On Fri, 12 Feb 2021 10:33:10 -0500 Steven Rostedt <[email protected]> wrote:
> > Hi Masami, > > I noticed theses sitting in my patchwork and I said I was going to hold off > to the next merge window, and these got pushed down in my stack :-/ Yeah, managing random topics is a hard task ;) > > > On Thu, 15 Oct 2020 23:55:25 +0900 > Masami Hiramatsu <[email protected]> wrote: > > > Add tracefs/options/hash-ptr option to show hashed pointer > > value by %p in event printk format string. > > > > For the security reason, normal printk will show the hashed > > pointer value (encrypted by random number) with %p to printk > > buffer to hide the real address. But the tracefs/trace always > > shows real address for debug. To bridge those outputs, add an > > option to switch the output format. Ftrace users can use it > > to find the hashed value corresponding to the real address > > in trace log. > > > > Signed-off-by: Masami Hiramatsu <[email protected]> > > --- > > Documentation/trace/ftrace.rst | 6 ++++++ > > kernel/trace/trace.c | 3 +++ > > kernel/trace/trace.h | 1 + > > 3 files changed, 10 insertions(+) > > > > diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst > > index 87cf5c010d5d..62c98e9bbdd9 100644 > > --- a/Documentation/trace/ftrace.rst > > +++ b/Documentation/trace/ftrace.rst > > @@ -1159,6 +1159,12 @@ Here are the available options: > > This simulates the original behavior of the trace file. > > When the file is closed, tracing will be enabled again. > > > > + hash-ptr > > + When set, "%p" in the event printk format displays the > > + hashed pointer value instead of real address. > > + This will be useful if you want to find out which hashed > > + value is corresponding to the real value in trace log. > > + > > I'm thinking of making this the default. I'll add a patch to make it > enabled by default "for security reasons", but still allow people to clear > it this value. > > Are you OK with that? Yes, I agreed. It will be good for both security and debug reasons. :) Thank you, > > -- Steve > > > > > record-cmd > > When any event or tracer is enabled, a hook is enabled > > in the sched_switch trace point to fill comm cache > > diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c > > index 75395293d8df..b88cccf224cd 100644 > > --- a/kernel/trace/trace.c > > +++ b/kernel/trace/trace.c > > @@ -3543,6 +3543,9 @@ const char *trace_event_format(struct trace_iterator > > *iter, const char *fmt) > > if (WARN_ON_ONCE(!fmt)) > > return fmt; > > > > + if (iter->tr->trace_flags & TRACE_ITER_HASH_PTR) > > + return fmt; > > + > > p = fmt; > > new_fmt = q = iter->fmt; > > while (*p) { > > diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h > > index 524502d1f60a..c34187bd22a9 100644 > > --- a/kernel/trace/trace.h > > +++ b/kernel/trace/trace.h > > @@ -1347,6 +1347,7 @@ extern int trace_get_user(struct trace_parser > > *parser, const char __user *ubuf, > > C(MARKERS, "markers"), \ > > C(EVENT_FORK, "event-fork"), \ > > C(PAUSE_ON_TRACE, "pause-on-trace"), \ > > + C(HASH_PTR, "hash-ptr"), /* Print hashed pointer > > */ \ > > FUNCTION_FLAGS \ > > FGRAPH_FLAGS \ > > STACK_FLAGS \ > -- Masami Hiramatsu <[email protected]>
