[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

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/dotest.py

def checkLibstdcxxSupport():
     result, reason = canRunLibstdcxxTests()
     if result:
         return # libstdcxx supported
     if "libstdcxx" in configuration.categoriesList:
         return # libstdcxx category explicitly requested, let it run.
     print("libstdcxx tests will not be run because: " + reason)
     configuration.skipCategories.append("libstdcxx")
 
+def canRunWatchpointTests():
+    from lldbsuite.test import lldbplatformutil
+
+    platform = lldbplatformutil.getPlatform()
+    if platform == "netbsd":
+      try:
+        output = subprocess.check_output(["/sbin/sysctl", "-n",
+          "security.models.extensions.user_set_dbregs"]).decode().strip()
+        if output == "1":
+          return True, "security.models.extensions.user_set_dbregs enabled"
+      except subprocess.CalledProcessError:
+        pass
+      return False, "security.models.extensions.user_set_dbregs disabled"
+    return True, "dbregs always writable"
+
+def checkWatchpointSupport():
+    result, reason = canRunWatchpointTests()
+    if result:
+        return # watchpoints supported
+    if "watchpoint" in configuration.categoriesList:
+        return # watchpoint category explicitly requested, let it run.
+    print("watchpoint tests will not be run because: " + reason)
+    configuration.skipCategories.append("watchpoint")
+
 def checkDebugInfoSupport():
     import lldb
 
     platform = lldb.DBG.GetSelectedPlatform().GetTriple().split('-')[2]
     compiler = configuration.compiler
     skipped = []
     for cat in test_categories.debug_info_categories:
         if cat in configuration.categoriesList:
def run_suite():
     import lldbsuite.test.lldbutil as lldbutil
     build_dir = configuration.test_build_dir
     lldbutil.mkdir_p(build_dir)
 
     target_platform = lldb.DBG.GetSelectedPlatform().GetTriple().split('-')[2]
 
     checkLibcxxSupport()
     checkLibstdcxxSupport()
+    checkWatchpointSupport()
     checkDebugInfoSupport()
 
     # Don't do debugserver tests on anything except OS X.
     configuration.dont_do_debugserver_test = "linux" in target_platform or "freebsd" in target_platform or "windows" in target_platform
 
     # Don't do lldb-server (llgs) tests on anything except Linux.
     configuration.dont_do_llgs_test = not ("linux" in target_platform)