[edk2-devel] [Patch V2 2/2] UefiPayloadPkg: Remove clearing CR0.WP when protecting pagetable

[Ni, Ray]

Reviewed-by: Ray Ni <ray.ni at intel.com>

> -----Original Message-----
> From: Tan, Dun <dun.tan at intel.com>
> Sent: Wednesday, August 10, 2022 1:34 PM
> To: devel at edk2.groups.io
> Cc: Dong, Guo <guo.dong at intel.com>; Ni, Ray <ray.ni at intel.com>; Maurice
> Ma <maurice.ma at intel.com>; You, Benjamin <benjamin.you at intel.com>;
> Rhodes, Sean <sean at starlabs.systems>
> Subject: [Patch V2 2/2] UefiPayloadPkg: Remove clearing CR0.WP when
> protecting pagetable
> 
> Remove clearing CR0.WP when marking the memory used for page table
> as read-only in the page table itself created by UefiPayloadEntry.
> This page table address is written to Cr3 after these protection
> steps. Till this, the memory used for page table is always RW.
> 
> Signed-off-by: Dun Tan <dun.tan at intel.com>
> Cc: Guo Dong <guo.dong at intel.com>
> Cc: Ray Ni <ray.ni at intel.com>
> Cc: Maurice Ma <maurice.ma at intel.com>
> Cc: Benjamin You <benjamin.you at intel.com>
> Cc: Sean Rhodes <sean at starlabs.systems>
> ---
>  UefiPayloadPkg/UefiPayloadEntry/X64/VirtualMemory.c | 7 +------
>  1 file changed, 1 insertion(+), 6 deletions(-)
> 
> diff --git a/UefiPayloadPkg/UefiPayloadEntry/X64/VirtualMemory.c
> b/UefiPayloadPkg/UefiPayloadEntry/X64/VirtualMemory.c
> index 74b667a62a..a586941352 100644
> --- a/UefiPayloadPkg/UefiPayloadEntry/X64/VirtualMemory.c
> +++ b/UefiPayloadPkg/UefiPayloadEntry/X64/VirtualMemory.c
> @@ -622,12 +622,7 @@ EnablePageTableProtection (
>    }
> 
>    //
> -  // Disable write protection, because we need to mark page table to be
> write
> -  // protected.
> -  //
> -  AsmWriteCr0 (AsmReadCr0 () & ~CR0_WP);
> -
> -  //
> +  // No need to clear CR0.WP since PageTableBase has't been written to CR3
> yet.
>    // SetPageTablePoolReadOnly might update mPageTablePool. It's safer to
>    // remember original one in advance.
>    //
> --
> 2.31.1.windows.1



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#92302): https://edk2.groups.io/g/devel/message/92302
Mute This Topic: https://groups.io/mt/92931316/1813853
Group Owner: devel+owner at edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/unsub [edk2-devel-archive at redhat.com]
-=-=-=-=-=-=-=-=-=-=-=-