diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index 112686ca652..1183344f4f1 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -1492,6 +1492,11 @@ namespace dmd {
 static bool
 ReportAndDump(JSContext *cx, unsigned argc, JS::Value *vp)
 {
+  if (!dmd::IsRunning()) {
+    JS_ReportError(cx, "DMD is not running");
+    return false;
+  }
+
   JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
   JSString *str = JS::ToString(cx, args.get(0));
   if (!str)
@@ -1508,7 +1513,6 @@ ReportAndDump(JSContext *cx, unsigned argc, JS::Value *vp)
   }
 
   dmd::ClearReports();
-  fprintf(stderr, "DMD: running reporters...\n");
   dmd::RunReportersForThisProcess();
   dmd::Writer writer(FpWrite, fp);
   dmd::Dump(writer);
diff --git a/memory/replace/dmd/DMD.cpp b/memory/replace/dmd/DMD.cpp
index ff5877e407c..7310f528a72 100644
--- a/memory/replace/dmd/DMD.cpp
+++ b/memory/replace/dmd/DMD.cpp
@@ -6,6 +6,7 @@
 
 #include "DMD.h"
 
+#include <alloca.h>
 #include <ctype.h>
 #include <errno.h>
 #include <limits.h>
@@ -178,10 +179,9 @@ StatusMsg(const char* aFmt, ...)
   __android_log_vprint(ANDROID_LOG_INFO, "DMD", aFmt, ap);
 #else
   // The +64 is easily enough for the "DMD[<pid>] " prefix and the NUL.
-  char* fmt = (char*) InfallibleAllocPolicy::malloc_(strlen(aFmt) + 64);
+  char* fmt = (char*) alloca(strlen(aFmt) + 64);
   sprintf(fmt, "DMD[%d] %s", getpid(), aFmt);
   vfprintf(stderr, fmt, ap);
-  InfallibleAllocPolicy::free_(fmt);
 #endif
   va_end(ap);
 }
@@ -1935,7 +1935,7 @@ ClearReports()
 }
 
 MOZ_EXPORT bool
-IsEnabled()
+IsRunning()
 {
   return gIsDMDRunning;
 }
diff --git a/memory/replace/dmd/DMD.h b/memory/replace/dmd/DMD.h
index 1628eb2d741..40c3e61c755 100644
--- a/memory/replace/dmd/DMD.h
+++ b/memory/replace/dmd/DMD.h
@@ -78,9 +78,9 @@ struct Sizes
 MOZ_EXPORT void
 SizeOf(Sizes* aSizes);
 
-// Indicates whether or not DMD is enabled.
+// Indicates whether or not DMD is running.
 MOZ_EXPORT bool
-IsEnabled();
+IsRunning();
 
 } // namespace mozilla
 } // namespace dmd
diff --git a/toolkit/components/aboutmemory/content/aboutMemory.js b/toolkit/components/aboutmemory/content/aboutMemory.js
index f1f55abb814..38258b3e0f8 100644
--- a/toolkit/components/aboutmemory/content/aboutMemory.js
+++ b/toolkit/components/aboutmemory/content/aboutMemory.js
@@ -295,8 +295,9 @@ function onLoad()
                             "WARNING: These logs may be large (>1GB).";
 
   const DMDEnabledDesc = "Run DMD analysis and save it to '" + DMDFile + "'.\n";
-  const DMDDisabledDesc = "DMD is not enabled. Please re-run with $DMD set " +
-                          "appropriately\n";
+  const DMDDisabledDesc = "DMD is not running. Please re-start with $DMD and " +
+                          "the other relevant environment variables set " +
+                          "appropriately.";
 
   let ops = appendElement(header, "div", "");
 
@@ -341,22 +342,19 @@ function onLoad()
   appendButton(row4, GCAndCCAllLogDesc,
                saveGCLogAndVerboseCCLog, "Save verbose", 'saveLogsVerbose');
 
