Re: [PATCH 1/1] MdeModulePkg/DxeIplPeim: Relocate the operation of PageMapLevel5Entry++

["Wu, Hao A" <hao.a.wu@intel.com>]

Hello Eric,

Could you help to take a look at this one as well?


> -----Original Message-----
> From: Zhang, Shenglei
> Sent: Monday, August 12, 2019 2:25 PM
> To: devel@edk2.groups.io
> Cc: Bi, Dandan; Gao, Liming; Wu, Hao A; Laszlo Ersek; Dong, Eric
> Subject: [PATCH 1/1] MdeModulePkg/DxeIplPeim: Relocate the operation of
> PageMapLevel5Entry++
> 
> PageMapLevel5Entry may be uninitialized in original code, which means
> uninitialized pointer will be modified at some circumstance.
> So relocate the operation of PageMapLevel5Entry++ in order to make sure
> the pointer could be modified only when it is uninitialized.
> 
> Cc: Dandan Bi <dandan.bi@intel.com>
> Cc: Liming Gao <liming.gao@intel.com>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
> ---
>  MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> b/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> index b40b7e0c9813..2389f3eb485b 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> +++ b/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> @@ -764,7 +764,7 @@ CreateIdentityMappingPageTables (
> 
>    for ( IndexOfPml5Entries = 0
>        ; IndexOfPml5Entries < NumberOfPml5EntriesNeeded
> -      ; IndexOfPml5Entries++, PageMapLevel5Entry++) {
> +      ; IndexOfPml5Entries++) {
>      //
>      // Each PML5 entry points to a page of PML4 entires.
>      // So lets allocate space for them and fill them in in the
> IndexOfPml4Entries loop.
> @@ -780,6 +780,7 @@ CreateIdentityMappingPageTables (
>        PageMapLevel5Entry->Uint64 = (UINT64) (UINTN) PageMapLevel4Entry |
> AddressEncMask;
>        PageMapLevel5Entry->Bits.ReadWrite = 1;
>        PageMapLevel5Entry->Bits.Present   = 1;
> +      PageMapLevel5Entry++;
>      }


I think the change is fine,
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>

Best Regards,
Hao Wu


> 
>      for ( IndexOfPml4Entries = 0
> --
> 2.18.0.windows.1