uefi 是如何找到grubaa64.efi的

来源：互联网发布：哪些论坛分享软件编辑：程序博客网时间：2024/06/06 17:29

我们使用的是intelframeworkmodule 这个包，因此bds的入口函数是在intelframeworkmodule/universal/bdsdxe/bsdentry.c其入口函数是BdsEntry
在BdsEntry->BdsBootDeviceSelect->BdsLibBootViaBootOption 这个函数中下面这段code
      Handle = BdsLibGetBootableHandle(DevicePath);
      if (Handle != NULL) {
        //
        // Load the default boot file \EFI\BOOT\boot{machinename}.EFI from removable Media
        // machinename is ia32, ia64, x64, ...
        //
        FilePath = FileDevicePath (Handle, EFI_REMOVABLE_MEDIA_FILE_NAME);
        if (FilePath != NULL) {
          REPORT_STATUS_CODE (EFI_PROGRESS_CODE, PcdGet32 (PcdProgressCodeOsLoaderLoad));
          Status = gBS->LoadImage (
                          TRUE,
                          gImageHandle,
                          FilePath,
                          NULL,
                          0,
                          &ImageHandle
                          );
        }
      }
    }

这里的filepath是通过EFI_REMOVABLE_MEDIA_FILE_NAME 这个变量来找到的

#define EFI_REMOVABLE_MEDIA_FILE_NAME_IA32    L"\\EFI\\BOOT\\BOOTIA32.EFI"
#define EFI_REMOVABLE_MEDIA_FILE_NAME_IA64    L"\\EFI\\BOOT\\BOOTIA64.EFI"
#define EFI_REMOVABLE_MEDIA_FILE_NAME_X64     L"\\EFI\\BOOT\\BOOTX64.EFI"
#define EFI_REMOVABLE_MEDIA_FILE_NAME_ARM     L"\\EFI\\BOOT\\BOOTARM.EFI"
#define EFI_REMOVABLE_MEDIA_FILE_NAME_AARCH64 L"\\EFI\\GRUB2\\grubaa64.efi"

#if   defined (MDE_CPU_IA32)
#define EFI_REMOVABLE_MEDIA_FILE_NAME   EFI_REMOVABLE_MEDIA_FILE_NAME_IA32
#elif defined (MDE_CPU_IPF)
#define EFI_REMOVABLE_MEDIA_FILE_NAME   EFI_REMOVABLE_MEDIA_FILE_NAME_IA64
#elif defined (MDE_CPU_X64)
#define EFI_REMOVABLE_MEDIA_FILE_NAME   EFI_REMOVABLE_MEDIA_FILE_NAME_X64
#elif defined (MDE_CPU_EBC)
#elif defined (MDE_CPU_ARM)
#define EFI_REMOVABLE_MEDIA_FILE_NAME   EFI_REMOVABLE_MEDIA_FILE_NAME_ARM
#elif defined (MDE_CPU_AARCH64)
#define EFI_REMOVABLE_MEDIA_FILE_NAME   EFI_REMOVABLE_MEDIA_FILE_NAME_AARCH64
#else
#error Unknown Processor Type
#endif

由于我们是MDE_CPU_AARCH64，因此EFI_REMOVABLE_MEDIA_FILE_NAME 就等于L"\\EFI\\GRUB2\\grubaa64.efi"
因此在BdsLibBootViaBootOption 中通过gBS->LoadImage 来找到grubaa64.efi，最后还是在BdsLibBootViaBootOption 中通过下面的code Status = gBS->StartImage (ImageHandle, ExitDataSize, ExitData);来跳转到grub的第一行代码。

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