amxmodx/modules/hamsandwich/Trampolines.h

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// vim: set ts=4 sw=4 tw=99 noet:
//
// AMX Mod X, based on AMX Mod by Aleksander Naszko ("OLO").
// Copyright (C) The AMX Mod X Development Team.
//
// This software is licensed under the GNU General Public License, version 3 or higher.
// Additional exceptions apply. For full license details, see LICENSE.txt or visit:
// https://alliedmods.net/amxmodx-license
//
// Ham Sandwich Module
//
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#ifndef TRAMPOLINES_H
#define TRAMPOLINES_H
#ifndef NDEBUG
#define TPRINT(msg) printf msg
#else
#define TPRINT(msg) /* nothing */
#endif
#if defined _WIN32
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif // WIN32_LEAN_AND_MEAN
#if _MSC_VER >= 1400
#ifdef offsetof
#undef offsetof
#endif // offsetof
#endif // _MSC_VER >= 1400
#include <windows.h>
#elif defined(__linux__) || defined(__APPLE__)
#include <sys/mman.h>
#if defined (__linux__)
#include <malloc.h>
#endif
#endif
#include <stddef.h> // size_t
#include <string.h> // memcpy
#include <stdlib.h> // memalign
#include <stdio.h>
#include <amtl/am-bits.h>
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namespace Trampolines
{
/**
* List of x86 bytecodes for creating
* basic trampolines at runtime.
* -
* These are defined here so that, should
* the need ever arise, this can be ported
* to other architectures fairly painlessly
*/
namespace Bytecode
{
/**
* Prologue for a function
*/
const unsigned char codePrologue[] = {
0x55, // push ebp
0x89, 0xE5, // mov ebp, esp
};
/**
* Align stack on 16 byte boundary
*/
const unsigned char codeAlignStack16[] = {
0x83, 0xE4, 0xF0, // and esp, 0xFFFFFFF0
};
/**
* Allocate stack space (8-bit) by adding to ESP
*/
const unsigned char codeAllocStack[] = {
0x83, 0xEC, 0xFF, // sub esp, 0xFF
};
/**
* Offset of codeAllocStack to modify at runtime
* to contain amount of stack space to allocate.
*/
const unsigned int codeAllocStackReplace = 2;
/**
* Takes a paramter from the trampoline's stack
* and pushes it onto the target's stack.
*/
const unsigned char codePushParam[] = {
0xFF, 0x75, 0xFF // pushl [ebp+0xFF]
};
/**
* Offset of codePushParam to modify at runtime
* that contains the stack offset
*/
const unsigned int codePushParamReplace = 2;
/**
* Takes the "this" pointer from the trampoline and
* pushes it onto the target's stack.
*/
const unsigned char codePushThis[] = {
#if defined(_WIN32)
0x51 // push ecx
#elif defined(__linux__) || defined(__APPLE__)
0xFF, 0x75, 0x04 // pushl [ebp+0x08h]
#endif
};
#if defined(__linux__) || defined(__APPLE__)
const int codePushThisReplace = 2;
#endif
/**
* Pushes a raw number onto the target's stack
*/
const unsigned char codePushID[] = {
0x68, 0xDE, 0xFA, 0xAD, 0xDE // push DEADFADEh
};
/**
* Offset of codePushID to modify at runtime
* to contain the number to push
*/
const unsigned int codePushIDReplace = 1;
/**
* Call our procedure
*/
const unsigned char codeCall[] = {
0xB8, 0xDE, 0xFA, 0xAD, 0xDE,// mov eax, DEADFADEh
0xFF, 0xD0 // call eax
};
/**
* Offset of codeCall to modify at runtime
* to contain the pointer to the function
*/
const unsigned int codeCallReplace = 1;
/**
* Adds to ESP, freeing up stack space
*/
const unsigned char codeFreeStack[] = {
0x81, 0xC4, 0xFF, 0xFF, 0xFF, 0xFF// add esp REPLACEME
};
/**
* Offset of codeFreeStack to modify at runtime
* to contain how much data to free
*/
const unsigned int codeFreeStackReplace = 2;
/**
* Epilogue of a simple function
*/
const unsigned char codeEpilogue[] = {
0x89, 0xEC, // mov esp, ebp
0x5D, // pop ebp
0xC3 // ret
};
const unsigned char codeEpilogueN[] = {
0x89, 0xEC, // mov esp, ebp
0x5D, // pop ebp
0xC2, 0xCD, 0xAB // retn 0xABCD
};
const int codeEpilogueNReplace = 4;
const unsigned char codeBreakpoint[] = {
0xCC // int 3
};
}
/**
* Our actual maker of the trampolines!!@$
* I've no idea why I made this a class and not a namespace
* Oh well!
