Kernel: All syscalls now validate users pointers

We now validate pointers passed by the user, to forbid arbitary
memory read/write. Now the user is only allowed to pass in pointers
in their own mapped memory space (or null).

kernel/kernel/Syscall.cpp

@@ -188,7 +188,7 @@ namespace Kernel
 			ret = Process::current().sys_sync();
 			break;
 		case SYS_MMAP:
-			ret = Process::current().sys_mmap(*(const sys_mmap_t*)arg1);
+			ret = Process::current().sys_mmap((const sys_mmap_t*)arg1);
 			break;
 		case SYS_MUNMAP:
 			ret = Process::current().sys_munmap((void*)arg1, (size_t)arg2);