[lldb] [POSIX-DYLD] Update the cached exe path after attach

Fix the POSIX-DYLD plugin to update the cached executable path after
attaching.  Previously, the path was cached in DYLDRendezvous
constructor and not updated afterwards.  This meant that if LLDB was
attaching to a process (e.g. via connecting to lldb-server), the code
stored the empty path before DidAttach() resolved it.  The fix updates
the cached path in DidAttach().

This fixes a new instance of https://llvm.org/pr17880

Differential Revision: https://reviews.llvm.org/D92264

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.cpp

@@ -94,12 +94,13 @@ DYLDRendezvous::DYLDRendezvous(Process *process)
     : m_process(process), m_rendezvous_addr(LLDB_INVALID_ADDRESS), m_current(),
       m_previous(), m_loaded_modules(), m_soentries(), m_added_soentries(),
       m_removed_soentries() {
-  Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
-
   m_thread_info.valid = false;
+  UpdateExecutablePath();
+}
 
-  // Cache a copy of the executable path
+void DYLDRendezvous::UpdateExecutablePath() {
   if (m_process) {
+    Log *log(GetLogIfAnyCategoriesSet(LIBLLDB_LOG_DYNAMIC_LOADER));
     Module *exe_mod = m_process->GetTarget().GetExecutableModulePointer();
     if (exe_mod) {
       m_exe_file_spec = exe_mod->GetPlatformFileSpec();

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DYLDRendezvous.h

@@ -60,6 +60,9 @@ public:
 
   DYLDRendezvous(lldb_private::Process *process);
 
+  /// Update the cached executable path.
+  void UpdateExecutablePath();
+
   /// Update the internal snapshot of runtime linker rendezvous and recompute
   /// the currently loaded modules.
   ///

lldb/source/Plugins/DynamicLoader/POSIX-DYLD/DynamicLoaderPOSIXDYLD.cpp

@@ -102,6 +102,7 @@ void DynamicLoaderPOSIXDYLD::DidAttach() {
 
   ModuleSP executable_sp = GetTargetExecutable();
   ResolveExecutableModule(executable_sp);
+  m_rendezvous.UpdateExecutablePath();
 
   // find the main process load offset
   addr_t load_offset = ComputeLoadOffset();

lldb/test/API/commands/process/attach/TestProcessAttach.py

@@ -20,6 +20,13 @@ class ProcessAttachTestCase(TestBase):
 
     NO_DEBUG_INFO_TESTCASE = True
 
+    def setUp(self):
+        # Call super's setUp().
+        TestBase.setUp(self)
+        # Find the line number to break for main.c.
+        self.line = line_number('main.cpp',
+                                '// Waiting to be attached...')
+
     @skipIfiOSSimulator
     def test_attach_to_process_by_id(self):
         """Test attach by process id"""
@@ -77,6 +84,28 @@ class ProcessAttachTestCase(TestBase):
         process = target.GetProcess()
         self.assertTrue(process, PROCESS_IS_VALID)
 
+    def test_attach_to_process_by_id_correct_executable_offset(self):
+        """
+        Test that after attaching to a process the executable offset
+        is determined correctly on FreeBSD.  This is a regression test
+        for dyld plugin getting the correct executable path,
+        and therefore being able to identify it in the module list.
+        """
+
+        self.build()
+        exe = self.getBuildArtifact(exe_name)
+
+        # In order to reproduce, we must spawn using a relative path
+        popen = self.spawnSubprocess(os.path.relpath(exe))
+
+        self.runCmd("process attach -p " + str(popen.pid))
+
+        # Make suer we did not attach to early
+        lldbutil.run_break_set_by_file_and_line(
+            self, "main.cpp", self.line, num_expected_locations=1, loc_exact=False)
+        self.runCmd("process continue")
+        self.expect("p g_val", substrs=["$0 = 12345"])
+
     def tearDown(self):
         # Destroy process before TestBase.tearDown()
         self.dbg.GetSelectedTarget().GetProcess().Destroy()

lldb/test/API/commands/process/attach/main.cpp

@@ -3,6 +3,8 @@
 #include <chrono>
 #include <thread>
 
+volatile int g_val = 12345;
+
 int main(int argc, char const *argv[]) {
     int temp;
     lldb_enable_attach();