What kind of tests / applications you think may trigger this issue to occur
under ARM LINUX?
Winnie
> -----Original Message-----
> From: Russell King - ARM Linux Admin [SMTP:[EMAIL PROTECTED]]
> Sent: Friday, March 12, 1999 8:50 AM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
> Subject: Re: MMU bug in Dec/Intel ARMs?
>
> 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.
> _____
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