FILO 0.4 [PMX:#]

ron minnich rminnich at
Sun Apr 4 23:56:01 CEST 2004

RE the bigger issue of compiling things direct into linuxbios. 

I've been thinking for some time of an experiment, namely turning this 
whole business inside-out. Think of it this way: there is a runtime 
startup for every program your write, called in old times crt0 (which is 
why I used that name for LinuxBIOS). But from your point of view, your 
program is not crt0, it's main(). 

So looking from the point of view of the compiler and library writers, who 
know nothing of your program when they write the compilers and libraries, 
the world is libc.a and crt0. You don't care about that, and from your 
point of view, the world is your program. You use the compiler to get your 
startup code and some library calls. 

This leads to a natural question: what if we think of linuxbios as
something to be linked into a boot loader such as openbios, filo, 9load,
or even a special linux kernel? In other words, invert our view of the
world: we don't compile a boot loader as part of building linuxbios; we
compile linuxbios into a bootloader. Linuxbios provides startup (analogous
to crt0) and some library functions the boot loader needs (print* support,
pci enumeration, etc) but the really important bit is the boot loader.

In this view, linuxbios is a library that you link your bootloader with to
build a bios. This really changes things around a bit. It also removes 
some nasty problems, as the bootloader no longer has to supply (e.g.) its 
own PCI enumeration code, and can use the linuxbios PCI enumeration code, 
which can help boot loaders avoid bugs in chips (consider the VT8601 and 
the PCI bugs it used to have). 

This view is sort of halfway from old bios ideas (INT xy) and current
ideas (the payload doesn't know linuxbios exists). It's a huge change --
maybe a very bad idea, as it means that now LinuxBIOS provides an API,
which we never intended it to do. I have no idea if it even makes sense --
just wondering.

Back to our irregularly scheduled arguments :-)


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