[U-Boot-Users] how does stack work?

[U-Boot-Users] how does stack work?

[Seingier François-Xavier]

hello,
I'm trying to understand how the initial stack works on a ppc4xx. According to start.S this is how the layout looks to me:
      ___________
     |           |
     |           |
     |           |
     |    gd_t   |
     |___________|  
     |     0     |
     |___________|  
     |     0     |  
     |___________|<-+
     | reset_vec |  |
SP ->|___________|  |
     |           |--+
     |___________|<-+
     |           |  |
     |___________|  |
     |           |--+
     |___________|
     |   ...     |

I can't figure out precisely how the last stack frame works:
- /* clear final stack frame so that	*/
  /* stack backtraces terminate cleanly	*/
I'm not sure to understand the "terminate cleanly".

- why will the reset_vec be used in case of a stack underflow?
I tried to find an answer in the "PowerPC compiler writer's guide" about the ABI, but I am not even sure gcc uses an AIX or System V implementation...

If somebody could explain how this works in details, I would be very grateful (or point me to the right doc)

Thanks in advance

Fran?ois-Xavier SEINGIER

[U-Boot-Users] how does stack work?

[Seingier François-Xavier]

sorry I did not put the SP at the right place on the figure ;)
 

[U-Boot-Users] how does stack work?

[Kenneth Johansson]

Seingier Fran?ois-Xavier wrote:

>hello,
>I'm trying to understand how the initial stack works on a ppc4xx. According to start.S this is how the layout looks to me:
>      ___________
>     |           |
>     |           |
>     |           |
>     |    gd_t   |
>     |___________|  
>     |     0     |
>     |___________|  
>     |     0     |  
>     |___________|<-+
>     | reset_vec |  |
>SP ->|___________|  |
>     |           |--+
>     |___________|<-+
>     |           |  |
>     |___________|  |
>     |           |--+
>     |___________|
>     |   ...     |
>
>I can't figure out precisely how the last stack frame works:
>- /* clear final stack frame so that	*/
>  /* stack backtraces terminate cleanly	*/
>I'm not sure to understand the "terminate cleanly".
>  
>
Some debug tool that get confused ??

>- why will the reset_vec be used in case of a stack underflow?
>I tried to find an answer in the "PowerPC compiler writer's guide" about the ABI, but I am not even sure gcc uses an AIX or System V implementation...
>  
>
You can not return from the first function but for some unknown reason 
you do that what should happen ?? a reboot is probably as good as anything.

The ABI for  u-boot is eabi
ftp://ftp.funet.fi/pub/mirrors/sourceware.cygnus.com/pub/binutils/ppc-docs/