[lldb] [test] Skip watchpoint tests on NetBSD if userdbregs is disabled

[mgorny]

Summary

Skip watchpoint tests if security.models.extensions.user_set_dbregs
is disabled. This indicates that unprivileged processes are not allowed
to write to debug registers which is a prerequisite for using hardware
watchpoints.

[labath]

This definitely aren't all of our watchpoint tests. What's the reason for picking this particular bunch? Are they the only ones enabled on NetBSD right now?

Anyway, given that all of the watchpoint tests are already annotated with the "watchpoint" category, I think it would be better to handle this similar to how we handle other category-based skips (debug info flavours, c++ library types, etc.). This would also enable us to get rid of the "expectedFailure(windows)" decorator on all of these tests by implementing the skip centrally (though you don't have to do that right now). The category-based skipping happens around here: https://github.com/llvm-mirror/lldb/blob/master/packages/Python/lldbsuite/test/dotest.py#L1143

[mgorny]

In D63380#1545428, @labath wrote:

This definitely aren't all of our watchpoint tests. What's the reason for picking this particular bunch? Are they the only ones enabled on NetBSD right now?

Buildbot was down at the moment, so I went only for those that I was sure started failing once I fixed dbreg error reporting.

Anyway, given that all of the watchpoint tests are already annotated with the "watchpoint" category, I think it would be better to handle this similar to how we handle other category-based skips (debug info flavours, c++ library types, etc.). This would also enable us to get rid of the "expectedFailure(windows)" decorator on all of these tests by implementing the skip centrally (though you don't have to do that right now). The category-based skipping happens around here: https://github.com/llvm-mirror/lldb/blob/master/packages/Python/lldbsuite/test/dotest.py#L1143

Will do that.

[mgorny]

Updated as suggested above.

[mgorny]

Removed stale decorator.

[labath]

lldb/packages/Python/lldbsuite/test/dotest.py

1197 ↗

(On Diff #204996)

The string isn't used anywhere, but I'd use a slightly more generic value here, because there are a number of reasons watchpoints can/cannot work on a given platform...

[krytarowski]

This check should contain additional check for uid==root. If we are root we can read and write to DB registers.

[mgorny]

In D63380#1545856, @krytarowski wrote:

This check should contain additional check for uid==root. If we are root we can read and write to DB registers.

Will do.

lldb/packages/Python/lldbsuite/test/decorators.py

def skipUnlessFeature(feature):
     return skipTestIfFn(is_feature_enabled)
 
 def skipIfSanitized(func):
     """Skip this test if the environment is set up to run LLDB itself under ASAN."""
     def is_sanitized():
         return (('DYLD_INSERT_LIBRARIES' in os.environ) and
                 'libclang_rt.asan' in os.environ['DYLD_INSERT_LIBRARIES'])
     return skipTestIfFn(is_sanitized)(func)
+
+def skipIfDbRegsReadOnly(func):
+    """Skip this test if platform does not permit writing to debug registers."""
+    def is_dbregs_rdonly():
+        if platform.system() != 'NetBSD':
+            return None
+        try:
+            output = subprocess.check_output(["/sbin/sysctl", "-n",
+                "security.models.extensions.user_set_dbregs"]).decode().strip()
+            if output == "1":
+                return None
+        except subprocess.CalledProcessError:
+            pass
+        return "security.models.extensions.user_set_dbregs is disabled"
+    return skipTestIfFn(is_dbregs_rdonly)(func)

lldb/packages/Python/lldbsuite/test/functionalities/watchpoint/multiple_threads/TestWatchpointMultipleThreads.py

def do_watchpoint_test(self, line):
         # Use the '-v' option to do verbose listing of the watchpoint.
         # The hit count should now be 1.
         self.expect("watchpoint list -v",
                     substrs=['hit_count = 1'])
 
