From: Jamie Lokier <jamie@shareable.org>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Oleg Nesterov <oleg@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Indan Zupancic <indan@nul.nu>, Andi Kleen <andi@firstfloor.org>,
Andrew Lutomirski <luto@mit.edu>, Will Drewry <wad@chromium.org>,
linux-kernel@vger.kernel.org, keescook@chromium.org,
john.johansen@canonical.com, serge.hallyn@canonical.com,
coreyb@linux.vnet.ibm.com, pmoore@redhat.com, eparis@redhat.com,
djm@mindrot.org, segoon@openwall.com, rostedt@goodmis.org,
jmorris@namei.org, scarybeasts@gmail.com, avi@redhat.com,
penberg@cs.helsinki.fi, viro@zeniv.linux.org.uk, mingo@elte.hu,
akpm@linux-foundation.org, khilman@ti.com,
borislav.petkov@amd.com, amwang@redhat.com, ak@linux.intel.com,
eric.dumazet@gmail.com, gregkh@suse.de, dhowells@redhat.com,
daniel.lezcano@free.fr, linux-fsdevel@vger.kernel.org,
linux-security-module@vger.kernel.org, olofj@chromium.org,
mhalcrow@google.com, dlaor@redhat.com,
Roland McGrath <mcgrathr@chromium.org>
Subject: Re: Compat 32-bit syscall entry from 64-bit task!?
Date: Thu, 26 Jan 2012 00:59:01 +0000 [thread overview]
Message-ID: <20120126005901.GC18613@jl-vm1.vm.bytemark.co.uk> (raw)
In-Reply-To: <201201260032.57937.vda.linux@googlemail.com>
Denys Vlasenko wrote:
> On Wednesday 25 January 2012 20:36, Oleg Nesterov wrote:
> > On 01/18, Linus Torvalds wrote:
> > >
> > > Using the high bits of 'eflags' might work.
> >
> > I thought about changing eflags too, this looks very natural to me.
> >
> > But I do not understand the result of this discussion, are you going
> > to apply this change?
> >
> > If not...
> >
> > Not sure this is really better, but there is another idea. Currently we
> > have PTRACE_O_TRACESYSGOOD to avoid the confusion with the real SIGTRAP.
> > Perhaps we can add PTRACE_O_TRACESYS_VERY_GOOD (or we can look at
> > PT_SEIZED instead) and report TS_COMPAT via ptrace_report_syscall ?
> >
> > IOW. Currently ptrace_report_syscall() does
> >
> > ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
> >
> > We can add the new events,
> >
> > PTRACE_EVENT_SYSCALL_ENTRY
> > PTRACE_EVENT_SYSCALL_COMPAT_ENTRY
> > PTRACE_EVENT_SYSCALL_EXIT
> > PTRACE_EVENT_SYSCALL_COMPAT_EXIT
>
> We can get away with just the first one.
> (1) It's unlikely people would want to get native sysentry events but not compat ones,
> thus first two options can be combined into one;
Tracers mainly want to know if it's a 32-bit or 64-bit syscall, not
whether it's compat as such.
I'm thinking it might be a little kinder like this:
#define PTRACE_EVENT_SYSCALL_ENTRY_ABI32 (...)
#define PTRACE_EVENT_SYSCALL_ENTRY_ABI64 (...)
#ifdef CONFIG_64BIT
# define PTRACE_EVENT_SYSCALL_ENTRY PTRACE_EVENT_SYSCALL_ENTRY_ABI64
# define PTRACE_EVENT_SYSCALL_ENTRY_COMPAT PTRACE_EVENT_SYSCALL_ENTRY_ABI32
#else
# define PTRACE_EVENT_SYSCALL_ENTRY PTRACE_EVENT_SYSCALL_ENTRY_ABI32
#endif
So the ABI is represented directly, with the _ENTRY referring to the
tracer's own. (Other ABI numbers can exist, e.g. OABI and EABI for
ARM, see below.)
