[lldb] [test] Add a test for watchpoint set error handling on NetBSD

[mgorny]

Summary

Add a test that verifies that when the user does not have permissions
to set watchpoints on NetBSD, the 'watchpoint set' errors out gracefully
and thread monitoring does not crash on being unable to copy watchpoints
to new threads.

[labath]

lldb/test/Shell/Watchpoint/Inputs/thread-dbreg.c

1–23

Maybe simplify this and remove the threads and stuff?

lldb/test/Shell/Watchpoint/netbsd-nouserdbregs.test

5

You should use %clang_host now. Are you sure that this even works on current master?

[mgorny]

lldb/test/Shell/Watchpoint/Inputs/thread-dbreg.c

1–23

Threads are intentional since new thread handler copies dbregs per the other patch. This makes sure that new thread handler will not crash when it is unable to set dbregs.

lldb/test/Shell/Watchpoint/netbsd-nouserdbregs.test

5

I have to admit that I'm at ~Oct 31 in my checkout. I've tried using %clang_host but it failed with fg saying that there is no job control.

[labath]

lldb/test/Shell/Watchpoint/Inputs/thread-dbreg.c

1–23

Hang on, isn't this test about what happens when you *cannot* set watchpoints? In that case there should be nothing to copy the dbregs from, right?

lldb/test/Shell/Watchpoint/netbsd-nouserdbregs.test

5

%clang_host was added *on* Oct 31, so maybe you need to sync a bit further... :)

[labath]

lldb/test/Shell/Watchpoint/Inputs/thread-dbreg.c

1–23

Hmm... or is it that you're testing that the act of trying to copy this "nothing" works? In that case, this might be fine, but it'd probably be worth mentioning this in the test case.

[mgorny]

lldb/test/Shell/Watchpoint/Inputs/thread-dbreg.c

1–23

Actually, since the whole dbreg support is rather stateless at the moment, we just unconditionally copy dbregs. I suppose this needs to be fixed, and now I see that my other patch misses error handling as well. However, the main point for this test is to prevent regressions, and this is a potential programmer's mistake.

lldb/test/Shell/Watchpoint/netbsd-nouserdbregs.test

5

Ok, I'll try.

[mgorny]

Combined into D70023.

lldb/test/Shell/Watchpoint/Inputs/thread-dbreg.c

+#include <pthread.h>
+
+int g_watchme = 0;
+
+void *thread_func(void *arg) {
+  /* watchpoint trigger from subthread */
+  g_watchme = 2;
+  return 0;
+}
+
+int main() {
+  pthread_t thread;
+  if (pthread_create(&thread, 0, thread_func, 0))
+    return 1;
+
+  /* watchpoint trigger from main thread */
+  g_watchme = 1;
+
+  if (pthread_join(thread, 0))
+    return 2;
+
+  return 0;
+}

lldb/test/Shell/Watchpoint/netbsd-nouserdbregs.test

+# Check that 'watchpoint set' errors out gracefully when we can't set dbregs
+# and that new threads are monitored correctly even though we can't copy dbregs.
+
+# REQUIRES: native && system-netbsd && (target-x86 || target-x86_64) && !dbregs-set
+# RUN: %clang %p/Inputs/thread-dbreg.c -pthread -g -o %t.out
+# RUN: %lldb -b -o 'settings set interpreter.stop-command-source-on-error false' -s %s %t.out 2>&1 | FileCheck %s
+
+settings show interpreter.stop-command-source-on-error
+# CHECK: interpreter.stop-command-source-on-error (boolean) = false
+
+b main
+# CHECK: Breakpoint {{[0-9]+}}: where = {{.*}}`main
+b thread_func
+# CHECK: Breakpoint {{[0-9]+}}: where = {{.*}}`thread_func
+run
+# CHECK: stop reason = breakpoint
+watchpoint set variable g_watchme
+# CHECK: error: Watchpoint creation failed
+cont
+# CHECK: stop reason = breakpoint
+cont
+# CHECK: Process {{[0-9]+}} exited with status = 0

lldb/test/Shell/lit.cfg.py

 # -*- Python -*-
 
 import os
 import platform
 import re
 import shutil
 import site
+import subprocess
 import sys
 
 import lit.formats
 from lit.llvm import llvm_config
 from lit.llvm.subst import FindTool
 from lit.llvm.subst import ToolSubst
 from distutils.spawn import find_executable
 

 if not config.lldb_disable_python:
     config.available_features.add('python')
 
 if config.lldb_enable_lzma:
     config.available_features.add('lzma')
 
 if find_executable('xz') != None:
     config.available_features.add('xz')
+
+# NetBSD permits setting dbregs either if one is root
+# or if user_set_dbregs is enabled
+can_set_dbregs = True
+if platform.system() == 'NetBSD' and os.geteuid() != 0:
+    try:
+        output = subprocess.check_output(["/sbin/sysctl", "-n",
+          "security.models.extensions.user_set_dbregs"]).decode().strip()
+        if output != "1":
+            can_set_dbregs = False
+    except subprocess.CalledProcessError:
+        can_set_dbregs = False
+if can_set_dbregs:
+    config.available_features.add('dbregs-set')