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diff --git a/PrmPkg/Readme.md b/PrmPkg/Readme.md new file mode 100644 index 0000000000..b67b3a391e --- /dev/null +++ b/PrmPkg/Readme.md @@ -0,0 +1,212 @@ +# **Platform Runtime Mechanism**
+
+Platform Runtime Mechanism (PRM) introduces the capability of moving platform-specific code out of SMM and into a
+code module that executes within the OS context. Moving this firmware to the OS context provides better transparency
+and mitigates the negative system impact currently accompanied with SMM solutions. Futhermore, the PRM code is
+packaged into modules with well-defined entry points, each representing a specific PRM functionality.
+
+The `PrmPkg` maintained in this branch provides a single cohesive set of generic PRM functionality that is intended
+to be leveraged by platform firmware with minimal overhead to integrate PRM functionality in the firmware.
+
+## **IMPORTANT NOTE**
+> The code provided in this package and branch are for proof-of-concept purposes only. The code does not represent a
+formal design and is not validated at product quality. The development of this feature is shared in the edk2-staging
+branch to simplify collaboration by allowing direct code contributions and early feedback throughout its development.
+
+## How to Build PrmPkg
+As noted earlier, resources in `PrmPkg` are intended to be referenced by a platform firmware so it can adopt support
+for PRM. In that case, the platform firmware should add the `PrmConfigDxe` and `PrmLoaderDxe` drivers to its DSC and
+FDF files so they are built in the platform firmware build and dispatched during its runtime. All that is left is to
+add individual PRM modules to the DSC and FDF. These can be built from source or included as binaries into the platform
+firmware flash map.
+
+### PrmPkg Standalone Build
+**All changes to `PrmPkg` must not regress the standalone package build**. Any time a change is made to `PrmPkg`, the
+package build must be tested. Since this is a forward looking package, to ease potential integration into the edk2
+project in the future, the build is tested against the tip of the master branch in the [edk2](https://github.com/tianocore/edk2)
+repository.
+
+To build `PrmPkg` as a standalone package:
+1. If new to EDK II, follow the directions in [Getting Started with EDK II](https://github.com/tianocore/tianocore.github.io/wiki/Getting-Started-with-EDK-II)
+
+2. Clone the *master* branch on the edk2 repository locally \
+ ``git clone https://github.com/tianocore/edk2.git``
+
+3. Clone the *PlatformRuntimeMechanism* branch on the edk2-staging repository locally \
+ ``git clone -b PlatformRuntimeMechanism --single-branch https://github.com/tianocore/edk2-staging.git``
+ > __*Note*__: The *--single-branch* argument is recommended since edk2-staging hosts many branches for completely
+ unrelated features. If you are just interested in PRM, this will avoid fetching all of the other branches.
+
+4. Change to the edk2 workspace directory \
+ ``cd edk2``
+
+5. Run *edksetup* to set local environment variables needed for build
+ * Windows:
+ * ``edksetup.bat``
+ * Linux:
+ * If you have not already built BaseTools:
+ * ``make -C BaseTools``
+ * ``. edksetup.sh``
+
+6. Set the PACKAGES_PATH environment variable to include the directory path that contains `PrmPkg`
+ * Windows example:
+ * ``set PACKAGES_PATH=c:\src\edk2-staging``
+
+7. Change to the edk2-staging workspace directory
+ * Example: ``cd ../edk2-staging``
+
+8. Build PrmPkg \
+ ``build -p PrmPkg/PrmPkg.dsc -a IA32 -a X64``
+ > __*Note*__: Due to the way PRM modules are compiled with exports, **only building on Visual Studio compiler tool
+ chains is currently supported**.
+
+### Build Flags
+As PRM is a new feature at a proof-of-concept (POC) level of maturity, there's some changes to the normal build
+available as build flags. By default, if no flags are specified, the build is done with the currently expected plan of
+record (POR) configuration.
+
+The following list are the currently defined build flags (if any) that may be passed to the `build` command
+(e.g. -D FLAG=VALUE).
+
+## Overview
+At a high-level, PRM can be viewed from three levels of granularity:
+
+1. PRM interface - Encompassing the entirety of firmware functionalities and data provided to OS runtime. Most
+ information is provided through ACPI tables to be agnostic to a UEFI implementation.
