kernel memory checks on boot vs. boot time

Alexander Best arundel at
Wed Mar 23 20:02:00 UTC 2011

On Wed Mar 23 11, Oliver Fromme wrote:
> Alexander Best wrote:
>  > just as a side note: booting a kernel directly from boot stage 2 is broken on
>  > amd64. :( so there's no way around using the boot loader, which will cost extra
>  > time (even with autoboot_delay=0).
>  > 
>  > so was the adbility to boot a kernel directly from boot2 abandoned? i heard
>  > reports it still works under i386. dunno about the other archs.
> The loader checks the type of the kernel binary (i386 vs
> amd64).  In case of amd64, it enables "long mode", among
> other things.  This is required for amd64, because the
> kernel expects to be started in long mode.  boot2 doesn't
> do that, so you can't start an amd64 kernel directly from
> boot2.

hmm...i can't seem to find the location in loader/main.c. could you pinpoint
me to the exact location? this is something i'd *really* like to try in amd64.


> In theory you could write a specialized amd64 variant of
> boot2 that prepares the system for starting an amd64 kernel
> directly.  Whether there's enough space for that in boot2
> (8 KB) and whether it's worth the effort, I don't know.
> To be honest, I don't think that loader takes so much time.
> When you set autoboot_delay="-1" and beastie_disable="YES",
> the time spent in loader is negligible.  (I'm assuming that
> you also set BOOTWAIT=0 in make.conf, so boot2 doesn't wait
> for a keypress either.  I think the default is to wait 3
> seconds.)
> Best regards
>    Oliver
> -- 
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