Can I write on my local file system using EFI

Question

I am working on this project to write files to the local file system as soon as the OS is launched through the EFI application. I need to know if this is possible. And if so, then kindly guide me a little. Thanks

Answer 1

OK, I will give you good cheers ...

• First you list all the FS protocols in the system.

  EFI_BOOT_SERVICES* bs = ...;
  EFI_GUID sfspGuid = EFI_SIMPLE_FILE_SYSTEM_PROTOCOL_GUID;
  EFI_HANDLE* handles = NULL;   
  UINTN handleCount = 0;
  
  efiStatus = bs->LocateHandleBuffer(ByProtocol, 
                                     &sfspGuid, 
                                     NULL, 
                                     &handleCount, 
                                     &handles);
  

• EFI_SIMPLE_FILE_SYSTEM_PROTOCOL , , , ect . / , , . , DP, (), .

  for (index = 0; index < (int)handleCount; ++ index)
  {
      EFI_SIMPLE_FILE_SYSTEM_PROTOCOL* fs = NULL;
  
      efiStatus = bs->HandleProtocol(
          handles[index],
          &sfspGuid,
          (void**)&fs);
  

• . .

  EFI_FILE_PROTOCOL* root = NULL;
  ...
  efiStatus = fs->OpenVolume(fs, &root);
  

• ect... , .

  EFI_FILE_PROTOCOL* token = NULL;
  
  efiStatus = root->Open(
          root, 
          &token,
          L"myfolder\\token.bin",
          EFI_FILE_MODE_READ,
          EFI_FILE_READ_ONLY | EFI_FILE_HIDDEN | EFI_FILE_SYSTEM);
  

EFI_FILE_PROTOCOL :

  EFI_FILE_OPEN         Open;
  EFI_FILE_CLOSE        Close;
  EFI_FILE_DELETE       Delete;
  EFI_FILE_READ         Read;
  EFI_FILE_WRITE        Write;
  EFI_FILE_GET_POSITION GetPosition;
  EFI_FILE_SET_POSITION SetPosition;
  EFI_FILE_GET_INFO     GetInfo;
  EFI_FILE_SET_INFO     SetInfo;
  EFI_FILE_FLUSH        Flush;