View OS: a Process with a View Files

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

From version 2.6.34:
- patchset having -utrace-ptrace* suffix are for kernels including utrace.
(must be used instead of the patch having just -ptrace*)
In this way it is possible to run kmview and optimized umview on the same
kernel.

From version 2.6.25:
- support for x86(32/64) ppc(32/64) um.
VM extensions to PTRACE_SYSCALL/SINGLESTEP/SINGLEBLOCK/CONT instead
of the deprecated PTRACE_SYSVM tag
- separate patches for ptrace_vm and ptrace_multi
The two patches are independent: can be applied in any order.

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.
PT_SYSVM has been deprecated in favour of extending the syntax of the
standard ptrace tags. This will lead eventually to a simple code both for the
kernel and for applications using this feature.

Credits: Cristian Greco for some patch updates.

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, version 2, as
 *   published by the Free Software Foundation.
 *
 *   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.,
 *   51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA.
 *
 */