1 files changed, 214 insertions, 0 deletions
diff --git a/OvmfPkg/Include/Library/MemDebugLogLib.h b/OvmfPkg/Include/Library/MemDebugLogLib.h
new file mode 100644
index 0000000..6dde585
--- /dev/null
+++ b/OvmfPkg/Include/Library/MemDebugLogLib.h
@@ -0,0 +1,214 @@
+/** @file
+  Interface functions for the Memory Debug Log Library.
+
+  Copyright (C) 2025, Oracle and/or its affiliates.
+
+  SPDX-License-Identifier: BSD-2-Clause-Patent
+**/
+
+#ifndef _MEM_DEBUG_LOG_LIB_H_
+#define _MEM_DEBUG_LOG_LIB_H_
+
+#include <Uefi/UefiBaseType.h>
+#include <Base.h>
+
+//
+// Cap max buffer at 2MB (0x200 4K pages)
+//
+#define MAX_MEM_DEBUG_LOG_PAGES  0x200
+
+#define MEM_DEBUG_LOG_MAGIC1  0x3167646d666d766f  // "ovmfmdg1"
+#define MEM_DEBUG_LOG_MAGIC2  0x3267646d666d766f  // "ovmfmdg2"
+
+#pragma pack(1)
+//
+// Mem Debug Log buffer header.
+// The Log buffer is circular. Only the most
+// recent messages are retained. Older messages
+// will be discarded if the buffer overflows.
+// The Debug Log starts just after the header.
+//
+typedef struct {
+  //
+  // Magic values
+  // These fields are used by tools to locate the buffer in
+  // memory. These MUST be the first two fields of the structure.
+  // Use a 128 bit Magic to vastly reduce the possibility of
+  // a collision with random data in memory.
+  UINT64             Magic1;
+  UINT64             Magic2;
+  //
+  // Header Size
+  // This MUST be the third field of the structure
+  //
+  UINT64             HeaderSize;
+  //
+  // Debug log size (minus header)
+  //
+  UINT64             DebugLogSize;
+  //
+  // Protect the log from potential MP access (by APs during
+  // vCPU init) to maintain integrity of the Head/Tail Offsets.
+  // NOTE: MemDebugLogLock is used as a SPIN_LOCK (which is type
+  // UINTN). Thus, we declared it as a UINT64 to ensure a
+  // consistent structure size.
+  //
+  volatile UINT64    MemDebugLogLock;
+  //
+  // Debug log head offset
+  //
+  UINT64             DebugLogHeadOffset;
+  //
+  //  Debug log tail offset
+  //
+  UINT64             DebugLogTailOffset;
+  //
+  // Flag to indicate if the buffer wrapped and was thus truncated.
+  //
+  UINT64             Truncated;
+  //
+  // Firmware Build Version (PcdFirmwareVersionString)
+  //
+  CHAR8              FirmwareVersion[128];
+} MEM_DEBUG_LOG_HDR;
+
+//
+// HOB used to pass the mem debug log buffer addr from PEI to DXE
+//
+typedef struct {
+  EFI_PHYSICAL_ADDRESS    MemDebugLogBufAddr;
+} MEM_DEBUG_LOG_HOB_DATA;
+
+#pragma pack()
+
+/**
+  Write a CHAR8 string to the memory debug log.
+  This is the interface function used by DebugLib.
+  There are several versions for each boot
+  phase (i.e. SEC, PEI, DXE, Runtime).
+  Each version will obtain the proper memory debug log
+  buffer address and call MemDebugLogWriteBuffer().
+
+  @param[in] Buffer              The buffer containing the string of CHAR8s
+
+  @param[in] Length              The buffer length (number of CHAR8s)
+                                 not including the NULL terminator byte.
+
+  @retval RETURN_SUCCESS         String succcessfully written to the memory log buffer.
+
+  @retval RETURN_NOT_FOUND       Memory log buffer is not properly initialized.
+
+  @retval EFI_INVALID_PARAMETER   Invalid input parameters.
+**/
+EFI_STATUS
+EFIAPI
+MemDebugLogWrite (
+  IN  CHAR8  *Buffer,
+  IN  UINTN  Length
+  );
+
+/**
+  Return the memory debug log buffer size (in pages).
+  This function is implemented by PEIM version of
+  MemDebugLogLib only.
+
+  @retval UINT32                 Buffer size in pages
+**/
+UINT32
+EFIAPI
+MemDebugLogPages (
+  VOID
+  );
+
+/**
+  Write a CHAR8 string to a memory debug log circular
+  buffer located at the given address.
+
+  @param MemDebugLogBufAddr       Address of the memory debug log buffer.
+
+  @param Buffer                   Pointer to a CHAR8 string to write to the
+                                  debug log buffer.
+
+  @param Length                   Length of the CHAR8 string to write to the
+                                  debug log buffer. Not including NULL terminator
+                                  byte.
+
+  @retval RETURN_SUCCESS          String succcessfully written to the memory log buffer.
+
+  @retval RETURN_NOT_FOUND        Memory log buffer is not properly initialized.
+
+  @retval EFI_INVALID_PARAMETER   Invalid input parameters.
+**/
+EFI_STATUS
+EFIAPI
+MemDebugLogWriteBuffer (
+  IN EFI_PHYSICAL_ADDRESS  MemDebugLogBufAddr,
+  IN CHAR8                 *Buffer,
+  IN UINTN                 Length
+  );
+
+/**
+  Initialize the memory debug log buffer header
+
+  @param MemDebugLogBufAddr       Address of the memory debug log buffer.
+
+  @param MemDebugLogBufSize       Size of the memory debug log buffer.
+
+  @retval RETURN_SUCCESS          Log buffer successfully initialized.
+
+  @retval EFI_INVALID_PARAMETER   Invalid input parameters.
+**/
+EFI_STATUS
+EFIAPI
+MemDebugLogInit (
+  IN EFI_PHYSICAL_ADDRESS  MemDebugLogBufAddr,
+  UINT32                   MemDebugLogBufSize
+  );
+
+/**
+  Copy the memory debug log buffer
+
+  @param MemDebugLogBufDestAddr   Address of destination memory debug log buffer.
+
+  @param MemDebugLogBufSrcAddr    Address of source memory debug log buffer.
+
+  @retval RETURN_SUCCESS          Log buffer successfuly copied.
+
+  @retval EFI_INVALID_PARAMETER   Invalid input parameters.
+**/
+EFI_STATUS
+EFIAPI
+MemDebugLogCopy (
+  IN EFI_PHYSICAL_ADDRESS  MemDebugLogBufDestAddr,
+  IN EFI_PHYSICAL_ADDRESS  MemDebugLogBufSrcAddr
+  );
+
+/**
+  Obtain the Memory Debug Log Buffer Addr from the HOB
+
+  @param MemDebugLogBufAddr       Address of memory debug log buffer.
+
+  @retval RETURN_SUCCESS          Log buffer address successfuly obtained.
+
+  @retval EFI_NOT_FOUND           HOB not found.
+**/
+EFI_STATUS
+EFIAPI
+MemDebugLogAddrFromHOB (
+  EFI_PHYSICAL_ADDRESS  *MemDebugLogBufAddr
+  );
+
+/**
+  Return whether the Memory Debug Logging feature is enabled
+
+  @retval TRUE                    Feature is enabled
+
+  @retval FALSE                   Feature is not enabled
+**/
+BOOLEAN
+EFIAPI
+MemDebugLogEnabled (
+  VOID
+  );
+
+#endif // _MEM_DEBUG_LOG_LIB_H_