On 3/7/2018 12:28 PM, Wu, Hao A wrote:
Hi Ray,

Below are the answers to your feedbacks:

-----Original Message-----
From: Yao, Jiewen
Sent: Wednesday, March 07, 2018 12:14 PM
To: Wang, Jian J; Ni, Ruiyu; Wu, Hao A; edk2-devel@lists.01.org
Cc: Zeng, Star; Dong, Eric
Subject: RE: [PATCH v2 0/2] Resolve feature conflict between NX and Stack
guard

I think the original patch is fine.

StackBase is already checked by using ASSERT before.
+        ASSERT ((StackBase & EFI_PAGE_MASK) == 0);

MemMap entry must be page aligned.

No additional check is required here.

Thank you
Yao Jiewen


-----Original Message-----
From: Wang, Jian J
Sent: Wednesday, March 7, 2018 11:40 AM
To: Ni, Ruiyu <ruiyu...@intel.com>; Wu, Hao A <hao.a...@intel.com>;
edk2-devel@lists.01.org
Cc: Zeng, Star <star.z...@intel.com>; Dong, Eric <eric.d...@intel.com>; Yao,
Jiewen <jiewen....@intel.com>
Subject: RE: [PATCH v2 0/2] Resolve feature conflict between NX and Stack
guard



Regards,
Jian


-----Original Message-----
From: Ni, Ruiyu
Sent: Wednesday, March 07, 2018 11:17 AM
To: Wu, Hao A <hao.a...@intel.com>; edk2-devel@lists.01.org
Cc: Wang, Jian J <jian.j.w...@intel.com>; Zeng, Star
<star.z...@intel.com>;
Dong, Eric <eric.d...@intel.com>; Yao, Jiewen <jiewen....@intel.com>
Subject: Re: [PATCH v2 0/2] Resolve feature conflict between NX and Stack
guard

On 3/6/2018 9:33 PM, Hao Wu wrote:
V2 changes:

A. Use Hoblib APIs to get the base of stack from Hob.
B. Remove unnecessary local variable used in function
     InitializeDxeNxMemoryProtectionPolicy().

V1 history:

If enabled, NX memory protection feature will mark some types of active
memory as NX (non-executable), which includes the first page of the stack.
This will overwrite the attributes of the first page of the stack if the
stack guard feature is also enabled.

The series will override the attributes setting to the first page of the
stack by adding back the 'EFI_MEMORY_RP' attribute when the stack
guard
feature is enabled.

Cc: Jian J Wang <jian.j.w...@intel.com>
Cc: Star Zeng <star.z...@intel.com>
Cc: Eric Dong <eric.d...@intel.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Ruiyu Ni <ruiyu...@intel.com>

Hao Wu (2):
    MdeModulePkg/Core: Refine handling NULL detection in NX setting
    MdeModulePkg/Core: Fix feature conflict between NX and Stack guard

   MdeModulePkg/Core/Dxe/DxeMain.inf             |  4 +-
   MdeModulePkg/Core/Dxe/Misc/MemoryProtection.c | 74
+++++++++++++++++++++++----
   2 files changed, 67 insertions(+), 11 deletions(-)


        if (MemoryMapEntry->PhysicalStart == 0 &&
            PcdGet8 (PcdNullPointerDetectionPropertyMask) != 0) {

          ASSERT (MemoryMapEntry->NumberOfPages > 0);
          //
          // Add EFI_MEMORY_RP attribute for page 0 if NULL pointer
detection is
          // enabled.
          //
[Ray] 1. I prefer to move the above comments before the "if (...)".

Yes. I agree that moving the comments block out of the 'if' statement is
more readable. I will update according to your suggestion when I pushing
the changes.


          SetUefiImageMemoryAttributes (
            0,
            EFI_PAGES_TO_SIZE (1),
            EFI_MEMORY_RP | Attributes);
        }

        if (StackBase != 0 &&
            (StackBase >= MemoryMapEntry->PhysicalStart &&
             StackBase <  MemoryMapEntry->PhysicalStart +
                          LShiftU64
(MemoryMapEntry->NumberOfPages,
EFI_PAGE_SHIFT)) &&
            PcdGetBool (PcdCpuStackGuard)) {

          //
          // Add EFI_MEMORY_RP attribute for the first page of the stack
if stack
          // guard is enabled.
          //
          SetUefiImageMemoryAttributes (
            StackBase,
            EFI_PAGES_TO_SIZE (1),
            EFI_MEMORY_RP | Attributes);
[Ray] 2. The StackBase is directly used here. So do we need to check
whether it's page aligned? Do we need to check whether the range
[StackBase, StackBase + 4KB) is inside the MemoryMapEntry?
        }

If PcdCpuStackGuard is TRUE, I think the owner who allocates memory for
StackBase
should make sure all the conditions you mentioned, but not here.


Just as Jiewen mentioned in the previous reply. An ASSERT:
ASSERT ((StackBase & EFI_PAGE_MASK) == 0);

is added to ensure the stack base fetched from Hob is page-size aligned.

And the below check:
(StackBase >= MemoryMapEntry->PhysicalStart &&
  StackBase <  MemoryMapEntry->PhysicalStart +
               LShiftU64 (MemoryMapEntry->NumberOfPages, EFI_PAGE_SHIFT))

together with the fact that MemMap is page aligned (also mentioned by
Jiewen) ensures that the first page of the stack is cover by the memory
range of the MemMap.

I agree. Thanks for the explanation.
Please move the comments location when checking in the patch.


Best Regards,
Hao Wu


--
Thanks,
Ray


--
Thanks,
Ray
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