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#include "detours.h"
#include "hde32.h"
// very MUCH comment i APPRECIATE cool
memory::c_detours memory::detours;
__forceinline static bool is_code_padding( uintptr_t address, size_t size )
{
uint8_t* code_ptr = (uint8_t*)address;
if ( code_ptr[0] != 0x00 && code_ptr[0] != 0x90 && code_ptr[0] != 0xCC )
return false;
for ( int i = 1; i < size; ++i )
{
if ( code_ptr[i] != code_ptr[0] )
return false;
}
return true;
}
bool memory::c_detours::create_trampoline( detour_hook_t* hook )
{
if ( !hook->allocate_trampoline( ) )
return false;
instructions::long_jump_t call = {
0xE8,
0x00000000
};
instructions::long_jump_t jmp = {
0xE9,
0x00000000
};
instructions::JCC_REL jcc = {
0x0F, 0x80,
0x00000000
};
uint8_t old_position = 0;
uint8_t new_position = 0;
uintptr_t jmp_dest = 0;
bool finished = false;
hook->short_patch = false;
const int max_instruction_boundaries = 8;
int instruction_boundaries = 0;
do
{
hde32s hs;
uint8_t copy_size;
uintptr_t copy_src;
uintptr_t old_instruction = hook->m_original + old_position;
uintptr_t new_instruction = hook->m_trampoline + new_position;
copy_size = hde32_disasm( (void*)old_instruction, &hs );
if ( hs.flags & F_ERROR )
return false;
copy_src = old_instruction;
if ( old_position >= sizeof( instructions::long_jump_t ) )
{
// the trampoline function is long enough.
// complete the function with the jump to the target function.
jmp.opcode = 0xE9;
jmp.operand = (uint32_t)( old_instruction - ( new_instruction + sizeof( instructions::long_jump_t ) ) );
copy_src = uintptr_t( &jmp );
copy_size = sizeof( jmp );
finished = true;
}
else if ( hs.opcode == 0xE8 )
{
// direct relative CALL
uintptr_t dest = old_instruction + hs.len + (int32_t)hs.imm.imm32;
call.opcode = 0xE8;
call.operand = (uint32_t)( dest - ( new_instruction + sizeof( instructions::long_jump_t ) ) );
copy_src = uintptr_t( &call );
copy_size = sizeof( call );
}
else if ( ( hs.opcode & 0xFD ) == 0xE9 )
{
// direct relative JMP (EB or E9)
uintptr_t dest = old_instruction + hs.len;
if ( hs.opcode == 0xEB ) // short jmp
dest += (int8_t)hs.imm.imm8;
else
dest += (int32_t)hs.imm.imm32;
// simply copy an internal jump.
if ( hook->m_original <= dest && dest < hook->m_original + sizeof( instructions::long_jump_t ) )
{
if ( jmp_dest < dest )
jmp_dest = dest;
}
else
{
jmp.operand = (uint32_t)( dest - ( new_instruction + sizeof( instructions::long_jump_t ) ) );
copy_src = uintptr_t( &jmp );
copy_size = sizeof( instructions::long_jump_t );
// exit the function if it is not in the branch
finished = ( old_instruction >= jmp_dest );
}
}
else if ( ( hs.opcode & 0xF0 ) == 0x70 || ( hs.opcode & 0xFC ) == 0xE0 || ( hs.opcode2 & 0xF0 ) == 0x80 )
{
// direct relative JCC
uintptr_t dest = old_instruction + hs.len;
if ( ( hs.opcode & 0xF0 ) == 0x70 // JCC
|| ( hs.opcode & 0xFC ) == 0xE0 ) // LOOPNZ/LOOPZ/LOOP/JECXZ
dest += (int8_t)hs.imm.imm8;
else
dest += (int32_t)hs.imm.imm32;
// simply copy an internal jump.
if ( (uintptr_t)hook->m_original <= dest && dest < ( (uintptr_t)hook->m_original + sizeof( instructions::long_jump_t ) ) )
{
if ( jmp_dest < dest )
jmp_dest = dest;
}
else if ( ( hs.opcode & 0xFC ) == 0xE0 )
{
// LOOPNZ/LOOPZ/LOOP/JCXZ/JECXZ to the outside are not supported.
return false;
}
else
{
uint8_t cond = ( ( hs.opcode != 0x0F ? hs.opcode : hs.opcode2 ) & 0x0F );
jcc.opcode1 = 0x80 | cond;
jcc.operand = (uint32_t)( dest - ( new_instruction + sizeof( jcc ) ) );
copy_src = uintptr_t( &jcc );
copy_size = sizeof( jcc );
}
}
else if ( ( hs.opcode & 0xFE ) == 0xC2 )
{
// RET (C2 or C3)
// complete the function if not in a branch.
