OvmfPkg/Library/HardwareInfoLib/QemuFwCfgHardwareInfoLib.c

   1 /*/@file
   2   Qemu fw-cfg wrappers for hardware info parsing.
   3   Provides an alternative to parse hardware information from a fw-cfg
   4   file without relying on dynamic memory allocations.
   5
   6   Copyright 2021 - 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   7   SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #include <Library/DebugLib.h>
  12 #include <Library/QemuFwCfgLib.h>
  13
  14 #include <Library/HardwareInfoLib.h>
  15
  16 /**
  17   Update an optional pointer value if possible
  18
  19   @param[out] DataSize     Pointer to variable to be updated
  20   @param[in]  Value        Value to set the pointed variable to.
  21 **/
  22 STATIC
  23 VOID
  24 UpdateDataSize (
  25   OUT UINTN  *DataSize,
  26   IN  UINTN  Value
  27   )
  28 {
  29   if (DataSize == NULL) {
  30     return;
  31   }
  32
  33   *DataSize = Value;
  34 }
  35
  36 EFI_STATUS
  37 QemuFwCfgReadNextHardwareInfoByType (
  38   IN      HARDWARE_INFO_TYPE  Type,
  39   IN      UINTN               TypeSize,
  40   IN      UINTN               TotalFileSize,
  41   OUT     VOID                *Data,
  42   OUT     UINTN               *DataSize         OPTIONAL,
  43   IN OUT  UINTN               *ReadIndex
  44   )
  45 {
  46   HARDWARE_INFO_HEADER  Header;
  47
  48   if ((Data == NULL) ||
  49       (ReadIndex == NULL) ||
  50       (TypeSize == 0) ||
  51       (Type == HardwareInfoTypeUndefined) ||
  52       (TotalFileSize == 0))
  53   {
  54     return EFI_INVALID_PARAMETER;
  55   }
  56
  57   UpdateDataSize (DataSize, 0);
  58
  59   while (*ReadIndex < TotalFileSize) {
  60     QemuFwCfgReadBytes (sizeof (Header), &Header);
  61     *ReadIndex += sizeof (Header);
  62
  63     if ((Header.Size > MAX_UINTN) || (((UINT64)*ReadIndex + Header.Size) > TotalFileSize)) {
  64       *ReadIndex = TotalFileSize;
  65       return EFI_ABORTED;
  66     }
  67
  68     if ((Header.Type.Value == Type) && (Header.Size <= TypeSize)) {
  69       QemuFwCfgReadBytes ((UINTN)Header.Size, Data);
  70
  71       *ReadIndex += (UINTN)Header.Size;
  72       UpdateDataSize (DataSize, (UINTN)Header.Size);
  73
  74       return EFI_SUCCESS;
  75     }
  76
  77     //
  78     // Skip the bytes corresponding to the next element as it is
  79     // not of the expected type and/or size. The TotalFileSize
  80     // and individual elements sizes should match so the size
  81     // check is skipped.
  82     //
  83     QemuFwCfgSkipBytes ((UINTN)Header.Size);
  84     *ReadIndex += (UINTN)Header.Size;
  85   }
  86
  87   return EFI_END_OF_FILE;
  88 }