This has the two specific advantages:
1. It can match on specific ABI or regular/compat, as suits the tracer's code.
2. When a 32-bit *tracer* is running a 64-bit *tracee* as least it knows ;-)
With your idea, what happens in situation 2? I'm not sure a 32-bit
tracee can do anything useful, because it can't get the 64-bit
registers, but at least it can see when it's got the wrong registers :-)
> (2) syscall exit compat-ness is known from entry type - no need to indicate it; and
> (3) if we would flag syscall entry with an event value in wait status, then syscall
> exit will be already distinquisable.
>
> Thus, minimally we need one new option, PTRACE_O_TRACE_SYSENTRY -
> "on syscall entry ptrace stop, set a nonzero event value in wait status"
> , and two event values: PTRACE_EVENT_SYSCALL_ENTRY (for native entry),
> PTRACE_EVENT_SYSCALL_ENTRY1 for compat one.
PTRACE_EVENT_SYSCALL_EXIT would cleanly indicate that the new option
is actually working without the tracer needing to do a fork+test, if
PTRACE_ATTACH is used and for some reason the tracer sees a syscall
exit first. I'm not sure if this can happen but I've heard rumour of
it on some archs or kernel versions.
> To future-proof this scheme we may reserve a few more event values
> PTRACE_EVENT_SYSCALL_ENTRY2, PTRACE_EVENT_SYSCALL_ENTRY3, etc,
> if we'll ever have arches with more than one non-native syscall
> entry.
> I'm no expert, but looking at strace code, ARM may already have
> more than one additional convention how to pass syscall args.
I was just looking at ARM and see exactly the same thing. The
difference between EABI and OABI calls is significant on ARM, even
though syscall numbers are the same; and the ABI is selected by the
syscall instruction used, not process personality. The __NR_name
values differ for each ABI, but (if I read arm/kernel/entry-common.S
properly) strace sees the same _NR_name values for both ABIs.
MIPS also has two different 32-bit ABIs, as well as 64-bit, but on
MIPS the syscall numbers are distinct, and should be seen by ptrace.
(Again if I read mips/kernel/ correctly.)
PA-RISC also has two different ABIs, the Linux one and the HPUX one.
The syscall numbers are different but overlap. I don't know if they
are distinct to ptrace, in which case using the HPUX entry point might
be used to subvert a ptracer unless the ABI number is exposed.
-- Jamie
next prev parent reply other threads:[~2012-01-26 0:59 UTC|newest]
Thread overview: 235+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-11 17:25 [RFC,PATCH 0/2] dynamic seccomp policies (using BPF filters) Will Drewry
2012-01-11 17:25 ` [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF Will Drewry
2012-01-12 8:53 ` Serge Hallyn