*/
class TrampolineMaker
{
private:
unsigned char *m_buffer; // the actual buffer containing the code
int m_size; // size of the buffer
int m_mystack; // stack for the trampoline itself
int m_calledstack; // stack for the target function
int m_paramstart;
int m_thiscall;
int m_maxsize;
/**
* Adds data to the buffer
* data must be pre-formatted before hand!
*/
void Append(const unsigned char *src, size_t size)
{
int orig=m_size;
m_size+=size;
if (m_buffer==NULL)
{
m_maxsize=512;
m_buffer=(unsigned char *)malloc(m_maxsize);
}
else if (m_size > m_maxsize)
{
m_maxsize = m_size + 512;
m_buffer=(unsigned char *)realloc(m_buffer,m_maxsize);
}
unsigned char *dat=m_buffer+orig; // point dat to the end of the prewritten
while (orig<m_size)
{
*dat++=*src++;
orig++;
};
};
public:
TrampolineMaker()
{
m_buffer=NULL;
m_size=0;
m_mystack=0;
m_calledstack=0;
m_paramstart=0;
m_thiscall=0;
m_maxsize=0;
};
/**
* Inserts a breakpoint (int 3) into the trampoline.
*/
void Breakpoint()
{
Append(&::Trampolines::Bytecode::codeBreakpoint[0],sizeof(::Trampolines::Bytecode::codeBreakpoint));
};
/**
* Adds the prologue, pushes registers, prepares the stack
*/
void Prologue()
{
Append(&::Trampolines::Bytecode::codePrologue[0],sizeof(::Trampolines::Bytecode::codePrologue));
m_paramstart=0;
m_thiscall=0;
};
/**
* Flags this trampoline as a thiscall trampoline, and prepares the prologue.
*/
void ThisPrologue()
{
this->Prologue();
m_thiscall=1;
};
/**
* Epilogue for a function pops registers but does not free any more of the stack!
*/
void Epilogue()
{
Append(&::Trampolines::Bytecode::codeEpilogue[0],sizeof(::Trampolines::Bytecode::codeEpilogue));
};
/**
* Epilogue that also frees it's estimated stack usage. Useful for stdcall/thiscall/fastcall.
*/
void EpilogueAndFree()
{
this->Epilogue(m_mystack);
};
/**
* Epilogue. Pops registers, and frees given amount of data from the stack.
*
* @param howmuch How many bytes to free from the stack.
*/
void Epilogue(int howmuch)
{
unsigned char code[sizeof(::Trampolines::Bytecode::codeEpilogueN)];
memcpy(&code[0],&::Trampolines::Bytecode::codeEpilogueN[0],sizeof(::Trampolines::Bytecode::codeEpilogueN));
unsigned char *c=&code[0];
union
{
int i;
unsigned char b[4];
} bi;
bi.i=howmuch;
c+=::Trampolines::Bytecode::codeEpilogueNReplace;
*c++=bi.b[0];
*c++=bi.b[1];
Append(&code[0],sizeof(::Trampolines::Bytecode::codeEpilogueN));
};
/**
* Aligns stack on 16 byte boundary for functions that use aligned SSE instructions.
* This also allocates extra stack space to allow the specified number of slots to be used
* for function paramaters that will be pushed onto the stack.
