Java example source code file (nativeLookup.cpp)

This example Java source code file (nativeLookup.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

cast_from_fn_ptr, catch, check_null, fn_ptr, include_jvmti, jnicall, klasshandle, null, resourcemark, symboltable\:\:new_symbol, tempnewsymbol, thread, traps

The nativeLookup.cpp Java example source code

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */

#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/systemDictionary.hpp"
#include "classfile/vmSymbols.hpp"
#include "memory/oopFactory.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.inline.hpp"
#include "oops/instanceKlass.hpp"
#include "oops/method.hpp"
#include "oops/oop.inline.hpp"
#include "oops/symbol.hpp"
#include "prims/jvm_misc.hpp"
#include "prims/nativeLookup.hpp"
#include "runtime/arguments.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/signature.hpp"
#include "utilities/macros.hpp"
#ifdef TARGET_OS_FAMILY_linux
# include "os_linux.inline.hpp"
#endif
#ifdef TARGET_OS_FAMILY_solaris
# include "os_solaris.inline.hpp"
#endif
#ifdef TARGET_OS_FAMILY_windows
# include "os_windows.inline.hpp"
#endif
#ifdef TARGET_OS_FAMILY_bsd
# include "os_bsd.inline.hpp"
#endif


static void mangle_name_on(outputStream* st, Symbol* name, int begin, int end) {
  char* bytes = (char*)name->bytes() + begin;
  char* end_bytes = (char*)name->bytes() + end;
  while (bytes < end_bytes) {
    jchar c;
    bytes = UTF8::next(bytes, &c);
    if (c <= 0x7f && isalnum(c)) {
      st->put((char) c);
    } else {
           if (c == '_') st->print("_1");
      else if (c == '/') st->print("_");
      else if (c == ';') st->print("_2");
      else if (c == '[') st->print("_3");
      else               st->print("_%.5x", c);
    }
  }
}


static void mangle_name_on(outputStream* st, Symbol* name) {
  mangle_name_on(st, name, 0, name->utf8_length());
}


char* NativeLookup::pure_jni_name(methodHandle method) {
  stringStream st;
  // Prefix
  st.print("Java_");
  // Klass name
  mangle_name_on(&st, method->klass_name());
  st.print("_");
  // Method name
  mangle_name_on(&st, method->name());
  return st.as_string();
}


char* NativeLookup::critical_jni_name(methodHandle method) {
  stringStream st;
  // Prefix
  st.print("JavaCritical_");
  // Klass name
  mangle_name_on(&st, method->klass_name());
  st.print("_");
  // Method name
  mangle_name_on(&st, method->name());
  return st.as_string();
}


char* NativeLookup::long_jni_name(methodHandle method) {
  // Signature ignore the wrapping parenteses and the trailing return type
  stringStream st;
  Symbol* signature = method->signature();
  st.print("__");
  // find ')'
  int end;
  for (end = 0; end < signature->utf8_length() && signature->byte_at(end) != ')'; end++);
  // skip first '('
  mangle_name_on(&st, signature, 1, end);
  return st.as_string();
}

extern "C" {
  void JNICALL JVM_RegisterUnsafeMethods(JNIEnv *env, jclass unsafecls);
  void JNICALL JVM_RegisterMethodHandleMethods(JNIEnv *env, jclass unsafecls);
  void JNICALL JVM_RegisterPerfMethods(JNIEnv *env, jclass perfclass);
  void JNICALL JVM_RegisterWhiteBoxMethods(JNIEnv *env, jclass wbclass);
}

#define CC (char*)  /* cast a literal from (const char*) */
#define FN_PTR(f) CAST_FROM_FN_PTR(void*, &f)

static JNINativeMethod lookup_special_native_methods[] = {
  { CC"Java_sun_misc_Unsafe_registerNatives",                      NULL, FN_PTR(JVM_RegisterUnsafeMethods)       },
  { CC"Java_java_lang_invoke_MethodHandleNatives_registerNatives", NULL, FN_PTR(JVM_RegisterMethodHandleMethods) },
  { CC"Java_sun_misc_Perf_registerNatives",                        NULL, FN_PTR(JVM_RegisterPerfMethods)         },
  { CC"Java_sun_hotspot_WhiteBox_registerNatives",                 NULL, FN_PTR(JVM_RegisterWhiteBoxMethods)     },
};

static address lookup_special_native(char* jni_name) {
  int count = sizeof(lookup_special_native_methods) / sizeof(JNINativeMethod);
  for (int i = 0; i < count; i++) {
    // NB: To ignore the jni prefix and jni postfix strstr is used matching.
    if (strstr(jni_name, lookup_special_native_methods[i].name) != NULL) {
      return CAST_FROM_FN_PTR(address, lookup_special_native_methods[i].fnPtr);
    }
  }
  return NULL;
}

address NativeLookup::lookup_style(methodHandle method, char* pure_name, const char* long_name, int args_size, bool os_style, bool& in_base_library, TRAPS) {
  address entry;
  // Compute complete JNI name for style
  stringStream st;
  if (os_style) os::print_jni_name_prefix_on(&st, args_size);
  st.print_raw(pure_name);
  st.print_raw(long_name);
  if (os_style) os::print_jni_name_suffix_on(&st, args_size);
  char* jni_name = st.as_string();