2012-01-12 16:54 ` Will Drewry
2012-01-12 14:50 ` Oleg Nesterov
2012-01-12 16:55 ` Will Drewry
2012-01-12 15:43 ` Steven Rostedt
2012-01-12 16:14 ` Oleg Nesterov
2012-01-12 16:38 ` Steven Rostedt
2012-01-12 16:47 ` Oleg Nesterov
2012-01-12 17:08 ` Will Drewry
2012-01-12 17:30 ` Jamie Lokier
2012-01-12 17:40 ` Steven Rostedt
2012-01-12 17:44 ` Jamie Lokier
2012-01-12 17:56 ` Steven Rostedt
2012-01-12 23:27 ` Alan Cox
2012-01-12 23:38 ` Linus Torvalds
2012-01-12 22:18 ` Will Drewry
2012-01-12 23:00 ` Andrew Lutomirski
2012-01-12 16:14 ` Andrew Lutomirski
2012-01-12 16:27 ` Steven Rostedt
2012-01-12 16:51 ` Andrew Lutomirski
2012-01-12 17:09 ` Linus Torvalds
2012-01-12 17:17 ` Steven Rostedt
2012-01-12 18:18 ` Andrew Lutomirski
2012-01-12 18:32 ` Linus Torvalds
2012-01-12 18:44 ` Andrew Lutomirski
2012-01-12 19:08 ` Kyle Moffett
2012-01-12 23:05 ` Eric Paris
2012-01-12 23:33 ` Andrew Lutomirski
2012-01-12 19:40 ` Will Drewry
2012-01-12 19:42 ` Will Drewry
2012-01-12 19:46 ` Andrew Lutomirski
2012-01-12 20:00 ` Linus Torvalds
2012-01-12 16:59 ` Will Drewry
2012-01-12 17:22 ` Jamie Lokier
2012-01-12 17:35 ` Will Drewry
2012-01-12 17:57 ` Jamie Lokier
2012-01-12 18:03 ` Will Drewry
2012-01-13 1:34 ` Jamie Lokier
2012-01-13 2:44 ` Indan Zupancic
2012-01-13 6:33 ` Chris Evans
2012-01-12 17:36 ` Jamie Lokier
2012-01-12 16:18 ` Alan Cox
2012-01-12 17:03 ` Will Drewry
2012-01-12 17:11 ` Alan Cox
2012-01-12 17:52 ` Will Drewry
2012-01-13 1:31 ` James Morris
2012-01-12 16:22 ` Oleg Nesterov
2012-01-12 17:10 ` Will Drewry
2012-01-12 17:23 ` Oleg Nesterov
2012-01-12 17:51 ` Will Drewry
2012-01-13 17:31 ` Oleg Nesterov
2012-01-13 19:01 ` Will Drewry
2012-01-13 23:10 ` Will Drewry
2012-01-13 23:12 ` Will Drewry
2012-01-13 23:30 ` Eric Paris
2012-01-15 3:40 ` Indan Zupancic
2012-01-16 1:40 ` Will Drewry
2012-01-16 6:49 ` Indan Zupancic
2012-01-16 20:12 ` Will Drewry
2012-01-17 6:46 ` Indan Zupancic
2012-01-17 17:37 ` Will Drewry
2012-01-18 4:06 ` Indan Zupancic
2012-01-18 4:38 ` Will Drewry
2012-01-17 20:34 ` Kees Cook
2012-01-17 20:42 ` Will Drewry
2012-01-17 21:09 ` Will Drewry
2012-01-18 4:47 ` Indan Zupancic
2012-01-16 18:37 ` Oleg Nesterov
2012-01-16 20:15 ` Will Drewry
2012-01-17 16:45 ` Oleg Nesterov
2012-01-17 16:56 ` Will Drewry
2012-01-17 17:01 ` Andrew Lutomirski
2012-01-17 17:05 ` Oleg Nesterov
2012-01-17 17:45 ` Andrew Lutomirski
2012-01-18 0:56 ` Compat 32-bit syscall entry from 64-bit task!? [was: Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF] Indan Zupancic
2012-01-18 1:01 ` Andrew Lutomirski
2012-01-19 1:06 ` Indan Zupancic
2012-01-19 1:19 ` Andrew Lutomirski
2012-01-19 1:47 ` Indan Zupancic
2012-01-18 1:07 ` Roland McGrath
2012-01-18 1:47 ` Indan Zupancic
