OvmfPkg/PlatformDxe/PlatformConfig.c

   1 /** @file
   2
   3   Utility functions for serializing (persistently storing) and deserializing
   4   OVMF's platform configuration.
   5
   6   Copyright (C) 2014, Red Hat, Inc.
   7
   8   SPDX-License-Identifier: BSD-2-Clause-Patent
   9
  10 **/
  11
  12 #include <Library/BaseMemoryLib.h>
  13 #include <Library/DebugLib.h>
  14 #include <Library/MemoryAllocationLib.h>
  15 #include <Library/UefiLib.h>
  16 #include <Library/UefiRuntimeServicesTableLib.h>
  17 #include <Guid/OvmfPlatformConfig.h>
  18
  19 #include "PlatformConfig.h"
  20
  21 //
  22 // Name of the UEFI variable that we use for persistent storage.
  23 //
  24 CHAR16  mVariableName[] = L"PlatformConfig";
  25 CHAR16  mHiiFormName[]  = L"MainFormState";
  26
  27 /**
  28   Serialize and persistently save platform configuration.
  29
  30   @param[in] PlatformConfig  The platform configuration to serialize and save.
  31
  32   @return  Status codes returned by gRT->SetVariable().
  33 **/
  34 EFI_STATUS
  35 EFIAPI
  36 PlatformConfigSave (
  37   IN PLATFORM_CONFIG  *PlatformConfig
  38   )
  39 {
  40   EFI_STATUS  Status;
  41
  42   //
  43   // We could implement any kind of translation here, as part of serialization.
  44   // For example, we could expose the platform configuration in separate
  45   // variables with human-readable contents, allowing other tools to access
  46   // them more easily. For now, just save a binary dump.
  47   //
  48   Status = gRT->SetVariable (
  49                   mVariableName,
  50                   &gOvmfPlatformConfigGuid,
  51                   EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS |
  52                   EFI_VARIABLE_RUNTIME_ACCESS,
  53                   sizeof *PlatformConfig,
  54                   PlatformConfig
  55                   );
  56   return Status;
  57 }
  58
  59 /**
  60   Load and deserialize platform configuration.
  61
  62   When the function fails, output parameters are indeterminate.
  63
  64   @param[out] PlatformConfig    The platform configuration to receive the
  65                                 loaded data.
  66
  67   @param[out] OptionalElements  This bitmap describes the presence of optional
  68                                 configuration elements that have been loaded.
  69                                 PLATFORM_CONFIG_F_DOWNGRADE means that some
  70                                 unknown elements, present in the wire format,
  71                                 have been ignored.
  72
  73   @retval  EFI_SUCCESS         Loading & deserialization successful.
  74   @return                      Error codes returned by GetVariable2().
  75 **/
  76 EFI_STATUS
  77 EFIAPI
  78 PlatformConfigLoad (
  79   OUT PLATFORM_CONFIG  *PlatformConfig,
  80   OUT UINT64           *OptionalElements
  81   )
  82 {
  83   VOID        *Data;
  84   UINTN       DataSize;
  85   EFI_STATUS  Status;
  86
  87   //
  88   // Any translation done in PlatformConfigSave() would have to be mirrored
  89   // here. For now, just load the binary dump.
  90   //
  91   // Versioning of the binary wire format is implemented based on size
  92   // (only incremental changes, ie. new fields), and on GUID.
  93   // (Incompatible changes require a GUID change.)
  94   //
  95   Status = GetVariable2 (
  96              mVariableName,
  97              &gOvmfPlatformConfigGuid,
  98              &Data,
  99              &DataSize
 100              );
 101   if (EFI_ERROR (Status)) {
 102     return Status;
 103   }
 104
 105   *OptionalElements = 0;
 106   if (DataSize > sizeof *PlatformConfig) {
 107     //
 108     // Handle firmware downgrade -- keep only leading part.
 109     //
 110     CopyMem (PlatformConfig, Data, sizeof *PlatformConfig);
 111     *OptionalElements |= PLATFORM_CONFIG_F_DOWNGRADE;
 112   } else {
 113     CopyMem (PlatformConfig, Data, DataSize);
 114
 115     //
 116     // Handle firmware upgrade -- zero out missing fields.
 117     //
 118     ZeroMem (
 119       (UINT8 *)PlatformConfig + DataSize,
 120       sizeof *PlatformConfig - DataSize
 121       );
 122   }
 123
 124   //
 125   // Based on DataSize, report the optional features that we recognize.
 126   //
 127   if (DataSize >= (OFFSET_OF (PLATFORM_CONFIG, VerticalResolution) +
 128                    sizeof PlatformConfig->VerticalResolution))
 129   {
 130     *OptionalElements |= PLATFORM_CONFIG_F_GRAPHICS_RESOLUTION;
 131   }
 132
 133   FreePool (Data);
 134   return EFI_SUCCESS;
 135 }