[Lldb-commits] [lldb] [LLDB] Ptrace seize dead processes on Linux (PR #137041)

[David Spickett via lldb-commits]

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@@ -444,6 +461,88 @@ NativeProcessLinux::NativeProcessLinux(::pid_t pid, int terminal_fd,
   SetState(StateType::eStateStopped, false);
 }
 
+llvm::Expected<std::vector<::pid_t>> NativeProcessLinux::Seize(::pid_t pid) {
+  Log *log = GetLog(POSIXLog::Process);
+
+  uint64_t options = GetDefaultPtraceOpts();
+  Status status;
+  // Use a map to keep track of the threads which we have attached/need to
+  // attach.
+  Host::TidMap tids_to_attach;
+  while (Host::FindProcessThreads(pid, tids_to_attach)) {
+    for (Host::TidMap::iterator it = tids_to_attach.begin();
+         it != tids_to_attach.end();) {
+      if (it->second == true) {
+        continue;
+      }
+      lldb::tid_t tid = it->first;
+      if ((status = PtraceWrapper(PTRACE_SEIZE, tid, nullptr, (void *)options))
+              .Fail()) {
+        // No such thread. The thread may have exited. More error handling
+        // may be needed.
+        if (status.GetError() == ESRCH) {
+          it = tids_to_attach.erase(it);
+          continue;
+        }
+        if (status.GetError() == EPERM) {
+          // Depending on the value of ptrace_scope, we can return a
+          // different error that suggests how to fix it.
+          return AddPtraceScopeNote(status.ToError());
+        }
+        return status.ToError();
+      }
+
+      if ((status = PtraceWrapper(PTRACE_INTERRUPT, tid)).Fail()) {
+        // No such thread. The thread may have exited. More error handling
+        // may be needed.
+        if (status.GetError() == ESRCH) {
+          it = tids_to_attach.erase(it);
+          continue;
+        }
+        if (status.GetError() == EPERM) {
+          // Depending on the value of ptrace_scope, we can return a
+          // different error that suggests how to fix it.
+          return AddPtraceScopeNote(status.ToError());
+        }
+        return status.ToError();
+      }
+
+      int wpid =
+          llvm::sys::RetryAfterSignal(-1, ::waitpid, tid, nullptr, __WALL);
+      // Need to use __WALL otherwise we receive an error with errno=ECHLD At
+      // this point we should have a thread stopped if waitpid succeeds.
+      if (wpid < 0) {
----------------
DavidSpickett wrote:

This could be `if (llvm::sys.....__WALL) < 0)`, since wpid is not used outside of this check.

https://github.com/llvm/llvm-project/pull/137041