Re: [PATCH v2 1/1] MdeModulePkg/PiSmmCore: Pad POOL_HEADER to be 8-byte aligned

["Zeng, Star" <star.zeng@intel.com>]

Good comments.
I plan to send the patch for https://bugzilla.tianocore.org/show_bug.cgi?id=407 this week.
Since the patch for https://bugzilla.tianocore.org/show_bug.cgi?id=407 can naturally fix the alignment issue, so we can skip this patch.

Thanks,
Star
-----Original Message-----
From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Yao, Jiewen
Sent: Tuesday, April 18, 2017 2:52 PM
To: Wu, Hao A <hao.a.wu@intel.com>; edk2-devel@lists.01.org
Subject: Re: [edk2] [PATCH v2 1/1] MdeModulePkg/PiSmmCore: Pad POOL_HEADER to be 8-byte aligned

Thanks, this is better.

I recall that I have submitted a bugzillar before to enhance Smm FreePool to catch buffer overflow https://bugzilla.tianocore.org/show_bug.cgi?id=407

Maybe we can use below structure, then we do not need PAD.
typedef struct { // Proposal for SMM core
   UINT32          Signature;
   BOOLEAN         Available;
   EFI_MEMORY_TYPE Type;
   UINTN           Size;
 } POOL_HEADER;


This is also similar to DXE version:
typedef struct { // Current DXE core
  UINT32          Signature;
  UINT32          Reserved;
  EFI_MEMORY_TYPE Type;
  UINTN           Size;
  CHAR8           Data[1];
} POOL_HEAD;

Thank you
Yao Jiewen


> -----Original Message-----
> From: Wu, Hao A
> Sent: Tuesday, April 18, 2017 10:37 AM
> To: edk2-devel@lists.01.org
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>
> Subject: [PATCH v2 1/1] MdeModulePkg/PiSmmCore: Pad POOL_HEADER to be 
> 8-byte aligned
> 
> According to the PI spec (Vol 4, Section 3.2 SmmAllocatePool()):
> The SmmAllocatePool() function ... All allocations are eight-byte aligned.
> 
> The commit adds a padding field in structure 'POOL_HEADER' to ensure 
> the above requirement is met.
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Hao Wu <hao.a.wu@intel.com>
> ---
>  MdeModulePkg/Core/PiSmmCore/PiSmmCore.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> b/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> index c12805a2dd..0692661114 100644
> --- a/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> +++ b/MdeModulePkg/Core/PiSmmCore/PiSmmCore.h
> @@ -1200,6 +1200,14 @@ typedef struct {
>    UINTN           Size;
>    BOOLEAN         Available;
>    EFI_MEMORY_TYPE Type;
> +  //
> +  // According to the PI spec, buffers allocated by SmmAllocatePool 
> + should  // be 8-byte aligned. Here, the pad bytes make sure that the 
> + structure  // is 8-byte aligned:
> +  // For IA32, sizeof (POOL_HEADER) is 16.
> +  // For X64, sizeof (POOL_HEADER) is 24.
> +  //
> +  UINT32          Padding;
>  } POOL_HEADER;
> 
>  typedef struct {
> --
> 2.12.0.windows.1

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