From: Oleg Nesterov <oleg@redhat.com>
To: Andrew Vagin <avagin@parallels.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
David Howells <dhowells@redhat.com>,
Pavel Emelyanov <xemul@parallels.com>,
linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
criu@openvz.org, Cyrill Gorcunov <gorcunov@openvz.org>,
Andrey Wagin <avagin@gmail.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-fsdevel@vger.kernel.org, Dave Jones <davej@redhat.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Denys Vlasenko <dvlasenk@redhat.com>
Subject: Re: [CRIU] [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2)
Date: Mon, 11 Feb 2013 17:47:27 +0100 [thread overview]
Message-ID: <20130211164727.GA27511@redhat.com> (raw)
In-Reply-To: <20130210100424.GA15978@paralelels.com>
On 02/10, Andrew Vagin wrote:
>
> On Sat, Feb 09, 2013 at 11:53:04PM +0100, Michael Kerrisk (man-pages) wrote:
> >
> > This looks promising, but I am not sure I understand the user-space
> > API. Could you explain how it would look to (say) pull all per-thread
> > signals from user space?
> >
>
> siginfo_t *signals = malloc(...);
> ...
>
> ret = ptrace(PTRACE_ATTACH, pid, NULL, NULL);
Yes. I assume this should not be a problem since c/r needs to ptrace
the task anyway?
> For shared (per-process) signals one line should be changed:
> ret = ptrace(PTRACE_PEEKSIGNAL, pid, PTRACE_PEEK_SHARED + i, signals + i);
Yes. Except I'd say "PTRACE_PEEK_SHARED | i" to clarify that
PTRACE_PEEK_SHARED is "flag". Note that we can more flags, say,
PTRACE_PEEK_DEQUEUE which obviously means "dequeue signal" (but in
this case we should filter out SIGKILL/SIGSTOP).
And note that either way (I mean ptrace or signalfd) this can not
actually peek a signal which doesn't have the sigqueue (say,
SEND_SIG_FORCED). I guess this is not the problem, c/r can look
at /proc/pid/status#*Pnd aditionally.
OK, you seem to agree with this approach, I'll try to make the
working patch tomorrow. At least ptrace_peek_signal() needs another
is_compat argument for compat_ptrace_request().
Oleg.
> > > --- x/kernel/ptrace.c
> > > +++ x/kernel/ptrace.c
> > > @@ -618,6 +618,35 @@ static int ptrace_setsiginfo(struct task
> > > return error;
> > > }
> > >
> > > +static int ptrace_peek_signal(struct task_struct *child,
> > > + unsigned long addr, siginfo_t __user *uinfo)
> > > +{
> > > + siginfo_t info;
> > > + struct sigpending *pending;
> > > + int ret = -ESOMETHING;
> > > +
> > > + pending = &child->pending;
> > > + if (addr & PTRACE_PEEK_SHARED) {
> > > + addr &= ~PTRACE_PEEK_SHARED;
> > > + pending = &child->signal->shared_pending;
> > > + }
> > > +
> > > + spin_lock_irq(&child->sighand->siglock);
> > > + list_for_each_entry(q, &pending->list, list) {
> > > + if (!addr--) {
> > > + copy_siginfo(info, &q->info);
> > > + ret = 0;
> > > + break;
> > > + }
> > > + }
> > > + spin_lock_irq(&child->sighand->siglock);
> > > +
> > > + if (!ret)
> > > + ret = copy_siginfo_to_user(uinfo, info);
> > > + if (!ret)
> > > + ret = __put_user(info, si_code);
> > > + return ret;
> > > +}
> > >
> > > #ifdef PTRACE_SINGLESTEP
> > > #define is_singlestep(request) ((request) == PTRACE_SINGLESTEP)
> > > @@ -742,6 +771,10 @@ int ptrace_request(struct task_struct *c
> > > ret = put_user(child->ptrace_message, datalp);
> > > break;
> > >
> > > + case PTRACE_PEEKSIGNAL:
> > > + ret = ptrace_peek_signal(child, addr, datavp);
> > > + break;
> > > +
> > > case PTRACE_GETSIGINFO:
> > > ret = ptrace_getsiginfo(child, &siginfo);
> > > if (!ret)
> > >
> >
> >
> >
> > --
> > Michael Kerrisk
> > Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> > Author of "The Linux Programming Interface"; http://man7.org/tlpi/
> > _______________________________________________
> > CRIU mailing list
> > CRIU@openvz.org
> > https://lists.openvz.org/mailman/listinfo/criu
next prev parent reply other threads:[~2013-02-11 16:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-22 10:15 [PATCH 0/3] signalfd: a kernel interface for dumping pending signals Andrey Vagin
2013-01-22 10:15 ` [PATCH 1/3] signal: add a helper for dequeuing signals from a specified queue Andrey Vagin
2013-02-05 12:00 ` [PATCH 1/3] signal: add a helper for dequeuing signals from a specified queue (v2) Andrey Vagin
2013-01-22 10:15 ` [PATCH 2/3] signalfd: add ability to choose a private or shared queue Andrey Vagin
2013-02-07 18:17 ` Oleg Nesterov
2013-02-08 0:35 ` Michael Kerrisk (man-pages)
2013-02-08 19:12 ` Oleg Nesterov
2013-01-22 10:15 ` [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals Andrey Vagin
2013-01-29 19:03 ` [PATCH 3/3] signalfd: add ability to read siginfo-s without dequeuing signals (v2) Andrey Vagin
[not found] ` <CAKgNAkgQA=zK=2ZnytPFU=DH6jr0sja0iy6K+j6c7unheLFniQ@mail.gmail.com>
2013-02-02 7:15 ` Andrey Wagin
2013-02-07 17:34 ` Oleg Nesterov
2013-02-07 21:13 ` Andrey Wagin
2013-02-08 0:51 ` Michael Kerrisk (man-pages)
2013-02-08 19:10 ` Oleg Nesterov
2013-02-08 20:15 ` Michael Kerrisk (man-pages)
2013-02-09 18:22 ` Oleg Nesterov
2013-02-09 22:53 ` Michael Kerrisk (man-pages)
2013-02-10 10:04 ` [CRIU] " Andrew Vagin
2013-02-11 16:47 ` Oleg Nesterov [this message]
2013-02-10 10:07 ` Andrew Vagin
2013-02-11 9:29 ` Denys Vlasenko
2013-02-11 10:59 ` [CRIU] " Andrew Vagin
2013-02-11 14:46 ` Denys Vlasenko
2013-02-11 14:53 ` Pavel Emelyanov
2013-02-11 17:25 ` Denys Vlasenko
2013-02-12 14:50 ` Pavel Emelyanov
2013-01-23 4:19 ` [PATCH 0/3] signalfd: a kernel interface for dumping pending signals Michael Kerrisk (man-pages)
2013-01-23 11:03 ` Andrew Vagin
2013-01-23 12:11 ` Michael Kerrisk (man-pages)
2013-01-23 13:03 ` Andrew Vagin
2013-02-07 18:20 ` Oleg Nesterov
2013-02-08 0:36 ` Michael Kerrisk (man-pages)
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