[Lldb-commits] [PATCH] D63791: [lldb] [Process/NetBSD] Fix segfault when handling watchpoint

[Michał Górny via Phabricator via lldb-commits]

mgorny created this revision.
mgorny added reviewers: krytarowski, labath.

Fix the watchpoint/breakpoint code to search for matching thread entry
in m_threads explicitly rather than assuming that it will be present
at specified index.  The previous code segfault since it wrongly assumed
that the index will match LWP ID which was incorrect even for a single
thread (where index was 0 and LWP ID was 1).

While fixing that off-by-one error would help for this specific task,
I believe it is better to be explicit in what we are searching for.


https://reviews.llvm.org/D63791

Files:
  lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp


Index: lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
===================================================================
--- lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
+++ lldb/source/Plugins/Process/NetBSD/NativeProcessNetBSD.cpp
@@ -238,12 +238,25 @@
     SetState(StateType::eStateStopped, true);
   } break;
   case TRAP_DBREG: {
+    // Find the thread.
+    NativeThreadNetBSD* thread = nullptr;
+    for (const auto &t : m_threads) {
+      if (t->GetID() == info.psi_lwpid) {
+        thread = static_cast<NativeThreadNetBSD *>(t.get());
+        break;
+      }
+    }
+    if (!thread) {
+      LLDB_LOG(log,
+               "thread not found in m_threads, pid = {0}, LWP = {1}",
+               GetID(), info.psi_lwpid);
+      break;
+    }
+
     // If a watchpoint was hit, report it
-    uint32_t wp_index;
-    Status error = static_cast<NativeThreadNetBSD &>(*m_threads[info.psi_lwpid])
-                       .GetRegisterContext()
-                       .GetWatchpointHitIndex(
-                           wp_index, (uintptr_t)info.psi_siginfo.si_addr);
+    uint32_t wp_index = LLDB_INVALID_INDEX32;
+    Status error = thread->GetRegisterContext().GetWatchpointHitIndex(
+        wp_index, (uintptr_t)info.psi_siginfo.si_addr);
     if (error.Fail())
       LLDB_LOG(log,
                "received error while checking for watchpoint hits, pid = "
@@ -258,11 +271,9 @@
     }
 
     // If a breakpoint was hit, report it
-    uint32_t bp_index;
-    error = static_cast<NativeThreadNetBSD &>(*m_threads[info.psi_lwpid])
-                .GetRegisterContext()
-                .GetHardwareBreakHitIndex(bp_index,
-                                           (uintptr_t)info.psi_siginfo.si_addr);
+    uint32_t bp_index = LLDB_INVALID_INDEX32;
+    error = thread->GetRegisterContext().GetHardwareBreakHitIndex(
+        bp_index, (uintptr_t)info.psi_siginfo.si_addr);
     if (error.Fail())
       LLDB_LOG(log,
                "received error while checking for hardware "


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