  // If the loader is null we have a system class, so we attempt a lookup in
  // the native Java library. This takes care of any bootstrapping problems.
  // Note: It is critical for bootstrapping that Java_java_lang_ClassLoader_00024NativeLibrary_find
  // gets found the first time around - otherwise an infinite loop can occure. This is
  // another VM/library dependency
  Handle loader(THREAD, method->method_holder()->class_loader());
  if (loader.is_null()) {
    entry = lookup_special_native(jni_name);
    if (entry == NULL) {
       entry = (address) os::dll_lookup(os::native_java_library(), jni_name);
    }
    if (entry != NULL) {
      in_base_library = true;
      return entry;
    }
  }

  // Otherwise call static method findNative in ClassLoader
  KlassHandle   klass (THREAD, SystemDictionary::ClassLoader_klass());
  Handle name_arg = java_lang_String::create_from_str(jni_name, CHECK_NULL);

  JavaValue result(T_LONG);
  JavaCalls::call_static(&result,
                         klass,
                         vmSymbols::findNative_name(),
                         vmSymbols::classloader_string_long_signature(),
                         // Arguments
                         loader,
                         name_arg,
                         CHECK_NULL);
  entry = (address) (intptr_t) result.get_jlong();

  if (entry == NULL) {
    // findNative didn't find it, if there are any agent libraries look in them
    AgentLibrary* agent;
    for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
      entry = (address) os::dll_lookup(agent->os_lib(), jni_name);
      if (entry != NULL) {
        return entry;
      }
    }
  }

  return entry;
}


address NativeLookup::lookup_critical_style(methodHandle method, char* pure_name, const char* long_name, int args_size, bool os_style) {
  if (!method->has_native_function()) {
    return NULL;
  }

  address current_entry = method->native_function();

  char dll_name[JVM_MAXPATHLEN];
  int offset;
  if (os::dll_address_to_library_name(current_entry, dll_name, sizeof(dll_name), &offset)) {
    char ebuf[32];
    void* dll = os::dll_load(dll_name, ebuf, sizeof(ebuf));
    if (dll != NULL) {
      // Compute complete JNI name for style
      stringStream st;
      if (os_style) os::print_jni_name_prefix_on(&st, args_size);
      st.print_raw(pure_name);
      st.print_raw(long_name);
      if (os_style) os::print_jni_name_suffix_on(&st, args_size);
      char* jni_name = st.as_string();
      return (address)os::dll_lookup(dll, jni_name);
    }
  }

  return NULL;
}


// Check all the formats of native implementation name to see if there is one
// for the specified method.
address NativeLookup::lookup_entry(methodHandle method, bool& in_base_library, TRAPS) {
  address entry = NULL;
  in_base_library = false;
  // Compute pure name
  char* pure_name = pure_jni_name(method);

  // Compute argument size
  int args_size = 1                             // JNIEnv
                + (method->is_static() ? 1 : 0) // class for static methods
                + method->size_of_parameters(); // actual parameters


  // 1) Try JNI short style
  entry = lookup_style(method, pure_name, "",        args_size, true,  in_base_library, CHECK_NULL);
  if (entry != NULL) return entry;

  // Compute long name
  char* long_name = long_jni_name(method);

  // 2) Try JNI long style
  entry = lookup_style(method, pure_name, long_name, args_size, true,  in_base_library, CHECK_NULL);
  if (entry != NULL) return entry;

  // 3) Try JNI short style without os prefix/suffix
  entry = lookup_style(method, pure_name, "",        args_size, false, in_base_library, CHECK_NULL);
  if (entry != NULL) return entry;

  // 4) Try JNI long style without os prefix/suffix
  entry = lookup_style(method, pure_name, long_name, args_size, false, in_base_library, CHECK_NULL);

  return entry; // NULL indicates not found
}

// Check all the formats of native implementation name to see if there is one
// for the specified method.
address NativeLookup::lookup_critical_entry(methodHandle method) {
  if (!CriticalJNINatives) return NULL;

  if (method->is_synchronized() ||
      !method->is_static()) {
    // Only static non-synchronized methods are allowed
    return NULL;
  }

  ResourceMark rm;
  address entry = NULL;

  Symbol* signature = method->signature();
  for (int end = 0; end < signature->utf8_length(); end++) {
    if (signature->byte_at(end) == 'L') {
      // Don't allow object types
      return NULL;
    }
  }

