Hi Pratyush, On 18/03/16 13:29, Pratyush Anand wrote: > Probably, I can see why does not it work. So, when we are single stepping an > instruction and page fault occurs, we will come to el1_da in entry.S. Here, we > do enable_dbg. As soon as we will do this, we will start receiving single step > exception after each instruction (not sure, probably for each alternate > instruction). Since, there will not be any matching single step handler for > these instructions, so we will see warning "Unexpected kernel single-step > exception at EL1". > > So, I think, we should > > (1) may be do not enable debug for el1_da, or > (2) enable_dbg only when single stepping is not enabled, or > (3) or disable single stepping during el1_da execution. > > (1) will solve the issue for sure, but not sure if it could be the best > choice.
A variation on (3): In kernel/entry.S when entered from EL0 we test for TIF_SINGLESTEP in the thread_info flags, and use disable_step_tsk/enable_step_tsk to save/restore the single-step state. Could we do this regardless of which EL we came from? Thanks, James
