test: v4l2_compat: Enable test with ASan

When libcamera is compiled with the address sanitizer enabled, the
v4l2_compat test generates failures in the link order runtime check, as
the host v4l2-ctl and v4l2-compliance tools are not (generally) linked
to ASan. For this reason, the test is disabled, which sadly shrinks test
coverage.

Fix this by loading the ASan runtime using LD_PRELOAD. This needs to be
done from within the v4l2_compat_test.py Python script, as the Python
interpreter itself leaks memory and would cause test failures if run
with ASan.

To LD_PRELOAD the ASan runtime, the path to the binary needs to be
known. gcc gives us a generic way to get the path, but that doesn't work
with clang as the ASan runtime file name depends on the clang version
and target architecture. We thus have to keep the v4l2_compat test
disabled when ASan is enabled and libcamera is compiled with clang.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

test/meson.build

@@ -7,6 +7,22 @@ endif
 
 test_enabled = true
 
+# When ASan is enabled, find the path to the ASan runtime needed by multiple
+# tests. This currently works with gcc only, as clang uses different file names
+# depending on the compiler version and target architecture.
+asan_enabled = false
+asan_runtime_missing = false
+
+if get_option('b_sanitize').contains('address')
+    asan_enabled = true
+
+    if cc.get_id() == 'gcc'
+        asan_runtime = run_command(cc, '-print-file-name=libasan.so', check : true).stdout().strip()
+    else
+        asan_runtime_missing = true
+    endif
+endif
+
 subdir('libtest')
 
 subdir('camera')

test/v4l2_compat/meson.build

@@ -4,19 +4,26 @@ if not is_variable('v4l2_compat')
     subdir_done()
 endif
 
-# If ASan is enabled, the link order runtime check will fail as v4l2-ctl and
+# If ASan is enabled but the ASan runtime shared library is missing,
-# v4l2-compliance are not linked to ASan. Skip the test in that case.
+# v4l2_compat_test.py won't be able to LD_PRELOAD it, resulting in a link order
-#
+# runtime check failure as v4l2-ctl and v4l2-compliance are not linked to ASan.
-# TODO: Find a way to LD_PRELOAD the ASan dynamic library instead, in a
+# Skip the test in that case.
-# cross-platform way with support for both gcc and clang.
 
-if get_option('b_sanitize').contains('address')
+if asan_runtime_missing
+    warning('Unable to get path to ASan runtime, v4l2_compat test disabled')
     subdir_done()
 endif
 
 v4l2_compat_test = files('v4l2_compat_test.py')
+v4l2_compat_args = []
+
+if asan_enabled
+    v4l2_compat_args += ['-s', asan_runtime]
+endif
+
+v4l2_compat_args += [v4l2_compat]
 
 test('v4l2_compat_test', v4l2_compat_test,
-     args : v4l2_compat,
+     args : v4l2_compat_args,
      suite : 'v4l2_compat',
      timeout : 60)

test/v4l2_compat/v4l2_compat_test.py

@@ -57,8 +57,8 @@ def extract_result(result):
     return ret
 
 
-def test_v4l2_compliance(v4l2_compliance, v4l2_compat, device, base_driver):
+def test_v4l2_compliance(v4l2_compliance, ld_preload, device, base_driver):
-    ret, output = run_with_stdout(v4l2_compliance, '-s', '-d', device, env={'LD_PRELOAD': v4l2_compat})
+    ret, output = run_with_stdout(v4l2_compliance, '-s', '-d', device, env={'LD_PRELOAD': ld_preload})
     if ret < 0:
         output.append(f'Test for {device} terminated due to signal {signal.Signals(-ret).name}')
         return TestFail, output
@@ -82,13 +82,21 @@ def main(argv):
     parser = argparse.ArgumentParser()
     parser.add_argument('-a', '--all', action='store_true',
                         help='Test all available cameras')
+    parser.add_argument('-s', '--sanitizer', type=str,
+                        help='Path to the address sanitizer (ASan) runtime')
     parser.add_argument('-v', '--verbose', action='store_true',
                         help='Make the output verbose')
     parser.add_argument('v4l2_compat', type=str,
                         help='Path to v4l2-compat.so')
     args = parser.parse_args(argv[1:])
 
-    v4l2_compat = args.v4l2_compat
+    # Compute the LD_PRELOAD value by first loading ASan (if specified) and
+    # then the V4L2 compat layer.
+    ld_preload = []
+    if args.sanitizer:
+        ld_preload.append(args.sanitizer)
+    ld_preload.append(args.v4l2_compat)
+    ld_preload = ':'.join(ld_preload)
 
     v4l2_compliance = shutil.which('v4l2-compliance')
     if v4l2_compliance is None:
@@ -118,7 +126,7 @@ def main(argv):
     failed = []
     drivers_tested = {}
     for device in dev_nodes:
-        ret, out = run_with_stdout(v4l2_ctl, '-D', '-d', device, env={'LD_PRELOAD': v4l2_compat})
+        ret, out = run_with_stdout(v4l2_ctl, '-D', '-d', device, env={'LD_PRELOAD': ld_preload})
         if ret < 0:
             failed.append(device)
             print(f'v4l2-ctl failed on {device} with v4l2-compat')
@@ -144,7 +152,7 @@ def main(argv):
             continue
 
         print(f'Testing {device} with {driver} driver... ', end='')
-        ret, msg = test_v4l2_compliance(v4l2_compliance, v4l2_compat, device, driver)
+        ret, msg = test_v4l2_compliance(v4l2_compliance, ld_preload, device, driver)
         if ret == TestFail:
             failed.append(device)
             print('failed')