Bug 1567390 - Add a stackwalking test to the profiler; r=canaltinova

Differential Revision: https://phabricator.services.mozilla.com/D40308

--HG--
extra : moz-landing-system : lando

tools/profiler/tests/xpcshell/head_profiler.js

@@ -48,6 +48,14 @@ function wait(time) {
   });
 }
 
+/**
+ * This function takes a thread, and a sample tuple from the "data" array, and inflates
+ * the frame to be an array of strings.
+ *
+ * @param {Object} thread - The thread from the profile.
+ * @param {Array} sample - The tuple from the thread.samples.data array.
+ * @returns {Array<string>} An array of function names.
+ */
 function getInflatedStackLocations(thread, sample) {
   let stackTable = thread.stackTable;
   let frameTable = thread.frameTable;
@@ -71,3 +79,85 @@ function getInflatedStackLocations(thread, sample) {
   // The profiler tree is inverted, so reverse the array.
   return locations.reverse();
 }
+
+/**
+ * It can be helpful to deterministically do at least one more profile sample. Sampling
+ * is done based on a timer. This function spins on a while loop until at least one more
+ * sample is collected.
+ *
+ * @return {number} The index of the collected sample.
+ */
+async function doAtLeastOnePeriodicSample() {
+  async function getProfileSampleCount() {
+    const profile = await Services.profiler.getProfileDataAsync();
+    return profile.threads[0].samples.data.length;
+  }
+
+  const sampleCount = await getProfileSampleCount();
+  // Create an infinite loop until a sample has been collected.
+  while (true) {
+    if (sampleCount < (await getProfileSampleCount())) {
+      return sampleCount;
+    }
+  }
+}
+
+/**
+ * This utility matches up stacks to see if they contain a certain sequence of stack
+ * frames. A correctly functioning profiler will have a certain sequence of stacks,
+ * but we can't always determine exactly which stacks will show up due to implementation
+ * changes, as well as memory addresses being arbitrary to that particular build.
+ *
+ * This function triggers a test failure with a nice debug message when it fails.
+ *
+ * @param {Array<string>} actualStackFrames - As generated by inflatedStackFrames.
+ * @param {Array<string | RegExp>} expectedStackFrames - Matches a subset of actualStackFrames
+ */
+function expectStackToContain(
+  actualStackFrames,
+  expectedStackFrames,
+  message = "The actual stack and expected stack do not match."
+) {
+  // Log the stacks that are being passed to this assertion, as it could be useful
+  // for when these tests fail.
+  console.log("Actual stack: ", actualStackFrames);
+  console.log(
+    "Expected to contain: ",
+    expectedStackFrames.map(s => s.toString())
+  );
+
+  let actualIndex = 0;
+
+  // Start walking the expected stack and look for matches.
+  for (
+    let expectedIndex = 0;
+    expectedIndex < expectedStackFrames.length;
+    expectedIndex++
+  ) {
+    const expectedStackFrame = expectedStackFrames[expectedIndex];
+
+    while (true) {
+      // Make sure that we haven't run out of actual stack frames.
+      if (actualIndex >= actualStackFrames.length) {
+        info(`Could not find a match for: "${expectedStackFrame.toString()}"`);
+        Assert.ok(false, message);
+      }
+
+      const actualStackFrame = actualStackFrames[actualIndex];
+      actualIndex++;
+
+      const itMatches =
+        typeof expectedStackFrame === "string"
+          ? expectedStackFrame === actualStackFrame
+          : actualStackFrame.match(expectedStackFrame);
+
+      if (itMatches) {
+        // We found a match, break out of this loop.
+        break;
+      }
+      // Keep on looping looking for a match.
+    }
+  }
+
+  Assert.ok(true, message);
+}

tools/profiler/tests/xpcshell/test_feature_stackwalking.js

@@ -0,0 +1,51 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Do a basic test to see if native frames are being collected for stackwalking. This
+ * test is fairly naive, as it does not attempt to check that these are valid symbols,
+ * only that some kind of stack walking is happening. It does this by making sure at
+ * least two native frames are collected.
+ */
+add_task(async () => {
+  if (!AppConstants.MOZ_GECKO_PROFILER) {
+    return;
+  }
+  const entries = 10000;
+  const interval = 1;
+  const threads = [];
+  const features = ["stackwalk"];
+
+  Services.profiler.StartProfiler(entries, interval, features, threads);
+  const sampleIndex = await doAtLeastOnePeriodicSample();
+
+  const profile = await Services.profiler.getProfileDataAsync();
+  const [thread] = profile.threads;
+  const { samples } = thread;
+
+  const inflatedStackFrames = getInflatedStackLocations(
+    thread,
+    samples.data[sampleIndex]
+  );
+  const nativeStack = /^0x[0-9a-f]+$/;
+
+  expectStackToContain(
+    inflatedStackFrames,
+    [
+      "(root)",
+      // There are probably more native stacks here.
+      nativeStack,
+      nativeStack,
+      // Since this is an xpcshell test we know that JavaScript will run:
+      "js::RunScript",
+      // There are probably more native stacks here.
+      nativeStack,
+      nativeStack,
+    ],
+    "Expected native stacks to be interleaved between some frame labels. There should" +
+      "be more than one native stack if stack walking is working correctly. There " +
+      "is no attempt here to determine if the memory addresses point to the correct " +
+      "symbols"
+  );
+});

tools/profiler/tests/xpcshell/xpcshell.ini

@@ -18,3 +18,4 @@ skip-if = !debug
 [test_asm.js]
 [test_feature_mainthreadio.js]
 skip-if = release_or_beta || (os == "win" && processor == "aarch64") # The IOInterposer is in an ifdef, aarch64 due to 1536657
+[test_feature_stackwalking.js]