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From: "Yao, Jiewen" <jiewen.yao@intel.com>
To: "Wang, Jian J" <jian.j.wang@intel.com>,
	"edk2-devel@lists.01.org" <edk2-devel@lists.01.org>
Cc: "Zeng, Star" <star.zeng@intel.com>,
	"Dong, Eric" <eric.dong@intel.com>,
	Laszlo Ersek <lersek@redhat.com>,
	"Kinney, Michael D" <michael.d.kinney@intel.com>,
	"Justen, Jordan L" <jordan.l.justen@intel.com>,
	 "Wolman, Ayellet" <ayellet.wolman@intel.com>
Subject: Re: [PATCH v2 2/6] MdeModulePkg/DxeIpl: Implement NULL pointer detection
Date: Mon, 25 Sep 2017 08:50:40 +0000	[thread overview]
Message-ID: <74D8A39837DF1E4DA445A8C0B3885C503A9C1BCE@shsmsx102.ccr.corp.intel.com> (raw)
In-Reply-To: <20170921052032.13652-3-jian.j.wang@intel.com>

Hi
I do not think NULL pointer is related to NX.
As long as NullPointer PCD is true and IA32PAE is supported, we can build page table.

+    BuildPageTablesIa32Pae = (BOOLEAN) (IsIa32PaeSupport ()
+                                        && IsExecuteDisableBitAvailable ()
+                                        && (PcdGetBool (PcdSetNxForStack)
+                                            || IsNullDetectionEnabled ()));




> -----Original Message-----
> From: Wang, Jian J
> Sent: Thursday, September 21, 2017 1:20 PM
> To: edk2-devel@lists.01.org
> Cc: Zeng, Star <star.zeng@intel.com>; Dong, Eric <eric.dong@intel.com>; Laszlo
> Ersek <lersek@redhat.com>; Yao, Jiewen <jiewen.yao@intel.com>; Kinney,
> Michael D <michael.d.kinney@intel.com>; Justen, Jordan L
> <jordan.l.justen@intel.com>; Wolman, Ayellet <ayellet.wolman@intel.com>
> Subject: [PATCH v2 2/6] MdeModulePkg/DxeIpl: Implement NULL pointer
> detection
> 
> NULL pointer detection is done by making use of paging mechanism of CPU.
> During page table setup, if enabled, the first 4-K page (0-4095) will be
> marked as NOT PRESENT. Any code which unintentionally access memory
> between
> 0-4095 will trigger a Page Fault exception which warns users that there's
> potential illegal code in BIOS.
> 
> This also means that legacy code which has to access memory between 0-4095
> should be cautious to temporarily disable this feature before the access
> and re-enable it afterwards; or disalbe this feature at all.
> 
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Michael Kinney <michael.d.kinney@intel.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Ayellet Wolman <ayellet.wolman@intel.com>
> Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> ---
>  MdeModulePkg/Core/DxeIplPeim/DxeIpl.h            | 25 +++++++++
>  MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf          |  1 +
>  MdeModulePkg/Core/DxeIplPeim/DxeLoad.c           | 65
> ++++++++++++++++++++++++
>  MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c  | 11 +++-
>  MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c   |  2 +
>  MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c | 31 ++++++++---
>  6 files changed, 126 insertions(+), 9 deletions(-)
> 
> diff --git a/MdeModulePkg/Core/DxeIplPeim/DxeIpl.h
> b/MdeModulePkg/Core/DxeIplPeim/DxeIpl.h
> index 72d2532f50..1654bcd2dc 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/DxeIpl.h
> +++ b/MdeModulePkg/Core/DxeIplPeim/DxeIpl.h
> @@ -240,4 +240,29 @@ Decompress (
>    OUT       UINTN                   *OutputSize
>    );
> 
> +/**
> +   Clear legacy memory located at the first 4K-page.
> +
> +   This function traverses the whole HOB list to check if memory from 0 to 4095
> +   exists and has not been allocated, and then clear it if so.
> +
> +   @param HoStart         The start of HobList passed to DxeCore.