finished = ( old_instruction >= jmp_dest );
}
// can't alter the instruction length in a branch.
if ( old_instruction < jmp_dest && copy_size != hs.len )
return false;
// trampoline function is too large.
if ( new_position + copy_size > MEMORY_SLOT_SIZE )
return false;
// trampoline function has too many instructions.
if ( instruction_boundaries >= max_instruction_boundaries )
return false;
instruction_boundaries++;
memcpy( (void*)( hook->m_trampoline + new_position ), (void*)copy_src, copy_size );
new_position += copy_size;
old_position += hs.len;
}
while ( !finished );
// can we do a regular 5 byte jmp patch?
if ( old_position < sizeof( instructions::long_jump_t ) && !is_code_padding( (uintptr_t)hook->m_original + old_position, sizeof( instructions::long_jump_t ) - old_position ) )
{
// can we put 2 byte jmp patch?
if ( old_position < sizeof( instructions::short_jump_t ) && !is_code_padding( (uintptr_t)hook->m_original + old_position, sizeof( instructions::short_jump_t ) - old_position ) )
return false;
// can we put a 5 byte jmp patch above it?
if ( !is_code_padding( (uintptr_t)hook->m_original - sizeof( instructions::long_jump_t ), sizeof( instructions::long_jump_t ) ) )
return false;
hook->short_patch = true;
}
return true;
}
bool memory::c_detours::set_hook( detour_hook_t* hook, bool enable )
{
// hook is already in place silly
if ( hook->enabled == enable )
return true;
if ( enable )
{
if ( hook->short_patch )
{
uint8_t* target = (uint8_t*)( hook->m_original - sizeof( instructions::long_jump_t ) );
// prepare patch
instructions::short_patch_t jmp_patch;
jmp_patch.jmp.opcode = 0xE9;
jmp_patch.jmp.operand = (uint32_t)( hook->m_custom - hook->m_original - sizeof( instructions::long_jump_t ) );
jmp_patch.jmp_short.opcode = 0xEB;
jmp_patch.jmp_short.operand = (uint8_t)( 0 - sizeof( instructions::short_patch_t ) );
// overwrite protection
DWORD original_protection;
VirtualProtect( target, sizeof( instructions::short_patch_t ), PAGE_EXECUTE_READWRITE, &original_protection );
// place hook
memcpy( target, &jmp_patch, sizeof( instructions::short_patch_t ) );
// restore protection
VirtualProtect( target, sizeof( instructions::short_patch_t ), original_protection, &original_protection );
// let cpu know we altered code
FlushInstructionCache( GetCurrentProcess( ), target, sizeof( instructions::short_patch_t ) );
}
else
{
// prepare patch
instructions::long_jump_t jmp_patch;
jmp_patch.opcode = 0xE9;
jmp_patch.operand = (uint32_t)( hook->m_custom - hook->m_original - sizeof( instructions::long_jump_t ) );
// overwrite protection
DWORD original_protection;
VirtualProtect( (void*)hook->m_original, sizeof( instructions::long_jump_t ), PAGE_EXECUTE_READWRITE, &original_protection );
// place hook
memcpy( (void*)hook->m_original, &jmp_patch, sizeof( instructions::long_jump_t ) );
// restore protection
VirtualProtect( (void*)hook->m_original, sizeof( instructions::long_jump_t ), original_protection, &original_protection );
// let cpu know we altered code
FlushInstructionCache( GetCurrentProcess( ), (void*)hook->m_original, sizeof( instructions::long_jump_t ) );
}
}
else
{
if ( hook->short_patch )
{
uint8_t* target = (uint8_t*)( hook->m_original - sizeof( instructions::long_jump_t ) );
// overwrite protection
DWORD original_protection;
VirtualProtect( target, sizeof( instructions::short_patch_t ), PAGE_EXECUTE_READWRITE, &original_protection );
// restore backup
memcpy( target, hook->m_original_bytes, sizeof( instructions::short_patch_t ) );
// restore protection
VirtualProtect( target, sizeof( instructions::short_patch_t ), original_protection, &original_protection );
// let cpu know we altered code
FlushInstructionCache( GetCurrentProcess( ), target, sizeof( instructions::short_patch_t ) );
}
else
{
uint8_t* target = (uint8_t*)hook->m_original;
// overwrite protection
DWORD original_protection;
VirtualProtect( target, sizeof( instructions::long_jump_t ), PAGE_EXECUTE_READWRITE, &original_protection );
// restore backup
memcpy( target, hook->m_original_bytes, sizeof( instructions::long_jump_t ) );
// restore protection
VirtualProtect( target, sizeof( instructions::long_jump_t ), original_protection, &original_protection );
// let cpu know we altered code
FlushInstructionCache( GetCurrentProcess( ), target, sizeof( instructions::long_jump_t ) );
}
}
hook->enabled = enable;
return true;
}
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