1 files changed, 88 insertions, 0 deletions
diff --git a/OvmfPkg/Library/HardwareInfoLib/QemuFwCfgHardwareInfoLib.c b/OvmfPkg/Library/HardwareInfoLib/QemuFwCfgHardwareInfoLib.c
new file mode 100644
index 0000000..48d9dcd
--- /dev/null
+++ b/OvmfPkg/Library/HardwareInfoLib/QemuFwCfgHardwareInfoLib.c
@@ -0,0 +1,88 @@
+/*/@file
+  Qemu fw-cfg wrappers for hardware info parsing.
+  Provides an alternative to parse hardware information from a fw-cfg
+  file without relying on dynamic memory allocations.
+
+  Copyright 2021 - 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+
+**/
+
+#include <Library/DebugLib.h>
+#include <Library/QemuFwCfgLib.h>
+
+#include <Library/HardwareInfoLib.h>
+
+/**
+  Update an optional pointer value if possible
+
+  @param[out] DataSize     Pointer to variable to be updated
+  @param[in]  Value        Value to set the pointed variable to.
+**/
+STATIC
+VOID
+UpdateDataSize (
+  OUT UINTN  *DataSize,
+  IN  UINTN  Value
+  )
+{
+  if (DataSize == NULL) {
+    return;
+  }
+
+  *DataSize = Value;
+}
+
+EFI_STATUS
+QemuFwCfgReadNextHardwareInfoByType (
+  IN      HARDWARE_INFO_TYPE  Type,
+  IN      UINTN               TypeSize,
+  IN      UINTN               TotalFileSize,
+  OUT     VOID                *Data,
+  OUT     UINTN               *DataSize         OPTIONAL,
+  IN OUT  UINTN               *ReadIndex
+  )
+{
+  HARDWARE_INFO_HEADER  Header;
+
+  if ((Data == NULL) ||
+      (ReadIndex == NULL) ||
+      (TypeSize == 0) ||
+      (Type == HardwareInfoTypeUndefined) ||
+      (TotalFileSize == 0))
+  {
+    return EFI_INVALID_PARAMETER;
+  }
+
+  UpdateDataSize (DataSize, 0);
+
+  while (*ReadIndex < TotalFileSize) {
+    QemuFwCfgReadBytes (sizeof (Header), &Header);
+    *ReadIndex += sizeof (Header);
+
+    if ((Header.Size > MAX_UINTN) || (((UINT64)*ReadIndex + Header.Size) > TotalFileSize)) {
+      *ReadIndex = TotalFileSize;
+      return EFI_ABORTED;
+    }
+
+    if ((Header.Type.Value == Type) && (Header.Size <= TypeSize)) {
+      QemuFwCfgReadBytes ((UINTN)Header.Size, Data);
+
+      *ReadIndex += (UINTN)Header.Size;
+      UpdateDataSize (DataSize, (UINTN)Header.Size);
+
+      return EFI_SUCCESS;
+    }
+
+    //
+    // Skip the bytes corresponding to the next element as it is
+    // not of the expected type and/or size. The TotalFileSize
+    // and individual elements sizes should match so the size
+    // check is skipped.
+    //
+    QemuFwCfgSkipBytes ((UINTN)Header.Size);
+    *ReadIndex += (UINTN)Header.Size;
+  }
+
+  return EFI_END_OF_FILE;
+}