ARM Initialization Question

[gds at chartertn.net (Gene Smith)]

Sebastian Huber wrote:
> Hi,
> I am quite new to the ARM architecture and try to develop a BSP for the 
> LPC2478.  I have a question to the initialization code (random start.S):
> 
> [...]
> /* Set up the SVC stack pointer last and stay in SVC mode */
> mov     r0, #(PSR_MODE_SVC | PSR_I | PSR_F)     /* No interrupts */
> msr     cpsr, r0
> ldr     r1, =_svc_stack_size
> ldr     sp, =_svc_stack
> add     sp, sp, r1
> sub     sp, sp, #0x64
> [...]
> 
> Why is 0x64 subtracted from the stack pointer?
> 

I ran my app and skipped the subtract of 100 and it still worked OK. 
Seems like it is just wasting 100 bytes!