     @expectedFailureAll(
         oslist=["windows"],
         bugnumber="llvm.org/pr24446: WINDOWS XFAIL TRIAGE - Watchpoints not supported on Windows")
+    @skipIfDbRegsReadOnly
     def test_watchpoint_multiple_threads_wp_set_and_then_delete(self):
         """Test that lldb watchpoint works for multiple threads, and after the watchpoint is deleted, the watchpoint event should no longer fires."""
         self.build()
         self.setTearDownCleanup()
 
         lldbutil.run_to_source_breakpoint(self, "After running the thread", self.main_spec)
 
         # Now let's set a write-type watchpoint for variable 'g_val'.

lldb/packages/Python/lldbsuite/test/functionalities/watchpoint/watchpoint_commands/TestWatchpointCommands.py

def test_rw_watchpoint(self):
         self.expect("watchpoint list -v",
                     substrs=['hit_count = 2'])
 
     @expectedFailureAll(
         oslist=["windows"],
         bugnumber="llvm.org/pr24446: WINDOWS XFAIL TRIAGE - Watchpoints not supported on Windows")
     # Read-write watchpoints not supported on SystemZ
     @expectedFailureAll(archs=['s390x'])
+    @skipIfDbRegsReadOnly
     def test_rw_watchpoint_delete(self):
         """Test delete watchpoint and expect not to stop for watchpoint."""
         self.build(dictionary=self.d)
         self.setTearDownCleanup(dictionary=self.d)
 
         exe = self.getBuildArtifact(self.exe_name)
         self.runCmd("file " + exe, CURRENT_EXECUTABLE_SET)
 

lldb/packages/Python/lldbsuite/test/functionalities/watchpoint/watchpoint_disable/TestWatchpointDisable.py

class TestWatchpointSetEnable(TestBase):
 
     def setUp(self):
         # Call super's setUp().
         TestBase.setUp(self)
 
     @expectedFailureAll(
         oslist=["windows"],
         bugnumber="llvm.org/pr24446: WINDOWS XFAIL TRIAGE - Watchpoints not supported on Windows")
+    @skipIfDbRegsReadOnly
     def test_disable_works (self):
         """Set a watchpoint, disable it, and make sure it doesn't get hit."""
         self.build()
         self.do_test(False)
 
     @expectedFailureAll(
         oslist=["windows"],
         bugnumber="llvm.org/pr24446: WINDOWS XFAIL TRIAGE - Watchpoints not supported on Windows")

lldb/packages/Python/lldbsuite/test/functionalities/watchpoint/watchpoint_events/TestWatchpointEvents.py

class TestWatchpointEvents (TestBase):
     @add_test_categories(['pyapi'])
     @expectedFailureAll(
         oslist=["linux"],
         archs=["aarch64"],
         bugnumber="llvm.org/pr27710")
     @expectedFailureAll(
         oslist=["windows"],
         bugnumber="llvm.org/pr24446: WINDOWS XFAIL TRIAGE - Watchpoints not supported on Windows")
+    @skipIfDbRegsReadOnly
     def test_with_python_api(self):
         """Test that adding, deleting and modifying watchpoints sends the appropriate events."""
         self.build()
 
         exe = self.getBuildArtifact("a.out")
 
         target = self.dbg.CreateTarget(exe)
         self.assertTrue(target, VALID_TARGET)

lldb/packages/Python/lldbsuite/test/functionalities/watchpoint/watchpoint_on_vectors/TestValueOfVectorVariable.py

 
 class TestValueOfVectorVariableTestCase(TestBase):
 
     mydir = TestBase.compute_mydir(__file__)
 
     @expectedFailureAll(
         oslist=["windows"],
         bugnumber="llvm.org/pr24446: WINDOWS XFAIL TRIAGE - Watchpoints not supported on Windows")
+    @skipIfDbRegsReadOnly
     def test_value_of_vector_variable_using_watchpoint_set(self):
         """Test verify displayed value of vector variable."""
         exe = self.getBuildArtifact("a.out")
         d = {'C_SOURCES': self.source, 'EXE': exe}
         self.build(dictionary=d)
         self.setTearDownCleanup(dictionary=d)
         self.value_of_vector_variable_with_watchpoint_set()