linux-kernel - [PATCH 3.16 063/148] perf probe: Fix to find range-only function instance

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Date:   Sat, 08 Feb 2020 18:20:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Namhyung Kim" <namhyung@...nel.org>,
        "Jiri Olsa" <jolsa@...hat.com>,
        "Masami Hiramatsu" <mhiramat@...nel.org>,
        "Arnaldo Carvalho de Melo" <acme@...hat.com>
Subject: [PATCH 3.16 063/148] perf probe: Fix to find range-only function
 instance

3.16.82-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Masami Hiramatsu <mhiramat@...nel.org>

commit b77afa1f810f37bd8a36cb1318178dfe2d7af6b6 upstream.

Fix die_is_func_instance() to find range-only function instance.

In some case, a function instance can be made without any low PC or
entry PC, but only with address ranges by optimization.  (e.g. cold text
partially in "text.unlikely" section) To find such function instance, we
have to check the range attribute too.

Fixes: e1ecbbc3fa83 ("perf probe: Fix to handle optimized not-inlined functions")
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Link: http://lore.kernel.org/lkml/157190835669.1859.8368628035930950596.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 tools/perf/util/dwarf-aux.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -288,10 +288,14 @@ bool die_is_func_def(Dwarf_Die *dw_die)
 bool die_is_func_instance(Dwarf_Die *dw_die)
 {
 	Dwarf_Addr tmp;
+	Dwarf_Attribute attr_mem;
 
 	/* Actually gcc optimizes non-inline as like as inlined */
-	return !dwarf_func_inline(dw_die) && dwarf_entrypc(dw_die, &tmp) == 0;
+	return !dwarf_func_inline(dw_die) &&
+	       (dwarf_entrypc(dw_die, &tmp) == 0 ||
+		dwarf_attr(dw_die, DW_AT_ranges, &attr_mem) != NULL);
 }
+
 /**
  * die_get_data_member_location - Get the data-member offset
  * @mb_die: a DIE of a member of a data structure