Re: [PATCH v3 00/11] Implement stack guard feature

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

Good enhancement. I think it resolved my compatibility concern for the old API.

Some comment:

1) Can we just use CPU_EXCEPTION_INIT_DATA instead of CPU_EXCEPTION_INIT_DATA_EX? I am not sure why we add _EX here.

2) Is CPU_EXCEPTION_INIT_DATA_EX for IA32 only or both IA32/X64? I found "Ia32" may bring confusing here. See EFI_DEBUG_SUPPORT_PROTOCOL, we have Ia32 for IA32 arch, X64 for X64 arch.

    //
    // Flag to indicate if default handlers should be initialized or not.
    //
    BOOLEAN                   InitDefaultHandlers;
  } Ia32;
} CPU_EXCEPTION_INIT_DATA_EX;

3) Can we add IdtTableSize in CPU_EXCEPTION_INIT_DATA_EX?

4) Can we add Version field in CPU_EXCEPTION_INIT_DATA_EX? I am not sure if we need add more entry later.

5) You mentioned "KnownGoodStackTop is for *ALL* exceptions".
Does ALL here mean StackSwitchExceptionNumber, or arch specific number such as 0x20 for X86 system?
I think StackSwitchExceptionNumber is enough.

6) There might be more than one TSS entry in GDT.
Does TssDesc/Tss in CPU_EXCEPTION_INIT_DATA_EX mean the exception Tss? (normal TSS does not need be reported here)
If so, I suggest we use ExceptionTss as the keyword.

7) Below code may cause buffer overrun on IST.

  for (Index = 0; Index < StackSwitchData->Ia32.StackSwitchExceptionNumber; ++Index) {
    //
    // Fixup IST
    //
    Tss->IST[Index] = StackTop;

I suggest we add some basic check for StackSwitchExceptionNumber.

8) Do you think we need mention the TssDesc/Tss size requirement for that?

  TssDesc = StackSwitchData->Ia32.TssDesc;
  Tss     = StackSwitchData->Ia32.Tss;
  for (Index = 0; Index < StackSwitchData->Ia32.StackSwitchExceptionNumber; ++Index) {
    TssDesc += 1;
    Tss     += 1;

I suggest we add TssDescSize and TssSize in CPU_EXCEPTION_INIT_DATA_EX and check the size in the code.

9) Last but not least important, have you evaluated if current CPU_EXCEPTION_INIT_DATA_EX is enough for SMM version stack guard exception?


