[ECOS] announcing: memory protection for eCos / PowerPC ...

[Thomas BINDER <Thomas dot Binder at frequentis dot com>]

Hi everybody!

I would like to announce an eCos extension that provides memory protection for the MPC8265A (603e) architecture.

The memory protection is realized in two stages. Stage-I implements the paging mode of the 603e. It allows to (statically) define an arbitrary number of pages that can be accessed at runtime. Exception vectors are set up to print a stack trace in case of a memory fault.

Stage-II implements a full process environment that allows to define several processes each with a private address space. The design more or less follows a proposal by Frank W. Miller ("Simple Memory Protection for Embedded Operating System Kernels"). By accessing all kernel primitives via a process api the kernel is fully protected from the application (i.e., the processes).

Care was taken to minimize necessary changes to the existing eCos version. Some parts, however, needed to be adapted. This includes the (PowerPC) HAL, the GDB stub, and parts of the kernel. New cdl options were introduced to enable / disable the paging mode, and to configure MMU related things (e.g. page table size and location, ...), respectively. Stage-II was implemented as a separate package which heavily relies on stage-I but should otherwise be architecture independent.

The GDB stub was extended to allow debugging of a protected application. In case the stub is enabled a SIGSEGV is reported to the debugger (instead of printing a stack trace).

Stage-I has been thoroughly tested for the last 3-4 months. Our application extensively uses eCos device drivers (serial, ethernet, PCI, flash, ...), the IP-stack, libc (sprintf), and the GDB stub. 

Stage-II is relatively new and was finished a month ago.

I'm soon going to prepare a patch to the eCos main branch. Any advice on what additional information needs to be prepared would be very welcome. Probably I need to start writing ChangeLog entries ...

best regards,
Tom
--

-- 
Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos
and search the list archive: http://sources.redhat.com/ml/ecos-discuss