Now that we have introduced new, generic ways for the OS loader to interface with Linux kernels during boot, we need to record this fact in a way that allows loaders to discover this information, and fall back to the existing methods for older kernels. Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> --- include/linux/pe.h | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/include/linux/pe.h b/include/linux/pe.h index e0869f3eadd6..8ad71d763a77 100644 --- a/include/linux/pe.h +++ b/include/linux/pe.h @@ -10,7 +10,25 @@ #include <linux/types.h> -#define LINUX_EFISTUB_MAJOR_VERSION 0x0 +/* + * Linux EFI stub v1.0 adds the following functionality: + * - Loading initrd from the LINUX_EFI_INITRD_MEDIA_GUID device path, + * - Loading/starting the kernel from firmware that targets a different + * machine type, via the entrypoint exposed in the .compat PE/COFF section. + * + * The recommended way of loading and starting v1.0 or later kernels is to use + * the LoadImage() and StartImage() EFI boot services, and expose the initrd + * via the LINUX_EFI_INITRD_MEDIA_GUID device path. + * + * Versions older than v1.0 support initrd loading via the image load options + * (using initrd=, limited to the volume from which the kernel itself was + * loaded), or via arch specific means (bootparams, DT, etc). + * + * On x86, LoadImage() and StartImage() can be omitted if the EFI handover + * protocol is implemented, which can be inferred from the version, + * handover_offset and xloadflags fields in the bootparams structure. + */ +#define LINUX_EFISTUB_MAJOR_VERSION 0x1 #define LINUX_EFISTUB_MINOR_VERSION 0x0 #define MZ_MAGIC 0x5a4d /* "MZ" */ -- 2.17.1
