Re: [PATCH v2] PeiLib : Inform UEFI memory to Linux

[Sakar Arora <Sakar.Arora@arm.com>]

Thanks for the information. Seems my understanding was not correct in this context. I have no other doubts on this change.

-----Original Message-----
From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
Sent: Wednesday, September 20, 2017 12:02 PM
To: Sakar Arora <Sakar.Arora@arm.com>
Cc: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>; edk2-devel@lists.01.org; leif.lindholm@linaro.org
Subject: Re: [edk2] [PATCH v2] PeiLib : Inform UEFI memory to Linux

On 19 September 2017 at 22:32, Sakar Arora <Sakar.Arora@arm.com> wrote:
> The DXE core dispatcher relies on the available memory to allocate space for loading the rest of the modules from the UEFI image. If we declare the UEFI image memory space (from which DXE dispatcher reads the efi modules) open to allocation, it might lead to data corruption, depending on the location of UEFI image and cumulative size of uncompressed EFI modules.
>
> Also, since UEFI allows unloading and loading of drivers at runtime, IMO, there is a need to preserve the UEFI image even after all the modules have been decompressed and loaded in the boot sequence.
>

None of this is relevant. The uncompressed firmware volume containing DXE core and everything else is preserved as before. The only thing that gets discarded is the outer FV, which only contains the PrePi SEC module, and the compressed FV, neither of which is ever touched again after DXE core has started executing. So we should not register the FV in the first place, and not reserve the memory so we don't lose it.

If you still think this may break anything, could you please elaborate?



> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: Tuesday, September 19, 2017 6:18 PM
> To: Sakar Arora <Sakar.Arora@arm.com>
> Cc: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>;
> edk2-devel@lists.01.org; leif.lindholm@linaro.org
> Subject: Re: [edk2] [PATCH v2] PeiLib : Inform UEFI memory to Linux
>
> On 19 September 2017 at 01:07, Sakar Arora <Sakar.Arora@arm.com> wrote:
>> This change will create the possibility for memory space holding the UEFI image to be over-written by the DXE core code, since this space will then be available for allocation.
>
> Yes. But why does this matter after the entire payload has been decompressed into memory already?
>
>
>> Any such change, if required, should be done just before booting the OS.
>>
>> -----Original Message-----
>> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf
>> Of Meenakshi Aggarwal
>> Sent: Tuesday, September 19, 2017 6:02 PM
>> To: edk2-devel@lists.01.org; leif.lindholm@linaro.org;
>> ard.biesheuvel@linaro.org
>> Subject: [edk2] [PATCH v2] PeiLib : Inform UEFI memory to Linux
>>
>> While creating Hob list, ArmPlatformPkg is hiding UEFI memory.
>> whereas this memory can be used by OS.
>>
>> This patch, allows OS to use UEFI code area.
>>
>> Contributed-under: TianoCore Contribution Agreement 1.1
>> Signed-off-by: Udit Kumar <udit.kumar@nxp.com>
>> Signed-off-by: Meenakshi Aggarwal <meenakshi.aggarwal@nxp.com>
>> ---
>>  ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c | 69
>> -------------------------
>>  1 file changed, 69 deletions(-)
>>
>> diff --git a/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> b/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> index 2feb11f..d03214b 100644
>> --- a/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> +++ b/ArmPlatformPkg/MemoryInitPei/MemoryInitPeiLib.c
>> @@ -70,11 +70,7 @@ 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 @@ -121,71 +117,6 @@ MemoryPeim (
>>      );
>>    }
>>
>> -  //
>> -  // Reserved 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 mark the region with the
>> attribute non-present
>> -  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) {
>> -            NextHob.ResourceDescriptor->ResourceAttribute = ResourceAttributes & ~EFI_RESOURCE_ATTRIBUTE_PRESENT;
>> -          } else {
>> -            // Create the System Memory HOB for the firmware with the non-present attribute
>> -            BuildResourceDescriptorHob (EFI_RESOURCE_SYSTEM_MEMORY,
>> -                                        ResourceAttributes & ~EFI_RESOURCE_ATTRIBUTE_PRESENT,
>> -                                        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 with the non-present attribute
>> -          BuildResourceDescriptorHob (EFI_RESOURCE_SYSTEM_MEMORY,
>> -                                      ResourceAttributes & ~EFI_RESOURCE_ATTRIBUTE_PRESENT,
>> -                                      PcdGet64 (PcdFdBaseAddress),
>> -                                      PcdGet32 (PcdFdSize));
>> -
>> -          // 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);
>> -          }
>> -        }
>> -        Found = TRUE;
>> -        break;
>> -      }
>> -      NextHob.Raw = GET_NEXT_HOB (NextHob);
>> -    }
>> -
>> -    ASSERT(Found);
>> -  }
>> -
>>    // Build Memory Allocation Hob
>>    InitMmu (MemoryTable);
>>
>> --
>> 1.9.1
>>
>> _______________________________________________
>> edk2-devel mailing list
>> edk2-devel@lists.01.org
>> https://lists.01.org/mailman/listinfo/edk2-devel
>> IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
> IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.