Messages in this thread Patch in this message | | | From | Masami Hiramatsu <> | Subject | [RFC PATCH v2 3/3] tracing: Add ptr-hash option to show the hashed pointer value | Date | Thu, 15 Oct 2020 18:00:25 +0900 |
| |
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 <mhiramat@kernel.org> --- Documentation/trace/ftrace.rst | 6 ++++++ kernel/trace/trace.c | 4 ++++ kernel/trace/trace.h | 1 + 3 files changed, 11 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. + 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 1ebcc83b1e23..414c40a579be 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3525,6 +3525,10 @@ 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; + retry: p = fmt; new_fmt = q = iter->fmt; 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 \
| |