8288003: log events for os::dll_unload

Reviewed-by: dholmes, stuefe

Author: MBaesken

src/hotspot/os/linux/os_linux.cpp

@@ -1786,6 +1786,18 @@ void * os::Linux::dll_load_in_vmthread(const char *filename, char *ebuf,
   return result;
 }
 
+const char* os::Linux::dll_path(void* lib) {
+  struct link_map *lmap;
+  const char* l_path = NULL;
+  assert(lib != NULL, "dll_path parameter must not be NULL");
+
+  int res_dli = ::dlinfo(lib, RTLD_DI_LINKMAP, &lmap);
+  if (res_dli == 0) {
+    l_path = lmap->l_name;
+  }
+  return l_path;
+}
+
 static bool _print_ascii_file(const char* filename, outputStream* st, const char* hdr = NULL) {
   int fd = ::open(filename, O_RDONLY);
   if (fd == -1) {

src/hotspot/os/linux/os_linux.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2022, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -120,6 +120,7 @@ class Linux {
   static bool _stack_is_executable;
   static void *dlopen_helper(const char *name, char *ebuf, int ebuflen);
   static void *dll_load_in_vmthread(const char *name, char *ebuf, int ebuflen);
+  static const char *dll_path(void* lib);
 
   static void init_thread_fpu_state();
   static int  get_fpu_control_word();

src/hotspot/os/posix/os_posix.cpp

@@ -706,7 +706,26 @@ void* os::dll_lookup(void* handle, const char* name) {
 }
 
 void os::dll_unload(void *lib) {
-  ::dlclose(lib);
+  const char* l_path = LINUX_ONLY(os::Linux::dll_path(lib))
+                       NOT_LINUX("<not available>");
+  if (l_path == NULL) l_path = "<not available>";
+  int res = ::dlclose(lib);
+
+  if (res == 0) {
+    Events::log_dll_message(NULL, "Unloaded shared library \"%s\" [" INTPTR_FORMAT "]",
+                            l_path, p2i(lib));
+    log_info(os)("Unloaded shared library \"%s\" [" INTPTR_FORMAT "]", l_path, p2i(lib));
+  } else {
+    const char* error_report = ::dlerror();
+    if (error_report == NULL) {
+      error_report = "dlerror returned no error description";
+    }
+
+    Events::log_dll_message(NULL, "Attempt to unload shared library \"%s\" [" INTPTR_FORMAT "] failed, %s",
+                            l_path, p2i(lib), error_report);
+    log_info(os)("Attempt to unload shared library \"%s\" [" INTPTR_FORMAT "] failed, %s",
+                  l_path, p2i(lib), error_report);
+  }
 }
 
 jlong os::lseek(int fd, jlong offset, int whence) {

src/hotspot/os/windows/os_windows.cpp

@@ -1236,7 +1236,18 @@ void os::die() {
 const char* os::dll_file_extension() { return ".dll"; }
 
 void  os::dll_unload(void *lib) {
-  ::FreeLibrary((HMODULE)lib);
+  char name[MAX_PATH];
+  if (::GetModuleFileName((HMODULE)lib, name, sizeof(name)) == 0) {
+    snprintf(name, MAX_PATH, "<not available>");
+  }
+  if (::FreeLibrary((HMODULE)lib)) {
+    Events::log_dll_message(NULL, "Unloaded dll \"%s\" [" INTPTR_FORMAT "]", name, p2i(lib));
+    log_info(os)("Unloaded dll \"%s\" [" INTPTR_FORMAT "]", name, p2i(lib));
+  } else {
+    const DWORD errcode = ::GetLastError();
+    Events::log_dll_message(NULL, "Attempt to unload dll \"%s\" [" INTPTR_FORMAT "] failed (error code %d)", name, p2i(lib), errcode);
+    log_info(os)("Attempt to unload dll \"%s\" [" INTPTR_FORMAT "] failed (error code %d)", name, p2i(lib), errcode);
+  }
 }
 
 void* os::dll_lookup(void *lib, const char *name) {