On Thu, Dec 14, 2017 at 10:58:35PM +0100, Jiri Slaby wrote: > On 11/30/2017, 08:57 PM, Josh Poimboeuf wrote: > > So with those changes in mind, how about something like this (plus > > comments)? > > > > for (unwind_start(&state, task, NULL, NULL); !unwind_done(&state); > > unwind_next_frame(&state)) { > > > > regs = unwind_get_entry_regs(&state); > > if (regs) { > > if (user_mode(regs)) > > goto success; > > > > if (IS_ENABLED(CONFIG_FRAME_POINTER)) > > return -EINVAL; > > } > > > > addr = unwind_get_return_address(&state); > > if (!addr) > > return -EINVAL; > > > > if (save_stack_address(trace, addr, false)) > > return -EINVAL; > > } > > > > return -EINVAL; > > Kthreads and idle tasks hit this error as they have no user regs on the > stack obviously :).
Doh, sorry, I forgot about that. > > So making it: > if (!(task->flags & (PF_KTHREAD | PF_IDLE))) > return -EINVAL; > > works, but is not reliable now. So I believe, we cannot live without > unwind->error to differentiate between "unwind_done() == true" because: > * full stack unwound and the stack type is set to UNKNOWN > * unwinding failed and the stack type is set to UNKNOWN > > Or perhaps introduce stack type BOTTOM, NONE, or NOMORE meaning the > bottom of the stacks reached? Yeah, we'll need something... I need to think about it a little more. -- Josh