Re: [PATCH 1/2] MdeModulePkg/Core: Refine handling NULL detection in NX setting

["Yao, Jiewen" <jiewen.yao@intel.com>]

reviewed-by: Jiewen.yao@intel.com

> -----Original Message-----
> From: Wu, Hao A
> Sent: Tuesday, March 6, 2018 8:11 PM
> To: edk2-devel@lists.01.org
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Wang, Jian J <jian.j.wang@intel.com>;
> Zeng, Star <star.zeng@intel.com>; Dong, Eric <eric.dong@intel.com>; Yao,
> Jiewen <jiewen.yao@intel.com>; Ni, Ruiyu <ruiyu.ni@intel.com>
> Subject: [PATCH 1/2] MdeModulePkg/Core: Refine handling NULL detection in
> NX setting
> 
> The commit rewrites the logic in function
> InitializeDxeNxMemoryProtectionPolicy() for handling the first page
> (page 0) when NULL pointer detection feature is enabled.
> 
> Instead of skip setting the page 0, the codes will now override the
> attribute setting of page 0 by adding the 'EFI_MEMORY_RP' attribute.
> 
> The purpose is to make it easy for other special handlings of pages
> (e.g. the first page of the stack when stack guard feature is enabled).
> 
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Hao Wu <hao.a.wu@intel.com>
> ---
>  MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 22
> +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
> b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
> index 455ed35f9a..a2ea445eef 100644
> --- a/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
> +++ b/MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c
> @@ -19,7 +19,7 @@
> 
>    Once the image is unloaded, the protection is removed automatically.
> 
> -Copyright (c) 2017, Intel Corporation. All rights reserved.<BR>
> +Copyright (c) 2017 - 2018, Intel Corporation. All rights reserved.<BR>
>  This program and the accompanying materials
>  are licensed and made available under the terms and conditions of the BSD
> License
>  which accompanies this distribution.  The full text of the license may be found
> at
> @@ -846,23 +846,23 @@ InitializeDxeNxMemoryProtectionPolicy (
> 
>      Attributes = GetPermissionAttributeForMemoryType
> (MemoryMapEntry->Type);
>      if (Attributes != 0) {
> +      SetUefiImageMemoryAttributes (
> +        MemoryMapEntry->PhysicalStart,
> +        LShiftU64 (MemoryMapEntry->NumberOfPages, EFI_PAGE_SHIFT),
> +        Attributes);
> +
>        if (MemoryMapEntry->PhysicalStart == 0 &&
>            PcdGet8 (PcdNullPointerDetectionPropertyMask) != 0) {
> 
>          ASSERT (MemoryMapEntry->NumberOfPages > 0);
>          //
> -        // Skip page 0 if NULL pointer detection is enabled to avoid attributes
> -        // overwritten.
> +        // Add EFI_MEMORY_RP attribute for page 0 if NULL pointer
> detection is
> +        // enabled.
>          //
>          SetUefiImageMemoryAttributes (
> -          MemoryMapEntry->PhysicalStart + EFI_PAGE_SIZE,
> -          LShiftU64 (MemoryMapEntry->NumberOfPages - 1,
> EFI_PAGE_SHIFT),
> -          Attributes);
> -      } else {
> -        SetUefiImageMemoryAttributes (
> -          MemoryMapEntry->PhysicalStart,
> -          LShiftU64 (MemoryMapEntry->NumberOfPages, EFI_PAGE_SHIFT),
> -          Attributes);
> +          0,
> +          EFI_PAGES_TO_SIZE (1),
> +          EFI_MEMORY_RP | Attributes);
>        }
>      }
>      MemoryMapEntry = NEXT_MEMORY_DESCRIPTOR (MemoryMapEntry,
> DescriptorSize);
> --
> 2.12.0.windows.1