linux-kernel - [RFC 6/6] perf probe: Make it possible to add a C++ uprobe

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Date:   Mon, 14 May 2018 12:19:40 +0800
From:   Holger Freyther <automatic+kernel@...yther.de>
To:     linux-kernel@...r.kernel.org
Cc:     Holger Hans Peter Freyther <holgar+kernel@...gle.com>
Subject: [RFC 6/6] perf probe: Make it possible to add a C++ uprobe

From: Holger Hans Peter Freyther <holgar+kernel@...gle.com>

If the linkage name looks like a common C++ ABI name use it instead of
the original function name. This makes adding a uprobe for a C++ symbol
possible.

./perf probe -x ./cxx-example  "std::vector<int, std::allocator<int> >::at"
Added new event:
  probe_foo:_ZNSt6vectorIiSaIiEE2atEm (on _ZN... in /cxx-example)

You can now use it in all perf tools, such as:

	perf record -e probe_foo:_ZNSt6vectorIiSaIiEE2atEm -aR sleep 1

Signed-off-by: Holger Hans Peter Freyther <holgar+kernel@...gle.com>
---
 tools/perf/util/probe-finder.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 4ba4b18..4cfa3de 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1317,6 +1317,7 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
 	struct perf_probe_point *pp = &pf->pev->point;
 	struct probe_trace_event *tev;
 	struct perf_probe_arg *args = NULL;
+	const char *linkage_name;
 	int ret, i;
 
 	/* Check number of tevs */
@@ -1333,6 +1334,16 @@ static int add_probe_trace_event(Dwarf_Die *sc_die, struct probe_finder *pf)
 	if (ret < 0)
 		goto end;
 
+	/*
+	 * Adding a C++ name like std::vector<int, std::allocator<int> >::at
+	 * will fail. Check if we want to use the linkage name instead.
+	 */
+	linkage_name = die_get_linkage_name(&pf->sp_die);
+	if (linkage_name && strncmp(linkage_name, "_Z", 2) == 0) {
+		free(pp->function);
+		pp->function = strdup(linkage_name);
+	}
+
 	tev->point.realname = strdup(dwarf_diename(sc_die));
 	if (!tev->point.realname) {
 		ret = -ENOMEM;
-- 
2.7.4