linux-kernel - [PATCH] Subject: perf jit: Fix incorrect file name in DWARF line table

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Date:   Wed, 31 May 2023 16:35:33 +0200
From:   elisabeth <paniii94@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     elisabeth <paniii94@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH] Subject: perf jit: Fix incorrect file name in DWARF line table

Fix an issue where an incorrect file name was added in the DWARF line table
due to not checking the filename against the repeated name marker (/xff/0).
This can be seen with `objdump --dwarf=line` on the ELF file after perf inject.

Signed-off-by: elisabeth <paniii94@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/genelf_debug.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/genelf_debug.c b/tools/perf/util/genelf_debug.c
index aa5dcc56b2ac..2928b59bb9a5 100644
--- a/tools/perf/util/genelf_debug.c
+++ b/tools/perf/util/genelf_debug.c
@@ -349,6 +349,7 @@ static void emit_lineno_info(struct buffer_ext *be,
 	 */
 
 	/* start state of the state machine we take care of */
+	char const repeated_name_marker[] = {'\xff', '\0'};
 	unsigned long last_vma = 0;
 	char const  *cur_filename = NULL;
 	unsigned long cur_file_idx = 0;
@@ -363,7 +364,8 @@ static void emit_lineno_info(struct buffer_ext *be,
 		/*
 		 * check if filename changed, if so add it
 		 */
-		if (!cur_filename || strcmp(cur_filename, ent->name)) {
+		if ((!cur_filename || strcmp(cur_filename, ent->name)) &&
+			memcmp(repeated_name_marker, ent->name, sizeof(repeated_name_marker)) != 0) {
 			emit_lne_define_filename(be, ent->name);
 			cur_filename = ent->name;
 			emit_set_file(be, ++cur_file_idx);
-- 
2.34.1