Re: [patch 1/7] ArmVirtPkg: Update UefiDecompressLib instance

["Laszlo Ersek" <lersek@redhat.com>]

On 04/04/19 15:52, Dandan Bi wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1683
> 
> BaseUefiDecompressLib in MdePkg is the
> base UEFI decompress Library.
> BaseUefiTianoCustomDecompressLib in IntelFrameworkModulePkg
> implements the base UEFI decompress functionality and
> Tiano decompress functionality.
> 
> 1. TIANOCOMPRESSED rule in ArmVirtRules.fdf.inc
> is not used, so remove it.

That's correct, the only FDF files that refer to any TIANOCOMPRESSED rules, with RuleOverride, are:

- Nt32Pkg.fdf (for EnglishDxe.inf)
- Quark.fdf (for Shell.inf)

And the GUID in the rule being removed, A31280AD-481E-41B6-95E8-127F4C984779, is indeed gTianoCustomDecompressGuid.

> 2. Platform doesn't use the TianoCompress, so do
> not have to use BaseUefiTianoCustomDecompressLib,
> can use the BaseUefiDecompressLib in MdePkg directly.

It looks like we have the following guid-ed section extractors in edk2:

  BrotliCustomDecompress          3D532050-5CDA-4FD0-879E-0F7F630D5AFB
  EfiCertTypeRsa2048Sha256        A7717414-C616-4977-9420-844712A735BF
  EfiCrc32GuidedSectionExtraction FC1BCDB0-7D31-49AA-936A-A4600D9DD083
  LzmaCustomDecompress            EE4E5898-3914-4259-9D6E-DC7BD79403CF
  LzmaF86CustomDecompress         D42AE6BD-1352-4BFB-909A-CA72A6EAE889
  TianoCustomDecompress           A31280AD-481E-41B6-95E8-127F4C984779

(with the leading "g" and trailing "Guid" stripped).

In order to see whether a platform uses an algorithm for section encoding, we should grep that platform's FDF files for the algorithm's GUID directly... And, indeed, under ArmVirtPkg, the only mention of A31280AD-481E-41B6-95E8-127F4C984779 is in the (unused) rule that's being removed.

The one algorithm that ArmVirtPkg does use, for section encoding, is LzmaCustomDecompress. For that, we have "MdeModulePkg/Library/LzmaCustomDecompressLib/LzmaCustomDecompressLib.inf" resolutions in place already.

So what needs UefiDecompressLib at all? ... Aha, both of these:
- MdeModulePkg/Core/DxeIplPeim/DxeIpl.inf
- MdeModulePkg/Core/Dxe/DxeMain.inf 

That's a good argument for preserving the lib class resolution at all.

I've compared "BaseUefiTianoCustomDecompressLib.c" to "BaseUefiDecompressLib.c". The main differences are:

* the latter has no constructor that registers a guid-ed section extractor -- and that's fine here, because in the code modified by this patch, the lib instance is not hooked into another module via NULL resolution,

* the following hunk:

   //
   // The length of the field 'Position Set Code Length Array Size' in Block Header.
   // For UEFI 2.0 de/compression algorithm(Version 1), mPBit = 4
-  // For Tiano de/compression algorithm(Version 2), mPBit = 5
   //
-  switch (Version) {
-    case 1 :
-      Sd->mPBit = 4;
-      break;
-    case 2 :
-      Sd->mPBit = 5;
-      break;
-    default:
-      ASSERT (FALSE);
-  }
+  Sd->mPBit     = 4;

So, let's see the patch:

