initrd getting overwritten with 1G memory and grub

[Pradeep Kanyar]

Hi,
I am new to grub and I am facing a problem. With 512MB RAM on my system,
I can boot linux using grub without any problems. We use a compact flash
based linux system that fits in a 8M flash, and we use an initrd based
ramdisk which in principle usually occupies half the memory on the 
system.

When I moved to 1G of memory, linux (2.4.10) complained that 

-----
initrd extends beyond end of memory (0x3bfff000 > 0x38000000) 
disabling initrd
-----

I have the HIGH_MEM option turned on in my linux kernel.

After going through the code to some extent, I noticed that the 
INITRD_START setup by grub has a flaw?

in function load_initrd()

....
  if (moveto + len >= LINUX_INITRD_MAX_ADDRESS)
    moveto = (LINUX_INITRD_MAX_ADDRESS - len) & 0xfffff000;
....

In my case it turns out,
LINUX_INITRD_MAX_ADDRESS  = 0x3C000000
len                       = 0x3E80000

So, the INITRD_START that is passed on to linux seems to be 3817F000.
With HIGHMEM turned on, I think linux expects the INITRD_START to be
below the 0x38000000 address (as the upper 127M is reserved for HIGHMEM).
However, the above values put the INITRD_START beyond the 0x38000000 value.

To fix this, I made a small change in the load_initrd() function
....
  if (moveto + len >= LINUX_INITRD_MAX_ADDRESS)
    moveto = (LINUX_INITRD_MAX_ADDRESS_2 - len) & 0xfffff000;
....

Where 
LINUX_INITRD_MAX_ADDRESS_2  = 0x38000000


That seemed to do the trick, and linux booted nicely. However, I have 
a question. If I move to 4G RAM on my system, I think I'll end up having
the same problem again, and I'll need to readjust.

Has anyone seen this problem? If you could please suggest on a clean way
to fix this, it would be of great help to me....

Thanks,
Pradeep