[bug #23615] EFI memory map size

[David Holloway]

URL:
  <http://savannah.gnu.org/bugs/?23615>

                 Summary: EFI memory map size
                 Project: GNU GRUB
            Submitted by: gwythaint
            Submitted on: Tuesday 06/17/2008 at 08:57
                Category: Booting
                Severity: Major
                Priority: 5 - Normal
              Item Group: Software Error
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: kern/efi/mm.c version 1.4
         Reproducibility: Every Time
         Planned Release: 

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Details:

grub_efi_get_memory_map() has two failure modes and one,
GRUB_EFI_BUFFER_TOO_SMALL is not handled gracefully.

The the problem occurs if a native EFI firmware requires more than
MEMORY_MAP_SIZE; 4096 bytes in this case.

By happenstance, the problem is mis-reported as "too little memory"  when in
fact, the memory map itself is not processor properly.

It probably takes a seriously large server board such as the Intel NSW1U
Network Server to report such a large memory map table.

As an example, the NSW1U, American Megatrends bios version
S5000.86B.10.00.0085 requires 7872 bytes.


The following is a workaround for this class of symptom and a differential
diagnostic message for the errors possible from grub_efi_get_memory_map().

Index: mm.c
===================================================================
RCS file: /sources/grub/grub2/kern/efi/mm.c,v
retrieving revision 1.4
diff -r1.4 mm.c
33c33
< #define MEMORY_MAP_SIZE       0x1000
---
> #define MEMORY_MAP_SIZE       0x2000
346a347
>   int efi_status;
367c368,373
<   if (grub_efi_get_memory_map (&map_size, memory_map, 0, &desc_size, 0) <
0)
---
>   efi_status = grub_efi_get_memory_map (&map_size, memory_map, 0,
&desc_size, 0);
> 
>   if (efi_status == 0)
>     grub_fatal ("buffer too small: need %d bytes", map_size);
> 
>   if (efi_status == -1)





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