EmbeddedPkg/Library/HalRuntimeServicesExampleLib/Mtc.c

   1 /** @file
   2   Generic Monotonic Counter services
   3
   4   Copyright (c) 2007, Intel Corporation. All rights reserved.<BR>
   5   Portions copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
   6
   7   This program and the accompanying materials
   8   are licensed and made available under the terms and conditions of the BSD License
   9   which accompanies this distribution.  The full text of the license may be found at
  10   http://opensource.org/licenses/bsd-license.php
  11
  12   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  13   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  14
  15
  16 **/
  17
  18
  19 //
  20 // The current Monotonic count value
  21 //
  22 UINT64      mEfiMtc = 0;
  23
  24
  25 //
  26 // Event to use to update the Mtc's high part when wrapping
  27 //
  28 EFI_EVENT   mEfiMtcEvent;
  29
  30 //
  31 // EfiMtcName - Variable name of the MTC value
  32 //
  33 CHAR16      *mEfiMtcName = L"MTC";
  34
  35 //
  36 // EfiMtcGuid - Guid of the MTC value
  37 //
  38 EFI_GUID    mEfiMtcGuid = { 0xeb704011, 0x1402, 0x11d3, { 0x8e, 0x77, 0x0, 0xa0, 0xc9, 0x69, 0x72, 0x3b } };
  39
  40
  41
  42 //
  43 // Worker functions
  44 //
  45
  46
  47 VOID
  48 EFIAPI
  49 EfiMtcEventHandler (
  50   IN EFI_EVENT                Event,
  51   IN VOID                     *Context
  52   )
  53 /*++
  54
  55 Routine Description:
  56
  57   Monotonic count event handler.  This handler updates the high monotonic count.
  58
  59 Arguments:
  60
  61   Event         The event to handle
  62   Context       The event context
  63
  64 Returns:
  65
  66   EFI_SUCCESS       The event has been handled properly
  67   EFI_NOT_FOUND     An error occurred updating the variable.
  68
  69 --*/
  70 {
  71   UINT32  HighCount;
  72
  73   EfiGetNextHighMonotonicCount (&HighCount);
  74   return;
  75 }
  76
  77
  78
  79 VOID
  80 LibMtcVirtualAddressChangeEvent (VOID)
  81 {
  82 }
  83
  84
  85 EFI_STATUS
  86 EFIAPI
  87 LibMtcGetNextHighMonotonicCount (
  88   OUT UINT32  *HighCount
  89   )
  90 {
  91   EFI_STATUS  Status;
  92   EFI_TPL     OldTpl;
  93
  94   //
  95   // Check input parameters
  96   //
  97   if (HighCount == NULL) {
  98     return EFI_INVALID_PARAMETER;
  99   }
 100
 101
 102   if (!EfiAtRuntime ()) {
 103     // Use a lock if called before ExitBootServices()
 104     OldTpl      = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
 105   }
 106
 107   *HighCount  = (UINT32) RShiftU64 (mEfiMtc, 32) + 1;
 108   mEfiMtc     = LShiftU64 (*HighCount, 32);
 109
 110   if (!EfiAtRuntime ()) {
 111     gBS->RestoreTPL (OldTpl);
 112   }
 113
 114   //
 115   // Update the NvRam store to match the new high part
 116   //
 117   Status = EfiSetVariable (
 118               mEfiMtcName,
 119               &mEfiMtcGuid,
 120               EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_BOOTSERVICE_ACCESS,
 121               sizeof (UINT32),
 122               HighCount
 123               );
 124
 125   return Status;
 126 }
 127
 128
 129 EFI_STATUS
 130 LibMtcGetNextMonotonicCount (
 131   OUT UINT64  *Count
 132   )
 133 {
 134   EFI_STATUS    Status;
 135   EFI_TPL       OldTpl;
 136   UINT32        HighCount;
 137   UINTN         BufferSize;
 138
 139   //
 140   // Can not be called after ExitBootServices()
 141   //
 142   if (EfiAtRuntime ()) {
 143     return EFI_UNSUPPORTED;
 144   }
 145
 146   //
 147   // Check input parameters
 148   //
 149   if (Count == NULL) {
 150     return EFI_INVALID_PARAMETER;
 151   }
 152
 153   if (mEfiMtc == 0) {
 154     //
 155     // If the MTC has not been initialized read the variable
 156     //
 157
 158     //
 159     // Read the last high part
 160     //
 161     BufferSize = sizeof (UINT32);
 162     Status = EfiGetVariable (
 163                 mEfiMtcName,
 164                 &mEfiMtcGuid,
 165                 NULL,
 166                 &BufferSize,
 167                 &HighCount
 168                 );
 169     if (EFI_ERROR (Status)) {
 170       HighCount = 0;
 171     }
 172
 173     //
 174     // Set the current value
 175     //
 176     mEfiMtc = LShiftU64 (HighCount, 32);
 177     //
 178     // Increment the upper 32 bits for this boot
 179     // Continue even if it fails.  It will only fail if the variable services are
 180     // not functional.
 181     //
 182     Status = EfiGetNextHighMonotonicCount (&HighCount);
 183   }
 184
 185
 186   //
 187   // Update the monotonic counter with a lock
 188   //
 189   OldTpl  = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);
 190   *Count  = mEfiMtc;
 191   mEfiMtc++;
 192   gBS->RestoreTPL (OldTpl);
 193
 194   //
 195   // If the MSB bit of the low part toggled, then signal that the high
 196   // part needs updated now
 197   //
 198   if ((((UINT32) mEfiMtc) ^ ((UINT32) *Count)) & 0x80000000) {
 199     gBS->SignalEvent (mEfiMtcEvent);
 200   }
 201
 202   return EFI_SUCCESS;
 203 }
 204
 205
 206
 207 VOID
 208 LibMtcInitialize (
 209   VOID
 210   )
 211 {
 212   EFI_STATUS  Status;
 213
 214   //
 215   // Initialize event to handle overflows
 216   //
 217   Status = gBS->CreateEvent (
 218                   EVT_NOTIFY_SIGNAL,
 219                   EFI_TPL_CALLBACK,
 220                   EfiMtcEventHandler,
 221                   NULL,
 222                   &mEfiMtcEvent
 223                   );
 224   ASSERT_EFI_ERROR (Status);
 225 }
 226