ShellPkg/for: Fix potential null pointer deference

[mirror_edk2.git] / OvmfPkg / VirtioNetDxe / SnpGetStatus.c

/** @file\r
\r
  Implementation of the SNP.GetStatus() function and its private helpers if\r
  any.\r
\r
  Copyright (C) 2013, Red Hat, Inc.\r
  Copyright (c) 2006 - 2014, Intel Corporation. All rights reserved.<BR>\r
\r
  This program and the accompanying materials are licensed and made available\r
  under the terms and conditions of the BSD License which accompanies this\r
  distribution. The full text of the license may be found at\r
  http://opensource.org/licenses/bsd-license.php\r
\r
  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT\r
  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
\r
**/\r
\r
#include <Library/BaseLib.h>\r
#include <Library/UefiBootServicesTableLib.h>\r
\r
#include "VirtioNet.h"\r
\r
/**\r
  Reads the current interrupt status and recycled transmit buffer status from\r
  a network interface.\r
\r
  @param  This            The protocol instance pointer.\r
  @param  InterruptStatus A pointer to the bit mask of the currently active\r
                          interrupts If this is NULL, the interrupt status will\r
                          not be read from the device. If this is not NULL, the\r
                          interrupt status will be read from the device. When\r
                          the  interrupt status is read, it will also be\r
                          cleared. Clearing the transmit  interrupt does not\r
                          empty the recycled transmit buffer array.\r
  @param  TxBuf           Recycled transmit buffer address. The network\r
                          interface will not transmit if its internal recycled\r
                          transmit buffer array is full. Reading the transmit\r
                          buffer does not clear the transmit interrupt. If this\r
                          is NULL, then the transmit buffer status will not be\r
                          read. If there are no transmit buffers to recycle and\r
                          TxBuf is not NULL, * TxBuf will be set to NULL.\r
\r
  @retval EFI_SUCCESS           The status of the network interface was\r
                                retrieved.\r
  @retval EFI_NOT_STARTED       The network interface has not been started.\r
  @retval EFI_INVALID_PARAMETER One or more of the parameters has an\r
                                unsupported value.\r
  @retval EFI_DEVICE_ERROR      The command could not be sent to the network\r
                                interface.\r
  @retval EFI_UNSUPPORTED       This function is not supported by the network\r
                                interface.\r
\r
**/\r
\r
EFI_STATUS\r
EFIAPI\r
VirtioNetGetStatus (\r
  IN EFI_SIMPLE_NETWORK_PROTOCOL *This,\r
  OUT UINT32                     *InterruptStatus OPTIONAL,\r
  OUT VOID                       **TxBuf OPTIONAL\r
  )\r
{\r
  VNET_DEV             *Dev;\r
  EFI_TPL              OldTpl;\r
  EFI_STATUS           Status;\r
  UINT16               RxCurUsed;\r
  UINT16               TxCurUsed;\r
  EFI_PHYSICAL_ADDRESS DeviceAddress;\r
\r
  if (This == NULL) {\r
    return EFI_INVALID_PARAMETER;\r
  }\r
\r
  Dev = VIRTIO_NET_FROM_SNP (This);\r
  OldTpl = gBS->RaiseTPL (TPL_CALLBACK);\r
  switch (Dev->Snm.State) {\r
  case EfiSimpleNetworkStopped:\r
    Status = EFI_NOT_STARTED;\r
    goto Exit;\r
  case EfiSimpleNetworkStarted:\r
    Status = EFI_DEVICE_ERROR;\r
    goto Exit;\r
  default:\r
    break;\r
  }\r
\r
  //\r
  // update link status\r
  //\r
  if (Dev->Snm.MediaPresentSupported) {\r
    UINT16 LinkStatus;\r
\r
    Status = VIRTIO_CFG_READ (Dev, LinkStatus, &LinkStatus);\r
    if (EFI_ERROR (Status)) {\r
      goto Exit;\r
    }\r
    Dev->Snm.MediaPresent =\r
      (BOOLEAN) ((LinkStatus & VIRTIO_NET_S_LINK_UP) != 0);\r
  }\r
\r
  //\r
  // virtio-0.9.5, 2.4.2 Receiving Used Buffers From the Device\r
  //\r
  MemoryFence ();\r
  RxCurUsed = *Dev->RxRing.Used.Idx;\r
  TxCurUsed = *Dev->TxRing.Used.Idx;\r
  MemoryFence ();\r
\r
  if (InterruptStatus != NULL) {\r
    //\r
    // report the receive interrupt if there is data available for reception,\r
    // report the transmit interrupt if we have transmitted at least one buffer\r
    //\r
    *InterruptStatus = 0;\r
    if (Dev->RxLastUsed != RxCurUsed) {\r
      *InterruptStatus |= EFI_SIMPLE_NETWORK_RECEIVE_INTERRUPT;\r
    }\r
    if (Dev->TxLastUsed != TxCurUsed) {\r
      ASSERT (Dev->TxCurPending > 0);\r
      *InterruptStatus |= EFI_SIMPLE_NETWORK_TRANSMIT_INTERRUPT;\r
    }\r
  }\r
\r
  if (TxBuf != NULL) {\r
    if (Dev->TxLastUsed == TxCurUsed) {\r
      *TxBuf = NULL;\r
    }\r
    else {\r
      UINT16 UsedElemIdx;\r
      UINT32 DescIdx;\r
\r
      //\r
      // fetch the first descriptor among those that the hypervisor reports\r
      // completed\r
      //\r
      ASSERT (Dev->TxCurPending > 0);\r
      ASSERT (Dev->TxCurPending <= Dev->TxMaxPending);\r
\r
      UsedElemIdx = Dev->TxLastUsed++ % Dev->TxRing.QueueSize;\r
      DescIdx = Dev->TxRing.Used.UsedElem[UsedElemIdx].Id;\r
      ASSERT (DescIdx < (UINT32) (2 * Dev->TxMaxPending - 1));\r
\r
      //\r
      // get the device address that has been enqueued for the caller's\r
      // transmit buffer\r
      //\r
      DeviceAddress = Dev->TxRing.Desc[DescIdx + 1].Addr;\r
\r
      //\r
      // now this descriptor can be used again to enqueue a transmit buffer\r
      //\r
      Dev->TxFreeStack[--Dev->TxCurPending] = (UINT16) DescIdx;\r
\r
      //\r
      // Unmap the device address and perform the reverse mapping to find the\r
      // caller buffer address.\r
      //\r
      Status = VirtioNetUnmapTxBuf (\r
                 Dev,\r
                 TxBuf,\r
                 DeviceAddress\r
                 );\r
      if (EFI_ERROR (Status)) {\r
        //\r
        // VirtioNetUnmapTxBuf should never fail, if we have reached here\r
        // that means our internal state has been corrupted\r
        //\r
        ASSERT (FALSE);\r
        Status = EFI_DEVICE_ERROR;\r
        goto Exit;\r
      }\r
    }\r
  }\r
\r
  Status = EFI_SUCCESS;\r
\r
Exit:\r
  gBS->RestoreTPL (OldTpl);\r
  return Status;\r
}\r