/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "NPL"); you may not use this file except in
 * compliance with the NPL.  You may obtain a copy of the NPL at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the NPL is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
 * for the specific language governing rights and limitations under the
 * NPL.
 *
 * The Initial Developer of this code under the NPL is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
 * Reserved.
 */
/*
	x86Linux_Support.cpp
*/

#include "NativeCodeCache.h"
#include <string.h>
#include "Fundamentals.h"
#include "MemoryAccess.h"
#include "x86Linux_Support.h"


void* JNIenv = 0; 

extern ClassWorld world;

#ifdef DEBUG
// Pointer to the instruction after the call (used by exception handler to check
// I wanted to use:
//		void* compileStubReEntryPoint =  (void*) ((Uint8*)staticCompileStub + 17);
// but MSDev appears to have a bug, in that compileStubReEntryPoint will be set == (void*)staticCompileStub
// which is clearly wrong.
void* compileStubAddress = (void*)staticCompileStub;
void* compileStubReEntryPoint = (Uint8*)compileStubAddress + 17;
#endif // DEBUG

void *
generateNativeStub(NativeCodeCache& inCache, const CacheEntry& inCacheEntry, void *nativeFunction)
{
	Method* method = inCacheEntry.descriptor.method;
	Uint32 nWords = method->getSignature().nArguments;

	assert(method->getModifiers() & CR_METHOD_NATIVE);

	extern Uint32 sysInvokeNativeStubs[];
    Uint8 stubSize = 10;
    void* stub;
		
	// Write out the native stub
	stub = inCache.acquireMemory(stubSize);
	Uint8* where = (Uint8*)stub;
	*where++ = 0x68; // pushl
	writeLittleWordUnaligned(where, (uint32)(nativeFunction));
	where += 4;
	*where++ = 0xe9; // jmp
	writeLittleWordUnaligned(where, (Uint8 *) sysInvokeNativeStubs[nWords] - (where + 4));

	// Return the address of the stub.
	return ((void*)stub);
}

void * 
generateJNIGlue(NativeCodeCache& inCache,
                const CacheEntry& inCacheEntry,
                void *nativeFunction)
{	
	void*	stub;
	Method* method = inCacheEntry.descriptor.method;
	assert(method->getModifiers() & CR_METHOD_NATIVE);
	
    Uint8 stubSize = 12;

	// Write out the JNI compile stub
	stub = inCache.acquireMemory(stubSize);
	Uint8* where = (Uint8*) stub;
	*where++ = 0x58; // popl %eax
	*where++ = 0x68; // pushl
	writeLittleWordUnaligned(where, (Uint32) JNIenv);
	where += 4;
	*where++ = 0xe9; // jmp
	writeLittleWordUnaligned(where, reinterpret_cast<Uint32>(nativeFunction) - Uint32(where + 4));
	return stub;
} 
    
void * 
generateCompileStub(NativeCodeCache& inCache, const CacheEntry& inCacheEntry)
{
    void*	stub;
    uint8 stubSize = 10;
		
	// Write out the dynamic compile stub
	stub = inCache.acquireMemory(stubSize);
	Uint8* where = (Uint8*)stub;

    // movl $inCacheEntry, %eax
    *where++ = 0xb8;

	writeLittleWordUnaligned(where, (uint32)(&inCacheEntry));
	where += 4;
	*where++ = 0xe9; // jmp
	writeLittleWordUnaligned(where, (Uint8 *) staticCompileStub - (where + 4));

	// Return the address of the dynamic stub.
	return ((void*)stub);
}

void*
backPatchMethod(void* inMethodAddress, void* inLastPC, void* /*inUserDefined*/)
{
		
	uint32 curAddress = (uint32) inLastPC;
	uint32 methodAddress = (uint32) inMethodAddress;
	
	// Compute the relative branch
	uint32*	relativeBranch = ((uint32*)inLastPC)-1;
	int32 offset = methodAddress - curAddress;

	// Backpatch the method.
	writeLittleWordUnaligned((void*)relativeBranch, offset);

	return (inMethodAddress);
}