Date: Tue, 03 Nov 1998 13:24:08 -0800 From: Mike Smith <mike@smith.net.au> To: Chuck Robey <chuckr@mat.net> Cc: Peter Wemm <peter@netplex.com.au>, Brian Feldman <green@zone.syracuse.net>, John Hay <jhay@mikom.csir.co.za>, freebsd-current@FreeBSD.ORG Subject: Re: Booting Elf Kernel Message-ID: <199811032124.NAA00500@dingo.cdrom.com> In-Reply-To: Your message of "Tue, 03 Nov 1998 08:03:28 EST." <Pine.BSF.4.05.9811030759560.300-100000@picnic.mat.net>
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> On Tue, 3 Nov 1998, Peter Wemm wrote: > > > Brian Feldman wrote: > > > Ahhhh, that's where it is! I have no good idea on how to allow, with this > > > code, lkm's and kld's to coexist.... so is it time to completely phase out > > > lkm's yet? > > > > I think the best way is to have mount(2) initiate a kldload if needed. We > > will need this functionality sooner or later. If mount(2) does it, we can > > garbage collect unused, unmounted filesystems after a while and unload > > them. > > Peter, you once told me that the new elf kernel has both aout and elf > linkers in it. Does an elf kernel have the ability to load lkm modules, > not the .ko things? If so, then the mount stuff is going to need to > know which kind of module to hunt for, to load, right? Or, if they both > work, maybe find both, and load the newest? With maybe a kld bias for a > tiebreaker? Peter has already answered this pretty well; let me just clarify a few things which will hopefully help understanding. The old LKM model was somewhat ugly; it worked like this: LKM's were built as relocatable objects. To load an LKM, you used the a.linker to link the LKM object against the kernel file. The newly relocated object was then copied into kernel space. This procedure was dependant on having writable disk space (for the relocated object), the a.out linker present, and could not be initiated from inside the kernel. In contrast, the new (KLD) approach works like this: A KLD module load is initiated by passing the pathname of the module to the kernel. The kernel itself reads the object into memory, relocates it at the new location, resolves any dependancies, connects SYSINITs, etc. This can be done off a completely read-only filestore, and in fact the kernel doesn't even have to read the modules in; they can be placed in advance by the bootloader. You could, theoretically, load both LKMs and KLD modules into an a.out kernel. You can't do anything with LKMs that involves an ELF object, either the LKM or the kernel. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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