> +
> +**/
> +VOID
> +ClearLegacyMemory (
> +  IN  VOID *HobStart
> +  );
> +
> +/**
> +   Return configure status of NULL pointer detection feature
> +
> +   @return TRUE   NULL pointer detection feature is enabled
> +   @return FALSE  NULL pointer detection feature is disabled
> +**/
> +BOOLEAN
> +IsNullDetectionEnabled (
> +  VOID
> +  );
> +
>  #endif
> diff --git a/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
> b/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
> index c54afe4aa6..9d0e76a293 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
> +++ b/MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
> @@ -115,6 +115,7 @@
>  [Pcd.IA32,Pcd.X64]
>    gEfiMdeModulePkgTokenSpaceGuid.PcdUse1GPageTable
> ## SOMETIMES_CONSUMES
> 
> gEfiMdeModulePkgTokenSpaceGuid.PcdPteMemoryEncryptionAddressOrMask
> ## CONSUMES
> +  gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask
> ## CONSUMES
> 
>  [Pcd.IA32,Pcd.X64,Pcd.ARM,Pcd.AARCH64]
>    gEfiMdeModulePkgTokenSpaceGuid.PcdSetNxForStack               ##
> SOMETIMES_CONSUMES
> diff --git a/MdeModulePkg/Core/DxeIplPeim/DxeLoad.c
> b/MdeModulePkg/Core/DxeIplPeim/DxeLoad.c
> index 50b5440d15..0a71b1f3de 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/DxeLoad.c
> +++ b/MdeModulePkg/Core/DxeIplPeim/DxeLoad.c
> @@ -825,3 +825,68 @@ UpdateStackHob (
>      Hob.Raw = GET_NEXT_HOB (Hob);
>    }
>  }
> +
> +/**
> +   Clear legacy memory located at the first 4K-page, if available.
> +
> +   This function traverses the whole HOB list to check if memory from 0 to 4095
> +   exists and has not been allocated, and then clear it if so.
> +
> +   @param HoStart                   The start of HobList passed to
> DxeCore.
> +
> +**/
> +VOID
> +ClearLegacyMemory (
> +  IN  VOID *HobStart
> +  )
> +{
> +  EFI_PEI_HOB_POINTERS          RscHob;
> +  EFI_PEI_HOB_POINTERS          MemHob;
> +  BOOLEAN                       DoClear;
> +
> +  RscHob.Raw = HobStart;
> +  MemHob.Raw = HobStart;
> +  DoClear = FALSE;
> +
> +  //
> +  // Check if page 0 exists and free
> +  //
> +  while ((RscHob.Raw = GetNextHob (EFI_HOB_TYPE_RESOURCE_DESCRIPTOR,
> +                                   RscHob.Raw)) != NULL) {
> +    if (RscHob.ResourceDescriptor->ResourceType ==
> EFI_RESOURCE_SYSTEM_MEMORY &&
> +        RscHob.ResourceDescriptor->PhysicalStart == 0) {
> +      DoClear = TRUE;
> +      //
> +      // Make sure memory at 0-4095 has not been allocated.
> +      //
> +      while ((MemHob.Raw = GetNextHob
> (EFI_HOB_TYPE_MEMORY_ALLOCATION,
> +                                       MemHob.Raw)) != NULL) {
> +        if (MemHob.MemoryAllocation->AllocDescriptor.MemoryBaseAddress
> +            < EFI_PAGE_SIZE) {
> +          DoClear = FALSE;
> +          break;
> +        }
> +        MemHob.Raw = GET_NEXT_HOB (MemHob);
> +      }
> +      break;
> +    }
> +    RscHob.Raw = GET_NEXT_HOB (RscHob);
> +  }
> +
> +  if (DoClear) {
> +    DEBUG ((DEBUG_INFO, "Clearing first 4K-page!\r\n"));
> +    SetMem (NULL, EFI_PAGE_SIZE, 0);
> +  }
> +
> +  return;
> +}
> +
> +BOOLEAN
> +IsNullDetectionEnabled (
> +  VOID
> +  )
> +{
> +  return (((PcdGet8 (PcdNullPointerDetectionPropertyMask) & BIT0) != 0) ?
