On Mon, 24 Sep 2001, Matt Dillon wrote:
> Yowzer. How the hell did that happen! Yes, you're right, the
> vm_page_array[] pointer has gotten corrupted. If we assume that
> the vm_page_t is valid (0xc0842acc), then the vm_page_buckets[]
> pointer should be that.
...
> This is very similar to the corruption I found on one of Yahoo's
> machines. Except on that machine two bits were changed. It's as though
> some other subsystem is trying to manipulate a flag in a structure using
> a bad structure pointer.
>
> -Matt
Ok, time to take a good stab at sticking my foot in my mouth here.
Would it be possible to have a kernel mode where the read-only bit was
turned on for malloc pools which shouldn't currently be accessed? This
could be gated through the spl() calls (or specific mutexes on -current),
ensuring that something like getpid couldn't stomp on the vm structures
w/o first doing a splvm().
Obviously this wouldn't help find bugs in interrupt handlers or other high
level calls, but it could help locate some memory corruption problems.
Actually, since memory regions roughly follow locks, this could be an even
more powerful tool on -current once it develops me.
Is this even feasible in ring 0?
Mike "Silby" Silbersack
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