. . common/dlmalloc.c

void mem_malloc_init(ulong start, ulong size)
{
        mem_malloc_start = start;
        mem_malloc_end = start + size;
        mem_malloc_brk = start;

        debug("using memory %#lx-%#lx for malloc()\n", mem_malloc_start,
              mem_malloc_end); 
#ifdef CONFIG_SYS_MALLOC_CLEAR_ON_INIT
        memset((void *)mem_malloc_start, 0x0, size);
#endif
        malloc_bin_reloc();
}

. .