8279797: JFR: Show .jfc options in JFR.start help

Reviewed-by: mgronlun

src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java

@@ -42,10 +42,14 @@
 import jdk.jfr.FlightRecorder;
 import jdk.jfr.Recording;
 import jdk.jfr.internal.JVM;
+import jdk.jfr.internal.LogLevel;
+import jdk.jfr.internal.LogTag;
+import jdk.jfr.internal.Logger;
 import jdk.jfr.internal.OldObjectSample;
 import jdk.jfr.internal.PlatformRecording;
 import jdk.jfr.internal.PrivateAccess;
 import jdk.jfr.internal.SecuritySupport.SafePath;
+import jdk.jfr.internal.SecuritySupport;
 import jdk.jfr.internal.Type;
 import jdk.jfr.internal.jfc.JFC;
 import jdk.jfr.internal.jfc.model.JFCModel;
@@ -364,7 +368,7 @@ Virtual Machine (JVM) shuts down. If set to 'true' and no value
                                  Turn on this flag only when you have an application that you
                                  suspect has a memory leak. If the settings parameter is set to
                                  'profile', then the information collected includes the stack
-                                 trace from where the potential leaking object wasallocated.
+                                 trace from where the potential leaking object was allocated.
                                  (BOOLEAN, false)
 
                  settings        (Optional) Name of the settings file that identifies which events
@@ -394,7 +398,7 @@ Virtual Machine (JVM) shuts down. If set to 'true' and no value
                take  precedence. The whitespace character can be omitted for timespan values,
                i.e. 20s. For more information about the settings syntax, see Javadoc of the
                jdk.jfr package.
-
+               %s
                Options must be specified using the <key> or <key>=<value> syntax.
 
                Example usage:
@@ -414,7 +418,28 @@ Virtual Machine (JVM) shuts down. If set to 'true' and no value
 
                Note, if the default event settings are modified, overhead may exceed 1%%.
 
-               """.formatted(exampleDirectory()).lines().toArray(String[]::new);
+               """.formatted(jfcOptions(), exampleDirectory()).lines().toArray(String[]::new);
+    }
+
+    private static String jfcOptions() {
+        try {
+            StringBuilder sb = new StringBuilder();
+            for (SafePath s : SecuritySupport.getPredefinedJFCFiles()) {
+                String name = JFC.nameFromPath(s.toPath());
+                JFCModel model = JFCModel.create(s, l -> {});
+                sb.append('\n');
+                sb.append("Options for ").append(name).append(":\n");
+                sb.append('\n');
+                for (XmlInput input : model.getInputs()) {
+                    sb.append("  ").append(input.getOptionSyntax()).append('\n');
+                    sb.append('\n');
+                }
+            }
+            return sb.toString();
+        } catch (IOException | ParseException e) {
+            Logger.log(LogTag.JFR_DCMD, LogLevel.DEBUG, "Could not list .jfc options for JFR.start. " + e.getMessage());
+            return "";
+        }
     }
 
     @Override