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tracing: Add ptr-hash option to show the hashed pointer value

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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 <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2020-10-15 23:55:25 +09:00 committed by Steven Rostedt (VMware)
parent 1600cbcf69
commit a345a6718b
3 changed files with 10 additions and 0 deletions
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6
Documentation/trace/ftrace.rst
View File

@ -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

3
kernel/trace/trace.c
View File

@ -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) {

1
kernel/trace/trace.h
View File

@ -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 \