linux-kernel - [PATCH 2/3] perf tools: Add callchain order support for libunwind DWARF unwinder

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Date:	Tue, 17 Nov 2015 16:05:38 +0100
From:	Jiri Olsa <jolsa@...nel.org>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Milian Wolff <milian.wolff@...b.com>,
	Wang Nan <wangnan0@...wei.com>
Subject: [PATCH 2/3] perf tools: Add callchain order support for libunwind DWARF unwinder

From: Jiri Olsa <jolsa@...hat.com>

As reported by Milian, currently for DWARF unwind (both libdw
and libunwind) we display callchain in callee order only.

Adding the support to follow callchain order setup to libunwind
DWARF unwinder, so we could get following output for report:

  $ perf record --call-graph dwarf ls
  ...
  $ perf report --no-children --stdio

    39.26%  ls       libc-2.21.so      [.] __strcoll_l
                 |
                 ---__strcoll_l
                    mpsort_with_tmp
                    mpsort_with_tmp
                    sort_files
                    main
                    __libc_start_main
                    _start
                    0

  $ perf report -g caller --no-children --stdio
    ...
    39.26%  ls       libc-2.21.so      [.] __strcoll_l
                 |
                 ---0
                    _start
                    __libc_start_main
                    main
                    sort_files
                    mpsort_with_tmp
                    mpsort_with_tmp
                    __strcoll_l

Reported-by: Milian Wolff <milian.wolff@...b.com>
Based-on-patch-by: Milian Wolff <milian.wolff@...b.com>
Link: http://lkml.kernel.org/n/tip-lmtbeqm403f3luw4jkjevsi5@git.kernel.org
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/util/unwind-libunwind.c | 47 ++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 17 deletions(-)

diff --git a/tools/perf/util/unwind-libunwind.c b/tools/perf/util/unwind-libunwind.c
index 0ae8844fe7a6..705e1c19f1ea 100644
--- a/tools/perf/util/unwind-libunwind.c
+++ b/tools/perf/util/unwind-libunwind.c
@@ -615,34 +615,47 @@ static int get_entries(struct unwind_info *ui, unwind_entry_cb_t cb,
 		       void *arg, int max_stack)
 {
 	u64 val;
+	unw_word_t ips[max_stack];
 	unw_addr_space_t addr_space;
 	unw_cursor_t c;
-	int ret;
+	int ret, i = 0;
 
 	ret = perf_reg_value(&val, &ui->sample->user_regs, PERF_REG_IP);
 	if (ret)
 		return ret;
 
-	ret = entry(val, ui->thread, cb, arg);
-	if (ret)
-		return -ENOMEM;
+	ips[i++] = (unw_word_t) val;
 
-	if (--max_stack == 0)
-		return 0;
-
-	addr_space = thread__priv(ui->thread);
-	if (addr_space == NULL)
-		return -1;
+	/*
+	 * If we need more than one entry, do the DWARF
+	 * unwind itself.
+	 */
+	if (max_stack - 1 > 0) {
+		addr_space = thread__priv(ui->thread);
+		if (addr_space == NULL)
+			return -1;
+
+		ret = unw_init_remote(&c, addr_space, ui);
+		if (ret)
+			display_error(ret);
+
+		while (!ret && (unw_step(&c) > 0) && i < max_stack) {
+			unw_get_reg(&c, UNW_REG_IP, &ips[i]);
+			++i;
+		}
 
-	ret = unw_init_remote(&c, addr_space, ui);
-	if (ret)
-		display_error(ret);
+		max_stack = i;
+	}
 
-	while (!ret && (unw_step(&c) > 0) && max_stack--) {
-		unw_word_t ip;
+	/*
+	 * Display what we got based on the order setup.
+	 */
+	for (i = 0; i < max_stack && !ret; i++) {
+		int j = i;
 
-		unw_get_reg(&c, UNW_REG_IP, &ip);
-		ret = ip ? entry(ip, ui->thread, cb, arg) : 0;
+		if (callchain_param.order == ORDER_CALLER)
+			j = max_stack - i - 1;
+		ret = entry(ips[j], ui->thread, cb, arg);
 	}
 
 	return ret;
-- 
2.4.3

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