+2. PRM module - An independently updatable package of PRM handlers. The PRM interface will be composed of multiple
+ PRM modules. This requirement allows for the separation of OEM and IHV PRM code, each of which can be serviced
+ independently.
+3. PRM handler - The implementation/callback of a single PRM functionality as identified by a GUID.
+
+## Firmware Design
+The firmware has three key generic drivers to support PRM:
+
+1. A PRM Loader driver - Functionality is split across three phases:
+ 1. Discover - Find all PRM modules in the firmware image made available by the platform firmware author.
+ * This phase includes verifying authenticity/integrity of the image, the image executable type, the export
+ table is present and the PRM Export Module Descriptor is present and valid.
+ 2. Process - Convert PRM handler GUID to name mappings in the PRM Module Export Descriptor to PRM handler Name
+ to physical address mappings required to construct the PRM ACPI table.
+ 3. Publish - Publish the PRM ACPI table using the information from the Process phase.
+
+2. A PRM Configuration driver - A generic driver responsible for processing PRM module configuration information
+ consumed through a `PRM_CONFIG_PROTOCOL` per PRM module instance. Therefore, the `PRM_CONFIG_PROTOCOL` serves
+ as the dynamic interface for this driver to process PRM module resources and prepare the module's data to be
+ configured properly for OS runtime.
+
+3. A PRM Module - Not a single driver but a user written PE/COFF image that follows the PRM module authoring process.
+ A PRM module groups together cohesive sets of PRM functionality into functions referred to as "PRM handlers".
+
+## PrmPkg Code Organization
+The package follows a standard EDK II style package format. The list below contains some notable areas to
+explore in the package:
+
+* [ACPI Table Definitions](PrmPkg/PrmLoaderDxe/PrmAcpiTable.h)
+* [Common Interface Definitions](PrmPkg/Include)
+* [PRM Config Driver](PrmPkg/PrmConfigDxe)
+* [PRM Loader Driver](PrmPkg/PrmLoaderDxe)
+* [Sample PRM Modules](PrmPkg/Samples)
+
+While the package does provide sample PRM modules to be used as a reference, actual PRM modules should not be
+maintained in PrmPkg. It is intended to only contain PRM infrastructure code and a few samples of how to use
+that infrastructure. The PrmPkg is meant to be used as-is by firmware that supports PRM. Any shortcomings that
+prevent the package from being used as-is should be addressed directly in PrmPkg.
+
+## PRM Module
+
+By default, the EDK II implementation of UEFI does not allow images with the subsystem type
+IMAGE_SUBSYSTEM_EFI_RUNTIME_DRIVER to be built with exports.
+
+```
+ERROR - Linker #1294 from LINK : fatal exports and import libraries are not supported with /SUBSYSTEM:EFI_RUNTIME_DRIVER
+```
+This can adjusted in the MSVC linker options.
+
+__For the purposes of this POC__, the subsystem type is changed in the firmware build to allow the export table to be
+added but the subsystem type in the final image is still 0xC (EFI Runtime Driver). This is important to allow the DXE
+dispatcher to use its standard image verification and loading algorithms to load the image into permanent memory during
+the DXE execution phase.
+
+All firmware-loaded PRM modules are loaded into a memory buffer of type EfiRuntimeServicesCode. This means the
+operating system must preserve all PRM handler code and the buffer will be reflected in the UEFI memory map. The
+execution for invoking PRM handlers is the same as that required for UEFI Runtime Services, notably 4KiB or more of
+available stack space must be provided and the stack must be 16-byte aligned.
+
+__*Note:*__ Long term it is possible to similarly load the modules into a EfiRuntimeServicesCode buffer and perform
+relocation fixups with a new EFI module type for PRM if desired. It was simply not done since it is not essential
+for this POC.
+
+Where possible, PRM module information is stored and generated using industry compiler tool chains. This is a key
+motivation behind using PE/COFF export tables to expose PRM module information and using a single PRM module binary
+definition consistent between firmware and OS load.
+
+### PRM Module Exports
+A PRM module must contain at least three exports: A PRM Module Export Descriptor, a PRM Module Update Lock Descriptor,
+and at least one PRM handler. Here's an example of an export table from a PRM module that has a single PRM handler:
+
+```
+ 0000000000005000: 00 00 00 00 FF FF FF FF 00 00 00 00 46 50 00 00 ....ÿÿÿÿ....FP..
+ 0000000000005010: 01 00 00 00 03 00 00 00 03 00 00 00 28 50 00 00 ............(P..
