Re: [Xen-devel] [PATCH v2 23/23] x86: add multiboot2 protocol support for relocatable images

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Fri, Aug 14, 2015 at 01:57:01PM +0200, Daniel Kiper wrote:
> On Tue, Aug 11, 2015 at 12:56:58PM -0400, Konrad Rzeszutek Wilk wrote:
> > On Mon, Jul 20, 2015 at 04:29:18PM +0200, Daniel Kiper wrote:
> > > Add multiboot2 protocol support for relocatable images. Only GRUB2
> > > with relevant patches understands that feature. Older multiboot
> >
> > You may want to enumerate what those 'relevant' patches are.
> >
> > > protocol (regardless of version) compatible loaders ignore it
> > > and everything works as usual.
> > >
> > > Signed-off-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
> > > ---
> > >  xen/arch/x86/boot/head.S          |   46 
> > > +++++++++++++++++++++++++++++--------
> > >  xen/arch/x86/x86_64/asm-offsets.c |    1 +
> > >  xen/include/xen/multiboot2.h      |   13 +++++++++++
> > >  3 files changed, 50 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> > > index d484f68..2520e48 100644
> > > --- a/xen/arch/x86/boot/head.S
> > > +++ b/xen/arch/x86/boot/head.S
> > > @@ -81,6 +81,13 @@ multiboot1_header_end:
> > >          /* Align modules at page boundry. */
> > >          mb2ht_init MB2_HT(MODULE_ALIGN), MB2_HT(REQUIRED)
> > >
> > > +        /* Load address preference. */
> > > +        mb2ht_init MB2_HT(RELOCATABLE), MB2_HT(OPTIONAL), \
> > > +                   sym_phys(start), /* Min load address. */ \
> >
> > We could go straight to __start?
> 
> This specifies lowest load address not entry point.

Ah right. And the __start can be moved somewhere inside the .text
code, while 'start' is always at offset 0. Thank you!

> 
> Daniel

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