Merge pull request #7078 from jasonmolenda/r101152233-improve-error-reporting-on-partial-attach

Improve error messaging when debugserver fails to complete attaching

Author: jasonmolenda

lldb/tools/debugserver/source/DNB.cpp

@@ -1846,3 +1846,11 @@ bool DNBGetAddressingBits(uint32_t &addressing_bits) {
 
   return addressing_bits > 0;
 }
+
+nub_process_t DNBGetParentProcessID(nub_process_t child_pid) {
+  return MachProcess::GetParentProcessID(child_pid);
+}
+
+bool DNBProcessIsBeingDebugged(nub_process_t pid) {
+  return MachProcess::ProcessIsBeingDebugged(pid);
+}

lldb/tools/debugserver/source/DNB.h

@@ -247,4 +247,9 @@ std::string DNBGetMacCatalystVersionString();
 bool DNBDebugserverIsTranslated();
 
 bool DNBGetAddressingBits(uint32_t &addressing_bits);
+
+nub_process_t DNBGetParentProcessID(nub_process_t child_pid);
+
+bool DNBProcessIsBeingDebugged(nub_process_t pid);
+
 #endif

lldb/tools/debugserver/source/MacOSX/MachProcess.h

@@ -126,6 +126,11 @@ class MachProcess {
   static bool GetOSVersionNumbers(uint64_t *major, uint64_t *minor,
                                   uint64_t *patch);
   static std::string GetMacCatalystVersionString();
+
+  static nub_process_t GetParentProcessID(nub_process_t child_pid);
+
+  static bool ProcessIsBeingDebugged(nub_process_t pid);
+
 #ifdef WITH_BKS
   static void BKSCleanupAfterAttach(const void *attach_token,
                                     DNBError &err_str);

lldb/tools/debugserver/source/MacOSX/MachProcess.mm

@@ -2821,16 +2821,21 @@ static uint64_t bits(uint64_t value, uint32_t msbit, uint32_t lsbit) {
           "attach to pid %d",
           getpid(), pid);
 
-      struct kinfo_proc kinfo;
-      int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
-      size_t len = sizeof(struct kinfo_proc);
-      if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), &kinfo, &len, NULL, 0) == 0 && len > 0) {
-        if (kinfo.kp_proc.p_flag & P_TRACED) {
-          ::snprintf(err_str, err_len, "%s - process %d is already being debugged", err.AsString(), pid);
+      if (ProcessIsBeingDebugged(pid)) {
+        nub_process_t ppid = GetParentProcessID(pid);
+        if (ppid == getpid()) {
+          snprintf(err_str, err_len,
+                   "%s - Failed to attach to pid %d, AttachForDebug() "
+                   "unable to ptrace(PT_ATTACHEXC)",
+                   err.AsString(), m_pid);
+        } else {
+          snprintf(err_str, err_len,
+                   "%s - process %d is already being debugged by pid %d",
+                   err.AsString(), pid, ppid);
           DNBLogError(
               "[LaunchAttach] (%d) MachProcess::AttachForDebug pid %d is "
-              "already being debugged",
-              getpid(), pid);
+              "already being debugged by pid %d",
+              getpid(), pid, ppid);
         }
       }
     }
@@ -2879,6 +2884,26 @@ static uint64_t bits(uint64_t value, uint32_t msbit, uint32_t lsbit) {
   return {};
 }
 
+nub_process_t MachProcess::GetParentProcessID(nub_process_t child_pid) {
+  struct proc_bsdshortinfo proc;
+  if (proc_pidinfo(child_pid, PROC_PIDT_SHORTBSDINFO, 0, &proc,
+                   PROC_PIDT_SHORTBSDINFO_SIZE) == sizeof(proc)) {
+    return proc.pbsi_ppid;
+  }
+  return INVALID_NUB_PROCESS;
+}
+
+bool MachProcess::ProcessIsBeingDebugged(nub_process_t pid) {
+  struct kinfo_proc kinfo;
+  int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
+  size_t len = sizeof(struct kinfo_proc);
+  if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), &kinfo, &len, NULL, 0) == 0 &&
+      (kinfo.kp_proc.p_flag & P_TRACED))
+    return true;
+  else
+    return false;
+}
+
 #if defined(WITH_SPRINGBOARD) || defined(WITH_BKS) || defined(WITH_FBS)
 /// Get the app bundle from the given path. Returns the empty string if the
 /// path doesn't appear to be an app bundle.
@@ -3401,7 +3426,13 @@ static uint64_t bits(uint64_t value, uint32_t msbit, uint32_t lsbit) {
                                       "%d (err = %i, errno = %i (%s))",
                          m_pid, err, ptrace_err.Status(),
                          ptrace_err.AsString());
-        launch_err.SetError(NUB_GENERIC_ERROR, DNBError::Generic);
+        char err_msg[PATH_MAX];
+
+        snprintf(err_msg, sizeof(err_msg),
+                 "Failed to attach to pid %d, LaunchForDebug() unable to "
+                 "ptrace(PT_ATTACHEXC)",
+                 m_pid);
+        launch_err.SetErrorString(err_msg);
       }
     } else {
       launch_err.Clear();
@@ -3777,6 +3808,10 @@ static CFStringRef CopyBundleIDForPath(const char *app_bundle_path,
       m_flags |= eMachProcessFlagsAttached;
       DNBLogThreadedIf(LOG_PROCESS, "successfully attached to pid %d", m_pid);
     } else {
+      launch_err.SetErrorString(
+          "Failed to attach to pid %d, SBLaunchForDebug() unable to "
+          "ptrace(PT_ATTACHEXC)",
+          m_pid);
       SetState(eStateExited);
       DNBLogThreadedIf(LOG_PROCESS, "error: failed to attach to pid %d", m_pid);
     }
@@ -3996,6 +4031,10 @@ static CFStringRef CopyBundleIDForPath(const char *app_bundle_path,
       m_flags |= eMachProcessFlagsAttached;
       DNBLog("[LaunchAttach] successfully attached to pid %d", m_pid);
     } else {
+      launch_err.SetErrorString(
+          "Failed to attach to pid %d, BoardServiceLaunchForDebug() unable to "
+          "ptrace(PT_ATTACHEXC)",
+          m_pid);
       SetState(eStateExited);
       DNBLog("[LaunchAttach] END (%d) error: failed to attach to pid %d",
              getpid(), m_pid);

lldb/tools/debugserver/source/RNBRemote.cpp

@@ -3630,14 +3630,8 @@ static bool attach_failed_due_to_uid_mismatch (nub_process_t pid,
 // processes and step through to find the one we're looking for
 // (as process_does_not_exist() does).
 static bool process_is_already_being_debugged (nub_process_t pid) {
-  struct kinfo_proc kinfo;
-  int mib[] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, pid};
-  size_t len = sizeof(struct kinfo_proc);
-  if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), &kinfo, &len, NULL, 0) != 0) {
-    return false; // pid doesn't exist? well, it's not being debugged...
-  }
-  if (kinfo.kp_proc.p_flag & P_TRACED)
-    return true; // is being debugged already
+  if (DNBProcessIsBeingDebugged(pid) && DNBGetParentProcessID(pid) != getpid())
+    return true;
   else
     return false;
 }