From: u3557@miso.sublimeip.com (Amnon Shiloh)
To: rostedt@goodmis.org (Steven Rostedt)
Cc: u3557@dialix.com.au, oleg@redhat.com (Oleg Nesterov),
palves@redhat.com (Pedro Alves),
dvlasenk@redhat.com (Denys Vlasenko),
jan.kratochvil@redhat.com (Jan Kratochvil),
gorcunov@openvz.org (Cyrill Gorcunov),
xemul@parallels.com (Pavel Emelyanov),
fweisbec@gmail.com (Frederic Weisbecker),
mingo@redhat.com (Ingo Molnar),
a.p.zijlstra@chello.nl (Peter Zijlstra),
linux-kernel@vger.kernel.org
Subject: Re: prctl(PR_SET_MM)
Date: Tue, 19 Feb 2013 03:33:59 +1100 (EST) [thread overview]
Message-ID: <20130218163359.25760592076@miso.sublimeip.com> (raw)
In-Reply-To: <1361200876.23152.149.camel@gandalf.local.home>
Steven Rostedt wrote:
> On Mon, 2013-02-18 at 12:39 +1100, Amnon Shiloh wrote:
> > Hello,
> >
> > The code in "kernel/sys.c" provides the "prctl(PR_SET_MM)" function,
> > which is the only way a process can set or modify the following 11
> > per-process fields:
> >
> > start_code, end_code, start_data, end_data, start_brk, brk,
> > start_stack, arg_start, arg_end, env_start, env_end.
> >
> > Being able to set those fields is important, even crucial,
> > for any conceivable user-level checkpointing software, as
> > well as for migrating processes between different computers.
>
> You're saying that this is useful for code not needing a kernel with
> CHECKPOINT_RESTORE enabled. Correct?
Correct, this is an important feature that is useful for a whole
general class of applications, not only those needing CHECKPOINT_RESTORE.
Had this not been done as part of the CHECKPOINT_RESTORE project, it
would have certainly been done, sooner or later, by some other developers:
it just so happened that the CHECKPOINT_RESTORE people were the first to
(publically) fill this gap, but in fact this code in "kernel/sys.c" should
be general kernel code, not part of CHECKPOINT_RESTORE.
>
> >
> > Unfortunately, this code (essentially "prctl_set_mm()") is presently
> > enclosed in "#ifdef CONFIG_CHECKPOINT_RESTORE" which is configured
> > as "default n" in "init/Kconfig". Many system-administrators who
> > may like to have a checkpoint/restore or process-migration facility,
> > but use standard pre-packaged kernels, find the requirement to
> > configure and compile their own non-standard kernel difficult or
> > too prohibitive.
> >
> > Would it be possible to have this code enabled by default?
> >
> > This could be done in one of 4 ways:
> > 1) Having CONFIG_CHECKPOINT_RESTORE enabled by default; or
>
> Nope, that wont due. Kernel policy is to have things default n. Have an
> issue with a config, talk with the distribution you are dealing with.
> They set the policy of what configs get set for their kernels.
Yes, Randy Dunlap already raised this point, but I have no dealings with
any particular Linux distribution or the right connections to chase them
all, one by one - I develop generic software for the general Linux community,
that is intended to work distribution-independently. Even if I had access
to all distributions, it may be hard to convince them to configure
CONFIG_CHECKPOINT_RESTORE as a whole since it contains so much other code.
BTW, Can anyone explain this policy of "have things default n"?
When I go over "init/Kconfig" or most other Kconfig's, I can
actually see lots of "default y".
>
> > 2) Releasing this code from the "#ifdef CONFIG_CHECK_RESTORE"; or
> > 3) Placing this code within a different kernel-configuration option
> > (say "CONFIG_BASIC_CHECKPOINTING") that is enabled by default; or
> > 4) Placing this code under a dual #if, so instead of:
> > #ifdef CONFIG_CHECKPOINT_RESTORE
> > have:
> > #if defined(CONFIG_CHECKPOINT_RESTORE) || defined(CONFIG_BASIC_CHECKPOINTING)
>
> One of the above 3 can probably be worked out.
