Still possible to directly boot without loader?
Bruce M. Simpson
bms at FreeBSD.org
Fri Oct 27 00:54:20 UTC 2006
Ruslan Ermilov wrote:
> I've been investigating this today. Here's what I've found:
> 1) You need hints statically compiled into your kernel.
> (This has been a long time requirement.)
> 2) You can only do it on i386, because boot2 only knows
> about ELF32, so attempts to load ELF64 amd64 kernels
> will fail. (loader(8) knows about both ELF32/64.)
Just FYI: This is indeed how I am succesfully able to boot FreeBSD via
PXE with QEMU + Etherboot, which of course cannot run pxeboot because
Etherboot's PXE code tries to enter protected mode on the i386.
Etherboot claims to be able to interpret and pass FreeBSD kernel
environment variables via PXE encapsulated DHCP options. I haven't tried
emulating an amd64, however.
> 3) It's currently broken even on i386; backing out
> rev. 1.71 of boot2.c by jhb@ fixes this for me.
Do we even need the PAGING code in btx any more? It might make the real
mode hackery less confusing to implement.
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