Re: [PATCH 2/2] UefiCpuPkg/CpuDxe: Fix multiple entries of RT_CODE in memory map

[Laszlo Ersek <lersek@redhat.com>]

On 11/16/17 08:27, Jian J Wang wrote:
>> v6:
>>    Add ExecuteDisable feature check to include/exclude EFI_MEMORY_XP

Another change relative to v5 is the fixing of the first DEBUG_WARN
message -- in my v5 review I had missed that the DEBUG_WARN arguments
didn't match the preceding gDS->SetMemorySpaceCapabilities() arguments.

Yet another change that could have been (maybe) possible for this patch
is to replace the remaining occurrences of EFI_MEMORY_PAGETYPE_MASK with
"Capabilities". Namely, in v6, the attributes are enforced on a mask
that is possibly wider than supported by the hardware (i.e., in case NX
is not supported).

However, this should not be a functionality problem, because with NX
unavailable, the GetAttributesFromPageEntry() function should never
return EFI_MEMORY_XP. Thus, the "wider than needed" attribute setting
will just clear EFI_MEMORY_XP.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

(I hope that Star and/or Jiewen will also R-b this patch.)

In addition, I will follow up with test results for the series.

Thanks
Laszlo

>> v5:
>>    Coding style clean-up
> 
>> v4:
>> a. Remove DoUpdate and check attributes mismatch all the time to avoid
>>    a logic hole
>> b. Add warning message if failed to update capability
>> c. Add local variable to hold new attributes to make code cleaner
> 
>> v3:
>> a. Add comment to explain more on updating memory capabilities
>> b. Fix logic hole in updating attributes
>> c. Instead of checking illegal memory space address and size, use return
>>    status of gDS->SetMemorySpaceCapabilities() to skip memory block which
>>    cannot be updated with new capabilities.
> 
>> v2
>> a. Fix an issue which will cause setting capability failure if size is smaller
>>    than a page.
> 
> More than one entry of RT_CODE memory might cause boot problem for some
> old OSs. This patch will fix this issue to keep OS compatibility as much
> as possible.
> 
> More detailed information, please refer to
>     https://bugzilla.tianocore.org/show_bug.cgi?id=753
> 
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Star Zeng <star.zeng@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> ---
>  UefiCpuPkg/CpuDxe/CpuPageTable.c | 94 +++++++++++++++++++++++++++++++---------
>  1 file changed, 73 insertions(+), 21 deletions(-)
> 
> diff --git a/UefiCpuPkg/CpuDxe/CpuPageTable.c b/UefiCpuPkg/CpuDxe/CpuPageTable.c
> index d312eb66f8..3297c1900b 100644
> --- a/UefiCpuPkg/CpuDxe/CpuPageTable.c
> +++ b/UefiCpuPkg/CpuDxe/CpuPageTable.c
> @@ -769,6 +769,20 @@ AssignMemoryPageAttributes (
>    return Status;
>  }
>  
> +/**
> + Check if Execute Disable feature is enabled or not.
> +**/
> +BOOLEAN
> +IsExecuteDisableEnabled (
> +  VOID
> +  )
> +{
> +  MSR_CORE_IA32_EFER_REGISTER    MsrEfer;
> +
> +  MsrEfer.Uint64 = AsmReadMsr64 (MSR_IA32_EFER);
> +  return (MsrEfer.Bits.NXE == 1);
> +}
> +
>  /**
>    Update GCD memory space attributes according to current page table setup.
>  **/
> @@ -790,7 +804,7 @@ RefreshGcdMemoryAttributesFromPaging (
>    UINT64                              PageStartAddress;
>    UINT64                              Attributes;
>    UINT64                              Capabilities;
> -  BOOLEAN                             DoUpdate;
> +  UINT64                              NewAttributes;
>    UINTN                               Index;
>  
>    //
> @@ -802,17 +816,50 @@ RefreshGcdMemoryAttributesFromPaging (
>  
>    GetCurrentPagingContext (&PagingContext);
>  
> -  DoUpdate      = FALSE;
> -  Capabilities  = 0;
> -  Attributes    = 0;
> -  BaseAddress   = 0;
> -  PageLength    = 0;
> +  Attributes      = 0;
> +  NewAttributes   = 0;
> +  BaseAddress     = 0;
> +  PageLength      = 0;
> +
> +  if (IsExecuteDisableEnabled ()) {
> +    Capabilities = EFI_MEMORY_RO | EFI_MEMORY_RP | EFI_MEMORY_XP;
> +  } else {
> +    Capabilities = EFI_MEMORY_RO | EFI_MEMORY_RP;
> +  }
>  
>    for (Index = 0; Index < NumberOfDescriptors; Index++) {
