remember that we hit almost this problem with the KSE stuff during
debugging?
The pointers in the last few entries of the vm_page_buckets array got
corrupted when an agument to a function that manipulated whatever was next
in ram was 0, and it turned out that it was 0 because
of some PTE flushing thing (you are the one that found it... remember?)
(there was a line of asm code missing)
On Mon, 24 Sep 2001, Matt Dillon wrote:
>
> :
> :In message <[EMAIL PROTECTED]>, Matt Dillon writes:
> :>
> :>$8 = 58630
> :>(kgdb) print vm_page_buckets[$8]
> :
> :What is vm_page_hash_mask? The chunk of memory you printed out below
> :looks alright; it is consistent with vm_page_array == 0xc051c000. Is
> :it just the vm_page_buckets[] pointer that is corrupt?
> :
> :The address 0xc08428cc is (char *)&vm_page_array[55060] + 28, and
> :sizeof(struct vm_page) is 60, so 0xc08428cc is in the middle of
> :a vm_page within vm_page_array[].
> :
> :Ian
>
> (kgdb) print vm_page_buckets[58630]
> $5 = (struct vm_page *) 0xc08428cc
> (kgdb) print vm_page_array
> $6 = 0xc051c000
> (kgdb) print vm_page_hash_mask
> $7 = 262143
> (kgdb) print &vm_page_array[55060]
> $11 = (struct vm_page *) 0xc08428b0
> (kgdb) print &vm_page_array[55061]
> $10 = (struct vm_page *) 0xc08428ec
>
> 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.
>
> vm_page_buckets[58630] -> c08428cc
> panic on vm_page_t m -> c0842acc
>
> Ok, so the corruption here is that an 'a' turned into an '8'. 1010 turned
> into 1000... a bit got cleared.
>
> 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
>
>
>
> To Unsubscribe: send mail to [EMAIL PROTECTED]
> with "unsubscribe freebsd-hackers" in the body of the message
>
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message
