeCode(libPath, classLoader);
	} else {
	LOGW("Unable to locate shared lib matching '%s'\n", libSysName);
	dvmThrowException("Ljava/lang/UnsatisfiedLinkError;", libName);
	}

	bail:
	free(libName);
	free(libSysName);
	free(libPath);
	}
	#endif

	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.
	*/
	bool dvmLoadNativeCode(const char* pathName, Object* classLoader)
	{
	const SharedLib* pEntry;
	void* handle;

	LOGD("Trying to load lib %s %p\n", pathName, classLoader);

	/*
	* 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) {
	LOGW("Shared lib '%s' already opened by CL %p; can't open in %p\n",
	pathName, pEntry->classLoader, classLoader);
	return false;
	}
	LOGD("Shared lib '%s' already loaded in same CL %p\n",
	pathName, classLoader);
	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.
	*
	* The current android-arm dynamic linker implementation tends to
	* return "Cannot find library" from dlerror() regardless of the actual
	* problem. A more useful diagnostic may be sent to stdout/stderr,
	* but often that's not visible. Some things to try:
	* - 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
	* - 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, this is a good one to check)
	*/
	handle = dlopen(pathName, RTLD_LAZY);
	if (handle == NULL) {
	LOGI("Unable to dlopen(%s): %s\n", pathName, dlerror());
	return false;
	}

	SharedLib* pNewEntry;
	pNewEntry = (SharedLib*) malloc(sizeof(SharedLib));
	pNewEntry->pathName = strdup(pathName);
	pNewEntry->handle = handle;
	pNewEntry->classLoader = classLoader;
	if (!addSharedLibEntry(pNewEntry)) {
	LOGI("WOW: we lost a race to add a shared lib (%s %p)\n",
	pathName, classLoader);
	/* free up our entry, and just return happy that one exists */
	freeSharedLibEntry(pNewEntry);
	} else {
	LOGD("Added shared lib %s %p\n", pathName, classLoader);

	void* vonLoad;
	int version;

	vonLoad = dlsym(handle, "JNI_OnLoad");
	if (vonLoad == NULL) {
	LOGD("No JNI_OnLoad found in %s %p\n", 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().
	*/
	OnLoadFunc func = vonLoad;
	Thread* self = dvmThreadSelf();
	Object* prevOverride = self->classLoaderOverride;

	self->classLoaderOverride = classLoader;
	dvmChangeStatus(NULL, THREAD_NATIVE);
	version = (*func)(gDvm.vmList, NULL);
	dvmChangeStatus(NULL, THREAD_RUNNING);
	self->classLoaderOverride = prevOverride;

	if (version != JNI_VERSION_1_2 && version != JNI_VERSION_1_4 &&
	version != JNI_VERSION_1_6)
	{
	LOGW("JNI_OnLoad returned bad version (%d) in %s %p\n",
	version, pathName, classLoader);
	// TODO: dlclose, remove hash table entry
	return false;
	}
	}
	}

	return true;
	}


	/*
	* ===========================================================================
	* 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 = 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)
	{
	u2* utf16 = NULL;
	char* mangle = NULL;
	int charLen;

	//LOGI("mangling '%s' %d\n", str, len);

	assert(str[len] == '\0');

	charLen = dvmUtf8Len(str);
	utf16 = (u2) malloc(sizeof(u2) charLen);
	if (utf16 == NULL)
	goto bail;

	dvmConvertUtf8ToUtf16(utf16, str);

	/*
	* Compute the length of the mangled string.
	*/
	int i, mangleLen = 0;

	for (i = 0; i < charLen; i++) {
	u2 ch = utf16[i];

	if (ch > 127) {
	mangleLen += 6;
	} else {
	switch (ch) {
	case '_':
	case ';':
	case '[':
	mangleLen += 2;
	break;
	default:
	mangleLen++;
	break;
	}
	}
	}

	char* cp;

	mangle = (char*) malloc(mangleLen +1);
	if (mangle == NULL)
	goto bail;

	for (i = 0, cp = mangle; i < charLen; i++) {
	u2 ch = utf16[i];

	if (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';

	bail:
	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.
	*/
	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) {
	LOGD("+++ not scanning '%s' for '%s' (wrong CL)\n",
	pLib->pathName, meth->name);
	return 0;
	} else
	LOGV("+++ scanning '%s' for '%s'\n", 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;

	LOGV("+++ calling dlsym(%s)\n", 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);

	LOGV("+++ calling dlsym(%s)\n", mangleCMSig);
	func = dlsym(pLib->handle, mangleCMSig);
	if (func != NULL) {
	LOGV("Found '%s' with dlsym\n", mangleCMSig);
	}
	} else {
	LOGV("Found '%s' with dlsym\n", 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) {
	LOGE("Unexpected init state: nativeLibs not ready\n");
	dvmAbort();
	}
	return (void*) dvmHashForeach(gDvm.nativeLibs, findMethodInLib,
	(void*) method);
	}