> +          TRUE : FALSE);
> +}
> +
> diff --git a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
> b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
> index 1957326caf..503cf88382 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
> +++ b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
> @@ -123,7 +123,9 @@ Create4GPageTablesIa32Pae (
>      PageDirectoryPointerEntry->Bits.Present = 1;
> 
>      for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512;
> IndexOfPageDirectoryEntries++, PageDirectoryEntry++, PhysicalAddress +=
> SIZE_2MB) {
> -      if ((PhysicalAddress < StackBase + StackSize) && ((PhysicalAddress +
> SIZE_2MB) > StackBase)) {
> +      if ((IsNullDetectionEnabled () && PhysicalAddress == 0)
> +          || ((PhysicalAddress < StackBase + StackSize)
> +              && ((PhysicalAddress + SIZE_2MB) > StackBase))) {
>          //
>          // Need to split this 2M page that covers stack range.
>          //
> @@ -240,6 +242,8 @@ HandOffToDxeCore (
>    EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi;
>    BOOLEAN                   BuildPageTablesIa32Pae;
> 
> +  ClearLegacyMemory (HobList.Raw);
> +
>    Status = PeiServicesAllocatePages (EfiBootServicesData, EFI_SIZE_TO_PAGES
> (STACK_SIZE), &BaseOfStack);
>    ASSERT_EFI_ERROR (Status);
> 
> @@ -379,7 +383,10 @@ HandOffToDxeCore (
>      TopOfStack = (EFI_PHYSICAL_ADDRESS) (UINTN) ALIGN_POINTER
> (TopOfStack, CPU_STACK_ALIGNMENT);
> 
>      PageTables = 0;
> -    BuildPageTablesIa32Pae = (BOOLEAN) (PcdGetBool (PcdSetNxForStack) &&
> IsIa32PaeSupport () && IsExecuteDisableBitAvailable ());
> +    BuildPageTablesIa32Pae = (BOOLEAN) (IsIa32PaeSupport ()
> +                                        && IsExecuteDisableBitAvailable
> ()
> +                                        && (PcdGetBool
> (PcdSetNxForStack)
> +                                            || IsNullDetectionEnabled
> ()));
>      if (BuildPageTablesIa32Pae) {
>        PageTables = Create4GPageTablesIa32Pae (BaseOfStack, STACK_SIZE);
>        EnableExecuteDisableBit ();
> diff --git a/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c
> b/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c
> index 6488880eab..d93a9c5a2d 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c
> +++ b/MdeModulePkg/Core/DxeIplPeim/X64/DxeLoadFunc.c
> @@ -42,6 +42,8 @@ HandOffToDxeCore (
>    EFI_VECTOR_HANDOFF_INFO         *VectorInfo;
>    EFI_PEI_VECTOR_HANDOFF_INFO_PPI *VectorHandoffInfoPpi;
> 
> +  ClearLegacyMemory (HobList.Raw);
> +
>    //
>    // Get Vector Hand-off Info PPI and build Guided HOB
>    //
> diff --git a/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> b/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> index 48150be4e1..80c1821eca 100644
> --- a/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> +++ b/MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c
> @@ -90,8 +90,16 @@ Split2MPageTo4K (
>      //
>      PageTableEntry->Uint64 = (UINT64) PhysicalAddress4K | AddressEncMask;
>      PageTableEntry->Bits.ReadWrite = 1;
> -    PageTableEntry->Bits.Present = 1;
> -    if ((PhysicalAddress4K >= StackBase) && (PhysicalAddress4K < StackBase +
> StackSize)) {
> +
> +    if (IsNullDetectionEnabled () && PhysicalAddress4K == 0) {
> +      PageTableEntry->Bits.Present = 0;
> +    } else {
> +      PageTableEntry->Bits.Present = 1;
> +    }
> +
> +    if (PcdGetBool (PcdSetNxForStack)
> +        && (PhysicalAddress4K >= StackBase)
> +        && (PhysicalAddress4K < StackBase + StackSize)) {
>        //
>        // Set Nx bit for stack.
>        //
> @@ -137,9 +145,12 @@ Split1GPageTo2M (
> 
>    PhysicalAddress2M = PhysicalAddress;
>    for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512;
> IndexOfPageDirectoryEntries++, PageDirectoryEntry++, PhysicalAddress2M +=
> SIZE_2MB) {
> -    if ((PhysicalAddress2M < StackBase + StackSize) && ((PhysicalAddress2M +
> SIZE_2MB) > StackBase)) {
> +    if ((IsNullDetectionEnabled () && PhysicalAddress2M == 0)
> +        || (PcdGetBool (PcdSetNxForStack)
> +            && (PhysicalAddress2M < StackBase + StackSize)
> +            && ((PhysicalAddress2M + SIZE_2MB) > StackBase))) {
>        //
> -      // Need to split this 2M page that covers stack range.
