Hi Song, On 08/13/2018 10:42 PM, Song Liu wrote: > On Mon, Aug 13, 2018 at 6:17 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote: >> On 08/13, Ravi Bangoria wrote: >>> >>>> But damn, process creation (exec) is trivial. We could add a new uprobe_exec() >>>> hook and avoid delayed_uprobe_install() in uprobe_mmap(). >>> >>> I'm sorry. I didn't get this. >> >> Sorry for confusion... >> >> I meant, if only exec*( could race with _register(), we could add another uprobe >> hook which updates all (delayed) counters before return to user-mode. >> >>>> Afaics, the really problematic case is dlopen() which can race with _register() >>>> too, right? >>> >>> dlopen() should internally use mmap() right? So what is the problem here? Can >>> you please elaborate. >> >> What I tried to say is that we can't avoid uprobe_mmap()->delayed_uprobe_install() >> because dlopen() can race with _register() too, just like exec. >> >> Oleg. >> > > How about we do delayed_uprobe_install() per file? Say we keep a list > of delayed_uprobe > in load_elf_binary(). Then we can install delayed_uprobe after loading > all sections of the > file. I'm not sure if I totally understood the idea. But how this approach can solve dlopen() race with _register()? Rather, making delayed_uprobe_list an mm field seems simple and effective idea to me. The only overhead will be list_empty(mm->delayed_list) check. Please let me know if I misunderstood you. Thanks, Ravi