  // Compute critical name
  char* critical_name = critical_jni_name(method);

  // Compute argument size
  int args_size = 1                             // JNIEnv
                + (method->is_static() ? 1 : 0) // class for static methods
                + method->size_of_parameters(); // actual parameters


  // 1) Try JNI short style
  entry = lookup_critical_style(method, critical_name, "",        args_size, true);
  if (entry != NULL) return entry;

  // Compute long name
  char* long_name = long_jni_name(method);

  // 2) Try JNI long style
  entry = lookup_critical_style(method, critical_name, long_name, args_size, true);
  if (entry != NULL) return entry;

  // 3) Try JNI short style without os prefix/suffix
  entry = lookup_critical_style(method, critical_name, "",        args_size, false);
  if (entry != NULL) return entry;

  // 4) Try JNI long style without os prefix/suffix
  entry = lookup_critical_style(method, critical_name, long_name, args_size, false);

  return entry; // NULL indicates not found
}

// Check if there are any JVM TI prefixes which have been applied to the native method name.
// If any are found, remove them before attemping the look up of the
// native implementation again.
// See SetNativeMethodPrefix in the JVM TI Spec for more details.
address NativeLookup::lookup_entry_prefixed(methodHandle method, bool& in_base_library, TRAPS) {
#if INCLUDE_JVMTI
  ResourceMark rm(THREAD);

  int prefix_count;
  char** prefixes = JvmtiExport::get_all_native_method_prefixes(&prefix_count);
  char* in_name = method->name()->as_C_string();
  char* wrapper_name = in_name;
  // last applied prefix will be first -- go backwards
  for (int i = prefix_count-1; i >= 0; i--) {
    char* prefix = prefixes[i];
    size_t prefix_len = strlen(prefix);
    if (strncmp(prefix, wrapper_name, prefix_len) == 0) {
      // has this prefix remove it
      wrapper_name += prefix_len;
    }
  }
  if (wrapper_name != in_name) {
    // we have a name for a wrapping method
    int wrapper_name_len = (int)strlen(wrapper_name);
    TempNewSymbol wrapper_symbol = SymbolTable::probe(wrapper_name, wrapper_name_len);
    if (wrapper_symbol != NULL) {
      KlassHandle kh(method->method_holder());
      Method* wrapper_method = kh()->lookup_method(wrapper_symbol,
                                                                  method->signature());
      if (wrapper_method != NULL && !wrapper_method->is_native()) {
        // we found a wrapper method, use its native entry
        method->set_is_prefixed_native();
        return lookup_entry(wrapper_method, in_base_library, THREAD);
      }
    }
  }
#endif // INCLUDE_JVMTI
  return NULL;
}

address NativeLookup::lookup_base(methodHandle method, bool& in_base_library, TRAPS) {
  address entry = NULL;
  ResourceMark rm(THREAD);

  entry = lookup_entry(method, in_base_library, THREAD);
  if (entry != NULL) return entry;

  // standard native method resolution has failed.  Check if there are any
  // JVM TI prefixes which have been applied to the native method name.
  entry = lookup_entry_prefixed(method, in_base_library, THREAD);
  if (entry != NULL) return entry;

  // Native function not found, throw UnsatisfiedLinkError
  THROW_MSG_0(vmSymbols::java_lang_UnsatisfiedLinkError(),
              method->name_and_sig_as_C_string());
}


address NativeLookup::lookup(methodHandle method, bool& in_base_library, TRAPS) {
  if (!method->has_native_function()) {
    address entry = lookup_base(method, in_base_library, CHECK_NULL);
    method->set_native_function(entry,
      Method::native_bind_event_is_interesting);
    // -verbose:jni printing
    if (PrintJNIResolving) {
      ResourceMark rm(THREAD);
      tty->print_cr("[Dynamic-linking native method %s.%s ... JNI]",
        method->method_holder()->external_name(),
        method->name()->as_C_string());
    }
  }
  return method->native_function();
}

address NativeLookup::base_library_lookup(const char* class_name, const char* method_name, const char* signature) {
  EXCEPTION_MARK;
  bool in_base_library = true;  // SharedRuntime inits some math methods.
  TempNewSymbol c_name = SymbolTable::new_symbol(class_name,  CATCH);
  TempNewSymbol m_name = SymbolTable::new_symbol(method_name, CATCH);
  TempNewSymbol s_name = SymbolTable::new_symbol(signature,   CATCH);

  // Find the class
  Klass* k = SystemDictionary::resolve_or_fail(c_name, true, CATCH);
  instanceKlassHandle klass (THREAD, k);

  // Find method and invoke standard lookup
  methodHandle method (THREAD,
                       klass->uncached_lookup_method(m_name, s_name));
  address result = lookup(method, in_base_library, CATCH);
  assert(in_base_library, "must be in basic library");
  guarantee(result != NULL, "must be non NULL");
  return result;
}