Problem with loading 64-bit ELF image with multiboot2

[Pawel Wojtalczyk]

Hello,

I use x86 64-bit GRUB2 under EFI and would like to load 64-bit ELF 
image. The image looks as following:

$ objdump -h Image

Image:     file format elf64-x86-64

Sections:
Idx Name          Size      VMA               LMA               File 
off  Algn
  0 .text         0019d870  ffffffff90008000  0000000010008000  
00000120  2**5
                  CONTENTS, ALLOC, LOAD, CODE
  1 .wrs_build_vars 00000150  ffffffff901a5870  00000000101a5870  
0019d990  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  2 .data         0000db50  ffffffff901a59c0  00000000101a59c0  
0019db00  2**6
                  CONTENTS, ALLOC, LOAD, DATA
  3 .bss          01016e40  ffffffff901b3520  00000000101b3520  
001ab660  2**5
                  ALLOC
$ objdump -f Image

Image:     file format elf64-x86-64
architecture: i386:x86-64, flags 0x00000012:
EXEC_P, HAS_SYMS
start address 0xffffffff90008000

I tried to load it via GRUB2, but unfortunately it displays 'invalid 
entry point for ELF64'. The problem is that for 64-bit ELF images the 
multiboot_elfxx.c library still requires 32-bit virtual address:

#ifdef MULTIBOOT_LOAD_ELF64
# if defined( __mips)
  /* We still in 32-bit mode.  */
  if (ehdr->e_entry < 0xffffffff80000000ULL)
    return grub_error (GRUB_ERR_BAD_OS, "invalid entry point for ELF64");
# else
  /* We still in 32-bit mode.  */
  if (ehdr->e_entry > 0xffffffff)
    return grub_error (GRUB_ERR_BAD_OS, "invalid entry point for ELF64");
# endif
#endif

Could you tell me why this assumption is required? The virtual address 
(e_entry is virtual following ELF specification) is related to the image 
itself, how it setup MMU, not the loader (GRUB2). GRUB2 should check 
only if the physical location of loaded image is in 32-bit physical memory.

Besides if we skip thich e_entry check, the image is properly loaded, 
because grub_multiboot_payload_eip is properly computed few lines below.

grub_multiboot_payload_eip = (ehdr->e_entry - phdr(i)->p_vaddr)
      + phdr(i)->p_paddr;

Could you tell me why GRUB2 checks for 64-bit images this e_entry 
virtual address (which can be everywhere in the 64-bit address space) 
and requires it to be 32-bit address space only?

Regards
Pawel Wojtalczyk