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SubjectRe: [PATCH 23/62] x86/idt: Move IDT to data segment
Date


> On Feb 12, 2020, at 3:55 AM, Joerg Roedel <joro@8bytes.org> wrote:
>
> On Tue, Feb 11, 2020 at 02:41:25PM -0800, Andy Lutomirski wrote:
>>> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@8bytes.org> wrote:
>>>
>>> From: Joerg Roedel <jroedel@suse.de>
>>>
>>> With SEV-ES, exception handling is needed very early, even before the
>>> kernel has cleared the bss segment. In order to prevent clearing the
>>> currently used IDT, move the IDT to the data segment.
>>
>> Ugh. At the very least this needs a comment in the code.
>
> Yes, right, added a comment for that.
>
>> I had a patch to fix the kernel ELF loader to clear BSS, which would
>> fix this problem once and for all, but it didn't work due to the messy
>> way that the decompressor handles memory. I never got around to
>> fixing this, sadly.
>
> Aren't there other ways of booting (Xen-PV?) which don't use the kernel
> ELF loader?

Dunno. I would hope the any sane loader would clear BSS before executing anything. This isn’t currently the case, though. Oh well.

>
> Regards,
>
> Joerg

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