Re: status of Linux ptrace on amd64?

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

Alexander Nasonov wrote:
> Christos Zoulas wrote:
> > Should not be that hard, but what is that tool reading from PEEKUSER?
> > Registers?
> 
> In both cases it reads from user_regs_struct, if I understand everything
> correctly. But it's the first step, the tool would definitely try other
> things if PEEKUSER didn't fail. In fact, I'm not sure that thing would
> work at all because it's a dynamic instrumentation tool called Pin. It
> updates code on the fly.

OK, I implemented reading orig_ax by PEEKUSER. It fixed ptrace failure
but it added two problems:

1. I had to disable compat_linux32 to fix compilation. I need
   to make linux_sys_ptrace_arch multiarch-aware.
2. PEEKUSER didn't change anything. The tool still detaches its child
   and exits. I can't debug to see what's going on, gdb receives SIGUSR1
   from the tool. I suspect PEEKUSER returns unexpected value.

Alex