Re: [PATCH] ArmPlatformPkg/MemoryInitPeiLib: mark primary FV region as boot services data

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 3 January 2018 at 05:09, Udit Kumar <udit.kumar@nxp.com> wrote:
> Thanks Ard,
> This works for us as well
> Few comments inline
>
>
> Regards
> Udit
>
>> -----Original Message-----
>> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
>> Sent: Tuesday, January 02, 2018 9:21 PM
>> To: edk2-devel@lists.01.org
>> Cc: leif.lindholm@linaro.org; vladimir.olovyannikov@broadcom.com; Udit
>> Kumar <udit.kumar@nxp.com>; Meenakshi Aggarwal
>> <meenakshi.aggarwal@nxp.com>; Ard Biesheuvel
>> <ard.biesheuvel@linaro.org>
>> Subject: [PATCH] ArmPlatformPkg/MemoryInitPeiLib: mark primary FV region
>> as boot services data
>>
>> Commit 8ae5fc182941 ("ArmPlatformPkg/MemoryInitPeiLib: don't reserve
>> primary FV in memory") deleted the code that removes the memory covering
>> the primary firmware volume from the memory map. The assumption was
>> that
>> this is no longer necessary now that we no longer expose compression and
>> PE/COFF loader library code from the PrePi module to DXE core.
>>
>> However, the FV is still declared, and so code may attempt to access it
>> anyway, which may cause unexpected results depending on whether the
>> memory has been reused for other purposes in the mean time.
>>
>> So reinstate the code that splits off the resource descriptor HOB that
>> describes the firmware device, but this time, don't mark the memory as
>> unusable, but create a memory allocation HOB that marks the region as
>> boot services data.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>> Vladimir, Udit, Meenakshi: please confirm whether this code works for you.
>>
>>  ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c | 74
>> ++++++++++++++++++++
>>  1 file changed, 74 insertions(+)
>>
>> diff --git a/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> b/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> index d03214b5df66..d1b5c0be9497 100644
>> --- a/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> +++ b/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> @@ -70,7 +70,11 @@ MemoryPeim (
>>  {
>>    ARM_MEMORY_REGION_DESCRIPTOR *MemoryTable;
>>    EFI_RESOURCE_ATTRIBUTE_TYPE  ResourceAttributes;
>> +  UINT64                       ResourceLength;
>>    EFI_PEI_HOB_POINTERS         NextHob;
>> +  EFI_PHYSICAL_ADDRESS         FdTop;
>> +  EFI_PHYSICAL_ADDRESS         SystemMemoryTop;
>> +  EFI_PHYSICAL_ADDRESS         ResourceTop;
>>    BOOLEAN                      Found;
>>
>>    // Get Virtual Memory Map from the Platform Library
>> @@ -117,6 +121,76 @@ MemoryPeim (
>>      );
>>    }
>>
>> +  //
>> +  // Reserve the memory space occupied by the firmware volume
>> +  //
>> +
>> +  SystemMemoryTop = (EFI_PHYSICAL_ADDRESS)PcdGet64
>> (PcdSystemMemoryBase) + (EFI_PHYSICAL_ADDRESS)PcdGet64
>> (PcdSystemMemorySize);
>> +  FdTop = (EFI_PHYSICAL_ADDRESS)PcdGet64 (PcdFdBaseAddress) +
>> (EFI_PHYSICAL_ADDRESS)PcdGet32 (PcdFdSize);
>> +
>> +  // EDK2 does not have the concept of boot firmware copied into DRAM. To
>> avoid the DXE
>> +  // core to overwrite this area we must create a memory allocation HOB for
>> the region,
>> +  // but this only works if we split off the underlying resource descriptor as
>> well.
>> +  if ((PcdGet64 (PcdFdBaseAddress) >= PcdGet64 (PcdSystemMemoryBase))
>> && (FdTop <= SystemMemoryTop)) {
>> +    Found = FALSE;
>> +
>> +    // Search for System Memory Hob that contains the firmware
>> +    NextHob.Raw = GetHobList ();
>> +    while ((NextHob.Raw = GetNextHob
>> (EFI_HOB_TYPE_RESOURCE_DESCRIPTOR, NextHob.Raw)) != NULL) {
>> +      if ((NextHob.ResourceDescriptor->ResourceType ==
>> EFI_RESOURCE_SYSTEM_MEMORY) &&
>> +          (PcdGet64 (PcdFdBaseAddress) >= NextHob.ResourceDescriptor-
>> >PhysicalStart) &&
>> +          (FdTop <= NextHob.ResourceDescriptor->PhysicalStart +
>> NextHob.ResourceDescriptor->ResourceLength))
>> +      {
>> +        ResourceAttributes = NextHob.ResourceDescriptor->ResourceAttribute;
>> +        ResourceLength = NextHob.ResourceDescriptor->ResourceLength;
>> +        ResourceTop = NextHob.ResourceDescriptor->PhysicalStart +
>> ResourceLength;
>> +
>> +        if (PcdGet64 (PcdFdBaseAddress) == NextHob.ResourceDescriptor-
>> >PhysicalStart) {
>> +          if (SystemMemoryTop != FdTop) {
>> +            // Create the System Memory HOB for the firmware with the non-
>> present attribute
>
> Please correct comments, now this memory is present
>