2012-01-18 1:48 ` Jamie Lokier
2012-01-18 1:50 ` Andi Kleen
2012-01-18 2:00 ` Steven Rostedt
2012-01-18 2:04 ` Jamie Lokier
2012-01-18 2:22 ` Andi Kleen
2012-01-18 2:25 ` Andrew Lutomirski
2012-01-18 4:22 ` Indan Zupancic
2012-01-18 5:23 ` Linus Torvalds
2012-01-18 6:25 ` Linus Torvalds
2012-01-18 13:12 ` Compat 32-bit syscall entry from 64-bit task!? Indan Zupancic
2012-01-18 19:31 ` Linus Torvalds
2012-01-18 19:36 ` Andi Kleen
2012-01-18 19:39 ` Linus Torvalds
2012-01-18 19:44 ` Andi Kleen
2012-01-18 19:47 ` Linus Torvalds
2012-01-18 19:52 ` Will Drewry
2012-01-18 19:58 ` Will Drewry
2012-01-18 19:41 ` Martin Mares
2012-01-18 19:38 ` Andrew Lutomirski
2012-01-19 16:01 ` Jamie Lokier
2012-01-19 16:13 ` Andrew Lutomirski
2012-01-19 19:21 ` Linus Torvalds
2012-01-19 19:30 ` Andrew Lutomirski
2012-01-19 19:37 ` Linus Torvalds
2012-01-19 19:41 ` Linus Torvalds
2012-01-19 23:54 ` Jamie Lokier
2012-01-20 0:05 ` Linus Torvalds
2012-01-20 15:35 ` Will Drewry
2012-01-20 17:56 ` Roland McGrath
2012-01-20 19:45 ` Will Drewry
2012-01-18 20:26 ` Linus Torvalds
2012-01-18 20:55 ` H. Peter Anvin
2012-01-18 21:01 ` Linus Torvalds
2012-01-18 21:04 ` H. Peter Anvin
2012-01-18 21:21 ` H. Peter Anvin
2012-01-18 21:51 ` Roland McGrath
2012-01-18 21:53 ` H. Peter Anvin
2012-01-18 23:28 ` Linus Torvalds
2012-01-19 0:38 ` H. Peter Anvin
2012-01-20 21:51 ` Denys Vlasenko
2012-01-20 22:40 ` Roland McGrath
2012-01-20 22:41 ` H. Peter Anvin
2012-01-20 23:49 ` Indan Zupancic
2012-01-20 23:55 ` Roland McGrath
2012-01-20 23:58 ` hpanvin@gmail.com
2012-01-23 2:14 ` Indan Zupancic
2012-01-21 0:07 ` Denys Vlasenko
2012-01-21 0:10 ` Roland McGrath
2012-01-21 1:23 ` Jamie Lokier
2012-01-23 2:37 ` Indan Zupancic
2012-01-23 16:48 ` Oleg Nesterov
2012-01-24 8:19 ` Indan Zupancic
2012-02-06 20:30 ` H. Peter Anvin
2012-02-06 20:39 ` Roland McGrath
2012-02-06 20:42 ` H. Peter Anvin
2012-01-18 21:26 ` Linus Torvalds
2012-01-18 21:30 ` H. Peter Anvin
2012-01-18 21:42 ` Linus Torvalds
2012-01-18 21:47 ` H. Peter Anvin
2012-01-19 1:45 ` Indan Zupancic
2012-01-19 2:16 ` H. Peter Anvin
2012-02-06 8:32 ` Indan Zupancic
2012-02-06 17:02 ` H. Peter Anvin
2012-02-07 1:52 ` Indan Zupancic
2012-02-09 0:19 ` H. Peter Anvin
2012-02-09 4:20 ` Indan Zupancic
2012-02-09 4:29 ` H. Peter Anvin
2012-02-09 6:03 ` Indan Zupancic
2012-02-09 14:47 ` H. Peter Anvin
2012-02-09 16:00 ` H.J. Lu
2012-02-10 1:09 ` Indan Zupancic
2012-02-10 1:15 ` H. Peter Anvin
2012-02-10 2:29 ` Indan Zupancic
2012-02-10 2:47 ` H. Peter Anvin
[not found] ` <cc95fcf4b1c28ee6f73e373d04593634.squirrel@webmail.greenhost.nl>
2012-02-10 15:53 ` H. Peter Anvin
2012-02-10 22:42 ` Indan Zupancic
2012-02-10 22:56 ` H. Peter Anvin
2012-02-12 12:07 ` Indan Zupancic
