On Tue, Mar 19, 2024 at 10:07 AM Roger Pau Monné <roger....@citrix.com> wrote: > > On Wed, Mar 13, 2024 at 03:07:43PM +0000, Ross Lagerwall wrote: > > Binaries may be built with entry points above 4G. While bootloaders may > > relocate them below 4G, it should be possible for the binary to specify > > those entry points. Therefore, extend the multiboot2 protocol such that > > 64 bit addresses are allowed for entry points. The extension is done in > > a backwards-compatible way. > > > > Signed-off-by: Ross Lagerwall <ross.lagerw...@citrix.com> > > --- > > doc/multiboot.texi | 32 +++++++++++++++++++------------- > > doc/multiboot2.h | 6 +++++- > > 2 files changed, 24 insertions(+), 14 deletions(-) > > > > diff --git a/doc/multiboot.texi b/doc/multiboot.texi > > index d12719c744eb..049afab53c1f 100644 > > --- a/doc/multiboot.texi > > +++ b/doc/multiboot.texi > > @@ -522,12 +522,12 @@ header. > > > > @example > > @group > > - +-------------------+ > > -u16 | type = 3 | > > -u16 | flags | > > -u32 | size | > > -u32 | entry_addr | > > - +-------------------+ > > + +-------------------+ > > +u16 | type = 3 | > > +u16 | flags | > > +u32 | size | > > +u32 / u64 | entry_addr | > > + +-------------------+ > > I might be confused, but this entry point is used in 32bit protected > mode, and hence a 64bit value is simply impossible to use according to > the protocol in "3.3 I386 machine state". > > Unless that section is expanded to describe other protocols that use > the entry address in a way where 64bits could be meaningful it seems > pointless to expand the field.
I changed this because the same binary is being used for both BIOS boot and UEFI boot, therefore it may have a base address above 4 GiB. Despite that, it is expected that GRUB would relocate the binary below 4 GiB so BIOS boot would still work. However, on reflection this is kind of nasty. I've managed to build Xen in such a way that this is no longer needed so I can drop this change from the next version of this series. Ross _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
