[$] Running code within another process's address space

One of the key resources that defines a process is its address space - theset of mappings that determines what any specific memory address meanswithin that process. An address space is normally privateto the process it belongs to, but there are situations where one processneeds to make changes to another process's memory; an interactive debuggerwould be one case in point. The ptrace()system call makes such changes possible, but it is slow and not always easyto use, so there has been a longstanding quest for better alternatives.One possibility, process_vm_exec()from Andrei Vagin, was recently posted for review.