[ECOS] Re: Memory protection

Kenneth Porter kenneth_porter@kensingtonlabs.com
Mon Nov 30 17:49:00 GMT 1998


On Fri, 27 Nov 1998 15:04:06 GMT, Bart Veer wrote:

>4) limited protection support, primarily for debugging purposes, for
>   example the ability to invalidate certain parts of the address
>   space like location 0.

I'd add the ability to write-protect code in RAM once it's read in,
both for debugging and to protect it from wild pointers in the field.
Same thing for memory-mapped non-volatile parameter memories (ie.
EEPROM).

Read-protecting code (ie. limiting it to execute-only access) would be
useful in chasing wild read pointers. (BTW, can GCC store vtables in
non-code read-only memory, so that it can have different access rights
than code or data pages? Such memory would hold read-only data objects
like strings and function pointers.)

I don't see a strong need for the MMU for multiple processes, myself.
Instead, it would serve the same purpose as a watchdog timer: to
protect a system from runtime problems.


Kenneth Porter
Kensington Laboratories, Inc.
mailto:kenneth_porter@kensingtonlabs.com
http://www.kensingtonlabs.com




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