On 07/28, Andy Lutomirski wrote: > > On Mon, Jul 28, 2014 at 10:37 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote: > > Hi Andy, > > > > I am really sorry for delay. > > > > This is on top of the recent change from Kees, right? Could me remind me > > where can I found the tree this series based on? So that I could actually > > apply these changes... > > https://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/log/?h=seccomp/fastpath > > The first four patches are already applied there. Thanks! > > If I understand correctly, syscall_trace_enter() can avoid _phase2() above. > > But we should always call user_exit() unconditionally? > > Damnit. I read that every function called by user_exit, and none of > them give any indication of why they're needed for traced syscalls but > not for untraced syscalls. On a second look, it seems that TIF_NOHZ > controls it. Yes, just to trigger the slow path, I guess. > I'll update the code to call user_exit iff TIF_NOHZ is > set. Or perhaps it would be better to not add another user of this (strange) flag and just call user_exit() unconditionally(). But, yes, you need to use from "work = flags & (_TIF_WORK_SYSCALL_ENTRY & ~TIF_NOHZ)" then. > > And we should always set X86_EFLAGS_TF if TIF_SINGLESTEP? IIRC, TF can be > > actually cleared on a 32bit kernel if we step over sysenter insn? > > I don't follow. If TIF_SINGLESTEP, then phase1 will return a nonzero > value, Ah yes, thanks, I missed this. Oleg.
