[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <170076903.5015.1530038711536.JavaMail.zimbra@efficios.com>
Date: Tue, 26 Jun 2018 14:45:11 -0400 (EDT)
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Andy Lutomirski <luto@...capital.net>
Cc: Peter Zijlstra <peterz@...radead.org>,
Boqun Feng <boqun.feng@...il.com>,
linux-kernel <linux-kernel@...r.kernel.org>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: rseq: How to test for compat task at signal delivery
----- On Jun 26, 2018, at 1:38 PM, Mathieu Desnoyers mathieu.desnoyers@...icios.com wrote:
> Hi Andy,
>
> I would like to make the behavior rseq on compat tasks more robust
> by ensuring that kernel/rseq.c:rseq_get_rseq_cs() clears the high
> bits of rseq_cs->abort_ip, rseq_cs->start_ip and
> rseq_cs->post_commit_offset when a 32-bit binary is run on a 64-bit
> kernel.
>
> The intent here is that if user-space has garbage rather than zeroes
> in its struct rseq_cs fields padding, the behavior will be the same
> whether the binary is run on 32-bit or 64 kernels.
>
> I know that internally, the kernel is making a transition from
> is_compat_task() to in_compat_syscall().
>
> I'm fine with using in_compat_syscall() when rseq_get_rseq_cs() is
> invoked from a system call, but is it OK to call it when it is
> invoked from signal delivery ? AFAIU, signals can be delivered
> upon return from interrupt as well.
>
> If not, what strategy do you recommend for arch-agnostic code ?
I think what we're missing here is a new "is_compat_frame(struct ksignal *ksig)"
which I could use in the rseq code. I'll prepare a patch and we can discuss
from there.
Thanks,
Mathieu
>
> Thanks,
>
> Mathieu
>
> --
> Mathieu Desnoyers
> EfficiOS Inc.
> http://www.efficios.com
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
Powered by blists - more mailing lists