On Mon, 30 Jul 2018 18:40:10 -0400 Steven Rostedt <[email protected]> wrote:
> On Mon, 30 Jul 2018 19:20:14 +0900 > Masami Hiramatsu <[email protected]> wrote: > > > Prohibit kprobe-events probing on notrace function. > > Since probing on the notrace function can cause recursive > > event call. In most case those are just skipped, but > > in some case it falls into infinit recursive call. > > > > This protection can be disabled by the kconfig > > CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, but it is highly > > recommended to keep it "n" for normal kernel. > > Note that this is only available if "kprobes on ftrace" > > has been implemented on target arch and > > CONFIG_KPROBES_ON_FTRACE=y. > > > > Signed-off-by: Masami Hiramatsu <[email protected]> > > > > Hi Masami, > > Note, I made the following changes for grammar. For the Change log I > have this: > > tracing: kprobes: Prohibit probing on notrace function > > Prohibit kprobe-events probing on notrace functions. Since probing on a > notrace function can cause a recursive event call. In most cases those > are just > skipped, but in some cases it falls into an infinite recursive call. > > This protection can be disabled by the kconfig > CONFIG_KPROBE_EVENTS_ON_NOTRACE=y, but it is highly recommended to keep it > "n" for normal kernel builds. Note that this is only available if > "kprobes on > ftrace" has been implemented on the target arch and > CONFIG_KPROBES_ON_FTRACE=y. > > Link: > http://lkml.kernel.org/r/153294601436.32740.10557881188933661239.stgit@devbox > > Signed-off-by: Masami Hiramatsu <[email protected]> > Tested-by: Francis Deslauriers <[email protected]> > [ Slight grammar and spelling fixes ] > Signed-off-by: Steven Rostedt (VMware) <[email protected]> Looks good to me. Thanks for fixing it! :) > > > And this change to the patch: > > diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig > index 4d4eb15cc7fd..23fc7c9abedb 100644 > --- a/kernel/trace/Kconfig > +++ b/kernel/trace/Kconfig > @@ -457,7 +457,7 @@ config KPROBE_EVENTS > If you want to use perf tools, this option is strongly recommended. > > config KPROBE_EVENTS_ON_NOTRACE > - bool "Do NOT protect notrace function from kprobe events" > + bool "Do NOT protect notrace functions from kprobe events" > depends on KPROBE_EVENTS > depends on KPROBES_ON_FTRACE > default n > @@ -465,13 +465,13 @@ config KPROBE_EVENTS_ON_NOTRACE > This is only for the developers who want to debug ftrace itself > using kprobe events. > > - If kprobes can use ftrace instead of breakpoint, ftrace related > - functions are protected from kprobe-events to prevent an infinit > - recursion or any unexpected execution path which leads to a kernel > - crash. > + If kprobes is using ftrace to hook to a function instead of a > + breakpoint, ftrace related functions are protected from > + kprobe-events to prevent an infinite recursion or any unexpected > + execution path which would lead to a kernel crash. > > This option disables such protection and allows you to put kprobe > - events on ftrace functions for debugging ftrace by itself. > + events on ftrace functions for debugging ftrace itself. > Note that this might let you shoot yourself in the foot. > > If unsure, say N. > > > Are you OK with this? > > -- Steve -- Masami Hiramatsu <[email protected]>