>      if (MemorySpaceMap[Index].GcdMemoryType == EfiGcdMemoryTypeNonExistent) {
>        continue;
>      }
>  
> +    //
> +    // Sync the actual paging related capabilities back to GCD service first.
> +    // As a side effect (good one), this can also help to avoid unnecessary
> +    // memory map entries due to the different capabilities of the same type
> +    // memory, such as multiple RT_CODE and RT_DATA entries in memory map,
> +    // which could cause boot failure of some old Linux distro (before v4.3).
> +    //
> +    Status = gDS->SetMemorySpaceCapabilities (
> +                    MemorySpaceMap[Index].BaseAddress,
> +                    MemorySpaceMap[Index].Length,
> +                    MemorySpaceMap[Index].Capabilities | Capabilities
> +                    );
> +    if (EFI_ERROR (Status)) {
> +      //
> +      // If we cannot udpate the capabilities, we cannot update its
> +      // attributes either. So just simply skip current block of memory.
> +      //
> +      DEBUG ((
> +        DEBUG_WARN,
> +        "Failed to update capability: [%lu] %016lx - %016lx (%016lx -> %016lx)\r\n",
> +        (UINT64)Index, MemorySpaceMap[Index].BaseAddress,
> +        MemorySpaceMap[Index].BaseAddress + MemorySpaceMap[Index].Length - 1,
> +        MemorySpaceMap[Index].Capabilities,
> +        MemorySpaceMap[Index].Capabilities | Capabilities
> +        ));
> +      continue;
> +    }
> +
>      if (MemorySpaceMap[Index].BaseAddress >= (BaseAddress + PageLength)) {
>        //
>        // Current memory space starts at a new page. Resetting PageLength will
> @@ -826,7 +873,9 @@ RefreshGcdMemoryAttributesFromPaging (
>        PageLength -= (MemorySpaceMap[Index].BaseAddress - BaseAddress);
>      }
>  
> -    // Sync real page attributes to GCD
> +    //
> +    // Sync actual page attributes to GCD
> +    //
>      BaseAddress       = MemorySpaceMap[Index].BaseAddress;
>      MemorySpaceLength = MemorySpaceMap[Index].Length;
>      while (MemorySpaceLength > 0) {
> @@ -842,23 +891,26 @@ RefreshGcdMemoryAttributesFromPaging (
>          PageStartAddress  = (*PageEntry) & (UINT64)PageAttributeToMask(PageAttribute);
>          PageLength        = PageAttributeToLength (PageAttribute) - (BaseAddress - PageStartAddress);
>          Attributes        = GetAttributesFromPageEntry (PageEntry);
> -
> -        if (Attributes != (MemorySpaceMap[Index].Attributes & EFI_MEMORY_PAGETYPE_MASK)) {
> -          DoUpdate = TRUE;
> -          Attributes |= (MemorySpaceMap[Index].Attributes & ~EFI_MEMORY_PAGETYPE_MASK);
> -          Capabilities = Attributes | MemorySpaceMap[Index].Capabilities;
> -        } else {
> -          DoUpdate = FALSE;
> -        }
>        }
>  
>        Length = MIN (PageLength, MemorySpaceLength);
> -      if (DoUpdate) {
> -        gDS->SetMemorySpaceCapabilities (BaseAddress, Length, Capabilities);
> -        gDS->SetMemorySpaceAttributes (BaseAddress, Length, Attributes);
> -        DEBUG ((DEBUG_INFO, "Update memory space attribute: [%02d] %016lx - %016lx (%08lx -> %08lx)\r\n",
> -                             Index, BaseAddress, BaseAddress + Length - 1,
> -                             MemorySpaceMap[Index].Attributes, Attributes));
> +      if (Attributes != (MemorySpaceMap[Index].Attributes &
> +                         EFI_MEMORY_PAGETYPE_MASK)) {
> +        NewAttributes = (MemorySpaceMap[Index].Attributes &
> +                         ~EFI_MEMORY_PAGETYPE_MASK) | Attributes;
> +        Status = gDS->SetMemorySpaceAttributes (
> +                        BaseAddress,
> +                        Length,
> +                        NewAttributes
> +                        );
> +        ASSERT_EFI_ERROR (Status);
> +        DEBUG ((
> +          DEBUG_INFO,
> +          "Updated memory space attribute: [%lu] %016lx - %016lx (%016lx -> %016lx)\r\n",
> +          (UINT64)Index, BaseAddress, BaseAddress + Length - 1,
> +          MemorySpaceMap[Index].Attributes,
> +          NewAttributes
> +          ));
>        }
>  
>        PageLength        -= Length;
>