Edk2-interrupt-console-redirection.c

#include <Library/BaseMemoryLib.h>
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/UefiRuntimeServicesTableLib.h>
#include <Library/DevicePathLib.h>
#include <Guid/GlobalVariable.h>

/**
  Scrubs all serial and UART device paths from the ConOut variable.
**/
VOID
PurgeSerialFromConOut (
  VOID
  )
{
  EFI_STATUS                Status;
  EFI_DEVICE_PATH_PROTOCOL  *FullConOutPath;
  EFI_DEVICE_PATH_PROTOCOL  *Instance;
  EFI_DEVICE_PATH_PROTOCOL  *NewConOutPath;
  EFI_DEVICE_PATH_PROTOCOL  *NextInstance;
  UINTN                     Size;
  BOOLEAN                   IsSerial;

  NewConOutPath = NULL;

  // 1. Fetch the existing ConOut variable string
  GetEfiGlobalVariable2 (L"ConOut", (VOID **)&FullConOutPath, &Size);
  if (FullConOutPath == NULL) {
    return; // ConOut is empty, nothing to purge
  }

  // 2. Loop through every device instance bound to the console output splitter
  Instance = FullConOutPath;
  while (Instance != NULL) {
    NextInstance = NextDevicePathInstance (Instance, &Size);
    IsSerial     = FALSE;

    // Check every node inside this specific device path instance
    EFI_DEVICE_PATH_PROTOCOL *Node = Instance;
    while (!IsDevicePathEnd (Node)) {
      // MESSAGING_DEVICE_PATH (0x03) + MSG_UART_DP (0x0E) or MSG_VENDOR_DP (0x0A)
      if ((DevicePathType (Node) == MESSAGING_DEVICE_PATH) && 
          ((DevicePathSubType (Node) == MSG_UART_DP) || (DevicePathSubType (Node) == MSG_VENDOR_DP))) {
        IsSerial = TRUE;
        break;
      }
      Node = NextDevicePathNode (Node);
    }

    // 3. If it is NOT a serial line, append it to our clean ConOut path structure
    if (!IsSerial) {
      NewConOutPath = AppendDevicePathInstance (NewConOutPath, Instance);
    }

    FreePool (Instance);
    Instance = NextInstance;
  }

  // 4. Commit the sanitized, video-only path back to the NVRAM / volatile storage
  if (NewConOutPath != NULL) {
    gRT->SetVariable (
           L"ConOut",
           &gEfiGlobalVariableGuid,
           EFI_VARIABLE_BOOTSERVICE_ACCESS | EFI_VARIABLE_RUNTIME_ACCESS | EFI_VARIABLE_VOLATILE,
           GetDevicePathSize (NewConOutPath),
           NewConOutPath
           );
    FreePool (NewConOutPath);
  } else {
    // If only serial existed, wipe the variable entirely to force standard display fallback
    gRT->SetVariable (L"ConOut", &gEfiGlobalVariableGuid, 0, 0, NULL);
  }
}