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tracing: Show real address for trace event arguments

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To help debugging kernel, show real address for trace event arguments
in tracefs/trace{,pipe} instead of hashed pointer value.

Since ftrace human-readable format uses vsprintf(), all %p are
translated to hash values instead of pointer address.

However, when debugging the kernel, raw address value gives a
hint when comparing with the memory mapping in the kernel.
(Those are sometimes used with crash log, which is not hashed too)
So converting %p with %px when calling trace_seq_printf().

Moreover, this is not improving the security because the tracefs
can be used only by root user and the raw address values are readable
from tracefs/percpu/cpu*/trace_pipe_raw file.

Link: https://lkml.kernel.org/r/160277370703.29307.5134475491761971203.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 23:55:07 +09:00 • committed by Steven Rostedt (VMware)
parent 7d5367539a
commit efbbdaa22b
5 changed files with 88 additions and 3 deletions
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4
include/linux/trace_events.h
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@ -55,6 +55,8 @@ struct trace_event;
int trace_raw_output_prep(struct trace_iterator *iter,
struct trace_event *event);
extern __printf(2, 3)
void trace_event_printf(struct trace_iterator *iter, const char *fmt, ...);
/*
* The trace entry - the most basic unit of tracing. This is what
@ -87,6 +89,8 @@ struct trace_iterator {
unsigned long iter_flags;
void *temp; /* temp holder */
unsigned int temp_size;
char *fmt; /* modified format holder */
unsigned int fmt_size;
/* trace_seq for __print_flags() and __print_symbolic() etc. */
struct trace_seq tmp_seq;