GUID FAQ

Laurie Jarlstrom edited this page Jan 28, 2016 · 1 revision
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Frequently asked questions about GUIDs

Table of Contents

How are GUIDs generated?

Globally” Unique Identity 128-bit quantity defined by Wired for Management WfM 2.0 specification on Intel Web site. There is a Web site where a GUID can be generated: http://www.guidgen.com Also, Microsoft Visual Studio also has a GUID generator. These unique identifies will and if you look at the wiki on this, the reality is that the probability of a collision is very, very, very small. From RFC 4122:

How do you decode all the GUIDs displayed on the console?

The output file Guid.xref gets generated as part of the build. This file will be located in the build output directory. This file will list all the GUIDs and the modules that are associated for each GUID Another way to decode GUIDs is to use a search utility on your WORKSPACE, and search only the .DEC and .INF files in your WORKSPACE. The DEC files contain declarations of all Protocols, PPIs, and GUIDs with a mapping between the GUID value and the C name for the global variable that is used from C sources. The INF files contain FILE_GUID defines for the GUID name of the FFS file that is stored in an FV.

DEC Examples [Guids]

  ## Guid specify the device is the console out device.
  #  Include/Guid/ConsoleOutDevice.h
  gEfiConsoleOutDeviceGuid       = { 0xD3B36F2C, 0xD551, 0x11D4, { 0x9A, 0x46, 0x00, 0x90, 0x27, 0x3F, 0xC1, 0x4D }}

[Protocols]

  ## Load File protocol provides capability to load and unload EFI image into memory and execute it.
  #  Include/Protocol/LoadPe32Image.h
  #  This protocol is deprecated. Native EDKII module should NOT use this protocol to load/unload image.
  #  If developer need implement such functionality, they should use BasePeCoffLib.
  gEfiLoadPeImageProtocolGuid    = { 0x5CB5C776, 0x60D5, 0x45EE, { 0x88, 0x3C, 0x45, 0x27, 0x08, 0xCD, 0x74, 0x3F }}

INF Example

[Defines]

  INF_VERSION                    = 1.25
  BASE_NAME                      = DiskIoDxe
  FILE_GUID                      = 6B38F7B4-AD98-40e9-9093-ACA2B5A253C4
  MODULE_TYPE                    = UEFI_DRIVER
  VERSION_STRING                 = 1.0
  ENTRY_POINT                    = InitializeDiskIo

Is there an easy way to decode the GUIDs including customer defined GUIDS and GUIDs defined in the Specs?

Request for a tool to manage this. Currently there is no tool to do this. A work around would be to use the Guid.xref file and import it to a spread sheet and compare to the GUIDs in the spec.

GUIDs used a Protocols, PPIs, and GUIDs in source code must be declared in a DEC file, and the DEC file supports comment blocks for GUIDs, so brief descriptions of the Protocol, PPI, and GUID are available. All the GUIDs from the Industry Standard Specifications are in the MdePkg, and are also in the Doxygen generated documentation for the MdePkg. The full .h file for each Protocol/PPI/GUID must be in the same package as the DEC file that declares the Protocol/PPI/GUID. Packages that are part of the UDK 2010 follow a recommended practice for the include file layout, so .h files associated with Protocols/PPIs/GUIDs can be easily found:

  <PackageName>\
    <PackageName>.dec
    Include\
      Protocol\
        <Protocol1.h>
        <Protocol2.h>
      Ppi\
        <Ppi1.h>
        <Ppi2.h>
      Guid\	
        <Guid1.h>
        <Guid2.h>

Is there a tool to track the chain of GUID to Protocol driver?

The build tool will generate a file xref file is built with every build GUID to guid name for that platform. This maps the GUID value to the name.




Where is the GUID name being used with a particular protocol?

Use the BUILD –Y to generate a report

What GUID maps to what drivers and how to find drivers installed?

The output file Guid.xref gets generated as part of the build. This file will list all the GUIDs and the modules that are associated for each GUID that get built into a platform. From the shell prompt the “Drivers” will list out the drivers installed.

Is there a data base for all the GUIDs installed in a platform?

Yes, from the EFI Shell prompt the “dh” command will list all of the handles with their associated GUIDs. In addition, the output file Guid.xref gets generated as part of the build. This file will be located in the build output directory. This file will list all the GUIDs and the modules that are associated for each GUID

Why is there a section GUID declared in the FDF file?

The GUIDed section is used for contiguous section guid, GUID keyword - used for signing- compression - encryption (encapsulation section -list of sections] as devided in the PI Spec.

Why use the GUID?

Because of where it gets mapped. Different compressions is another reason. The GUID has a cross reference in the tools to call used with tools_def.txt in the conf directory.