[Devel] Re: [PATCH] namespaces: introduce sys_hijack (v4)
Cedric Le Goater
clg at fr.ibm.com
Fri Oct 12 02:30:33 PDT 2007
Serge E. Hallyn wrote:
> Quoting Serge E. Hallyn (serue at us.ibm.com):
>> >From 945fe66259cd0cfdc2fe846287b7821e329a558c Mon Sep 17 00:00:00 2001
>> From: sergeh at us.ibm.com <hallyn at kernel.(none)>
>> Date: Tue, 9 Oct 2007 08:30:30 -0700
>> Subject: [PATCH] namespaces: introduce sys_hijack (v4)
>>
>> Move most of do_fork() into a new do_fork_task() which acts on
>> a new argument, task, rather than on current. do_fork() becomes
>> a call to do_fork_task(current, ...).
>>
>> Introduce sys_hijack (for x86 only so far). It is like clone, but
>> in place of a stack pointer (which is assumed null) it accepts a
>> pid. The process identified by that pid is the one which is
>> actually cloned. Some state - include the file table, the signals
>> and sighand (and hence tty), and the ->parent are taken from the
>> calling process.
>>
>> The effect is a sort of namespace enter. The following program
>> uses sys_hijack to 'enter' all namespaces of the specified pid.
>> For instance in one terminal, do
>>
>> mount -t cgroup -ons /cgroup
>> hostname
>> qemu
>> ns_exec -u /bin/sh
>> hostname serge
>> echo $$
>> 1073
>> cat /proc/$$/cgroup
>> ns:/node_1073
>>
>> In another terminal then do
>>
>> hostname
>> qemu
>> cat /proc/$$/cgroup
>> ns:/
>> hijack 1073
>> hostname
>> serge
>> cat /proc/$$/cgroup
>> ns:/node_1073
>>
>> sys_hijack is arch-dependent and is only implemented for i386 so far.
>>
>> Changelog:
>> Aug 23: send a stop signal to the hijacked process
>> (like ptrace does).
>> Oct 09: Update for 2.6.23-rc8-mm2 (mainly pidns)
>> Don't take task_lock under rcu_read_lock
>> Send hijacked process to cgroup_fork() as
>> the first argument.
>> Removed some unneeded task_locks.
>
> Thanks to Cedric for finding an oops when using pid namespaces. The
> following patch fixes the problem.
it works fine now.
Thanks !
C.
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