Yes

>> +            BuildResourceDescriptorHob (EFI_RESOURCE_SYSTEM_MEMORY,
>> +                                        ResourceAttributes,
>> +                                        PcdGet64 (PcdFdBaseAddress),
>> +                                        PcdGet32 (PcdFdSize));
>> +
>> +            // Top of the FD is system memory available for UEFI
>> +            NextHob.ResourceDescriptor->PhysicalStart += PcdGet32(PcdFdSize);
>> +            NextHob.ResourceDescriptor->ResourceLength -=
>> PcdGet32(PcdFdSize);
>> +          }
>> +        } else {
>> +          // Create the System Memory HOB for the firmware
>> +          BuildResourceDescriptorHob (EFI_RESOURCE_SYSTEM_MEMORY,
>> +                                      ResourceAttributes,
>> +                                      PcdGet64 (PcdFdBaseAddress),
>> +                                      PcdGet32 (PcdFdSize));
>
> Hob List is already created for PcdSystemMemoryBase and its size
> Within this, we got Fd, then do we want to create another Hob here
>

The resource descriptor for PcdSystemMemoryBase/Size is updated in the
next line so it no longer covers the FD

>> +
>> +          // Update the HOB
>> +          NextHob.ResourceDescriptor->ResourceLength = PcdGet64
>> (PcdFdBaseAddress) - NextHob.ResourceDescriptor->PhysicalStart;
>> +
>> +          // If there is some memory available on the top of the FD then create
>> a HOB
>> +          if (FdTop < NextHob.ResourceDescriptor->PhysicalStart +
>> ResourceLength) {
>> +            // Create the System Memory HOB for the remaining region (top of
>> the FD)
>> +            BuildResourceDescriptorHob (EFI_RESOURCE_SYSTEM_MEMORY,
>> +                                        ResourceAttributes,
>> +                                        FdTop,
>> +                                        ResourceTop - FdTop);
>> +          }
>> +        }
>> +
>> +        // Mark the memory covering the Firmware Device as boot services
>> data
>> +        BuildMemoryAllocationHob (PcdGet64 (PcdFdBaseAddress),
>> +                                  PcdGet32 (PcdFdSize),
>> +                                  EfiBootServicesData);
>
> IMO, only this call should be enough to protect FD area.
>

I agree, but the reality is that it is not enough. in
CoreInitializeGcdServices, the first system memory resource descriptor
is claimed before the memory allocations are processed, and any memory
allocation HOBs that intersect that region are ignored.

>> +
>> +        Found = TRUE;
>> +        break;
>> +      }
>> +      NextHob.Raw = GET_NEXT_HOB (NextHob);
>> +    }
>> +
>> +    ASSERT(Found);
>> +  }
>> +
>>    // Build Memory Allocation Hob
>>    InitMmu (MemoryTable);
>>
>> --
>> 2.11.0
>