[PATCH 3/4] perf test probe_vfs_getname: Fix missing debuginfo detection

[James Clark <james.clark@linaro.org>]

skip_if_no_debuginfo() looks for the errors that 'perf probe' prints when
there is no debuginfo in the output of add_probe_vfs_getname(). But since
commit 92b664dcefab ("perf test probe_vfs_getname: Skip if no suitable
line detected"), add_probe_vfs_getname() returns early without adding a
probe if 'perf probe -L' doesn't find the line, which is also what
happens when there is no debuginfo. The error from 'perf probe -L' is
discarded, so the debuginfo errors are never found.

This causes the debuginfo dependent subtests of the
"perftool-testsuite_probe" test to fail instead of being skipped on
kernels without debuginfo, because test_adding_kernel.sh calls
skip_if_no_debuginfo() unconditionally. The other users only call it
when add_probe_vfs_getname() returns 1, so they aren't affected.

Fix it by doing a dry run of a probe that needs debuginfo instead. This
works without libdw too, where 'perf probe -L' isn't available, and also
avoids adding a real probe just to check for debuginfo. This fixes the
"perftool-testsuite_probe" test:

  $ sudo perf test -vvv "perftool-testsuite_probe"
  ...
  -- [ FAIL ] -- perf_probe :: test_adding_kernel :: listing added probe :: perf probe -l (output regexp parsing)
  ...
  -- [ FAIL ] -- perf_probe :: test_adding_kernel :: wildcard adding support (command exitcode + output regexp parsing)
  ...
  -- [ FAIL ] -- perf_probe :: test_adding_kernel :: non-existing variable (output regexp parsing)
  ...
  ## [ FAIL ] ## perf_probe :: test_adding_kernel SUMMARY :: 3 failures found
  ...
  189: perftool-testsuite_probe : FAILED!

Fixes: 92b664dcefab ("perf test probe_vfs_getname: Skip if no suitable line detected")
Signed-off-by: James Clark <james.clark@linaro.org>
---
 tools/perf/tests/shell/lib/probe_vfs_getname.sh | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/shell/lib/probe_vfs_getname.sh b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
index 57a59ae7d4ae..1c3af5771bcf 100644
--- a/tools/perf/tests/shell/lib/probe_vfs_getname.sh
+++ b/tools/perf/tests/shell/lib/probe_vfs_getname.sh
@@ -64,7 +64,8 @@ add_probe_vfs_getname() {
 }
 
 skip_if_no_debuginfo() {
-	add_probe_vfs_getname -v 2>&1 | grep -E -q "^(Failed to find the path for the kernel|Debuginfo-analysis is not supported)|(file has no debug information)" && return 2
+	# Dry run a probe that needs debuginfo.
+	perf probe -n -v 'getname_flags $params' 2>&1 | grep -E -q "^(Failed to find the path for the kernel|Debuginfo-analysis is not supported)|(file has no debug information)" && return 2
 	return 1
 }
 

-- 
2.43.0