linux-kernel - [BUGFIX PATCH 1/3] perf/probe: Fix to find range-only function instance

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Date:   Thu, 24 Oct 2019 18:12:36 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [BUGFIX PATCH 1/3] perf/probe: Fix to find range-only function instance

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>
---
 tools/perf/util/dwarf-aux.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index df6cee5c071f..2ec24c3bed44 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -318,10 +318,14 @@ 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