Question

我正在使用GNU-EFI进行各种引导加载程序。到目前为止，我已经能够读取Boot#### NVRAM变量，因此我有一个半人口FilePathList[]，看起来像这样（用DevicePathToStr打印）：

HD(Part2, SigCD0400E6-54F3-49F4-81F2-65B21E8278A8)/\EFI\Microsoft\Boot\bootmgfw.efi

传递给LoadImage时，EFI_NOT_FOUND失败。据我了解(UEFI Doc Section 3.1.2)，我需要在我已经拥有之前添加完整路径。我发现正确的路径是PciRoot(0x0)/Pci(0x1, 0x1)/Ata(0x0)，但我不确定我是如何根据我拥有的路径以编程方式找到此路径，以便可以预先添加。

我到目前为止的代码如下，请原谅低质量，我到目前为止一直在努力工作。

   EFI_STATUS status;
   EFI_GUID vendor = EFI_GLOBAL_VARIABLE;
   UINT32 Attr;

   UINTN size = 256;
   UINT16 *buf = AllocateZeroPool(size);
   if (buf == NULL)
      Print(L"Failed to allocate buffer\n");

   status = uefi_call_wrapper(RT->GetVariable, 5,
         L"BootOrder", /*VariableName*/
         &vendor, /*VendorGuid*/
         &Attr, /*Attributes*/
         &size, /*DataSize*/
         buf /*Data*/
         );
   if (status != EFI_SUCCESS)
      Print(L"Failed to read BootOrder (%d)\n", status);

   // should contain an int for the correct boot option
   UINT16 bootopt = buf[0];
   FreePool(buf);

   CHAR16 *name = AllocateZeroPool(18); // Bootxxxx\0 unicode
   SPrint(name, 18, L"Boot%04x", bootopt);

   Print(L"Next boot: %s\n", name);

   size = 0;
   do {
      buf = AllocateZeroPool(size);
      if (buf == NULL)
         Print(L"Failed to allocate buffer\n");

      status = uefi_call_wrapper(RT->GetVariable, 5,
            name,
            &vendor,
            &Attr,
            &size,
            buf
            );
      if (status == EFI_SUCCESS) break;

      FreePool(buf);
      // if it fails, size is set to what it needs to be
      // handy that
   } while(status == EFI_BUFFER_TOO_SMALL);

   if (!(buf[0]&LOAD_OPTION_ACTIVE)) Print(L"BootOption not active\n");
   Print(L"%s: 0x%r\n\n", name, buf);

   UINT8 *OrigFilePathList = ((UINT8*)buf) + (sizeof(UINT32) + sizeof(UINT16) + StrSize(buf+3));
   UINT16 *FilePathListLength = ((UINT16*)OrigFilePathList)+2;

   Print(L"&OrigFilePathList = 0x%r\n", OrigFilePathList);
   Print(L"sizeof(_EFI_LOAD_OPTION) = %d\n", size);
   Print(L"struct _EFI_LOAD_OPTION {\n");
   Print(L"    Attributes = %d\n", *(UINT32 *)(buf));
   Print(L"    FilePathListLength = %d,\n", *FilePathListLength);
   Print(L"    Description = %s,\n", buf+3);
   Print(L"    FilePathList[] = {\n");

   UINT16 totallength = 0;

   UINT8 *FilePathList = OrigFilePathList;
   for (UINT8 i = 0; i < *FilePathListLength+1; i++) {
      Print(L"        &FilePathList[%d] = 0x%r\n", i, OrigFilePathList);
      Print(L"        FilePathList[%d].Type = %d ", i, *OrigFilePathList);
      switch (*OrigFilePathList) {
         case 0x01:
            Print(L"(Hardware Device Path)\n");
            break;
         case 0x02:
            Print(L"(ACPI Device Path)\n");
            break;
         case 0x03:
            Print(L"(Messaging Device Path)\n");
            break;
         case 0x04:
            Print(L"(Media Device Path)\n");
            break;
         case 0x05:
            Print(L"(BIOS Boot Specification Device Path)\n");
            break;
         case 0x7f:
            Print(L"(End Of Hardware Device Path)\n");
            break;
         default:
            Print(L"(Unknown Device Path)\n");
            break;
      }
      Print(L"        FilePathList[%d].SubType = %d\n", i, *(OrigFilePathList+1));
      Print(L"        FilePathList[%d].Length = %d\n", i, *(UINT16*)(OrigFilePathList+2));
      totallength += *(UINT16*)(OrigFilePathList+2);

      OrigFilePathList += *(UINT16*)(OrigFilePathList+2);
   }
   Print(L"    }\n");
   Print(L"    &OptionalData = 0x%r\n", OrigFilePathList);
   Print(L"    OptionalDataLength = %d\n", size-totallength);
   Print(L"}\n");

   // The hard drive device path can be appended to the matching hardware
   // device path and normal boot behavior can then be used.

   // We need to locate the Type 1 FilePathList and prepend it to what we've already got

   // Need to prefix PciRoot(0x0)/Pci(0x1, 0x1)/Ata(0x0)
   // but automatically find it
   // in theory we should be able to use the list of handles to devices that support SIMPLE_FILE_SYSTEM_PROTOCOL
   // to find the right device

   Print(L"%s\n", DevicePathToStr((EFI_DEVICE_PATH *)FilePathList));

   /* EFI_STATUS (EFIAPI *EFI_IMAGE_LOAD) (
      IN BOOLEAN BootPolicy,
      IN EFI_HANDLE ParentImageHandle,
      IN EFI_DEVICE_PATH_PROTOCOL *DevicePath,
      IN VOID *SourceBuffer OPTIONAL,
      IN UINTN SourceSize,
      OUT EFI_HANDLE *ImageHandle
      ); */

   EFI_HANDLE *NextHandle = AllocateZeroPool(sizeof(EFI_HANDLE));

   status = uefi_call_wrapper(BS->LoadImage, 6,
   /* status = BS->LoadImage( */
         TRUE, /* BootPolicy */
         ImageHandle, /* ParentImageHandle */
         (EFI_DEVICE_PATH *)FilePathList, /* DevicePath */
         NULL, /* SourceBuffer */
         0, /* SourceSize */
         NextHandle /* ImageHandle */
         );

   if (status != EFI_SUCCESS)
      Print(L"Failed to LoadImage (%d)\n", status);
   else
      Print(L"LoadImage OK\n");

我需要哪些功能和流程才能完全符合FilePathList的要求，以便LoadImage可以使用它？

Answer 1

相信当我寻求帮助时，我会把它解决。

一般的想法是使用related_name查找LocateHandleBuffer的所有句柄。使用这些句柄，将路径（使用SIMPLE_FILE_SYSTEM_PROTOCOL）与我们已经找到的相应设备进行比较。 DevicePathFromHandle现在适合我。

以下示例代码（LoadImage是来自buf的{{1}}变量的值：

Boot####

UEFI解析完整路径

1 个答案: