Embedded heap allocation?

I've done a number of embedded ARM7 projects using ADS1.2 without much trouble. Now all of a sudden I can't get the heap to allocate correctly.

My entry.s code does some standard startup things like setting the stacks, clocks, etc. It ends by branching to __main as usual. When I make the first call to malloc() looking for about 24Kbytes, it doesn't have enough space. There should be 3 MB. I am using a simple stackheap.s shown below.

__main calls _init_alloc to create the heap. I have some old code that shows that it puts the bottom of the heap in R0 and the bottom of the stack in R1. If I make a manual call to this with the values filled in I get a

3MB heap. If I break on __main calling this, it has the bottom of heap in both registers and I get no heap.

Anyone have any suggestions?



EXPORT top_of_stacks EXPORT top_of_memory ; ; Physical location of our memory system ;

MEMORY_Limit EQU 0x20400000

top_of_memory equ MEMORY_Limit ; ; = Total 4M SDRAM on Pixter2005 board, end of memory is 0x003f, ffff ; ; We will mirror the memory 0x20000000 to 0x203fffff at 0x00000000 to

0x003fffff ; with the MMU. This is done so that we have a copy of the interrupt vectors at ; 0x0 as required for the ARM ; Stack_Limit EQU MEMORY_Limit - 0x100 SVC_Stack EQU Stack_Limit ; = 0x400 bytes ABT_Stack EQU SVC_Stack - 0x100 ; = 0x200 bytes UNDEF_Stack EQU ABT_Stack - 0x100 ; = 0x200 bytes IRQ_Stack EQU UNDEF_Stack - 0x100 ; = 0x200 bytes FIQ_Stack EQU IRQ_Stack - 0x100 ; = 0x200

; Create dummy variable used to locate stacks in memory

top_of_stacks SPACE 1


EXPORT bottom_of_heap

; Create dummy variable used to locate bottom of heap

bottom_of_heap SPACE 1


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