linux-kernel - [PATCH 4.9 052/171] perf probe: Walk function lines in lexical blocks

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Date:   Thu,  2 Jan 2020 23:06:23 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 052/171] perf probe: Walk function lines in lexical blocks

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

[ Upstream commit acb6a7047ac2146b723fef69ee1ab6b7143546bf ]

Since some inlined functions are in lexical blocks of given function, we
have to recursively walk through the DIE tree.  Without this fix,
perf-probe -L can miss the inlined functions which is in a lexical block
(like if (..) { func() } case.)

However, even though, to walk the lines in a given function, we don't
need to follow the children DIE of inlined functions because those do
not have any lines in the specified function.

We need to walk though whole trees only if we walk all lines in a given
file, because an inlined function can include another inlined function
in the same file.

Fixes: b0e9cb2802d4 ("perf probe: Fix to search nested inlined functions in CU")
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/157190836514.1859.15996864849678136353.stgit@devnote2
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/perf/util/dwarf-aux.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 3d0a9e09d00a..7e7e57208323 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -688,10 +688,9 @@ static int __die_walk_funclines_cb(Dwarf_Die *in_die, void *data)
 			if (lw->retval != 0)
 				return DIE_FIND_CB_END;
 		}
+		if (!lw->recursive)
+			return DIE_FIND_CB_SIBLING;
 	}
-	if (!lw->recursive)
-		/* Don't need to search recursively */
-		return DIE_FIND_CB_SIBLING;
 
 	if (addr) {
 		fname = dwarf_decl_file(in_die);
@@ -738,6 +737,10 @@ static int __die_walk_culines_cb(Dwarf_Die *sp_die, void *data)
 {
 	struct __line_walk_param *lw = data;
 
+	/*
+	 * Since inlined function can include another inlined function in
+	 * the same file, we need to walk in it recursively.
+	 */
 	lw->retval = __die_walk_funclines(sp_die, true, lw->callback, lw->data);
 	if (lw->retval != 0)
 		return DWARF_CB_ABORT;
@@ -827,8 +830,9 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 	 */
 	if (rt_die != cu_die)
 		/*
-		 * Don't need walk functions recursively, because nested
-		 * inlined functions don't have lines of the specified DIE.
+		 * Don't need walk inlined functions recursively, because
+		 * inner inlined functions don't have the lines of the
+		 * specified function.
 		 */
 		ret = __die_walk_funclines(rt_die, false, callback, data);
 	else {
-- 
2.20.1