> +      // Need to split this 2M page that covers NULL or stack range.
>        //
>        Split2MPageTo4K (PhysicalAddress2M, (UINT64 *) PageDirectoryEntry,
> StackBase, StackSize);
>      } else {
> @@ -279,7 +290,10 @@ CreateIdentityMappingPageTables (
>        PageDirectory1GEntry = (VOID *) PageDirectoryPointerEntry;
> 
>        for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries < 512;
> IndexOfPageDirectoryEntries++, PageDirectory1GEntry++, PageAddress +=
> SIZE_1GB) {
> -        if (PcdGetBool (PcdSetNxForStack) && (PageAddress < StackBase +
> StackSize) && ((PageAddress + SIZE_1GB) > StackBase)) {
> +        if ((IsNullDetectionEnabled () && PageAddress == 0)
> +            || (PcdGetBool (PcdSetNxForStack)
> +                && (PageAddress < StackBase + StackSize)
> +                && ((PageAddress + SIZE_1GB) > StackBase))) {
>            Split1GPageTo2M (PageAddress, (UINT64 *) PageDirectory1GEntry,
> StackBase, StackSize);
>          } else {
>            //
> @@ -308,9 +322,12 @@ CreateIdentityMappingPageTables (
>          PageDirectoryPointerEntry->Bits.Present = 1;
> 
>          for (IndexOfPageDirectoryEntries = 0; IndexOfPageDirectoryEntries <
> 512; IndexOfPageDirectoryEntries++, PageDirectoryEntry++, PageAddress +=
> SIZE_2MB) {
> -          if (PcdGetBool (PcdSetNxForStack) && (PageAddress < StackBase +
> StackSize) && ((PageAddress + SIZE_2MB) > StackBase)) {
> +          if ((IsNullDetectionEnabled () && PageAddress == 0)
> +              || (PcdGetBool (PcdSetNxForStack)
> +                  && (PageAddress < StackBase + StackSize)
> +                  && ((PageAddress + SIZE_2MB) > StackBase))) {
>              //
> -            // Need to split this 2M page that covers stack range.
> +            // Need to split this 2M page that covers NULL or stack range.
>              //
>              Split2MPageTo4K (PageAddress, (UINT64 *) PageDirectoryEntry,
> StackBase, StackSize);
>            } else {
> --
> 2.14.1.windows.1



  reply	other threads:[~2017-09-25  8:47 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <Add NULL pointer detection feature>
2017-09-21  5:20 ` [PATCH v2 0/6] Add NULL pointer detection feature Jian J Wang
2017-09-21  5:20   ` [PATCH v2 1/6] MdeModulePkg/MdeModulePkg.dec: Add NULL pointer detection PCD Jian J Wang
2017-09-25  8:01     ` Zeng, Star
2017-09-25  8:25       ` Wang, Jian J
2017-09-21  5:20   ` [PATCH v2 2/6] MdeModulePkg/DxeIpl: Implement NULL pointer detection Jian J Wang
2017-09-25  8:50     ` Yao, Jiewen [this message]
2017-09-26  0:54       ` Wang, Jian J
2017-09-21  5:20   ` [PATCH v2 3/6] UefiCpuPkg/PiSmmCpuDxeSmm: Implement NULL pointer detection for SMM code Jian J Wang
2017-09-21  5:20   ` [PATCH v2 4/6] MdeModulePkg/Core/Dxe: Add EndOfDxe workaround for NULL pointer detection Jian J Wang
2017-09-21  5:20   ` [PATCH v2 5/6] IntelFrameworkModulePkg/Csm: Add code to bypass " Jian J Wang
2017-09-21  5:20   ` [PATCH v2 6/6] OvmfPkg/QemuVideoDxe: Bypass NULL pointer detection during VBE SHIM installing Jian J Wang
2017-09-22 11:50     ` Laszlo Ersek
2017-09-22 15:29       ` Laszlo Ersek
2017-09-25  1:04         ` Wang, Jian J

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