*/
void AlignStack16(int slots)
{
const size_t stackNeeded = slots * sizeof(void *);
const size_t stackReserve = ke::Align(stackNeeded, 16);
const size_t stackExtra = stackReserve - stackNeeded;
// Stack space should fit in a byte
assert(stackExtra <= 0xFF);
const size_t codeAlignStackSize = sizeof(::Trampolines::Bytecode::codeAlignStack16);
const size_t codeAllocStackSize = sizeof(::Trampolines::Bytecode::codeAllocStack);
unsigned char code[codeAlignStackSize + codeAllocStackSize];
memcpy(&code[0], &::Trampolines::Bytecode::codeAlignStack16[0], codeAlignStackSize);
if (stackExtra > 0)
{
unsigned char *c = &code[codeAlignStackSize];
memcpy(c, &::Trampolines::Bytecode::codeAllocStack[0], codeAllocStackSize);
c += ::Trampolines::Bytecode::codeAllocStackReplace;
*c = (unsigned char)stackExtra;
Append(&code[0], codeAlignStackSize + codeAllocStackSize);
}
else
{
Append(&code[0], codeAlignStackSize);
}
}
/**
* Pushes the "this" pointer onto the callee stack. Pushes ECX for MSVC, and param0 on GCC.
*/
void PushThis()
{
if (!m_thiscall)
{
return;
}
unsigned char code[sizeof(::Trampolines::Bytecode::codePushThis)];
memcpy(&code[0],&::Trampolines::Bytecode::codePushThis[0],sizeof(::Trampolines::Bytecode::codePushThis));
#if defined(__linux__) || defined(__APPLE__)
unsigned char *c=&code[0];
union
{
int i;
unsigned char b[4];
} bi;
bi.i=m_paramstart+8;
c+=::Trampolines::Bytecode::codePushThisReplace;
*c++=bi.b[0];
#endif
Append(&code[0],sizeof(::Trampolines::Bytecode::codePushThis));
#if defined(__linux__) || defined(__APPLE__)
m_mystack+=4;
#endif
m_calledstack+=4;
};
/**
* Frees what is estimated as the stack usage of the trampoline.
*/
void FreeMyStack(void)
{
this->FreeStack(m_mystack);
};
/**
* Frees the estimated stack usage of the callee.
*/
void FreeTargetStack(void)
{
this->FreeStack(m_calledstack);
};
/**
* Frees the estimated stack usage of the callee and the trampoline.
*/
void FreeBothStacks(void)
{
this->FreeStack(m_calledstack + m_mystack);
};
/**
* Frees a given amount of bytes from the stack.
*
* @param howmuch How many bytes to free.
*/
void FreeStack(int howmuch)
{
unsigned char code[sizeof(::Trampolines::Bytecode::codeFreeStack)];
memcpy(&code[0],&::Trampolines::Bytecode::codeFreeStack[0],sizeof(::Trampolines::Bytecode::codeFreeStack));
unsigned char *c=&code[0];
union
{
int i;
unsigned char b[4];
} bi;
bi.i=howmuch;
c+=::Trampolines::Bytecode::codeFreeStackReplace;
*c++=bi.b[0];
*c++=bi.b[1];
*c++=bi.b[2];
*c++=bi.b[3];
Append(&code[0],sizeof(::Trampolines::Bytecode::codeFreeStack));
};
/**
* Pushes a raw number onto the callee stack.
*
* @param Number The number to push onto the callee stack.
*/
void PushNum(int Number)
{
unsigned char code[sizeof(::Trampolines::Bytecode::codePushID)];
memcpy(&code[0],&::Trampolines::Bytecode::codePushID[0],sizeof(::Trampolines::Bytecode::codePushID));
unsigned char *c=&code[0];
union
{
int i;
unsigned char b[4];
} bi;
bi.i=Number;
c+=::Trampolines::Bytecode::codePushIDReplace;
*c++=bi.b[0];
*c++=bi.b[1];
*c++=bi.b[2];
*c++=bi.b[3];
Append(&code[0],sizeof(::Trampolines::Bytecode::codePushID));
m_calledstack+=4; // increase auto detected stack size
};
/**
* Takes a parameter passed on the trampoline's stack and inserts it into the callee's stack.
