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 :).
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?
> success:
> if (trace->nr_entries < trace->max_entries)
> trace->entries[trace->nr_entries++] = ULONG_MAX;
>
> return 0;
>
> After these changes I believe we can enable
> CONFIG_HAVE_RELIABLE_STACKTRACE for ORC.
thanks,
--
js
suse labs
