linux-kernel - [tip:perf/urgent] perf annotate browser: Be more robust when drawing jump arrows

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Message-ID: <tip-5tzvb875ep2sel03aeefgmud@git.kernel.org>
Date:   Wed, 7 Mar 2018 00:25:45 -0800
From:   tip-bot for Arnaldo Carvalho de Melo <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     yao.jin@...el.com, acme@...hat.com, hpa@...or.com,
        mingo@...nel.org, wangnan0@...wei.com, adrian.hunter@...el.com,
        namhyung@...nel.org, tglx@...utronix.de, kan.liang@...el.com,
        dsahern@...il.com, torvalds@...ux-foundation.org, jolsa@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip:perf/urgent] perf annotate browser: Be more robust when
 drawing jump arrows

Commit-ID:  9cf195f80c5e8a6d779119a7d292e537315d2ea6
Gitweb:     https://git.kernel.org/tip/9cf195f80c5e8a6d779119a7d292e537315d2ea6
Author:     Arnaldo Carvalho de Melo <acme@...hat.com>
AuthorDate: Thu, 1 Mar 2018 11:33:59 -0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Mon, 5 Mar 2018 11:50:15 -0300

perf annotate browser: Be more robust when drawing jump arrows

This first happened with a gcc function, _cpp_lex_token, that has the
usual jumps:

 │1159e6c: ↓ jne    115aa32 <_cpp_lex_token@@Base+0xf92>

I.e. jumps to a label inside that function (_cpp_lex_token), and those
works, but also this kind:

 │1159e8b: ↓ jne    c469be <cpp_named_operator2name@@Base+0xa72>

I.e. jumps to another function, outside _cpp_lex_token, which are not
being correctly handled generating as a side effect references to
ab->offset[] entries that are set to NULL, so to make this code more
robust, check that here.

A proper fix for will be put in place, looking at the function name
right after the '<' token and probably treating this like a 'call'
instruction.

For now just don't draw the arrow.

Reported-by: Ingo Molnar <mingo@...nel.org>
Tested-by: Ingo Molnar <mingo@...nel.org>
Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: David Ahern <dsahern@...il.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Wang Nan <wangnan0@...wei.com>
Cc: Jin Yao <yao.jin@...el.com>
Cc: Kan Liang <kan.liang@...el.com>
Link: https://lkml.kernel.org/n/tip-5tzvb875ep2sel03aeefgmud@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/ui/browsers/annotate.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/tools/perf/ui/browsers/annotate.c b/tools/perf/ui/browsers/annotate.c
index 286427975112..fbf927cf775d 100644
--- a/tools/perf/ui/browsers/annotate.c
+++ b/tools/perf/ui/browsers/annotate.c
@@ -327,7 +327,32 @@ static void annotate_browser__draw_current_jump(struct ui_browser *browser)
 	if (!disasm_line__is_valid_jump(cursor, sym))
 		return;
 
+	/*
+	 * This first was seen with a gcc function, _cpp_lex_token, that
+	 * has the usual jumps:
+	 *
+	 *  │1159e6c: ↓ jne    115aa32 <_cpp_lex_token@@Base+0xf92>
+	 *
+	 * I.e. jumps to a label inside that function (_cpp_lex_token), and
+	 * those works, but also this kind:
+	 *
+	 *  │1159e8b: ↓ jne    c469be <cpp_named_operator2name@@Base+0xa72>
+	 *
+	 *  I.e. jumps to another function, outside _cpp_lex_token, which
+	 *  are not being correctly handled generating as a side effect references
+	 *  to ab->offset[] entries that are set to NULL, so to make this code
+	 *  more robust, check that here.
+	 *
+	 *  A proper fix for will be put in place, looking at the function
+	 *  name right after the '<' token and probably treating this like a
+	 *  'call' instruction.
+	 */
 	target = ab->offsets[cursor->ops.target.offset];
+	if (target == NULL) {
+		ui_helpline__printf("WARN: jump target inconsistency, press 'o', ab->offsets[%#x] = NULL\n",
+				    cursor->ops.target.offset);
+		return;
+	}
 
 	bcursor = browser_line(&cursor->al);
 	btarget = browser_line(target);