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 :-/
On Thu, 15 Oct 2020 23:55:25 +0900
Masami Hiramatsu <mhira...@kernel.org> 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 <mhira...@kernel.org>
> ---
> 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?
-- 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 \