Thank you
Yao Jiewen



> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of Jian J
> Wang
> Sent: Friday, December 1, 2017 10:37 AM
> To: edk2-devel@lists.01.org
> Subject: [edk2] [PATCH v3 00/11] Implement stack guard feature
> 
> > v3:
> >  a. Change new API InitializeCpuExceptionStackSwitchHandlers() to
> >     InitializeCpuExceptionHandlersEx(). Related code are updated
> accordingly.
> >  b. Move EXCEPTION_STACK_SWITCH_DATA to CpuExceptionHandlerLib.h
> >     and change the name to CPU_EXCEPTION_INIT_DATA_EX for the sake
> >     of the API name change.
> >  c. Add more general macros in BaseLib.h.
> >  d. Add dummy implementation of InitializeCpuExceptionHandlersEx for
> >     SEC, PEI and SMM but implement a full version for DXE.
> >  e. Add dummy InitializeCpuExceptionHandlersEx for ARM's
> CpuExceptionHandlerLib
> >     and NULL version of CpuExceptionHandlerLib
> >  f. Call InitializeCpuExceptionHandlersEx() in DxeMain instead of
> >     InitializeCpuExceptionHandlers().
> 
> 
> > v2:
> >  a. Introduce and implement new API
> InitializeCpuExceptionStackSwitchHandlers().
> >  b. Add stack switch related general definitions of IA32 in BaseLib.h.
> >  c. Add two new PCDs to configure exception vector list and stack size.
> >  d. Add code to save/restore GDTR, IDTR and TR for AP.
> >  e. Refactor exception handler code for stack switch.
> >  f. Add code to setup stack switch for AP besides BSP.
> 
> Stack guard feature makes use of paging mechanism to monitor if there's a
> stack overflow occurred during boot. A new PCD PcdCpuStackGuard is added to
> enable/disable this feature. PCD PcdCpuStackSwitchExceptionList and
> PcdCpuKnownGoodStackSize are introduced to configure the required
> exceptions
> and stack size.
> 
> If this feature is enabled, DxeIpl will setup page tables and set page where
> the stack bottom is at to be NON-PRESENT. If stack overflow occurs, Page
> Fault exception will be triggered.
> 
> In order to make sure exception handler works normally even when the stack
> is corrupted, stack switching is implemented in exception library.
> 
> Due to the mechanism behind Stack Guard, this feature is only avaiable for
> UEFI drivers (memory avaiable). That also means it doesn't support NT32
> emulated platform (paging not supported).
> 
> Jian J Wang (11):
>   MdeModulePkg/metafile: Add PCD PcdCpuStackGuard
>   UefiCpuPkg/UefiCpuPkg.dec: Add two new PCDs for stack switch
>   MdeModulePkg/CpuExceptionHandlerLib.h: Add a new API
>     InitializeCpuExceptionHandlersEx
>   MdePkg/BaseLib: Add stack switch related definitions for IA32
>   UefiCpuPkg/CpuExceptionHandlerLib: Add stack switch support
>   MdeModulePkg/CpuExceptionHandlerLibNull: Add new API implementation
>   ArmPkg/ArmExceptionLib: Add implementation of new API
>   UefiCpuPkg/MpLib: Add GDTR, IDTR and TR in saved AP data
>   UefiCpuPkg/CpuDxe: Initialize stack switch for MP
>   MdeModulePkg/Core/Dxe: Call new API InitializeCpuExceptionHandlersEx
>     instead
>   MdeModulePkg/DxeIpl: Enable paging for Stack Guard
> 
>  ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.c   |  33 ++
>  MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c            |   2 +-
>  MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf            |   5 +-
>  MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c    |   4 +
>  MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c     |   1 +
>  MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c   |  51 ++-
>  .../Include/Library/CpuExceptionHandlerLib.h       |  78 ++++
>  .../CpuExceptionHandlerLibNull.c                   |  34 ++
>  MdeModulePkg/MdeModulePkg.dec                      |   7 +
>  MdeModulePkg/MdeModulePkg.uni                      |   7 +
>  MdePkg/Include/Library/BaseLib.h                   | 117 ++++++
>  MdePkg/Library/BaseLib/BaseLib.inf                 |   3 +
>  MdePkg/Library/BaseLib/Ia32/WriteTr.nasm           |  36 ++
>  MdePkg/Library/BaseLib/X64/WriteTr.nasm            |  37 ++
>  UefiCpuPkg/CpuDxe/CpuDxe.inf                       |   3 +
>  UefiCpuPkg/CpuDxe/CpuMp.c                          | 177 +++++++++
>  .../CpuExceptionHandlerLib/CpuExceptionCommon.h    |  39 ++
>  .../DxeCpuExceptionHandlerLib.inf                  |   6 +
>  .../Library/CpuExceptionHandlerLib/DxeException.c  |  79 ++++
>  .../Ia32/ArchExceptionHandler.c                    | 167 +++++++++
>  .../Ia32/ArchInterruptDefs.h                       |   8 +
>  .../Ia32/ExceptionTssEntryAsm.nasm                 | 398
> +++++++++++++++++++++
>  .../CpuExceptionHandlerLib/PeiCpuException.c       |  34 +-
>  .../PeiCpuExceptionHandlerLib.inf                  |   1 +
>  .../CpuExceptionHandlerLib/SecPeiCpuException.c    |  34 +-
>  .../SecPeiCpuExceptionHandlerLib.inf               |   1 +
>  .../SmmCpuExceptionHandlerLib.inf                  |   1 +
>  .../Library/CpuExceptionHandlerLib/SmmException.c  |  34 +-
>  .../X64/ArchExceptionHandler.c                     | 134 +++++++
>  .../CpuExceptionHandlerLib/X64/ArchInterruptDefs.h |   3 +
>  UefiCpuPkg/Library/MpInitLib/MpLib.c               |  17 +
>  UefiCpuPkg/Library/MpInitLib/MpLib.h               |   3 +
>  UefiCpuPkg/UefiCpuPkg.dec                          |  12 +
>  33 files changed, 1547 insertions(+), 19 deletions(-)
>  create mode 100644 MdePkg/Library/BaseLib/Ia32/WriteTr.nasm
>  create mode 100644 MdePkg/Library/BaseLib/X64/WriteTr.nasm
>  create mode 100644
> UefiCpuPkg/Library/CpuExceptionHandlerLib/Ia32/ExceptionTssEntryAsm.nasm
> 
> --
> 2.14.1.windows.1
> 
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