From: Oleg Nesterov <oleg@redhat.com>
To: u3557@miso.sublimeip.com
Cc: Steven Rostedt <rostedt@goodmis.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arch_check_bp_in_kernelspace: fix the range check
Date: Wed, 21 Nov 2012 15:16:27 +0100 [thread overview]
Message-ID: <20121121141627.GB21030@redhat.com> (raw)
In-Reply-To: <3501c254c970c4dbd933022651622f79.squirrel@mail.sublimeip.com>
Hi Amnon,
Please read my previous email ;)
http://marc.info/?l=linux-kernel&m=135342649119153
On 11/21, u3557@miso.sublimeip.com wrote:
>
> Hi Oleg,
>
> > Or. Perhaps we can define TRAP_VSYSCALL and change emulate_vsyscall() to
> > do
> >
> >
> > if (current->ptrace && test_thread_flag(TIF_SYSCALL_TRACE))
> > send_sigtrap(TRAP_VSYSCALL, ...);
> >
> > if it returns true?
> >
>
> I wish it were possible, but the vsyscall page is entered in user-mode,
Only in NATIVE mode. emulate_vsyscall() runs in kernel mode.
And in the NATIVE mode PTRACE_SYSCALL should work just fine, because:
> The vsyscall page was designed in order to avoid user/kernel context
> switches,
True, it was. But not today. Please look at __vsyscall_page:
__vsyscall_page:
mov $__NR_gettimeofday, %rax
syscall
ret
If you want the "fast" sys_time() without entering the kernel, you can
use __vdso_time(). And since vdso has the user-space mapping you can
insert "int3" or use hw breakpoints.
At least this is my understanding after I glanced at the new implementation.
However. It is not that I think that TRAP_VSYSCALL is really good idea.
At least it needs another option...
Oleg.
next prev parent reply other threads:[~2012-11-21 14:16 UTC|newest]
Thread overview: 60+ 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 [this message]
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 ` prctl(PR_SET_MM) Amnon Shiloh
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
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