Allocating memory in u-boot application

hi,
I am working on PPC440EP base custom board. I managed to port u-boot successfully.
The requirement is, there should be no OS running on-board and run an application in u-boot. I have successfully ported and example application also.
The part of my requirement is to read data as large as 10MB from NVRAM and load it to PC.
I am not able to allocate more than 64kB to a buffer. When i allocate even 1MB, my application hangs when i try to access the buffer. I have 64MB DDR-RAM interface to PPC440EP.

The size of my application is 300kB and i don't think u-boot uses large memory.
How can I malloc big size to a buffer in this case. Please help me fix this issue, thanks in advance.

Regards,
Prathika R