[PATCH 2/7] perf callchain: Add order support for libunwind DWARF unwinder

From: Arnaldo Carvalho de Melo
Date: Mon Nov 23 2015 - 17:01:44 EST


From: Jiri Olsa <jolsa@xxxxxxxxxx>

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

Based-on-patch-by: Milian Wolff <milian.wolff@xxxxxxxx>
Reported-by: Milian Wolff <milian.wolff@xxxxxxxx>
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Tested-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20151118075247.GA5416@xxxxxxxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
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..3c258a0e4092 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 = ips[j] ? entry(ips[j], ui->thread, cb, arg) : 0;
}

return ret;
--
2.1.0

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