What is tools/firmware/rombios/32bit/... used for?

What is tools/firmware/rombios/32bit/... used for?

[Anthony Wright]

I'm trying to build xen on a pure 64 bit system, but the build is
failing when it tries to build
tools/firmware/rombios/32bit/tcgbios/tcgbios.c with the error:

/usr/include/gnu/stubs.h:7:27: fatal error: gnu/stubs-32.h: No such file
or directory

>From reading around the error, it's caused by a lack of a 32 bit libc
which would make sense as I only have a 64 bit libc on the system at the
moment. To reduce the size of the distro (see my earlier Perl dependency
post), I'd prefer to avoid having to build a 32 bit libc. I therefore
wondered what tcgbios does and what the impact of failing to build the
32 bit support for it would be?

thanks,

Anthony.

Re: What is tools/firmware/rombios/32bit/... used for?

[Andrew Cooper]

On 28/07/2014 22:14, Anthony Wright wrote:
> I'm trying to build xen on a pure 64 bit system, but the build is
> failing when it tries to build
> tools/firmware/rombios/32bit/tcgbios/tcgbios.c with the error:
>
> /usr/include/gnu/stubs.h:7:27: fatal error: gnu/stubs-32.h: No such file
> or directory
>
> From reading around the error, it's caused by a lack of a 32 bit libc
> which would make sense as I only have a 64 bit libc on the system at the
> moment. To reduce the size of the distro (see my earlier Perl dependency
> post), I'd prefer to avoid having to build a 32 bit libc. I therefore
> wondered what tcgbios does and what the impact of failing to build the
> 32 bit support for it would be?
>
> thanks,
>
> Anthony.

hvmloader is a 32bit binary.  It is the first bit of code executed in
any HVM domain and has the job of preparing certain architectural bits
for the BIOS, followed by dropping into 16bit mode to execute the
provided BIOS image.  Irrespective of the rest of your install, it does
have to be built as a 32bit ELF file, as 32bit is the start mode of HVM
domains.

There is no way of avoiding the need for a 32bit set of headers if you
want to build the base components Xen needs to function.

~Andrew

Re: What is tools/firmware/rombios/32bit/... used for?

[Ian Campbell]

On Mon, 2014-07-28 at 23:58 +0100, Andrew Cooper wrote:
> On 28/07/2014 22:14, Anthony Wright wrote:
> > I'm trying to build xen on a pure 64 bit system, but the build is
> > failing when it tries to build
> > tools/firmware/rombios/32bit/tcgbios/tcgbios.c with the error:
> >
> > /usr/include/gnu/stubs.h:7:27: fatal error: gnu/stubs-32.h: No such file
> > or directory
> >
> > From reading around the error, it's caused by a lack of a 32 bit libc
> > which would make sense as I only have a 64 bit libc on the system at the
> > moment. To reduce the size of the distro (see my earlier Perl dependency
> > post), I'd prefer to avoid having to build a 32 bit libc. I therefore
> > wondered what tcgbios does and what the impact of failing to build the
> > 32 bit support for it would be?
> >
> > thanks,
> >
> > Anthony.
> 
> hvmloader is a 32bit binary.  It is the first bit of code executed in
> any HVM domain and has the job of preparing certain architectural bits
> for the BIOS, followed by dropping into 16bit mode to execute the
> provided BIOS image.  Irrespective of the rest of your install, it does
> have to be built as a 32bit ELF file, as 32bit is the start mode of HVM
> domains.
> 
> There is no way of avoiding the need for a 32bit set of headers if you
> want to build the base components Xen needs to function.

Note that this is a build time requirement only, I think. The final
hvmloader binary is essentially statically linked and can be deployed
onto a system without any 32bit headers/libc/etc present.

To answer the original question /rombios/32bit is the parts of the
ROMBIOS bios which run in 32-bit mode (the BIOS will thunk from 16-
to/from 32-bit mode as necessary for various things). ROMBIOS is used
with qemu-xen-traditional only so removing it will mean you can't use
that. The header requirement for this is also build time only.

Ian.