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Re: [PATCH] Mini-OS: x86: zero out .bss segment at boot


  • To: Jürgen Groß <jgross@xxxxxxxx>, Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>, minios-devel@xxxxxxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, wl@xxxxxxx
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Wed, 7 Feb 2024 10:47:16 +0000
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  • Delivery-date: Wed, 07 Feb 2024 10:47:20 +0000
  • List-id: Mini-os development list <minios-devel.lists.xenproject.org>

On 07/02/2024 10:42 am, Jürgen Groß wrote:
> On 07.02.24 11:38, Samuel Thibault wrote:
>> Juergen Gross, le mer. 07 févr. 2024 11:31:38 +0100, a ecrit:
>>> The .bss segment should be zeroed at very early boot.
>>
>> Is that not done by the elf loader of Xen?
>
> It might be done by Xen tools today, but I'm quite sure it is not part
> of the ABI. The hypervisor doesn't clear .bss when loading a domain (e.g.
> dom0).

It is a requirement of loading an ELF file.

If we're not doing it for dom0, that's a bug.

> I stumbled over it while implementing kexec in Mini-OS. For that I need
> it for sure.

A kexec kernel does need to do this, unless the kexec-loader is going to
guarantee to do it, and I don't believe it does.

~Andrew



 


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