[lldb-vscode] Fix two issues with runInTerminal test.

With ptrace_scope = 1 the kernel only allows tracing descendants of a
process. When using runInTerminal, the target process is not launched
by the debugger, so we need to modify LaunchRunInTerminal to explicitly
allow tracing. This should fix a problem reported in
https://reviews.llvm.org/D84974#3903716

In order to allow only the main lldb-vscode process to attach to the
target, this change introduces a new `--debugger-pid` flag that needs
to be passed with `--launch-target` and `--comm-file`.

Also, remove a special case from the launch method in the
lldbvscode_testcase test harness. The existing test was using
stopOnEntry, so the first stop didn't happen at the expected breakpoint
unless the harness did configurationDone first.

Differential Revision: https://reviews.llvm.org/D147805

4 files changed, 54 insertions, 9 deletions

diff --git a/lldb/tools/lldb-vscode/JSONUtils.cpp b/lldb/tools/lldb-vscode/JSONUtils.cpp
index 8ec38a495777..67455abb9916 100644
--- a/lldb/tools/lldb-vscode/JSONUtils.cpp
+++ b/lldb/tools/lldb-vscode/JSONUtils.cpp
@@ -1102,7 +1102,8 @@ llvm::json::Value CreateCompileUnit(lldb::SBCompileUnit unit) {
 llvm::json::Object
 CreateRunInTerminalReverseRequest(const llvm::json::Object &launch_request,
                                   llvm::StringRef debug_adaptor_path,
-                                  llvm::StringRef comm_file) {
+                                  llvm::StringRef comm_file,
+                                  lldb::pid_t debugger_pid) {
   llvm::json::Object reverse_request;
   reverse_request.try_emplace("type", "request");
   reverse_request.try_emplace("command", "runInTerminal");
@@ -1115,8 +1116,13 @@ CreateRunInTerminalReverseRequest(const llvm::json::Object &launch_request,
   auto launch_request_arguments = launch_request.getObject("arguments");
   // The program path must be the first entry in the "args" field
   std::vector<std::string> args = {
-      debug_adaptor_path.str(), "--comm-file", comm_file.str(),
-      "--launch-target", GetString(launch_request_arguments, "program").str()};
+      debug_adaptor_path.str(), "--comm-file", comm_file.str()};
+  if (debugger_pid != LLDB_INVALID_PROCESS_ID) {
+    args.push_back("--debugger-pid");
+    args.push_back(std::to_string(debugger_pid));
+  }
+  args.push_back("--launch-target");
+  args.push_back(GetString(launch_request_arguments, "program").str());
   std::vector<std::string> target_args =
       GetStrings(launch_request_arguments, "args");
   args.insert(args.end(), target_args.begin(), target_args.end());
diff --git a/lldb/tools/lldb-vscode/JSONUtils.h b/lldb/tools/lldb-vscode/JSONUtils.h
index b67da7191cde..73cfb425ee29 100644
--- a/lldb/tools/lldb-vscode/JSONUtils.h
+++ b/lldb/tools/lldb-vscode/JSONUtils.h
@@ -479,13 +479,19 @@ llvm::json::Value CreateCompileUnit(lldb::SBCompileUnit unit);
 /// \param[in] comm_file
 ///     The fifo file used to communicate the with the target launcher.
 ///
+/// \param[in] debugger_pid
+///     The PID of the lldb-vscode instance that will attach to the target. The
+///     launcher uses it on Linux tell the kernel that it should allow the
+///     debugger process to attach.
+///
 /// \return
 ///     A "runInTerminal" JSON object that follows the specification outlined by
 ///     Microsoft.
 llvm::json::Object
 CreateRunInTerminalReverseRequest(const llvm::json::Object &launch_request,
                                   llvm::StringRef debug_adaptor_path,
-                                  llvm::StringRef comm_file);
+                                  llvm::StringRef comm_file,
+                                  lldb::pid_t debugger_pid);
 