-  // This only succeeds in --enable-dmd builds.
-  if (typeof DMDReportAndDump == 'function') {
-    let env = Components.classes["@mozilla.org/process/environment;1"]
-                        .getService(Components.interfaces.nsIEnvironment);
-
-    // Gray the button out if DMD isn't enabled at start-up.
-    let dmd = env.get('DMD');
-    let disabled = dmd === '' || dmd === '0';
-
+  // Three cases here:
+  // - DMD is disabled (i.e. not built): don't show the button.
+  // - DMD is enabled but is not running: show the button, but disable it.
+  // - DMD is enabled and is running: show the button and enable it.
+  if (gMgr.isDMDEnabled) {
     let row5 = appendElement(ops, "div", "opsRow");
 
     appendElementWithText(row5, "div", "opsRowLabel", "Save DMD output");
+    let enableButton = gMgr.isDMDRunning;
     let dmdButton =
-      appendButton(row5, disabled ? DMDDisabledDesc : DMDEnabledDesc, doDMD,
-                   "Save", "dmdButton");
-    dmdButton.disabled = disabled;
+      appendButton(row5, enableButton ? DMDEnabledDesc : DMDDisabledDesc,
+                   doDMD, "Save", "dmdButton");
+    dmdButton.disabled = !enableButton;
   }
 
   // Generate the main div, where content ("section" divs) will go.  It's
@@ -440,8 +438,12 @@ function saveGCLogAndVerboseCCLog()
 function doDMD()
 {
   updateMainAndFooter('Saving DMD output...', HIDE_FOOTER);
-  DMDReportAndDump('out.dmd');
-  updateMainAndFooter('Saved DMD output to ' + DMDFile, HIDE_FOOTER);
+  try {
+    let x = DMDReportAndDump('out.dmd');
+    updateMainAndFooter('Saved DMD output to ' + DMDFile, HIDE_FOOTER);
+  } catch (ex) {
+    updateMainAndFooter(ex.toString(), HIDE_FOOTER);
+  }
 }
 
 function dumpGCLogAndCCLog(aVerbose)
diff --git a/xpcom/base/nsIMemoryReporter.idl b/xpcom/base/nsIMemoryReporter.idl
index 5d98be5ed47..6709c044906 100644
--- a/xpcom/base/nsIMemoryReporter.idl
+++ b/xpcom/base/nsIMemoryReporter.idl
@@ -178,7 +178,7 @@ interface nsIFinishReportingCallback : nsISupports
   void callback(in nsISupports data);
 };
 
-[scriptable, builtinclass, uuid(b6e5ec8a-71d9-48db-8ae9-68b4c5bbf2c3)]
+[scriptable, builtinclass, uuid(c27f8662-a0b7-45b3-8207-14d66b02b9c5)]
 interface nsIMemoryReporterManager : nsISupports
 {
   /*
@@ -371,6 +371,13 @@ interface nsIMemoryReporterManager : nsISupports
    */
   [infallible] readonly attribute boolean hasMozMallocUsableSize;
 
+  /*
+   * These attributes indicate DMD's status. "Enabled" means enabled at
+   * build-time.
+   */
+  [infallible] readonly attribute boolean isDMDEnabled;
+  [infallible] readonly attribute boolean isDMDRunning;
+
   /*
    * Run a series of GC/CC's in an attempt to minimize the application's memory
    * usage.  When we're finished, we invoke the given runnable if it's not
diff --git a/xpcom/base/nsMemoryInfoDumper.cpp b/xpcom/base/nsMemoryInfoDumper.cpp
index 79c8e40220f..f7e32036709 100644
--- a/xpcom/base/nsMemoryInfoDumper.cpp
+++ b/xpcom/base/nsMemoryInfoDumper.cpp
@@ -667,7 +667,7 @@ nsMemoryInfoDumper::DumpMemoryInfoToTempDir(const nsAString& aIdentifier,
 nsresult
 nsMemoryInfoDumper::DumpDMD(const nsAString& aIdentifier)
 {
-  if (!dmd::IsEnabled()) {
+  if (!dmd::IsRunning()) {
     return NS_OK;
   }
 
diff --git a/xpcom/base/nsMemoryReporterManager.cpp b/xpcom/base/nsMemoryReporterManager.cpp
index f12b350b656..22b10b3f70c 100644
--- a/xpcom/base/nsMemoryReporterManager.cpp
+++ b/xpcom/base/nsMemoryReporterManager.cpp
@@ -1644,6 +1644,28 @@ nsMemoryReporterManager::GetHasMozMallocUsableSize(bool* aHas)
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsMemoryReporterManager::GetIsDMDEnabled(bool* aIsEnabled)
+{
+#ifdef MOZ_DMD
+  *aIsEnabled = true;
+#else
+  *aIsEnabled = false;
+#endif
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMemoryReporterManager::GetIsDMDRunning(bool* aIsRunning)
+{
+#ifdef MOZ_DMD
+  *aIsRunning = dmd::IsRunning();
+#else
+  *aIsRunning = false;
+#endif
+  return NS_OK;
+}
+
 namespace {
 
 /**