Re: [PATCH v2 0/2] Resolve feature conflict between NX and Stack guard

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

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.ni@intel.com>; Wu, Hao A <hao.a.wu@intel.com>;
> edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Dong, Eric <eric.dong@intel.com>; Yao,
> Jiewen <jiewen.yao@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.wu@intel.com>; edk2-devel@lists.01.org
> > Cc: 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>
> > 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.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>
> > >
> > > 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 (...)".
> >
> >          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.
> 
> >
> > --
> > Thanks,
> > Ray