 /// Create a "Terminated" JSON object that contains statistics
 ///
diff --git a/lldb/tools/lldb-vscode/Options.td b/lldb/tools/lldb-vscode/Options.td
index ff2ffd59de03..a73671ad749c 100644
--- a/lldb/tools/lldb-vscode/Options.td
+++ b/lldb/tools/lldb-vscode/Options.td
@@ -28,9 +28,14 @@ def launch_target: Separate<["--", "-"], "launch-target">,
   MetaVarName<"<target>">,
   HelpText<"Launch a target for the launchInTerminal request. Any argument "
     "provided after this one will be passed to the target. The parameter "
-    "--comm-files-prefix must also be specified.">;
+    "--comm-file must also be specified.">;
 
 def comm_file: Separate<["--", "-"], "comm-file">,
   MetaVarName<"<file>">,
-  HelpText<"The fifo file used to communicate the with the debug adaptor"
+  HelpText<"The fifo file used to communicate the with the debug adaptor "
     "when using --launch-target.">;
+
+def debugger_pid: Separate<["--", "-"], "debugger-pid">,
+  MetaVarName<"<pid>">,
+  HelpText<"The PID of the lldb-vscode instance that sent the launchInTerminal "
+    "request when using --launch-target.">;
diff --git a/lldb/tools/lldb-vscode/lldb-vscode.cpp b/lldb/tools/lldb-vscode/lldb-vscode.cpp
index 51a72f2b03c9..8257a1ffbe9b 100644
--- a/lldb/tools/lldb-vscode/lldb-vscode.cpp
+++ b/lldb/tools/lldb-vscode/lldb-vscode.cpp
@@ -32,6 +32,10 @@
 #include <unistd.h>
 #endif
 
+#if defined(__linux__)
+#include <sys/prctl.h>
+#endif
+
 #include <algorithm>
 #include <chrono>
 #include <fstream>
@@ -1562,8 +1566,12 @@ llvm::Error request_runInTerminal(const llvm::json::Object &launch_request) {
 
   RunInTerminalDebugAdapterCommChannel comm_channel(comm_file.m_path);
 
+  lldb::pid_t debugger_pid = LLDB_INVALID_PROCESS_ID;
+#if !defined(_WIN32)
+  debugger_pid = getpid();
+#endif
   llvm::json::Object reverse_request = CreateRunInTerminalReverseRequest(
-      launch_request, g_vsc.debug_adaptor_path, comm_file.m_path);
+      launch_request, g_vsc.debug_adaptor_path, comm_file.m_path, debugger_pid);
   llvm::json::Object reverse_response;
   lldb_vscode::PacketStatus status =
       g_vsc.SendReverseRequest(reverse_request, reverse_response);
@@ -3141,11 +3149,21 @@ EXAMPLES:
 // In case of errors launching the target, a suitable error message will be
 // emitted to the debug adaptor.
 void LaunchRunInTerminalTarget(llvm::opt::Arg &target_arg,
-                               llvm::StringRef comm_file, char *argv[]) {
+                               llvm::StringRef comm_file,
+                               lldb::pid_t debugger_pid, char *argv[]) {
 #if defined(_WIN32)
   llvm::errs() << "runInTerminal is only supported on POSIX systems\n";
   exit(EXIT_FAILURE);
 #else
+
+  // On Linux with the Yama security module enabled, a process can only attach
+  // to its descendants by default. In the runInTerminal case the target
+  // process is launched by the client so we need to allow tracing explicitly.
+#if defined(__linux__)
+  if (debugger_pid != LLDB_INVALID_PROCESS_ID)
+    (void)prctl(PR_SET_PTRACER, debugger_pid, 0, 0, 0);
+#endif
+
   RunInTerminalLauncherCommChannel comm_channel(comm_file);
   if (llvm::Error err = comm_channel.NotifyPid()) {
     llvm::errs() << llvm::toString(std::move(err)) << "\n";
@@ -3238,13 +3256,23 @@ int main(int argc, char *argv[]) {
 
   if (llvm::opt::Arg *target_arg = input_args.getLastArg(OPT_launch_target)) {
     if (llvm::opt::Arg *comm_file = input_args.getLastArg(OPT_comm_file)) {
+      lldb::pid_t pid = LLDB_INVALID_PROCESS_ID;
+      llvm::opt::Arg *debugger_pid = input_args.getLastArg(OPT_debugger_pid);
+      if (debugger_pid) {
+        llvm::StringRef debugger_pid_value = debugger_pid->getValue();
+        if (debugger_pid_value.getAsInteger(10, pid)) {
+          llvm::errs() << "'" << debugger_pid_value << "' is not a valid "
+                          "PID\n";
+          return EXIT_FAILURE;
+        }
+      }
       int target_args_pos = argc;
       for (int i = 0; i < argc; i++)
         if (strcmp(argv[i], "--launch-target") == 0) {
           target_args_pos = i + 1;
           break;
         }
-      LaunchRunInTerminalTarget(*target_arg, comm_file->getValue(),
+      LaunchRunInTerminalTarget(*target_arg, comm_file->getValue(), pid,
                                 argv + target_args_pos);
     } else {
       llvm::errs() << "\"--launch-target\" requires \"--comm-file\" to be "