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From: Ross Lagerwall <ross.lagerwall@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Julien Grall" <julien@xen.org>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH v2 1/2] x86: Add support for building a multiboot2 PE binary
Date: Wed, 17 Apr 2024 16:05:25 +0100	[thread overview]
Message-ID: <CAG7k0EpKRVpbfBOSA9tsQsGM9_nLCmrZNYzV6G9u5g46oZWKwQ@mail.gmail.com> (raw)
In-Reply-To: <0d84a96a-c1ec-4c4e-9cb5-44a6542e0d43@suse.com>

On Wed, Apr 17, 2024 at 3:15 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 10.04.2024 11:41, Ross Lagerwall wrote:
> > On Mon, Apr 8, 2024 at 11:25 AM Jan Beulich <jbeulich@suse.com> wrote:
> >> On 28.03.2024 16:11, Ross Lagerwall wrote:
> >>> * The image base address is set to 0 since it must necessarily be below
> >>>   4 GiB and the loader will relocate it anyway.
> >>
> >> While technically okay, what is the reason for this adjustment?
> >
> > The multiboot2 spec generally uses 32 bit addresses for everything and
> > says:
> >
> > "The bootloader must not load any part of the kernel, the modules, the
> > Multiboot2 information structure, etc. higher than 4 GiB - 1."
> >
> > An image base address above 4 GiB causes trouble because multiboot2
> > wasn't designed for this.
>
> Yet mb2 doesn't care about that PE header field at all, does it? In which
> case my question remains: What purpose does this particular modification
> of the image have?
>

With the currently published version of mb2, it doesn't look at the PE
header field since it has no knowledge about PE binaries.

With the proposal on the grub-devel list [1], mb2 would use the PE
header to load the new xen-mbi binary in which case, the image base
address is indeed relevant.

Ross

[1] https://lists.gnu.org/archive/html/grub-devel/2024-03/msg00081.html


  reply	other threads:[~2024-04-17 15:05 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-28 15:11 [PATCH v2 0/2] x86: Multiboot PE support Ross Lagerwall
2024-03-28 15:11 ` [PATCH v2 1/2] x86: Add support for building a multiboot2 PE binary Ross Lagerwall
2024-04-08 10:25   ` Jan Beulich
2024-04-10  9:41     ` Ross Lagerwall
2024-04-17 14:14       ` Jan Beulich
2024-04-17 15:05         ` Ross Lagerwall [this message]
2024-04-17 16:07           ` Jan Beulich
2024-03-28 15:11 ` [PATCH v2 2/2] x86: Call Shim Verify in the multiboot2 path Ross Lagerwall
2024-04-08 10:42   ` Jan Beulich
2024-04-10 10:00     ` Ross Lagerwall

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