On Tue, 18 Feb 2020 13:33:35 +0900 Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > On Mon, 17 Feb 2020 08:31:12 -0800 > "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote: > > > > > BTW, if you consider the x86 specific code is in the generic file, > > > we can move NOKPROBE_SYMBOL() in arch/x86/kernel/traps.c. > > > (Sorry, I've hit this idea right now) > > > > Might this affect other architectures with NMIs and probe-like things? > > If so, it might make sense to leave it where it is. > > Yes, git grep shows that arm64 is using rcu_nmi_enter() in > debug_exception_enter(). > OK, let's keep it, but maybe it is good to update the comment for > arm64 too. What about following? > > +/* > + * All functions in do_int3() on x86, do_debug_exception() on arm64 must be > + * marked NOKPROBE before kprobes handler is called. > + * ist_enter() on x86 and debug_exception_enter() on arm64 which is called > + * before kprobes handle happens to call rcu_nmi_enter() which means > + * that rcu_nmi_enter() must be marked NOKRPOBE. > + */ > Ah, why don't we just say... /* * All functions called in the breakpoint trap handler (e.g. do_int3() * on x86), must not allow kprobes until the kprobe breakpoint handler * is called, otherwise it can cause an infinite recursion. * On some archs, rcu_nmi_enter() is called in the breakpoint handler * before the kprobe breakpoint handler is called, thus it must be * marked as NOKPROBE. */ And that way we don't make this an arch specific comment. -- Steve
