8366154: Validate thread type requirements in debug commands

src/hotspot/share/utilities/debug.cpp

@@ -296,20 +296,49 @@ void report_java_out_of_memory(const char* message) {
 
 class Command : public StackObj {
  private:
-  ResourceMark _rm;
+  static int level;
   DebuggingContext _debugging;
+  bool _has_rm;
+  // ResourceMark is only created if a Thread or a JavaThread is required,
+  // and we are actually on a Thread.
+  union { ResourceMark _rm; };
  public:
-  static int level;
-  Command(const char* str) {
-    if (level++ > 0)  return;
-    tty->cr();
-    tty->print_cr("\"Executing %s\"", str);
+  Command(const char* str) : _has_rm(false) {
+    if (level++ == 0) {
+      tty->cr();
+      tty->print_cr("\"Executing %s\"", str);
+    }
+    tty->flush();
   }
-
   ~Command() {
+    if (_has_rm) _rm.~ResourceMark();
     tty->flush();
     level--;
   }
+
+  bool onThread() {
+    Thread* thread = Thread::current_or_null();
+    if (thread == nullptr) {
+      tty->print_cr("Failed: Current thread is not attached");
+      return false;
+    }
+
+    if (!_has_rm) {
+      ::new (&_rm) ResourceMark();
+      _has_rm = true;
+    }
+    return true;
+  }
+
+  bool onJavaThread() {
+    if (!onThread()) return false;
+
+    if (JavaThread::active() == nullptr) {
+      tty->print_cr("Failed: Current thread is not a java thread or the vm thread");
+      return  false;
+    }
+    return true;
+  }
 };
 
 int Command::level = 0;
@@ -370,6 +399,7 @@ extern "C" DEBUGEXPORT void printnm(intptr_t p) {
 
 extern "C" DEBUGEXPORT void universe() {
   Command c("universe");
+  if (!c.onThread()) return;
   Universe::print_on(tty);
 }
 
@@ -379,6 +409,7 @@ extern "C" DEBUGEXPORT void verify() {
   // note: this may not be safe if we're not at a safepoint; for debugging,
   // this manipulates the safepoint settings to avoid assertion failures
   Command c("universe verify");
+  if (!c.onThread()) return;
   bool safe = SafepointSynchronize::is_at_safepoint();
   if (!safe) {
     tty->print_cr("warning: not at safepoint -- verify may fail");
@@ -393,6 +424,7 @@ extern "C" DEBUGEXPORT void verify() {
 
 extern "C" DEBUGEXPORT void pp(void* p) {
   Command c("pp");
+  if (!c.onThread()) return;
   FlagSetting fl(DisplayVMOutput, true);
   if (p == nullptr) {
     tty->print_cr("null");
@@ -419,8 +451,8 @@ extern "C" DEBUGEXPORT void pp(void* p) {
 extern "C" DEBUGEXPORT void findpc(intptr_t x);
 
 extern "C" DEBUGEXPORT void ps() { // print stack
-  if (Thread::current_or_null() == nullptr) return;
   Command c("ps");
+  if (!c.onJavaThread()) return;
 
   // Prints the stack of the current Java thread
   JavaThread* p = JavaThread::active();
@@ -450,6 +482,7 @@ extern "C" DEBUGEXPORT void ps() { // print stack
 extern "C" DEBUGEXPORT void pfl() {
   // print frame layout
   Command c("pfl");
+  if (!c.onJavaThread()) return;
   JavaThread* p = JavaThread::active();
   tty->print(" for thread: ");
   p->print();
@@ -460,34 +493,36 @@ extern "C" DEBUGEXPORT void pfl() {
 }
 
 extern "C" DEBUGEXPORT void psf() { // print stack frames
-  {
-    Command c("psf");
-    JavaThread* p = JavaThread::active();
-    tty->print(" for thread: ");
-    p->print();
-    tty->cr();
-    if (p->has_last_Java_frame()) {
-      p->trace_frames();
-    }
+  Command c("psf");
+  if (!c.onJavaThread()) return;
+  JavaThread* p = JavaThread::active();
+  tty->print(" for thread: ");
+  p->print();
+  tty->cr();
+  if (p->has_last_Java_frame()) {
+    p->trace_frames();
   }
 }
 
 
 extern "C" DEBUGEXPORT void threads() {
   Command c("threads");
+  if (!c.onThread()) return;
   Threads::print(false, true);
 }
 
 
 extern "C" DEBUGEXPORT void psd() {
   Command c("psd");
+  if (!c.onThread()) return;
+
   SystemDictionary::print();
 }
 
 
 extern "C" DEBUGEXPORT void pss() { // print all stacks
-  if (Thread::current_or_null() == nullptr) return;
   Command c("pss");
+  if (!c.onThread()) return;
   Threads::print(true, PRODUCT_ONLY(false) NOT_PRODUCT(true));
 }
 
@@ -534,12 +569,14 @@ extern "C" DEBUGEXPORT nmethod* findnm(intptr_t addr) {
 
 extern "C" DEBUGEXPORT void find(intptr_t x) {
   Command c("find");
+  if (!c.onThread()) return;
   os::print_location(tty, x, false);
 }
 
 
 extern "C" DEBUGEXPORT void findpc(intptr_t x) {
   Command c("findpc");
+  if (!c.onThread()) return;
   os::print_location(tty, x, true);
 }
 
@@ -551,13 +588,15 @@ extern "C" DEBUGEXPORT void findpc(intptr_t x) {
 //   call findmethod("*ang/Object*", "wait:(*J*)V", 0x1) -> list all "wait" methods in j.l.Object that have a long parameter
 extern "C" DEBUGEXPORT void findclass(const char* class_name_pattern, int flags) {
   Command c("findclass");
+  if (!c.onThread()) return;
   ClassPrinter::print_flags_help(tty);
   ClassPrinter::print_classes(class_name_pattern, flags, tty);
 }
 
 extern "C" DEBUGEXPORT void findmethod(const char* class_name_pattern,
                                      const char* method_pattern, int flags) {
   Command c("findmethod");
+  if (!c.onThread()) return;
   ClassPrinter::print_flags_help(tty);
   ClassPrinter::print_methods(class_name_pattern, method_pattern, flags, tty);
 }
@@ -644,6 +683,7 @@ void help() {
 #ifndef PRODUCT
 extern "C" DEBUGEXPORT void pns(void* sp, void* fp, void* pc) { // print native stack
   Command c("pns");
+  if (!c.onThread()) return;
   static char buf[O_BUFLEN];
   // Call generic frame constructor (certain arguments may be ignored)
   frame fr(sp, fp, pc);
@@ -662,6 +702,7 @@ extern "C" DEBUGEXPORT void pns(void* sp, void* fp, void* pc) { // print native
 //
 extern "C" DEBUGEXPORT void pns2() { // print native stack
   Command c("pns2");
+  if (!c.onThread()) return;
   static char buf[O_BUFLEN];
   address lastpc = nullptr;
   NativeStackPrinter nsp(Thread::current_or_null());