Re: binutils: [mips] ar doesn't recognize ELF64

[Thiemo Seufer <ths@networkno.de>]

Florian Lohoff wrote:
> On Fri, Apr 21, 2006 at 01:07:13AM +0200, Ulrich Teichert wrote:
> > [trimmed the cc list a bit]
> > >> It would also make it difficult to netboot a DECstation - the firmware
> > >> only boots ECOFF kernels. I don't know if it will break delo (the
> > >> DECstation boot loader), too.
> > >
> > >Delo uses ELF. Netbooting a DECstation works via a t-rex generated
> > >image which fakes an ECOFF header.
> > 
> > Ah, good to know.
> 
> addition - The Decstations firmware boots a binary blob to an address
> specified in the first 512bytes of the boot disk. There no format just
> binary instructions. Delo which gets copied with objdump to that blob
> itself knows how to boot ELF.  So for disk booting the decstations does
> not need ECOFF.

Early versions of Delo probably used to do that, but the current one
uses the firmware loader in a more sophisticated way. The firmware
expects in a certain part of the first 512 bytes a list of offset/size
pairs describing disk blocks, which it loads to a load address also
specified there. The whole scheme was intended for Ultrix disklabels,
but happens to fit in a DOS partition table, where it uses some of the
space where a PC BIOS would expect executable code.

The /sbin/delo analyses the next stage bootloader /boot/delo.2nd,
which is an ELF file, and writes the offset/size list of its
binary contents to the aforementioned 512 bytes.

No objcopy involved, no raw binary, no second copy of the loader. :-)

The same works for iso9660 images, btw.


Thiemo