int hot_patch(struct patch_entry *begin, struct patch_entry *end)
{
struct patch_entry *i;
for(i = begin; i != end; i++) {
wchar_t wmodule[PATH_MAX];
MultiByteToWideChar(CP_UTF8, 0, i->module, -1, wmodule, PATH_MAX);
HMODULE mod = GetModuleHandle(wmodule);
if(!mod)
continue;
void *old_proc = GetProcAddress(mod, i->name);
if(!old_proc)
continue;
if(hot_patch_int(old_proc, i->new_proc, i->orig_proc) != 0) {
DEBUG_HOOK("not hot-patchable (%s)\n", i->name);
} else {
DEBUG_HOOK("hot-patched (%s)\n", i->name);
i->skip = 1;
}
}
return 0;
}
static int hot_patch_int( void *old_proc, void *new_proc, void **orig_proc )
{
static const BYTE signature[] =
{
0x90, // nop
0x90,
0x90,
0x90,
0x90,
// <- function start here
0x8b, 0xff // movl %edi,%edi
};
BYTE *begin = (BYTE*)old_proc - 5;
DWORD old_protect;
if( !VirtualProtect( (PVOID)begin, sizeof( signature ),
PAGE_EXECUTE_WRITECOPY, &old_protect ) )
return -1;
int ret = -1;
if( memcmp( (PVOID)begin, signature, sizeof( signature ) ) )
{
DEBUG_HOOK( "%x %x %x %x %x %x %x\n",
begin[0], begin[1],begin[2],begin[3],begin[4],begin[5],begin[6] );
goto exit;
}
*( begin + 0 ) = 0xe9; // long jump
*(DWORD*)( begin + 1 ) = (DWORD)new_proc - (DWORD)old_proc;
*(WORD*)( begin + 5 ) = 0xf9eb; // short jump back
if( orig_proc )
*orig_proc = (BYTE*)old_proc + 2;
ret = 0;
exit:;
VirtualProtect( begin, sizeof( signature ), old_protect, &old_protect );
return ret;
}
int hot_patch( patch_entry *begin, patch_entry *end )
{
patch_entry *i;
for( i = begin; i != end; i++ )
{
HMODULE mod = GetModuleHandle( i->module );
if( !mod )
continue;
void *old_proc = GetProcAddress( mod, i->name );
if( !old_proc )
continue;
if( hot_patch_int( old_proc, i->new_proc, i->orig_proc ) != 0 )
DEBUG_HOOK( "not hot-patchable (%s)\n", i->name );
else
{
i->skip = 1;
}
}
return 0;
}
