Hi,

In the irq_save_user_regs in start.S, the "user mode" SP and LR are saved on the stack using : stmdb r8,{sp,lr}^

This is a multiple register transfer instruction with the S bit set. When this bit is set and the pc register is not listed among the register to be saved, this means the user mode register will be saved, instead of the current mode register.

However, I can't see any place in u-boot where we switch to user mode. What is the signification of this instruction ?

Does it mean : save sp_svc and lr_svc in the location pointed to by r8,

Or save sp_user and lr_user in the location pointed to by r8.

In the first case it could be useful, but in the latter it is useless since we never switch to user mode.

Am I right ?

TIA for any informations.

JP Francois