About privileged instructions on L4android

Stefan Kalkowski stefan.kalkowski at ...1...
Mon Nov 3 09:58:33 CET 2014


On 10/31/2014 04:23 PM, li94575 wrote:
> Hi All,
> Can someone tells me how to execute  ARM privileged instruction on
> L4android, such as " MCR, MRC......"
> I have a piece of code that needs to execute privileged instructions,
> but I don't want to put it all into the kernel ----Fiasco.OC. I want to
> know if L4android have any good ways to solve this problem.

You say: you want to execute privileged instructions, but don't want to
execute them in the kernel, so you don't want to execute it in
privileged mode. That obviously can't work.

L4Android is a para-virtualized version of the Linux kernel including
Android kernel patches. Para-virtualization means that the Linux kernel
doesn't run in privileged mode, but in user mode instead. All privileged
instructions of the kernel code are replaced e.g. by function calls to
the underlying system, like Fiasco.OC system calls, and L4Re function calls.

If you want to enable Linux kernel parts that aren't enabled right now,
which include privileged instructions, you will have to paravirtualize
that code parts too. Just for curiosity: what kernel code, and
privileged instructions are you trying to enable?

BTW. this mailing list is actually limited to Genode related problems,
general third party code questions that are not related to Genode are
better directed to the corresponding mailing lists. With respect to
L4android this is the l4-hackers mailing list.


Stefan Kalkowski
Genode Labs

http://www.genode-labs.com/ ยท http://genode.org/

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