7062856: Disassembler needs to be smarter about finding hsdis after 1.7 launcher changes

Do explicit lookup emulating old LD_LIBRARY_PATH search

Reviewed-by: kvn, jrose

hotspot/src/share/tools/hsdis/README

@@ -75,8 +75,16 @@ will build the Win32 cross compiled version of hsdis based on 2.19.1.
 * Installing
 
 Products are named like build/$OS-$LIBARCH/hsdis-$LIBARCH.so.  You can
-install them on your LD_LIBRARY_PATH, or inside of your JRE next to
+install them on your LD_LIBRARY_PATH, or inside of your JRE/JDK.  The
-$LIBARCH/libjvm.so.
+search path in the JVM is:
+
+1. <home>/jre/lib/<arch>/<vm>/libhsdis-<arch>.so
+2. <home>/jre/lib/<arch>/<vm>/hsdis-<arch>.so
+3. <home>/jre/lib/<arch>/hsdis-<arch>.so
+4. hsdis-<arch>.so  (using LD_LIBRARY_PATH)
+
+Note that there's a bug in hotspot versions prior to hs22 that causes
+steps 2 and 3 to fail when used with JDK7.
 
 Now test:
 

hotspot/src/share/vm/compiler/disassembler.cpp

@@ -78,21 +78,46 @@ bool Disassembler::load_library() {
   char buf[JVM_MAXPATHLEN];
   os::jvm_path(buf, sizeof(buf));
   int jvm_offset = -1;
+  int lib_offset = -1;
   {
     // Match "jvm[^/]*" in jvm_path.
     const char* base = buf;
     const char* p = strrchr(buf, '/');
+    if (p != NULL) lib_offset = p - base + 1;
     p = strstr(p ? p : base, "jvm");
     if (p != NULL)  jvm_offset = p - base;
   }
+  // Find the disassembler shared library.
+  // Search for several paths derived from libjvm, in this order:
+  // 1. <home>/jre/lib/<arch>/<vm>/libhsdis-<arch>.so  (for compatibility)
+  // 2. <home>/jre/lib/<arch>/<vm>/hsdis-<arch>.so
+  // 3. <home>/jre/lib/<arch>/hsdis-<arch>.so
+  // 4. hsdis-<arch>.so  (using LD_LIBRARY_PATH)
   if (jvm_offset >= 0) {
-    // Find the disassembler next to libjvm.so.
+    // 1. <home>/jre/lib/<arch>/<vm>/libhsdis-<arch>.so
     strcpy(&buf[jvm_offset], hsdis_library_name);
     strcat(&buf[jvm_offset], os::dll_file_extension());
     _library = os::dll_load(buf, ebuf, sizeof ebuf);
+    if (_library == NULL) {
+      // 2. <home>/jre/lib/<arch>/<vm>/hsdis-<arch>.so
+      strcpy(&buf[lib_offset], hsdis_library_name);
+      strcat(&buf[lib_offset], os::dll_file_extension());
+      _library = os::dll_load(buf, ebuf, sizeof ebuf);
     }
     if (_library == NULL) {
-    // Try a free-floating lookup.
+      // 3. <home>/jre/lib/<arch>/hsdis-<arch>.so
+      buf[lib_offset - 1] = '\0';
+      const char* p = strrchr(buf, '/');
+      if (p != NULL) {
+        lib_offset = p - buf + 1;
+        strcpy(&buf[lib_offset], hsdis_library_name);
+        strcat(&buf[lib_offset], os::dll_file_extension());
+        _library = os::dll_load(buf, ebuf, sizeof ebuf);
+      }
+    }
+  }
+  if (_library == NULL) {
+    // 4. hsdis-<arch>.so  (using LD_LIBRARY_PATH)
     strcpy(&buf[0], hsdis_library_name);
     strcat(&buf[0], os::dll_file_extension());
     _library = os::dll_load(buf, ebuf, sizeof ebuf);
@@ -249,7 +274,13 @@ address decode_env::handle_event(const char* event, address arg) {
       return arg;
     }
   } else if (match(event, "mach")) {
+    static char buffer[32] = { 0, };
+    if (strcmp(buffer, (const char*)arg) != 0 ||
+        strlen((const char*)arg) > sizeof(buffer) - 1) {
+      // Only print this when the mach changes
+      strncpy(buffer, (const char*)arg, sizeof(buffer) - 1);
       output()->print_cr("[Disassembling for mach='%s']", arg);
+    }
   } else if (match(event, "format bytes-per-line")) {
     _bytes_per_line = (int) (intptr_t) arg;
   } else {