>
> -- Steve
Great!
Naturally I prefer option 2 (but the other two will do as well).
Thanks,
Amnon.
next prev parent reply other threads:[~2013-02-18 16:34 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-09 18:29 [PATCH] arch_check_bp_in_kernelspace: fix the range check Oleg Nesterov
2012-11-09 18:30 ` Oleg Nesterov
2012-11-19 17:47 ` Oleg Nesterov
2012-11-19 18:25 ` Steven Rostedt
2012-11-20 10:33 ` u3557
2012-11-20 15:48 ` Oleg Nesterov
2012-11-20 15:55 ` Steven Rostedt
2012-11-20 18:32 ` Oleg Nesterov
2012-11-20 23:16 ` u3557
2012-11-21 14:16 ` Oleg Nesterov
2012-11-21 17:30 ` Amnon Shiloh
2012-11-22 16:12 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range check) Oleg Nesterov
2012-11-22 20:57 ` Pavel Emelyanov
2012-11-23 0:20 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range Amnon Shiloh
2012-11-23 17:45 ` Oleg Nesterov
2012-11-24 12:47 ` Amnon Shiloh
2012-11-23 17:42 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range check) Oleg Nesterov
2012-11-23 9:14 ` arch_check_bp_in_kernelspace: fix the range check Amnon Shiloh
2012-11-23 16:33 ` Oleg Nesterov
2012-11-23 17:05 ` Oleg Nesterov
2012-11-24 14:14 ` Amnon Shiloh
2012-11-24 13:45 ` Amnon Shiloh
2012-11-25 22:55 ` Oleg Nesterov
2012-11-25 23:48 ` Amnon Shiloh
2012-12-02 19:30 ` PTRACE_SYSCALL && vsyscall (Was: arch_check_bp_in_kernelspace: fix the range check) Oleg Nesterov
2012-12-02 23:54 ` u3557
2012-12-04 17:59 ` Oleg Nesterov
2012-12-04 22:44 ` u3557
2013-01-08 17:08 ` Pedro Alves
2013-01-09 17:52 ` Oleg Nesterov
2013-01-10 6:54 ` u3557
2013-01-12 18:12 ` Oleg Nesterov
2013-01-14 2:31 ` u3557
2013-01-14 16:01 ` Oleg Nesterov
2013-02-18 1:39 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-18 5:44 ` prctl(PR_SET_MM) Randy Dunlap
2013-02-18 15:21 ` prctl(PR_SET_MM) Steven Rostedt
2013-02-18 16:33 ` Amnon Shiloh [this message]
2013-02-18 19:49 ` prctl(PR_SET_MM) Steven Rostedt
2013-02-19 6:25 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-20 8:39 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-20 9:38 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-20 10:51 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-20 11:16 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-21 7:46 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-21 8:00 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-21 8:03 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-21 8:09 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-21 22:18 ` prctl(PR_SET_MM) Andrew Morton
2013-02-21 22:42 ` prctl(PR_SET_MM) Cyrill Gorcunov
2013-02-22 1:18 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-22 14:23 ` prctl(PR_SET_MM) Denys Vlasenko
2012-12-05 9:29 ` PTRACE_SYSCALL && vsyscall (Was: arch_check_bp_in_kernelspace: fix the range check) Jan Kratochvil
2012-12-05 13:14 ` u3557
2012-11-26 9:44 ` vdso && cr " Cyrill Gorcunov
2012-11-26 12:27 ` Andrey Wagin
2012-11-26 12:55 ` Amnon Shiloh
2012-11-26 14:18 ` Cyrill Gorcunov
2012-11-26 14:26 ` vdso && cr (Was: arch_check_bp_in_kernelspace: fix the range Amnon Shiloh
2012-11-26 14:41 ` vdso && cr Cyrill Gorcunov
[not found] <20130222142603.987c6e3c.akpm@linux-foundation.org>
2013-02-24 6:24 ` prctl(PR_SET_MM) Amnon Shiloh
2013-02-24 6:28 ` prctl(PR_SET_MM) Amnon Shiloh
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