Re: [Qemu-devel] [PATCH] Add multi-boot kernel loading support

[Alexander Graf]

On 03.02.2009, at 11:53, Jamie Lokier wrote:

> Alexander Graf wrote:
> > > > --- elf_ops.h    (revision 6501)
> > > > +++ elf_ops.h    (working copy)
> > > > @@ -195,6 +195,10 @@
> > > >   }
> > > >
> > > >   if (ELF_MACHINE != ehdr.e_machine)
> > > > +#if (ELF_MACHINE == EM_X86_64) && !defined(CONFIG_USER_ONLY)
> > > > +      /* x86_64 systems can run i386 code as well */
> > > > +      if(ehdr.e_machine != EM_386)
> > > > +#endif
> > > >       goto fail;
> > > >
> > > >   if (pentry)
> > >
> > > Seems like an unrelated fix.
> >
> > Actually it's not. If you want to load a 32-bit elf (multiboot)
> > executable on an x86_64 system, you need this patch.
>
> Why CONFIG_USER_ONLY?
>
> Does it mean qemu-x86_64 (the user one) will behave differently given
> a 32-bit ELF file if you built qemu-system-x86_64 at the same time?

It's !defined(), to ensure the userspace emulation behavior doesn't  
change. Right now, loading an i386 binary with qemu-x86_64 does not  
work - and I don't want to change that for now.

AFAIK CONFIG_USER_ONLY is defined when building qemu-x86_64, but not  
when building qemu-system-x86_64.

Alex