linux-kernel - [PATCH 05/12] perf, tools, probe: Print location for resolved variables

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Date:   Mon, 27 Nov 2017 16:23:14 -0800
From:   Andi Kleen <andi@...stfloor.org>
To:     acme@...nel.org
Cc:     jolsa@...nel.org, mhiramat@...nel.org, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 05/12] perf, tools, probe: Print location for resolved variables

From: Andi Kleen <ak@...ux.intel.com>

Print the location, e.g. the register, for resolved variables
with perf probe -V. This is useful for debugging, and manually
making sense of disassembly. I also have some scripts
which can make use of this information.

Before:

% perf probe  -x  ./tsrc/tstruct  -V  main+20
Available variables at main+20
        @<main+20>
                struct str*     xp

After:

% perf probe  -x  ./tsrc/tstruct  -V  main+20
Available variables at main+20
        @<main+20>
                struct str*     xp      %ax

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 tools/perf/util/probe-finder.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 0149428d453e..699f29d8a28e 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1369,6 +1369,7 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
 	if (tag == DW_TAG_formal_parameter ||
 	    tag == DW_TAG_variable) {
 		struct probe_trace_arg ta;
+		struct probe_trace_arg_ref *ref;
 
 		memset(&ta, 0, sizeof(struct probe_trace_arg));
 		ret = convert_variable_location(die_mem, af->pf.addr,
@@ -1401,6 +1402,10 @@ static int collect_variables_cb(Dwarf_Die *die_mem, void *data)
 							die_mem, &buf);
 			}
 
+			strbuf_addf(&buf, "\t%s", ta.value);
+			for (ref = ta.ref; ref; ref = ref->next)
+				strbuf_addf(&buf, " off %ld", ref->offset);
+
 			pr_debug("Add new var: %s\n", buf.buf);
 			if (ret2 == 0) {
 				struct str_node *sn;
-- 
2.13.6