On Thu, Sep 23, 2021 at 06:16:16PM -0700, Kees Cook wrote: > On Thu, Sep 23, 2021 at 05:22:30PM -0700, Vito Caputo wrote: > > Instead of unwinding stacks maybe the kernel should be sticking an > > entrypoint address in the current task struct for get_wchan() to > > access, whenever userspace enters the kernel? > > wchan is supposed to show where the kernel is at the instant the > get_wchan() happens. (i.e. recording it at syscall entry would just > always show syscall entry.) It's supposed to show where a blocked task is blocked; the "wait channel". I'd wanted to remove get_wchan since it requires cross-task stack walking, which is generally painful. We could instead have the scheduler entrypoints snapshot their caller into a field in task_struct. If there are sufficiently few callers, that could be an inline wrapper that passes a __func__ string. Otherwise, we still need to symbolize. Thanks, Mark.
