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SubjectRe: Aerospace and linux
On 06/10/2010 12:38 PM, Brian Gordon wrote:

> On the more exotic end, I have also seen systems that have dual
> redundant processors / memories. Then they add compare logic between
> the redundant processors that compare most pins each clock cycle. If
> any pins are not identical at a clock cycle, then something has gone
> wrong (SEU, hardware failure, etc..)

Some phone switches do this. Some of them also have at least two copies
of everything in memory and will do transactional operations that can be
rolled back if there is a hardware glitch.

> So, some pages of RAM are going to be read-only and the data in those
> pages came from some source (file system?). Can anyone describe a
> high level strategy to occasionaly provide some coverage of this data?

> So far I have thought about page descriptors adding an MD5 hash
> whenever they are read-only and first being "loaded/mapped?" and then
> a background daemon could occasionaly verify.

Makes sense to me. You might also pick an on-disk format with extra
checksumming so you could compare the on-disk checksum with the
in-memory checksum.

Chris

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