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Loader.cpp
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Loader.cpp
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#include "Loader.hpp"
#include "Encoding.hpp"
#include "Error.hpp"
#include "Linker.hpp"
#include <string.h>
#ifdef WIN32
#include <windows.h>
#elif __unix__
#include <sys/mman.h>
#endif
namespace SoftWire
{
Loader::Loader(const Linker &linker, bool x64) : linker(linker), x64(x64)
{
machineCode = 0;
instructions = 0;
listing = 0;
possession = true;
reset();
}
Loader::~Loader()
{
if(possession)
{
delete[] machineCode;
machineCode = 0;
}
delete instructions;
instructions = 0;
delete[] listing;
listing = 0;
}
void (*Loader::callable(const char *entryLabel))()
{
if(finalized) throw Error("Cannot retrieve callable from finalized code");
if(!machineCode)
{
loadCode();
}
if(!entryLabel)
{
return (void(*)())machineCode;
}
const unsigned char *entryPoint = resolveLocal(entryLabel, 0);
if(!entryPoint)
{
throw Error("Entry point '%s' not found", entryLabel);
}
return (void(*)())entryPoint;
}
void (*Loader::finalize(const char *entryLabel))()
{
if(!machineCode)
{
loadCode();
}
finalized = true;
delete instructions;
instructions = 0;
delete[] listing;
listing = 0;
if(!entryLabel)
{
return (void(*)())machineCode;
}
const unsigned char *entryPoint = resolveLocal(entryLabel, 0);
if(!entryPoint)
{
throw Error("Entry point '%s' not found", entryLabel);
}
return (void(*)())entryPoint;
}
void *Loader::acquire()
{
possession = false;
return machineCode;
}
Encoding *Loader::appendEncoding(const Encoding &encoding)
{
if(!instructions) instructions = new Instruction();
instructions->append(encoding);
return instructions->tail();
}
void Loader::loadCode(const char *entryLabel)
{
int length = codeLength() + 64; // NOTE: Code length is not accurate due to alignment issues
machineCode = new unsigned char[length];
unsigned char *currentCode = machineCode;
#ifdef WIN32
unsigned long oldProtection;
VirtualProtect(machineCode, length, PAGE_EXECUTE_READWRITE, &oldProtection);
#elif __unix__
mprotect(machineCode, length, PROT_READ | PROT_WRITE | PROT_EXEC);
#endif
Instruction *instruction = instructions;
while(instruction)
{
Encoding &encoding = *instruction;
encoding.setAddress(currentCode);
const char *reference = encoding.getReference();
const char *label = encoding.getLabel();
if(reference)
{
if(encoding.relativeReference())
{
int offset = resolveReference(reference, instruction) - currentCode - encoding.length(currentCode);
encoding.setJumpOffset(offset);
}
else
{
int address = (int)resolveReference(reference, instruction);
// Encoded as memory reference or immediate?
if(encoding.hasDisplacement())
{
encoding.addDisplacement(address);
}
else if(encoding.hasImmediate())
{
encoding.setImmediate(address);
}
else
{
INTERNAL_ERROR;
}
}
}
else if(encoding.hasImmediate() && encoding.relativeReference())
{
__int64 offset = encoding.getImmediate() - (__int64)currentCode - encoding.length(currentCode);
encoding.setCallOffset(offset);
}
if(x64 && encoding.isRipRelative())
{
__int64 displacement = encoding.getDisplacement() - (__int64)currentCode - encoding.length(currentCode);
encoding.setDisplacement(displacement);
}
currentCode += encoding.writeCode(currentCode);
instruction = instruction->next();
}
}
const unsigned char *Loader::resolveReference(const char *name, const Instruction *position) const
{
const unsigned char *reference = resolveLocal(name, position);
if(reference)
{
return reference;
}
else
{
reference = resolveExternal(name);
}
if(reference)
{
return reference;
}
else
{
throw Error("Unresolved identifier '%s'", name);
}
}
const unsigned char *Loader::resolveLocal(const char *name, const Instruction *position) const
{
const Instruction *instruction = instructions;
unsigned char *target = machineCode;
unsigned char *local = 0; // Closest match before, or after position
while(instruction)
{
if(local && (instruction == position || position == 0))
{
return local;
}
else if(instruction == position)
{
position = 0; // Return first match following position
}
if(instruction->getLabel() && strcmp(instruction->getLabel(), name) == 0)
{
local = target;
}
else
{
target += instruction->length(target);
}
instruction = instruction->next();
}
if(local)
{
return local;
}
return 0;
}
const unsigned char *Loader::resolveExternal(const char *name) const
{
return (unsigned char*)linker.resolveExternal(name);
}
int Loader::codeLength() const
{
const Instruction *instruction = instructions;
unsigned char *end = machineCode;
while(instruction)
{
end += instruction->length(end);
instruction = instruction->next();
}
return end - machineCode;
}
const char *Loader::getListing()
{
if(!machineCode)
{
return 0;
}
if(listing)
{
return listing;
}
listing = new char[codeLength() * 4];
char *buffer = listing;
for(Instruction *instruction = instructions; instruction; instruction = instruction->next())
{
buffer += instruction->printCode(buffer);
}
*(buffer - 1) = '\0';
return listing;
}
void Loader::clearListing()
{
delete[] listing;
listing = 0;
}
void Loader::reset()
{
if(possession)
{
delete[] machineCode;
machineCode = 0;
}
machineCode = 0;
delete instructions;
instructions = 0;
delete[] listing;
listing = 0;
possession = true;
finalized = false;
}
int Loader::instructionCount()
{
Instruction *instruction = instructions;
int count = 0;
while(instruction)
{
if(instruction->isEmitting())
{
count++;
}
instruction = instruction->next();
}
return count;
}
}