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我正在编写一个适用于 efi 环境的应用程序（fe 可以从 EFI shell 运行）。我的问题是我无法在我的机器卷上创建任何文件。我在 WMVare 和带有 ntfs 的真实机器上测试它，甚至在带有 hfs+ 的 mac 上测试它（获得驱动程序 frim http://efi.akeo.ie/）。我可以阅读所有内容，但是当我尝试写入时，我得到了错误代码 8 (EFI_WRITE_PROTECTED)。

有没有办法避免这种保护？也许我应该更深入地使用块设备而不是文件系统（真的不想这样做）？

我的代码。驱动程序加载（我认为它工作正常，仅适用于这种情况）：

Print(L"\nLoading NTFS Driver... ");
Status = BS->LocateHandleBuffer(ByProtocol, &FileSystemProtocol, NULL, &NumHandles, &Handle);
if (EFI_ERROR(Status)) 
{
    PrintStatusError(Status, L"\n  Failed to list file systems");
    goto exit;
}

for (i = 0; i < NumHandles; i++) 
{
    // Look for our NTFS driver. Note: the path MUST be specified using backslashes!
    DevicePath = FileDevicePath(Handle[i], DriverPath);
    if (DevicePath == NULL)
        continue;

    // Attempt to load the driver. If that fails, it means we weren't on the right partition
    Status = BS->LoadImage(FALSE, ImageHandle, DevicePath, NULL, 0, &DriverHandle);
    SafeFree(DevicePath);
    if (EFI_ERROR(Status))
        continue;

    // Load was a success - attempt to start the driver
    Status = BS->StartImage(DriverHandle, NULL, NULL);
    if (EFI_ERROR(Status)) 
    {
        PrintStatusError(Status, L"\n  Driver did not start");
        goto exit;
    }
    Print(L"LOADED");
    break;
}
SafeFree(Handle);
if (i >= NumHandles) 
{
    Print(L"\n  Failed to locate driver. Please check that '%s' exists on the FAT partition", DriverPath);
    Status = EFI_NOT_FOUND;
    goto exit;
}

文件读/写：

// Now enumerate all disk handles again
Status = BS->LocateHandleBuffer(ByProtocol, &DiskIoProtocol, NULL, &NumHandles, &Handle);
if (EFI_ERROR(Status)) 
{
    PrintStatusError(Status, L"\n  Failed to list disks");
    goto exit;
}

// Go through the partitions and find the NTFS one
for (i = 0; i < NumHandles; i++)
{
    dev_path = DevicePathFromHandle(Handle[i]);
    Print(L"\nVolume [%d]: ", i);

    // Calling ConnectController() on a handle starts all the drivers that can service it
    Status = BS->ConnectController(Handle[i], NULL, NULL, TRUE);
    if (Status == EFI_SUCCESS)
    {
        Print(L"Driver connected! ");
    }

    // Open the the volume
    Status = BS->HandleProtocol(Handle[i], &FileSystemProtocol, (VOID**)&Volume);
    if (EFI_ERROR(Status))
    {
        PrintStatusError(Status, L"\n  Could not find volume");
        continue;
    }

    // Open the root directory
    Root = NULL;
    Status = Volume->OpenVolume(Volume, &Root);
    if ((EFI_ERROR(Status)) || (Root == NULL))
    {
        PrintStatusError(Status, L"\n  Could not open Root directory");
        continue;
    }

    Status = Root->Open(Root, &FileHandle, L"bb.txt", EFI_FILE_MODE_READ, 0);
    Print(L"\n  Read %d", Status);
    if (Status == EFI_SUCCESS)
    {
        UINTN fsize = 5;
        char fdata[5];
        Status = FileHandle->Read(FileHandle, &fsize, fdata);
        fdata[4] = 0;
        Print(L" %d [%x%x%x%x] ", Status, fdata[0], fdata[1], fdata[2], fdata[3]);
        FileHandle->Close(FileHandle);
    }

    Status = Root->Open(Root, &FileHandle, L"aa.txt", EFI_FILE_MODE_CREATE | EFI_FILE_MODE_WRITE | EFI_FILE_MODE_READ, 0);
    Print(L"  Create %d", Status);
    if (Status == EFI_SUCCESS)
    {
        UINTN fsize = 4;
        Status = FileHandle->Write(FileHandle, &fsize, file_content);
        Print(L"    Wr %d", Status);
        Status = FileHandle->Flush(FileHandle);
        Print(L"    Fl %d", Status);
        Status = FileHandle->Close(FileHandle);
        Print(L"    Cl %d", Status);
    }
}

<---------------- 经过一番调查 ------------------------------------>

事实证明，我们对机器文件系统唯一能做的就是改变现有的文件内容。似乎这是没有几个月研究的唯一可能方法。但是，它仍然不容易做到：

我有“EFI_FILE *fileHandle”变量，可以读取我预先创建的文件。如何找到对应的 LBA（或 DiskIO 的偏移量）？

我查看了 EFI 源（来自 AMI bios 源），发现在 EFI_FILE 结构之后放置了隐藏数据：

    typedef struct _FILE_HANDLE_INSTANCE {

    EFI_FILE_PROTOCOL FileHandle;                       // Should be the first entry in the structure
    EFI_STATUS HandleInstanceStatus;
    FILE_HANDLE *pFH;
    UINT64 OpenMode;                            // Open Modes
    UINT64 Position;                            //
    UINT32 CurrentCluster;                      // will point to sector number where the position is pointing currently
    UINT32 CurrentClusterOffset;                        // will point to sector number where the position is pointing currently
    BOOLEAN MEDIA_NOT_VALID;                    // Will be true if for any reason current instances cannot use the volume Eg: Change in Media
    DLINK ViFILink;                             // This link is for the DLIST OpenFIs in the VOLUME_INFO
    } FILE_HANDLE_INSTANCE;

他们像这样使用它：

void example_read_inside_efi(EFI_FILE *FileHandle, ...)
{
FILE_HANDLE_INSTANCE    *fhi = (FILE_HANDLE_INSTANCE *)FileHandle;
...

但是当我尝试读取该结构时，该结构似乎没有正确的字段值（fe FILE_HANDLE 指针无效）。我不知道接下来该怎么办。没想法。。

所以，问题是：如果我有有效的 EFI_FILE 指针，我如何找到相应的 LBA（或 diskIO 的偏移量）？

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