On 3/14/2012 3:55 PM, Jecel Assumpcao Jr. wrote:
<snip, interesting, but no comment>
If you have a good version of confinement (which is pretty simple HW-wise) you
can use Butler Lampson's schemes for Cal-TSS to make a workable version of a
capability system.
The 286 protected mode was good enough for this, and was extended in the
386. I am not sure all modern x86 processors still implement these, and
if they do it is likely that actually using them will hurt performance
so much that it isn't an option in practice.
the TSS?...
it is still usable on x86 in 32-bit Protected-Mode.
however, it generally wasn't used much by operating systems, and in the
transition to x86-64, was (along with the GDT and LDT) mostly reduced to
a semi-vestigial structure.
its role is generally limited to holding register state and the stack
pointers when doing inter-ring switches (such as an interrupt-handler
transferring control into the kernel, or when transferring control into
userspace).
however, it can no longer be used to implement process switching or
similar on modern chips.
And, yep, I managed to get them to allow interpreters to run on the iPad, but
was
not able to get Steve to countermand the "no sharing" rule.
That is a pity, though at least having native languages makes these
devices a reasonable replacement for my old Radio Shack PC-4 calculator.
I noticed that neither Matlab nor Mathematica are available for the
iPad, but only simple terminal apps that allow you to access these
applications running on your PC. What a waste!
IMHO, this is at least one reason to go for Android instead...
not that Android is perfect though, as admittedly I would prefer if I
could have a full/generic ARM version of Linux or similar, but alas.
sadly, I am not getting a whole lot of the tablet I have development
wise, which is lame considering that was a major reason I bought it
(ended up doing far more development in Linux ARMv5TEL in QEMU preparing
to try to port stuff to Android).
more preferable would have been:
if the NDK didn't suck as badly;
if there were, say, a C API for the GUI stuff (so one could more easily
just use C without having to deal with Java or the JNI).
would have likely been a little happier had Android been more like just
a ARM build of a more generic Linux distro or something.
or such...
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