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Re: [PATCH 8/8] x86: Drop the vm86 segments selectors from struct cpu_user_regs


  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Mon, 17 Mar 2025 13:16:09 +0100
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  • Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Mon, 17 Mar 2025 12:16:13 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 11.03.2025 22:10, Andrew Cooper wrote:
> The data segment registers are part of the on-stack IRET frame when
> interrupting Virtual 8086 mode, but this ceased being relevant for Xen in
> commit 5d1181a5ea5e ("xen: Remove x86_32 build target.") in 2012.
> 
> With all other cleanup in place, delete the fields so we can introduce FRED
> support which uses this space for different data.
> 
> Everywhere which used the es field as an offset in cpu_user_regs needs
> adjusting.  However, they'll change again for FRED, so no cleanup is performed
> at this juncture.
> 
> This also undoes the OoB Read workaround in show_registers(), which can now
> switch back to being simple structure copy.
> 
> No functional change, but a lot of rearranging of stack and struct layout
> under the hood.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>





 


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