+ 0000000000005020: 34 50 00 00 40 50 00 00 78 13 00 00 30 40 00 00 4P..@P..x...0@..
+ 0000000000005030: 20 40 00 00 67 50 00 00 86 50 00 00 A0 50 00 00 @..gP...P...P..
+ 0000000000005040: 00 00 01 00 02 00 50 72 6D 53 61 6D 70 6C 65 43 ......PrmSampleC
+ 0000000000005050: 6F 6E 74 65 78 74 42 75 66 66 65 72 4D 6F 64 75 ontextBufferModu
+ 0000000000005060: 6C 65 2E 64 6C 6C 00 44 75 6D 70 53 74 61 74 69 le.dll.DumpStati
+ 0000000000005070: 63 44 61 74 61 42 75 66 66 65 72 50 72 6D 48 61 cDataBufferPrmHa
+ 0000000000005080: 6E 64 6C 65 72 00 50 72 6D 4D 6F 64 75 6C 65 45 ndler.PrmModuleE
+ 0000000000005090: 78 70 6F 72 74 44 65 73 63 72 69 70 74 6F 72 00 xportDescriptor.
+ 00000000000050A0: 50 72 6D 4D 6F 64 75 6C 65 55 70 64 61 74 65 4C PrmModuleUpdateL
+ 00000000000050B0: 6F 63 6B 00 ock.
+
+ 00000000 characteristics
+ FFFFFFFF time date stamp
+ 0.10 version
+ 1 ordinal base
+ 3 number of functions
+ 3 number of names
+
+ ordinal hint RVA name
+ 1 0 00001378 DumpStaticDataBufferPrmHandler
+ 2 1 00004030 PrmModuleExportDescriptor
+ 3 2 00004020 PrmModuleUpdateLock
+```
+### PRM Image Format
+PRM modules are ultimately PE/COFF images. However, when packaged in firmware the PE/COFF image is placed into a
+Firmware File System (FFS) file. This is transparent to the operating system but done to better align with the typical
+packaging of PE32(+) images managed in the firmware binary image. In the dump of the PRM FV binary image shown earlier,
+the FFS sections placed by EDK II build tools ("DXE dependency", "User interface", "Version") that reside alongside the
+PE/COFF binary are shown. A PRM module can be placed into a firmware image as a pre-built PE/COFF binary or built
+during the firmware build process. In either case, the PE/COFF section is contained in a FFS file as shown in that
+image.
+
+### PRM Module Implementation
+To simplify building the PRM Module Export Descriptor, a PRM module implementation can use the following macros to mark
+functions as PRM handlers. In this example, a PRM module registers three functions by name as PRM handlers with the
+associated GUIDs.
+
+```
+//
+// Register the PRM export information for this PRM Module
+//
+PRM_MODULE_EXPORT (
+ PRM_HANDLER_EXPORT_ENTRY (PRM_HANDLER_1_GUID, PrmHandler1),
+ PRM_HANDLER_EXPORT_ENTRY (PRM_HANDLER_2_GUID, PrmHandler2),
+ PRM_HANDLER_EXPORT_ENTRY (PRM_HANDLER_N_GUID, PrmHandlerN)
+ );
+```
+
+`PRM_MODULE_EXPORT` take a variable-length argument list of `PRM_HANDLER_EXPORT_ENTRY` entries that each describe an
+individual PRM handler being exported for the module. Ultimately, this information is used to define the structure
+necessary to statically allocate the PRM Module Export Descriptor Structure (and its PRM Handler Export Descriptor
+substructures) in the image.
+
+Another required export for PRM modules is automatically provided in `PrmModule.h`, a header file that pulls together
+all the includes needed to author a PRM module. This export is `PRM_MODULE_UPDATE_LOCK_EXPORT`. By including,
+`PrmModule.h`, a PRM module has the `PRM_MODULE_UPDATE_LOCK_DESCRIPTOR` automatically exported.
+
+## PRM Handler Constraints
+At this time, PRM handlers are restricted to a maximum identifier length of 128 characters. This is checked when using
+the `PRM_HANDLER_EXPORT` macro by using a static assert that reports a violation at build-time.
+
+PRM handlers are **not** allowed to use UEFI Runtime Services and should not rely upon any UEFI constructs. For the
+purposes of this POC, this is currently not explicitly enforced but should be in the final changes.
|