* Does anything ever enter through startup_64 in head_64.S?
@ 2016-12-07 15:11 David Howells
2016-12-07 15:24 ` Matt Fleming
0 siblings, 1 reply; 3+ messages in thread
From: David Howells @ 2016-12-07 15:11 UTC (permalink / raw)
To: Matt Fleming; +Cc: dhowells, linux-efi, linux-kernel
Hi Matt,
Does anything ever enter the kernel through startup_64 in head_64.S?[*] Do
all 64-bit mode entries always enter through one of the EFI entry points?
Thanks,
David
[*] I know startup_32 goes through there, but that's internal
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Does anything ever enter through startup_64 in head_64.S?
2016-12-07 15:11 Does anything ever enter through startup_64 in head_64.S? David Howells
@ 2016-12-07 15:24 ` Matt Fleming
2016-12-07 16:47 ` David Howells
0 siblings, 1 reply; 3+ messages in thread
From: Matt Fleming @ 2016-12-07 15:24 UTC (permalink / raw)
To: David Howells; +Cc: linux-efi, linux-kernel
On Wed, 07 Dec, at 03:11:17PM, David Howells wrote:
> Hi Matt,
>
> Does anything ever enter the kernel through startup_64 in head_64.S?[*] Do
> all 64-bit mode entries always enter through one of the EFI entry points?
Which head_64.S? There are two ;-)
Assuming you mean startup_64 in boot/compressed/head_64.S, then the
answer is "yes". 64-bit BIOS boot loaders will jump there.
I'm fairly sure it's possible to boot that way on EFI too, you just
lose some of the newer functionality that is dependent on the EFI boot
stub. But I don't remember the last time I tried it.
In general, we've always tried to maintain backwards compat, but you
don't get the new features without switching to the EFI entry points.
Whether or not any distros are still using the old 0x200 entry point
for EFI is a good question, though.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Does anything ever enter through startup_64 in head_64.S?
2016-12-07 15:24 ` Matt Fleming
@ 2016-12-07 16:47 ` David Howells
0 siblings, 0 replies; 3+ messages in thread
From: David Howells @ 2016-12-07 16:47 UTC (permalink / raw)
To: Matt Fleming; +Cc: dhowells, linux-efi, linux-kernel
Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > Does anything ever enter the kernel through startup_64 in head_64.S?[*] Do
> > all 64-bit mode entries always enter through one of the EFI entry points?
>
> Which head_64.S? There are two ;-)
>
> Assuming you mean startup_64 in boot/compressed/head_64.S, then the
> answer is "yes". 64-bit BIOS boot loaders will jump there.
Sorry, yes, that one.
> I'm fairly sure it's possible to boot that way on EFI too, you just
> lose some of the newer functionality that is dependent on the EFI boot
> stub. But I don't remember the last time I tried it.
>
> In general, we've always tried to maintain backwards compat, but you
> don't get the new features without switching to the EFI entry points.
>
> Whether or not any distros are still using the old 0x200 entry point
> for EFI is a good question, though.
I think I have to assume that there might be.
David
^ permalink raw reply [flat|nested] 3+ messages in thread
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