From: Paolo Bonzini <pbonzini@redhat.com>
To: Thomas Huth <huth@tuxfamily.org>,
Gonzo FWS <fwsgonzo@hotmail.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Cc: Richard Henderson <rth@twiddle.net>,
Eduardo Habkost <ehabkost@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Subject: Re: [Qemu-devel] i386: don't require elf64 for multiboot kernel
Date: Wed, 5 Dec 2018 13:20:51 +0100 [thread overview]
Message-ID: <ced8df86-4fe3-f11e-005c-e9b8127434d6@redhat.com> (raw)
In-Reply-To: <a3fe5633-d031-6a58-40c2-aee43b2bec45@tuxfamily.org>
On 05/12/18 06:35, Thomas Huth wrote:
> On 2018-12-04 17:55, Gonzo FWS wrote:
>> Right now IncludeOS on x86_64 must use a chainloader for multiboot
>> support. The chainloader is an ELF32 kernel that loads the real
>> ELF64 kernel and jumps to it. As long as the ELF has the .multiboot
>> section and conforms to the spec, meaning _start is be a 32-bit
>> entry, it should be fine.
>>
>> By removing the extra check in multiboot.c, we can also boot ELF64
>> files. As can be seen here:
>> https://cloud.fwsnet.net/index.php/s/XrkBkC8zy7MLa9p
>>
>> Signed-off-by: Alf-André Walla <fwsgonzo@hotmail.com>
I think a 64-bit multiboot specification doesn't exist, but if it
existed, it would require an EM_X86_64 ELF file to be booted already in
long mode. I don't think it's a good idea to allow booting into an
EM_X86_64 ELF file with the processor in 32-bit mode.
Paolo
next prev parent reply other threads:[~2018-12-05 12:26 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-04 16:55 [Qemu-devel] i386: don't require elf64 for multiboot kernel Gonzo FWS
2018-12-05 5:35 ` Thomas Huth
2018-12-05 12:20 ` Paolo Bonzini [this message]
2018-12-05 13:03 ` Gonzo FWS
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