Re: [PATCH 0/2] Reserve page 0 for NULL pointer detection

["Ni, Ray" <ray.ni@intel.com>]

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

> -----Original Message-----
> From: Wang, Jian J <jian.j.wang@intel.com>
> Sent: Wednesday, November 6, 2019 9:14 PM
> To: devel@edk2.groups.io
> Cc: Bi, Dandan <dandan.bi@intel.com>; Gao, Liming <liming.gao@intel.com>; Ni, Ray <ray.ni@intel.com>; Wu, Hao A
> <hao.a.wu@intel.com>; Sean Brogan <sean.brogan@microsoft.com>
> Subject: [PATCH 0/2] Reserve page 0 for NULL pointer detection
> 
> When a boot loader examines the memory map, it can see that location 0
> is available memory. If it chooses to use that memory, and
> PcdNullPointerDetectionPropertyMask is enabled, use of memory in page 0
> will cause an exception. This does occur when running the memtest86
> program.
> 
> Leaving page 0 available is for legacy support purpose. Since we have
> deprecated the support of legacy, the solution is just reserving it so
> that it cannot be allocated for other uses.
> 
> Tests:
>   - run memtest86 with PcdNullPointerDetectionPropertyMask set to 0x03
>   - run memtest86 with PcdNullPointerDetectionPropertyMask set to 0x83
>   - boot OVMF into Windows 7 with PcdNullPointerDetectionPropertyMask set to 0x83
> 
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1885
> Cc: Dandan Bi <dandan.bi@intel.com>
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Sean Brogan <sean.brogan@microsoft.com>
> 
> Jian J Wang (2):
>   MdeModulePkg/DxeIplPeim: reserve page 0 for NULL pointer detection
>   MdeModulePkg/Core/Dxe: free page 0 after disabling NULL pointer
>     detection
> 
>  MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c   | 5 +++++
>  MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 4 ++++
>  MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c  | 4 ++++
>  3 files changed, 13 insertions(+)
> 
> --
> 2.17.1.windows.2