On Mon, Jun 21, 2021 at 12:22:06PM -0700, Linus Torvalds wrote:
On Mon, Jun 21, 2021 at 11:59 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:There's a large mess around do_exit() - we have a bunch of callers all over arch/*; if nothing else, I very much doubt that really want to let tracer play with a thread in the middle of die_if_kernel() or similar.Right you are. I'm really beginning to hate ptrace_{event,notify}() and those PTRACE_EVENT_xyz things. I don't even know what uses them, honestly. How very annoying. I guess it's easy enough (famous last words) to move the ptrace_event() call out of do_exit() and into the actual exit/exit_group system calls, and the signal handling path. The paths that actually have proper pt_regs. Looks like sys_exit() and do_group_exit() would be the two places to do it (do_group_exit() would handle the signal case and sys_group_exit()).
Maybe... I'm digging through that pile right now, will follow up when I get a reasonably complete picture. In the meanwhile, do kernel/kthread.c uses look even remotely sane? Intentional - sure, but it really looks wrong to use thread exit code as communication channel there...
