occupy memory

Till Straumann strauman at SLAC.Stanford.EDU
Mon Feb 9 20:38:01 UTC 2004

Chris Caudle wrote:
>>I want to know how RTEMS protect the memory that has been used.
> There is no protection.
>>If I access an address in other process,
> There is only one process.  Tasks are treated as threads in a UNIX style system, that is, all tasks share a single address space, with no protection of one task accessing resources of another task.
> -- Chris Caudle

With hardware support, there is at least _some_ protection.

 >= 604 powerpc CPUs can use pagetables to

  o write-protect the text segment and read-only data
    (this is already implemented) which I find very
    helpful (end up with an exception instead of a
    frozen system when text is overwritten).

  o I recently was thinking that it should be possible
    to use the powerpc VSID ('segment ID') to protect
    task stacks from overflowing (no implementation
    so far - just a few ideas).

-- Till

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