From: Masami Hiramatsu Date: Thu, 15 Oct 2020 14:55:25 +0000 (+0900) Subject: tracing: Add ptr-hash option to show the hashed pointer value X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=a345a6718bd5689f7cff7715e902d8739e0d5beb;p=linux.git tracing: Add ptr-hash option to show the hashed pointer value 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. Link: https://lkml.kernel.org/r/160277372504.29307.14909828808982012211.stgit@devnote2 Signed-off-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index 87cf5c010d5dd..62c98e9bbdd9d 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 39f8a537196ed..16e252d390169 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -3558,6 +3558,9 @@ 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 6c3ea6f95e680..dec13ff66077e 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -1175,6 +1175,7 @@ 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 \