[PATCH] perf test: Fix dwarf unwind test

[Naveen N. Rao]

Dwarf unwind perf test can sometimes fail:
  $ perf test -v 74
  Couldn't bump rlimit(MEMLOCK), failures may take place when creating BPF maps, etc
   74: Test dwarf unwind                                               :
  --- start ---
  test child forked, pid 3785254
  Problems creating module maps, continuing anyway...
  Problems creating module maps, continuing anyway...
  unwind: test__arch_unwind_sample:ip = 0x102d0ad4c (0x36ad4c)
  unwind: access_mem addr 0x7fffc33128c8, val 1031c3228, offset 120
  unwind: access_mem addr 0x7fffc33128d0, val 12427cc70, offset 128
  <snip>
  unwind: test_dwarf_unwind__krava_3:ip = 0x102b8768b (0x1e768b)
  unwind: access_mem addr 0x7fffc3313048, val 7fffc3313050, offset 2040
  unwind: access_mem addr 0x7fffc3313060, val 102b8777c, offset 2064
  unwind: test_dwarf_unwind__krava_2:ip = 0x102b8770b (0x1e770b)
  unwind: access_mem addr 0x7fffc3313088, val 7fffc3313090, offset 2104
  unwind: access_mem addr 0x7fffc33130a0, val 102b87890, offset 2128
  unwind: test_dwarf_unwind__krava_1:ip = 0x102b8777b (0x1e777b)
  unwind: access_mem addr 0x7fffc3313108, val 10323a274, offset 2232
  unwind: access_mem addr 0x7fffc3313110, val ffffffffffffffff, offset 2240
  unwind: access_mem addr 0x7fffc3313118, val 102c08ed0, offset 2248
  unwind: access_mem addr 0x7fffc3313120, val 1031db000, offset 2256
  unwind: access_mem addr 0x7fffc3313128, val 7fffc3313130, offset 2264
  unwind: access_mem addr 0x7fffc3313140, val 102b45ee8, offset 2288
  unwind: '':ip = 0x102b8788f (0x1e788f)
  failed: got unresolved address 0x102b8788f
  unwind: failed with 'no error'
  got wrong number of stack entries 0 != 8
  test child finished with -1
  ---- end ----
  Test dwarf unwind: FAILED!

We expect to resolve test__dwarf_unwind as the last symbol, but that
function can be optimized away:
  $ objdump -tT /usr/bin/perf | grep dwarf_unwind
  000000000083b018 g    DO .data	0000000000000040  Base        tests__dwarf_unwind
  00000000001e7750 g    DF .text	0000000000000068  Base        0x60 test_dwarf_unwind__krava_1
  00000000001e76e0 g    DF .text	0000000000000068  Base        0x60 test_dwarf_unwind__krava_2
  00000000001e7620 g    DF .text	00000000000000b4  Base        0x60 test_dwarf_unwind__krava_3
  00000000001e74f0 g    DF .text	0000000000000128  Base        0x60 test_dwarf_unwind__compare
  00000000001e7350 g    DF .text	000000000000019c  Base        0x60 test_dwarf_unwind__thread
  000000000083b000 g    DO .data	0000000000000018  Base        suite__dwarf_unwind

Fix this similar to commit fdf7c49c200d1b ("perf tests: Fix dwarf unwind
for stripped binaries") by marking the function as a global and adding
the 'noinline' attribute to it.

With this patch:
  $ objdump -tT perf | grep dwarf_unwind
  000000000083b018 g    DO .data	0000000000000040  Base        tests__dwarf_unwind
  00000000001e80f0 g    DF .text	0000000000000068  Base        0x60 test_dwarf_unwind__krava_1
  00000000001e8080 g    DF .text	0000000000000068  Base        0x60 test_dwarf_unwind__krava_2
  00000000001e7fc0 g    DF .text	00000000000000b4  Base        0x60 test_dwarf_unwind__krava_3
  00000000001e7e90 g    DF .text	0000000000000128  Base        0x60 test_dwarf_unwind__compare
  00000000001e7cf0 g    DF .text	000000000000019c  Base        0x60 test_dwarf_unwind__thread
  00000000001e8160 g    DF .text	0000000000000248  Base        0x60 test__dwarf_unwind
  000000000083b000 g    DO .data	0000000000000018  Base        suite__dwarf_unwind
  $ ./perf test 74
   74: Test dwarf unwind                                               : Ok

Reported-by: Disha Goel <disgoel@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
---
 tools/perf/tests/dwarf-unwind.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/perf/tests/dwarf-unwind.c b/tools/perf/tests/dwarf-unwind.c
index afdca7f2959f07..ee983b677a6ae0 100644
--- a/tools/perf/tests/dwarf-unwind.c
+++ b/tools/perf/tests/dwarf-unwind.c
@@ -67,6 +67,7 @@ int test_dwarf_unwind__compare(void *p1, void *p2);
 int test_dwarf_unwind__krava_3(struct thread *thread);
 int test_dwarf_unwind__krava_2(struct thread *thread);
 int test_dwarf_unwind__krava_1(struct thread *thread);
+int test__dwarf_unwind(struct test_suite *test, int subtest);
 
 #define MAX_STACK 8
 
@@ -195,8 +196,8 @@ NO_TAIL_CALL_ATTRIBUTE noinline int test_dwarf_unwind__krava_1(struct thread *th
 	return ret;
 }
 
-static int test__dwarf_unwind(struct test_suite *test __maybe_unused,
-			      int subtest __maybe_unused)
+noinline int test__dwarf_unwind(struct test_suite *test __maybe_unused,
+				int subtest __maybe_unused)
 {
 	struct machine *machine;
 	struct thread *thread;

base-commit: 5670ebf54bd26482f57a094c53bdc562c106e0a9
-- 
2.39.1