/*****************************************************************************
* Copyright (c) 2014 Ted John
* OpenRCT2, an open source clone of Roller Coaster Tycoon 2.
*
* This file is part of OpenRCT2.
*
* OpenRCT2 is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program 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 for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see .
*****************************************************************************/
#ifdef _WIN32
#include
#else
#include
#endif // _WIN32
#include "hook.h"
#include "platform/platform.h"
void* g_hooktableaddress = 0;
int g_hooktableoffset = 0;
int g_maxhooks = 1000;
// This macro writes a little-endian 4-byte long value into *data
// It is used to avoid type punning.
#define write_address_strictalias(data, addr) \
*(data + 0) = ((addr) & 0x000000ff) >> 0; \
*(data + 1) = ((addr) & 0x0000ff00) >> 8; \
*(data + 2) = ((addr) & 0x00ff0000) >> 16; \
*(data + 3) = ((addr) & 0xff000000) >> 24;
void hookfunc(int address, int newaddress, int stacksize, int registerargs[], int registersreturned, int eaxDestinationRegister)
{
int i = 0;
char data[100];
registersreturned |= eaxDestinationRegister;
int registerssaved = 7;
int n = registersreturned;
for (; n; registerssaved--) {
n &= n - 1;
}
int numrargs = 0;
for (int j = 0; ; j++) {
if (registerargs[j] != END) {
numrargs++;
} else {
break;
}
}
int rargssize = numrargs * 4;
if (!(registersreturned & EAX)) {
data[i++] = 0x50; // push eax
}
if (!(registersreturned & EBX)) {
data[i++] = 0x53; // push ebx
}
if (!(registersreturned & ECX)) {
data[i++] = 0x51; // push ecx
}
if (!(registersreturned & EDX)) {
data[i++] = 0x52; // push edx
}
if (!(registersreturned & EBP)) {
data[i++] = 0x55; // push ebp
}
if (!(registersreturned & ESI)) {
data[i++] = 0x56; // push esi
}
if (!(registersreturned & EDI)) {
data[i++] = 0x57; // push edi
}
data[i++] = 0x50; //push eax
data[i++] = 0x89; //mov eax, esp
data[i++] = 0xE0;
data[i++] = 0x83; //sub eax, (0xC + numargs*4) & 0xF
data[i++] = 0xE8;
data[i++] = (0xC + numrargs * 4) & 0xF;
data[i++] = 0x83; //and eax, 0xC
data[i++] = 0xE0;
data[i++] = 0x0C;
data[i++] = 0xA3; //mov [0x9ABDA8], eax
data[i++] = 0xA8;
data[i++] = 0xBD;
data[i++] = 0x9A;
data[i++] = 0x00;
data[i++] = 0x58; //pop eax
data[i++] = 0x2B; //sub esp, [0x9ABDA8]
data[i++] = 0x25;
data[i++] = 0xA8;
data[i++] = 0xBD;
data[i++] = 0x9A;
data[i++] = 0x00;
// work out distance to nearest 0xC
// (esp - numargs * 4) & 0xC
// move to align - 4
// save that amount
if (numrargs > 0) {
// push the registers to be on the stack to access as arguments
for (signed int j = numrargs - 1; j >= 0; j--) {
switch (registerargs[j]) {
case EAX: data[i++] = 0x50; break;
case EBX: data[i++] = 0x53; break;
case ECX: data[i++] = 0x51; break;
case EDX: data[i++] = 0x52; break;
case ESI: data[i++] = 0x56; break;
case EDI: data[i++] = 0x57; break;
case EBP: data[i++] = 0x55; break;
}
}
}
data[i++] = 0xE8; // call
write_address_strictalias(&data[i], newaddress - address - i - 4);
i += 4;
// returnlocation:
switch (eaxDestinationRegister) {
case EBX:
// mov ebx, eax
data[i++] = 0x8B;
data[i++] = 0xD8;
break;
case ECX:
// mov ecx, eax
data[i++] = 0x8B;
data[i++] = 0xC8;
break;
case EDX:
// mov ecx, eax
data[i++] = 0x8B;
data[i++] = 0xD0;
break;
case ESI:
// mov ecx, eax
data[i++] = 0x8B;
data[i++] = 0xF0;
break;
case EDI:
// mov ecx, eax
data[i++] = 0x8B;
data[i++] = 0xF8;
break;
case EBP:
// mov ecx, eax
data[i++] = 0x8B;
data[i++] = 0xE8;
break;
}
data[i++] = 0x83; // sub esp, x
data[i++] = 0xEC;
data[i++] = (signed char)(stacksize * -4) - rargssize;
data[i++] = 0x03; //add esp, [0x9ABDA8]
data[i++] = 0x25;
data[i++] = 0xA8;
data[i++] = 0xBD;
data[i++] = 0x9A;
data[i++] = 0x00;
if (!(registersreturned & EDI)) {
data[i++] = 0x5F; // pop edi
}
if (!(registersreturned & ESI)) {
data[i++] = 0x5E; // pop esi
}
if (!(registersreturned & EBP)) {
data[i++] = 0x5D; // pop ebp
}
if (!(registersreturned & EDX)) {
data[i++] = 0x5A; // pop edx
}
if (!(registersreturned & ECX)) {
data[i++] = 0x59; // pop ecx
}
if (!(registersreturned & EBX)) {
data[i++] = 0x5B; // pop ebx
}
if (!(registersreturned & EAX)) {
data[i++] = 0x58; // pop eax
}
data[i++] = 0xC3; // retn
#ifdef _WIN32
WriteProcessMemory(GetCurrentProcess(), (LPVOID)address, data, i, 0);
#else
// We own the pages with PROT_WRITE | PROT_EXEC, we can simply just memcpy the data
memcpy((void *)address, data, i);
#endif // _WIN32
}
void addhook(int address, int newaddress, int stacksize, int registerargs[], int registersreturned, int eaxDestinationRegister)
{
if (!g_hooktableaddress) {
size_t size = g_maxhooks * 100;
#ifdef _WIN32
g_hooktableaddress = VirtualAllocEx(GetCurrentProcess(), NULL, size, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
#else
g_hooktableaddress = mmap(NULL, size, PROT_EXEC | PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (g_hooktableaddress == MAP_FAILED)
{
perror("mmap");
exit(1);
}
#endif // _WIN32
}
if (g_hooktableoffset > g_maxhooks) {
return;
}
unsigned int hookaddress = (unsigned int)g_hooktableaddress + (g_hooktableoffset * 100);
char data[9];
int i = 0;
data[i++] = 0xE9; // jmp
write_address_strictalias(&data[i], hookaddress - address - i - 4);
i += 4;
data[i++] = 0xC3; // retn
#ifdef _WIN32
WriteProcessMemory(GetCurrentProcess(), (LPVOID)address, data, i, 0);
#else
// We own the pages with PROT_WRITE | PROT_EXEC, we can simply just memcpy the data
memcpy((void *)address, data, i);
#endif // _WIN32
hookfunc(hookaddress, newaddress, stacksize, registerargs, registersreturned, eaxDestinationRegister);
g_hooktableoffset++;
}