Dave Baukus writes:
> Stephen Noftall wrote:
> > I just heard from Intel that they are coming out with a new SA-110, that
> > supposedly fixes a bug only found in demand paged memory management OS's. The
> > new part numbers are 21281-xB.
>
> The errata reads:
> "There is an anomaly in the SA-110 device that may occur during DATA_ABORT
> in environments that use demand-paging management schemes. This problem
> has been seen only in demand-page memory-management operating systems when
> a memory access crosses a page boundary from a mapped page to an unmapped
> page during the sequence of data fetches."
>
> It goes on to list some RTOSs that, since they do not use demand paging,
> are not susceptible to the problem.
>
> I heard that via a 3id party that and Intel rep. said Linux was not susceptible
> to this problem. If true I'd like to know why.
>
> Any know the real answer ?
Any program in a demand paged OS would be susceptible to this problem. However,
The Linux kernel itself is not. The routines which use the ldm instruction are
carefully coded to handle the user space permissions anyway, so a ldm instruction
is never used to cross a page boundary.
It is, however, an issue for user programs. The user stack is a conventional
full decending stack, which means that the affected instruction (ldmib) will not
be used.
Hence, I think the answer to this is that the ARM Linux OS is not susceptible
to this problem, but user programs could be. My current experiance suggests that
no user programs currently exist which hit this problem.
_____
|_____| ------------------------------------------------- ---+---+-
| | Russell King [EMAIL PROTECTED] --- ---
| | | | http://www.arm.linux.org.uk/~rmk/armlinux.html / / |
| +-+-+ --- -+-
/ | THE developer of ARM Linux |+| /|\
/ | | | --- |
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