[Vm-dev] Mars, stuck on callbacks (again)... need opinions
siguctua at gmail.com
Fri Dec 24 00:31:25 UTC 2010
On 24 December 2010 00:12, John M McIntosh
<johnmci at smalltalkconsulting.com> wrote:
> At WWDC 2009 I had a long chat with the manager of the iOS security team at the time I was exploring options for JIT VMs.
> mmap & mprotect are BSD unix/etc non-compliant as there is no way for *you* to set the execute bit on a page. We did discuss perhaps in
> an enterprise environment you could have certificates and signing to give you different rights, like say to set page tags, but that has never been offered.
> Obviously you *can* set it, but only if you jail break or root the iOS. But I do recall seeing an article pass my desk the other day saying that Apple was
> slowing winning the war there because the time between IOS revisions and jail breaking was increasing and at some point it tips over the fence where
> it takes too long to break. This is not to say it's impossible, rather it becomes not worth pursuing for *casual enjoyment*...
So, why simply don't ask user, if he wants to use JITs or not? Why
limiting the choice?
Maybe JIT for casual enjoyment is too much.. but if you go 10-15 years
back and show iphone to people, they would say:
- what a waste.. why it using color display? why so expensive, why
it has wifi? it is running an operating system? for what tasks? to
call my mom i need OS on phone?.. and so on so on..
because people at that time were wanting just make a calls using cell phones :)
> On 2010-12-23, at 3:00 PM, Andreas Raab wrote:
>> On 12/23/2010 2:49 PM, John M McIntosh wrote:
>>> Well I"m not sure what is being suggested here, but on iOS a shared library is marked as read and executable, NOT writable. so you can't do self modifying code...
>>> Unless you are saying you'd like to on macintel generate arm code and stick it into a shared library for later loading and execution on iOS?
>> Yup. Of course. It's pretty obvious that shared libs would've to be read-only on iOS. And I would also expect that there's no call to set the executable bit on a file (otherwise you could create a new shared lib).
>> - Andreas
> John M. McIntosh <johnmci at smalltalkconsulting.com> Twitter: squeaker68882
> Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com
Igor Stasenko AKA sig.
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