125 lines
4.0 KiB
C++
125 lines
4.0 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* The contents of this file are subject to the Netscape Public
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* License Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.mozilla.org/NPL/
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing
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* rights and limitations under the License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is Netscape
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* Communications Corporation. Portions created by Netscape are
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* Copyright (C) 1998 Netscape Communications Corporation. All
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* Rights Reserved.
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*
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* Contributor(s):
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*/
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#include "NativeMethodStubs.h"
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#include "NativeCodeCache.h"
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#include "MemoryAccess.h"
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#include "jni.h"
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extern JNIEnv *jniEnv;
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extern void throwJNIExceptionIfNeeded();
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// XXX This will eventually have to be done on a per-thread basis!!
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static Uint32 JNIReturnAddressInteger = 0;
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static void *JNIReturnAddress = &JNIReturnAddressInteger;
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// Stub sizes
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static const JNIStaticStubSize = 34;
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static const JNIInstanceStubSize = 32;
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// x86 opcodes that we're interested in
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static const Uint8 popEax = 0x58;
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static const Uint8 pushl = 0x68;
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static const Uint8 jmpl = 0xe9;
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static const Uint8 pushEax = 0x50;
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static const Uint8 calll = 0xe8;
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static const Uint8 moveFromEax = 0xa3;
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static const Uint16 jmplIndirectLow = 0xff;
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static const Uint16 jmplIndirectHigh = 0x25;
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#define writeRelativeDisplacement(symbol) \
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writeLittleWordUnaligned(where, reinterpret_cast<Uint32>(symbol) - Uint32(where + 4));\
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where += 4;
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#define writeGlobalLocation(symbol) \
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writeLittleWordUnaligned(where, reinterpret_cast<Uint32>(symbol));\
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where += 4;
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/* Generate stub glue for a native JNI function.
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* The net effect is to generate code that does the following:
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*
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* pop eax // Save return address in EAX
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* mov JNIReturnAddress, eax // Tuck return address safely away
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* push declaringClass // Push declaring class; static methods only
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* push JNIenv // Push JNI pointer
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* call nativeMethod // Jump to the actual JNI native method
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* push eax // Store the return value on the stack
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* call throwJNIExceptionIfNeeded // Check and throw JNI exceptions if needed
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* pop eax // Restore the return value
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* jmp [JNIReturnAddress] // jump to previously stored return address
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*/
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void *generateJNIGlue(const Method &method,
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void *nativeFunction)
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{
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void* stub;
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int stubSize = (method.getModifiers() & CR_METHOD_STATIC) ?
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JNIStaticStubSize : JNIInstanceStubSize;
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assert(method.getModifiers() & CR_METHOD_NATIVE);
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assert(nativeFunction);
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// Write out the JNI stub
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stub = NativeCodeCache::sNativeCodeCache.acquireMemory(stubSize);
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Uint8* where = (Uint8*) stub;
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*where++ = popEax; // popl eax
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*where++ = moveFromEax;
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writeGlobalLocation(JNIReturnAddress);
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// We're pushing arguments right-to-left, so the jclass
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// argument is pushed before the JNIEnv.
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if (method.getModifiers() & CR_METHOD_STATIC) {
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*where++ = pushl; // pushl
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writeGlobalLocation((method.getDeclaringClass()));
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}
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*where++ = pushl; // pushl
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writeGlobalLocation(jniEnv);
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// Put the return address back on the stack
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//*where++ = pushEax; // push eax
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*where++ = calll; // call
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writeRelativeDisplacement(nativeFunction);
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// Store the return value on the stack
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*where++ = pushEax; // push eax
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// Call throwJNIExceptionIfNeeded
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*where++ = calll;
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writeRelativeDisplacement(&throwJNIExceptionIfNeeded);
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// Restore return value
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*where++ = popEax; // pop eax
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// Get back to where we once belonged...
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*where++ = jmplIndirectLow;
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*where++ = jmplIndirectHigh;
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writeGlobalLocation(JNIReturnAddress);
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return stub;
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}
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