Bruce Dubbs wrote: > I've noticed an irritating message when klogd starts up. It says: > > Cannot find map file.
Meh. I've been skipping the System.map copy (as part of the kernel install) *forever* -- or at least ever since I moved to kernel 2.6, I believe -- and never cared enough to fix this. (When I even noticed. What's one line in kern.log? :-) ) > Researching some more, it looks like the kernel removed this symbol > by default somewhere around 2.6.27. sysklogd has not been updated > since 2007. Yeah, but the kernel does all this already, so my opinion is that it's pointless to try to get the right file to pass to klogd. Better (IMO) to just silence the warning, if we care at all. (I don't, myself, but I can see why people might.) > My understanding is that klogd reads the symbols to translate kernel > oops to symbols. Well, it tries to. There are no addresses to convert anymore, so it's a bit hard for it to actually do anything. :-) > I think I saw that the kernel is now doing that internally. Yep, ever since 2.6 was released I believe. "kksymoops" was the feature name, I think. > In that case, there is no need for klogd to read System.map at all. Indeed. > To stop klogd from trying to read System.map, it requires passing -x > in the command line. We can do that easily in the boot scripts. Which I would suggest if we want to silence the warning. Given the (total lack of) need for System.map for the past seven years, I think we should also expunge any reference to it from the book, but whatever. > What this also implies is that we don't need to copy System.map to > /boot at all. Indeed. As above, I've been skipping it ever since I moved to 2.6, with zero problems at all. (Even in an initramfs, where klogd isn't running and System.map is nowhere to be found, the occasional BUG_ON() output that I see due to race conditions in the block driver -- or at least, I think that's the cause; something is trying to register a second /sys/block/sdb kobject -- has symbol names.) > P.S. It appears that the Version string can be turned on in the > kernel's make menuconfig, but it's not particularly easy: Yeah, but why? kksymoops obviates all of this. :-) > Change (for small systems) to yes, select the submenu, turn off "Load > all symbols" This seems backwards. You have to turn *off* "all symbols" to *add* Version_xxxx to the symbol table? Wouldn't be the first strange thing I've seen, but it does seem ... uh, strange. :-)
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