Re: KMSGDUMP: dump kernel messages to a diskette

Dan Hollis (goemon@sasami.anime.net)
Sat, 10 Jul 1999 17:14:16 -0700 (PDT)

On Sat, 10 Jul 1999, Willy Tarreau wrote:
> Concerning the possibilities of executing code upon a manual reset, I've
> tested it and it doesn't work. The PC simply reboots. I remember that some
> chipsets clean all the memory themselves upon reset. But what I can't
> understand is why the bios doesn't hang instead of rebooting. Since my
> CMOS register contains 0xA or 0x9 or anything else, the bios should notice it.

I have done some investigation and it seems that at least on Award BIOS,
the "quick post"/"quick power on selftest" option in BIOS causes the BIOS
to skip memory testing. Possibly this leaves RAM untouched after a hard
reset.

So another possibility is to have a "clean/dirty" flag at the top of RAM,
similar to what is used for mounted filesystems. If the OS cleanly shuts
down, this flag is set "clean", it indicates it was a clean shutdown and
no crashdump is needed. If it is left "dirty", then lilo can do a memory
dump to the swap partition, which is then picked up by 'swapon' and
written to the filesystem.

-Dan

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