> 
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Julien Grall <julien.grall@arm.com>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Dandan Bi <dandan.bi@intel.com>
> ---
>  ArmVirtPkg/ArmVirt.dsc.inc      | 4 ++--
>  ArmVirtPkg/ArmVirtRules.fdf.inc | 9 ---------
>  2 files changed, 2 insertions(+), 11 deletions(-)
> 
> diff --git a/ArmVirtPkg/ArmVirt.dsc.inc b/ArmVirtPkg/ArmVirt.dsc.inc
> index d172a082c9..556ec0dcb1 100644
> --- a/ArmVirtPkg/ArmVirt.dsc.inc
> +++ b/ArmVirtPkg/ArmVirt.dsc.inc
> @@ -223,17 +223,17 @@
>    SecurityManagementLib|MdeModulePkg/Library/DxeSecurityManagementLib/DxeSecurityManagementLib.inf
>    PerformanceLib|MdeModulePkg/Library/DxePerformanceLib/DxePerformanceLib.inf
>    MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf
>  
>  [LibraryClasses.common.UEFI_APPLICATION]
> -  UefiDecompressLib|IntelFrameworkModulePkg/Library/BaseUefiTianoCustomDecompressLib/BaseUefiTianoCustomDecompressLib.inf
> +  UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
>    PerformanceLib|MdeModulePkg/Library/DxePerformanceLib/DxePerformanceLib.inf
>    MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf
>    HiiLib|MdeModulePkg/Library/UefiHiiLib/UefiHiiLib.inf
>  
>  [LibraryClasses.common.UEFI_DRIVER]
> -  UefiDecompressLib|IntelFrameworkModulePkg/Library/BaseUefiTianoCustomDecompressLib/BaseUefiTianoCustomDecompressLib.inf
> +  UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
>    ExtractGuidedSectionLib|MdePkg/Library/DxeExtractGuidedSectionLib/DxeExtractGuidedSectionLib.inf
>    PerformanceLib|MdeModulePkg/Library/DxePerformanceLib/DxePerformanceLib.inf
>    MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf
>  
>  [LibraryClasses.common.DXE_RUNTIME_DRIVER]
> diff --git a/ArmVirtPkg/ArmVirtRules.fdf.inc b/ArmVirtPkg/ArmVirtRules.fdf.inc
> index 5ff3004786..bed06364e1 100644
> --- a/ArmVirtPkg/ArmVirtRules.fdf.inc
> +++ b/ArmVirtPkg/ArmVirtRules.fdf.inc
> @@ -56,19 +56,10 @@
>       PEI_DEPEX PEI_DEPEX Optional       $(INF_OUTPUT)/$(MODULE_NAME).depex
>       TE       TE Align = Auto           $(INF_OUTPUT)/$(MODULE_NAME).efi
>       UI       STRING="$(MODULE_NAME)" Optional
>    }
>  
> -[Rule.Common.PEIM.TIANOCOMPRESSED]
> -  FILE PEIM = $(NAMED_GUID) DEBUG_MYTOOLS_IA32 {
> -    PEI_DEPEX PEI_DEPEX Optional        $(INF_OUTPUT)/$(MODULE_NAME).depex
> -    GUIDED A31280AD-481E-41B6-95E8-127F4C984779 PROCESSING_REQUIRED = TRUE {
> -      PE32      PE32                    $(INF_OUTPUT)/$(MODULE_NAME).efi
> -      UI        STRING="$(MODULE_NAME)" Optional
> -    }
> -  }
> -
>  [Rule.Common.DXE_CORE]
>    FILE DXE_CORE = $(NAMED_GUID) {
>      PE32     PE32                       $(INF_OUTPUT)/$(MODULE_NAME).efi
>      UI       STRING="$(MODULE_NAME)" Optional
>    }
> 

The patch seems good, but we could improve it: in "ArmVirtPkg", we already have the following UefiDecompressLib resolutions:

ArmVirt.dsc.inc:44:  UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
ArmVirt.dsc.inc:192:  UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
ArmVirt.dsc.inc:208:  UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
ArmVirt.dsc.inc:219:  UefiDecompressLib|MdePkg/Library/BaseUefiDecompressLib/BaseUefiDecompressLib.inf
ArmVirt.dsc.inc:228:  UefiDecompressLib|IntelFrameworkModulePkg/Library/BaseUefiTianoCustomDecompressLib/BaseUefiTianoCustomDecompressLib.inf
ArmVirt.dsc.inc:234:  UefiDecompressLib|IntelFrameworkModulePkg/Library/BaseUefiTianoCustomDecompressLib/BaseUefiTianoCustomDecompressLib.inf

On line 44, the resolution is for [LibraryClasses.common]. So, rather than multiplying the same resolution for UEFI_APPLICATION and UEFI_DRIVER too, I suggest removing *all* the resolutions, except the one on line 44 (i.e., in section [LibraryClasses.common]).

The commit message needs a minimal change only -- please append a sentence about the default resolution being right already, and relying on that for all module types.

The "ArmVirtRules.fdf.inc" hunk is good as-is, of course.

Thanks!
Laszlo