Re: More linux emulation

[Matt Thomas <matt%3am-software.com@localhost>]

On Apr 3, 2014, at 12:42 PM, Christos Zoulas <christos%astron.com@localhost> 
wrote:

> In article <20140403192802.9D98112967%ren.fdy2.co.uk@localhost>,
> Robert Swindells  <rjs%fdy2.co.uk@localhost> wrote:
>> 
>> I have added a change to the arm copy of linux_syscall.c that lets
>> it start running Debian armel binaries, I would expect armhf ones
>> to run too.
>> 
>> Current ARM Linux expects there to be some helper functions at the top
>> of the high vectors page that can be called from userspace.
>> 
>> These functions do things like compare-and-swap, memory barrier and
>> give fast access to the TLS pointer. The idea is that they can have
>> processor specific versions of these with a generic userland.
>> 
>> Do people think it would be a bad idea to add this feature ?
>> 
>> I haven't worked out what security issues there might be with it.
>> 
>> Robert Swindells
> 
> I don't see that this is a problem. There is a lot of prior art doing similar
> things (getpid() fast memcpy(), timer access etc).

well, most platforms don't use high vectors anymore.  And that page is
usually not user-readable.