2012-01-25 19:36 ` Oleg Nesterov
2012-01-25 20:20 ` Pedro Alves
2012-01-25 23:36 ` Denys Vlasenko
2012-01-25 23:32 ` Denys Vlasenko
2012-01-26 0:40 ` Indan Zupancic
2012-01-26 1:08 ` Jamie Lokier
2012-01-26 1:22 ` Denys Vlasenko
2012-01-26 6:34 ` Indan Zupancic
2012-01-26 10:31 ` Jamie Lokier
2012-01-26 10:40 ` Denys Vlasenko
2012-01-26 11:01 ` Jamie Lokier
2012-01-26 14:02 ` Denys Vlasenko
2012-01-26 11:19 ` Indan Zupancic
2012-01-26 11:20 ` Indan Zupancic
2012-01-26 11:47 ` Jamie Lokier
2012-01-26 14:05 ` Denys Vlasenko
2012-01-27 7:23 ` Indan Zupancic
2012-02-10 2:02 ` Jamie Lokier
2012-02-10 3:37 ` Indan Zupancic
2012-02-10 21:19 ` Denys Vlasenko
2012-01-26 1:09 ` Denys Vlasenko
2012-01-26 3:47 ` Linus Torvalds
2012-01-26 18:03 ` Denys Vlasenko
2017-03-08 23:41 ` Dmitry V. Levin
2017-03-09 4:39 ` Andrew Lutomirski
2017-03-14 2:57 ` Dmitry V. Levin
2012-01-26 5:57 ` Indan Zupancic
2012-01-26 0:59 ` Jamie Lokier [this message]
2012-01-26 1:21 ` Denys Vlasenko
2012-01-26 8:23 ` Pedro Alves
2012-01-26 8:53 ` Denys Vlasenko
2012-01-26 9:51 ` Pedro Alves
2012-01-26 18:44 ` Oleg Nesterov
2012-02-10 2:51 ` Jamie Lokier
2012-01-18 15:04 ` Compat 32-bit syscall entry from 64-bit task!? [was: Re: [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF] Eric Paris
2012-01-18 17:51 ` Linus Torvalds
2012-01-18 5:43 ` Chris Evans
2012-01-18 12:12 ` Indan Zupancic
2012-01-18 21:13 ` Chris Evans
2012-01-19 0:14 ` Indan Zupancic
2012-01-19 8:16 ` Chris Evans
2012-01-19 11:34 ` Indan Zupancic
2012-01-19 16:11 ` Jamie Lokier
2012-01-19 15:40 ` Jamie Lokier
2012-01-18 17:00 ` Oleg Nesterov
2012-01-18 17:12 ` Oleg Nesterov
2012-01-18 21:09 ` Chris Evans
2012-01-23 16:56 ` Oleg Nesterov
2012-01-23 22:23 ` Chris Evans
2012-02-07 11:45 ` Indan Zupancic
2012-01-19 0:29 ` Indan Zupancic
2012-01-18 2:27 ` Linus Torvalds
2012-01-18 2:31 ` Andi Kleen
2012-01-18 2:46 ` Linus Torvalds
2012-01-18 14:06 ` Martin Mares
2012-01-18 18:24 ` Andi Kleen
2012-01-19 16:04 ` Jamie Lokier
2012-01-20 0:21 ` Indan Zupancic
2012-01-20 0:53 ` Linus Torvalds
2012-01-20 2:02 ` Indan Zupancic
2012-01-17 17:06 ` [RFC,PATCH 1/2] seccomp_filters: system call filtering using BPF Will Drewry
2012-01-17 19:35 ` Will Drewry
2012-01-12 17:02 ` Andrew Lutomirski
2012-01-16 20:28 ` Will Drewry
2012-01-11 17:25 ` [RFC,PATCH 2/2] Documentation: prctl/seccomp_filter Will Drewry
2012-01-11 20:03 ` Jonathan Corbet
2012-01-11 20:10 ` Will Drewry
2012-01-11 23:19 ` [PATCH v2 " Will Drewry
2012-01-12 0:29 ` Will Drewry
2012-01-12 18:16 ` Randy Dunlap
2012-01-12 17:23 ` Will Drewry
2012-01-12 17:34 ` Steven Rostedt
2012-01-12 13:13 ` [RFC,PATCH " Łukasz Sowa
2012-01-12 17:25 ` Will Drewry
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