OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSec.c

   1 /** @file
   2
   3   Stateless fw_cfg library implementation.
   4
   5   Clients must call QemuFwCfgIsAvailable() first.
   6
   7   Copyright (C) 2013, Red Hat, Inc.
   8   Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
   9   Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
  10
  11   SPDX-License-Identifier: BSD-2-Clause-Patent
  12 **/
  13
  14 #include <Library/BaseLib.h>
  15 #include <Library/DebugLib.h>
  16 #include <Library/QemuFwCfgLib.h>
  17
  18 #include "QemuFwCfgLibInternal.h"
  19
  20 /**
  21   Returns a boolean indicating if the firmware configuration interface
  22   is available or not.
  23
  24   This function may change fw_cfg state.
  25
  26   @retval    TRUE   The interface is available
  27   @retval    FALSE  The interface is not available
  28
  29 **/
  30 BOOLEAN
  31 EFIAPI
  32 QemuFwCfgIsAvailable (
  33   VOID
  34   )
  35 {
  36   UINT32  Signature;
  37   UINT32  Revision;
  38
  39   QemuFwCfgSelectItem (QemuFwCfgItemSignature);
  40   Signature = QemuFwCfgRead32 ();
  41   DEBUG ((DEBUG_INFO, "FW CFG Signature: 0x%x\n", Signature));
  42   QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
  43   Revision = QemuFwCfgRead32 ();
  44   DEBUG ((DEBUG_INFO, "FW CFG Revision: 0x%x\n", Revision));
  45   if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
  46       (Revision < 1)
  47       )
  48   {
  49     DEBUG ((DEBUG_INFO, "QemuFwCfg interface not supported.\n"));
  50     return FALSE;
  51   }
  52
  53   DEBUG ((DEBUG_INFO, "QemuFwCfg interface is supported.\n"));
  54   return TRUE;
  55 }
  56
  57 /**
  58   Returns a boolean indicating if the firmware configuration interface is
  59   available for library-internal purposes.
  60
  61   This function never changes fw_cfg state.
  62
  63   @retval    TRUE   The interface is available internally.
  64   @retval    FALSE  The interface is not available internally.
  65 **/
  66 BOOLEAN
  67 InternalQemuFwCfgIsAvailable (
  68   VOID
  69   )
  70 {
  71   //
  72   // We always return TRUE, because the consumer of this library ought to have
  73   // called QemuFwCfgIsAvailable before making other calls which would hit this
  74   // path.
  75   //
  76   return TRUE;
  77 }
  78
  79 /**
  80   Returns a boolean indicating whether QEMU provides the DMA-like access method
  81   for fw_cfg.
  82
  83   @retval    TRUE   The DMA-like access method is available.
  84   @retval    FALSE  The DMA-like access method is unavailable.
  85 **/
  86 BOOLEAN
  87 InternalQemuFwCfgDmaIsAvailable (
  88   VOID
  89   )
  90 {
  91   return FALSE;
  92 }
  93
  94 /**
  95   Transfer an array of bytes, or skip a number of bytes, using the DMA
  96   interface.
  97
  98   @param[in]     Size     Size in bytes to transfer or skip.
  99
 100   @param[in,out] Buffer   Buffer to read data into or write data from. Ignored,
 101                           and may be NULL, if Size is zero, or Control is
 102                           FW_CFG_DMA_CTL_SKIP.
 103
 104   @param[in]     Control  One of the following:
 105                           FW_CFG_DMA_CTL_WRITE - write to fw_cfg from Buffer.
 106                           FW_CFG_DMA_CTL_READ  - read from fw_cfg into Buffer.
 107                           FW_CFG_DMA_CTL_SKIP  - skip bytes in fw_cfg.
 108 **/
 109 VOID
 110 InternalQemuFwCfgDmaBytes (
 111   IN     UINT32  Size,
 112   IN OUT VOID    *Buffer OPTIONAL,
 113   IN     UINT32  Control
 114   )
 115 {
 116   //
 117   // We should never reach here
 118   //
 119   ASSERT (FALSE);
 120   CpuDeadLoop ();
 121 }