The patches here included add the PTRACE_MULTI tag to the
ptrace system call into the linux kernel of the hosting machine.

This patch add PTRACE MULTI for the following architectures:
i386 ppc um (subarch i386)

UMVIEW does not need any patch in the kernel of the hosting computer to 
work but with PTRACE_MULTI there is a dramatic increase in performance.

(Tech detail: standard ptrace needs one system call invocation for
each word of memory to be tranferred between the process memory
and the umview memory. System calls like read/write need one context
switch each 4 bytes - on 32bits machine. With PTRACE_MULTI one single
system call invocation suffices).

PT_VM is a more advanced patch.
It is a more efficient support of PTRACE for Virtual Machine.
with PT_VM it is possible to use the PTRACE_SYSVM call instead
of PTRACE_SYSCALL. PTRACE_SYSVM has a parameter that can be set to skip
the syscall execution and/or the after-syscall trace upcall.

As usual:

/*   This is part of um-ViewOS
 *   The user-mode implementation of OSVIEW -- A Process with a View
 *
 *   LINUX KERNEL PATCH for PTRACE_MULTI support.
 *   
 *   Copyright 2005 Renzo Davoli
 *   
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License along
 *   with this program; if not, write to the Free Software Foundation, Inc.,
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */
