Re: Etherboot 5.5

On Thu, 19 May 2005, Timothy Legge wrote:
> >   The ability to operate completely in 16-bit real mode, never
> >   switching to protected mode.  This is necessary in order to comply
> >   fully with the PXE "specification".  This is controlled by a
> >   compile-time option -DKEEP_IT_REAL; off by default.
> 
> I understand that this is one of the more difficult parts of the PXE
> spec.  Doesn't it contradict some other requirement in the spec (not
> that that s unusual?

Operating in real mode is not the really tricky part; that would be
operating in 16-bit protected mode (which we're supposed to do with the
same binary code).  There are a few interesting theoretical
impossibilities that the spec throws at us, such as requiring us to write
to specified arbitrary physical addresses when we're in 16-bit pmode and
have enforced 64kB segment limits.

> BTW, do we need an updated compiler/build tools?  I received the 
> following message from the first build I tried:
> 
> In file included from arch/i386/core/hooks.c:1:
> arch/i386/include/registers.h:19: warning: declaration does not declare 
> anything
> arch/i386/include/registers.h:87: warning: declaration does not declare 
> anything
> arch/i386/include/registers.h:88: warning: declaration does not declare 
> anything
> In file included from include/etherboot.h:157,
>                   from include/buffer.h:4,
>                   from include/dev.h:6,
>                   from include/main.h:4,
>                   from arch/i386/core/hooks.c:2:
> include/tftp.h:88: warning: "struct buffer" declared inside parameter list
> include/tftp.h:88: warning: its scope is only this definition or 
> declaration, which is probably not what you want
> arch/i386/core/hooks.c: In function `arch_main':
> arch/i386/core/hooks.c:20: error: structure has no member named `eax'
> arch/i386/core/hooks.c:23: error: structure has no member named `eax'
> make: *** [bin/hooks.o] Error 1

The "struct buffer" issue is due to a tweak I had to make today to get 
doxygen to work; I've fixed this now.  The "does not declare anything" is 
because gcc 3.4.3 apparently doesn't like having unnamed structs.  I 
though that this was supported; I'll have to check.  We don't make 
significant use of the structures in registers.h, so changing them to 
named structs will not be too hard, though it will make the code a little 
less clean.

Michael



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