*
* @param which The parameter number to push. 1-based. "thiscall" trampolines automatically compensate for the off-number on GCC.
*/
void PushParam(int which)
{
#if defined(__linux__) || defined(__APPLE__)
if (m_thiscall)
{
which++;
}
#endif
which=which*4;
which+=m_paramstart+4;
unsigned char value=which;
unsigned char code[sizeof(::Trampolines::Bytecode::codePushParam)];
memcpy(&code[0],&::Trampolines::Bytecode::codePushParam[0],sizeof(::Trampolines::Bytecode::codePushParam));
unsigned char *c=&code[0];
c+=::Trampolines::Bytecode::codePushParamReplace;
*c=value;
Append(&code[0],sizeof(::Trampolines::Bytecode::codePushParam));
m_calledstack+=4; // increase auto detected stack size
m_mystack+=4;
};
/**
* Insert a function to call into the trampoline.
*
* @param ptr The function to call, cast to void*.
*/
void Call(void *ptr)
{
unsigned char code[sizeof(::Trampolines::Bytecode::codeCall)];
memcpy(&code[0],&::Trampolines::Bytecode::codeCall[0],sizeof(::Trampolines::Bytecode::codeCall));
unsigned char *c=&code[0];
union
{
void *p;
unsigned char b[4];
} bp;
bp.p=ptr;
c+=::Trampolines::Bytecode::codeCallReplace;
*c++=bp.b[0];
*c++=bp.b[1];
*c++=bp.b[2];
*c++=bp.b[3];
Append(&code[0],sizeof(::Trampolines::Bytecode::codeCall));
};
/**
* Finalizes the trampoline. Do not try to modify it after this.
*
* @param size A pointer to retrieve the size of the trampoline. Ignored if set to NULL.
* @return The trampoline pointer, cast to void*.
*/
void *Finish(int *size)
{
//void *ret=(void *)m_buffer;
if (size)
{
*size=m_size;
}
// Reallocate with proper flags
#if defined(_WIN32)
void *ret=VirtualAlloc(NULL, m_size, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
#elif defined(__GNUC__)
# if defined(__APPLE__)
void *ret = valloc(m_size);
mprotect(ret,m_size,PROT_READ|PROT_WRITE|PROT_EXEC);
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# else
void *ret=mmap(nullptr, m_size, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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# endif
#endif
memcpy(ret, m_buffer, m_size);
m_size=0;
free(m_buffer);
m_buffer=NULL; // so we don't accidentally rewrite!
m_mystack=0;
m_calledstack=0;
m_maxsize=512;
return ret;
};
};
};
/**
* Utility to make a generic trampoline.
*/
inline void *CreateGenericTrampoline(bool thiscall, bool voidcall, bool retbuf, int paramcount, void *extraptr, void *callee, int *size)
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{
Trampolines::TrampolineMaker tramp;
if (thiscall)
{
tramp.ThisPrologue();
tramp.AlignStack16(paramcount + 2); // Param count + this ptr + extra ptr
}
else
{
tramp.Prologue();
tramp.AlignStack16(paramcount + 1); // Param count + extra ptr
}
while (paramcount)
{
tramp.PushParam(paramcount--);
}
if (thiscall)
{
tramp.PushThis();
}
tramp.PushNum(reinterpret_cast<int>(extraptr));
tramp.Call(callee);
tramp.FreeTargetStack();
#if defined(_WIN32)
tramp.EpilogueAndFree();
#elif defined(__linux__) || defined(__APPLE__)
if (retbuf)
{
tramp.Epilogue(4);
}
else
{
tramp.Epilogue();
}
#endif
return tramp.Finish(size);
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};
#endif // TRAMPOLINEMANAGER_H