Messages in this thread | | | Date | Tue, 26 Jun 2018 14:45:11 -0400 (EDT) | From | Mathieu Desnoyers <> | Subject | Re: rseq: How to test for compat task at signal delivery |
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----- On Jun 26, 2018, at 1:38 PM, Mathieu Desnoyers mathieu.desnoyers@efficios.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
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