ShellPkg/for: Fix potential null pointer deference

[mirror_edk2.git] / OvmfPkg / AcpiPlatformDxe / PciDecoding.c

/** @file\r
  Temporarily enable IO and MMIO decoding for all PCI devices while QEMU\r
  regenerates the ACPI tables.\r
\r
  Copyright (C) 2016, Red Hat, Inc.\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
#include <Library/MemoryAllocationLib.h>\r
\r
#include "AcpiPlatform.h"\r
\r
\r
/**\r
  Collect all PciIo protocol instances in the system. Save their original\r
  attributes, and enable IO and MMIO decoding for each.\r
\r
  This is a best effort function; it doesn't return status codes. Its\r
  caller is supposed to proceed even if this function fails.\r
\r
  @param[out] OriginalAttributes  On output, a dynamically allocated array of\r
                                  ORIGINAL_ATTRIBUTES elements. The array lists\r
                                  the PciIo protocol instances found in the\r
                                  system at the time of the call, plus the\r
                                  original PCI attributes for each.\r
\r
                                  Before returning, the function enables IO and\r
                                  MMIO decoding for each PciIo instance it\r
                                  finds.\r
\r
                                  On error, or when no such instances are\r
                                  found, OriginalAttributes is set to NULL.\r
\r
  @param[out] Count               On output, the number of elements in\r
                                  OriginalAttributes. On error it is set to\r
                                  zero.\r
**/\r
VOID\r
EnablePciDecoding (\r
  OUT ORIGINAL_ATTRIBUTES **OriginalAttributes,\r
  OUT UINTN               *Count\r
  )\r
{\r
  EFI_STATUS          Status;\r
  UINTN               NoHandles;\r
  EFI_HANDLE          *Handles;\r
  ORIGINAL_ATTRIBUTES *OrigAttrs;\r
  UINTN               Idx;\r
\r
  *OriginalAttributes = NULL;\r
  *Count              = 0;\r
\r
  if (PcdGetBool (PcdPciDisableBusEnumeration)) {\r
    //\r
    // The platform downloads ACPI tables from QEMU in general, but there are\r
    // no root bridges in this execution. We're done.\r
    //\r
    return;\r
  }\r
\r
  Status = gBS->LocateHandleBuffer (ByProtocol, &gEfiPciIoProtocolGuid,\r
                  NULL /* SearchKey */, &NoHandles, &Handles);\r
  if (Status == EFI_NOT_FOUND) {\r
    //\r
    // No PCI devices were found on either of the root bridges. We're done.\r
    //\r
    return;\r
  }\r
\r
  if (EFI_ERROR (Status)) {\r
    DEBUG ((EFI_D_WARN, "%a: LocateHandleBuffer(): %r\n", __FUNCTION__,\r
      Status));\r
    return;\r
  }\r
\r
  OrigAttrs = AllocatePool (NoHandles * sizeof *OrigAttrs);\r
  if (OrigAttrs == NULL) {\r
    DEBUG ((EFI_D_WARN, "%a: AllocatePool(): out of resources\n",\r
      __FUNCTION__));\r
    goto FreeHandles;\r
  }\r
\r
  for (Idx = 0; Idx < NoHandles; ++Idx) {\r
    EFI_PCI_IO_PROTOCOL *PciIo;\r
    UINT64              Attributes;\r
\r
    //\r
    // Look up PciIo on the handle and stash it\r
    //\r
    Status = gBS->HandleProtocol (Handles[Idx], &gEfiPciIoProtocolGuid,\r
                    (VOID**)&PciIo);\r
    ASSERT_EFI_ERROR (Status);\r
    OrigAttrs[Idx].PciIo = PciIo;\r
\r
    //\r
    // Stash the current attributes\r
    //\r
    Status = PciIo->Attributes (PciIo, EfiPciIoAttributeOperationGet, 0,\r
                      &OrigAttrs[Idx].PciAttributes);\r
    if (EFI_ERROR (Status)) {\r
      DEBUG ((EFI_D_WARN, "%a: EfiPciIoAttributeOperationGet: %r\n",\r
        __FUNCTION__, Status));\r
      goto RestoreAttributes;\r
    }\r
\r
    //\r
    // Retrieve supported attributes\r
    //\r
    Status = PciIo->Attributes (PciIo, EfiPciIoAttributeOperationSupported, 0,\r
                      &Attributes);\r
    if (EFI_ERROR (Status)) {\r
      DEBUG ((EFI_D_WARN, "%a: EfiPciIoAttributeOperationSupported: %r\n",\r
        __FUNCTION__, Status));\r
      goto RestoreAttributes;\r
    }\r
\r
    //\r
    // Enable IO and MMIO decoding\r
    //\r
    Attributes &= EFI_PCI_IO_ATTRIBUTE_IO | EFI_PCI_IO_ATTRIBUTE_MEMORY;\r
    Status = PciIo->Attributes (PciIo, EfiPciIoAttributeOperationEnable,\r
                      Attributes, NULL);\r
    if (EFI_ERROR (Status)) {\r
      DEBUG ((EFI_D_WARN, "%a: EfiPciIoAttributeOperationEnable: %r\n",\r
        __FUNCTION__, Status));\r
      goto RestoreAttributes;\r
    }\r
  }\r
\r
  //\r
  // Success\r
  //\r
  FreePool (Handles);\r
  *OriginalAttributes = OrigAttrs;\r
  *Count              = NoHandles;\r
  return;\r
\r
RestoreAttributes:\r
  while (Idx > 0) {\r
    --Idx;\r
    OrigAttrs[Idx].PciIo->Attributes (OrigAttrs[Idx].PciIo,\r
                            EfiPciIoAttributeOperationSet,\r
                            OrigAttrs[Idx].PciAttributes,\r
                            NULL\r
                            );\r
  }\r
  FreePool (OrigAttrs);\r
\r
FreeHandles:\r
  FreePool (Handles);\r
}\r
\r
\r
/**\r
  Restore the original PCI attributes saved with EnablePciDecoding().\r
\r
  @param[in] OriginalAttributes  The array allocated and populated by\r
                                 EnablePciDecoding(). This parameter may be\r
                                 NULL. If OriginalAttributes is NULL, then the\r
                                 function is a no-op; otherwise the PciIo\r
                                 attributes will be restored, and the\r
                                 OriginalAttributes array will be freed.\r
\r
  @param[in] Count               The Count value stored by EnablePciDecoding(),\r
                                 the number of elements in OriginalAttributes.\r
                                 Count may be zero if and only if\r
                                 OriginalAttributes is NULL.\r
**/\r
VOID\r
RestorePciDecoding (\r
  IN ORIGINAL_ATTRIBUTES *OriginalAttributes,\r
  IN UINTN               Count\r
  )\r
{\r
  UINTN Idx;\r
\r
  ASSERT ((OriginalAttributes == NULL) == (Count == 0));\r
  if (OriginalAttributes == NULL) {\r
    return;\r
  }\r
\r
  for (Idx = 0; Idx < Count; ++Idx) {\r
    OriginalAttributes[Idx].PciIo->Attributes (\r
                                     OriginalAttributes[Idx].PciIo,\r
                                     EfiPciIoAttributeOperationSet,\r
                                     OriginalAttributes[Idx].PciAttributes,\r
                                     NULL\r
                                     );\r
  }\r
  FreePool (OriginalAttributes);\r
}\r