Add SeccompSupportDetector for Android.

chrome/browser/android/seccomp_support_detector.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/android/seccomp_support_detector.h"
+
+#include <stdio.h>
+#include <sys/utsname.h>
+
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/metrics/histogram_macros.h"
+#include "chrome/common/chrome_utility_messages.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/utility_process_host.h"
+
+using content::BrowserThread;
+
+enum AndroidSeccompStatus {
+  DETECTION_FAILED,  // The process crashed during detection.
+  NOT_SUPPORTED,     // Kernel has no seccomp support.
+  SUPPORTED,         // Kernel has seccomp support.
+  LAST_STATUS
+};
+
+// static
+void SeccompSupportDetector::StartDetection() {
+  // This is instantiated here, and then ownership is maintained by the
+  // Closure objects when the object is being passed between threads. A
+  // reference is also taken by the UtilityProcessHost, which will release
+  // it when the process exits.
+  scoped_refptr<SeccompSupportDetector> detector(new SeccompSupportDetector());
+  BrowserThread::PostTask(BrowserThread::FILE, FROM_HERE,

[Lei Zhang, 2015/03/19 00:42:23]

BrowserThread::PostBlockingPoolTask

[Robert Sesek, 2015/03/19 14:57:29]

Done.

+      base::Bind(&SeccompSupportDetector::DetectKernelVersion, detector));
+}
+
+SeccompSupportDetector::SeccompSupportDetector() : prctl_detected_(false) {
+}
+
+SeccompSupportDetector::~SeccompSupportDetector() {
+}
+
+void SeccompSupportDetector::DetectKernelVersion() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+
+  // This method will report the kernel major and minor versions by
+  // taking the lower 16 bits of each version number and combining
+  // the two into a 32-bit number.
+
+  // Support known Android kernel versions, and leave room up to 4.10.
+  const int kVersionRanges[] = {
+    0x00020006,
+    0x00030000,
+    0x00030003,
+    0x00030004,
+    0x00030008,
+    0x00030010,
+    0x00030014,
+    0x00030017,
+    0x00030018,
+    0x00030019,
+    0x00040000,
+    0x00040001,
+    0x00040010,
+  };
+
+  utsname uts;
+  if (uname(&uts) == 0) {
+    int major, minor;
+    if (sscanf(uts.release, "%d.%d", &major, &minor) == 2) {
+      int version = ((major & 0xFFFF) << 16) | (minor & 0xFFFF);
+      UMA_HISTOGRAM_CUSTOM_ENUMERATION(

[Ilya Sherman, 2015/03/19 00:37:43]

nit: Maybe a sparse enum would be simpler to use here?

[Robert Sesek, 2015/03/19 14:57:29]

I didn't know about that. Yes, done.

+          "Android.KernelVersion", version,
+          base::CustomHistogram::ArrayToCustomRanges(
+              kVersionRanges, arraysize(kVersionRanges)));
+    }
+  }
+
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+      base::Bind(&SeccompSupportDetector::DetectSeccomp, this));
+}
+
+void SeccompSupportDetector::DetectSeccomp() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));

[Lei Zhang, 2015/03/19 00:42:23]

DCHECK_CURRENTLY_ON() is the new hotness. Add it to the various OnFoo() methods?

[Robert Sesek, 2015/03/19 14:57:29]

Nifty. Thanks for the tip.

+
+  content::UtilityProcessHost* utility_process_host =
+      content::UtilityProcessHost::Create(
+          this, base::MessageLoopProxy::current());
+  utility_process_host->Send(new ChromeUtilityMsg_DetectSeccompSupport());
+}
+
+void SeccompSupportDetector::OnProcessCrashed(int exit_code) {
+  // The process crashed. Since prctl detection happens first, report which
+  // probe failed.
+  if (prctl_detected_) {
+    UMA_HISTOGRAM_ENUMERATION("Android.SeccompStatus.Syscall",
+                              DETECTION_FAILED,
+                              LAST_STATUS);
+  } else {
+    UMA_HISTOGRAM_ENUMERATION("Android.SeccompStatus.Prctl",

[Ilya Sherman, 2015/03/19 00:37:44]

Optional: I'd recommend having a single codepath per histogram name, so that
there's less chance of typos sneaking into one of the parallel codepaths.

[Robert Sesek, 2015/03/19 14:57:29]

I gave this a go, but it results in two one-line methods for setting the
histograms. It made the code a little less readable IMO, but if you feel
strongly I can reapply that change.

+                              DETECTION_FAILED,
+                              LAST_STATUS);
+  }
+}
+
+bool SeccompSupportDetector::OnMessageReceived(const IPC::Message& message) {
+  bool handled = false;
+  IPC_BEGIN_MESSAGE_MAP(SeccompSupportDetector, message)
+    IPC_MESSAGE_HANDLER(ChromeUtilityHostMsg_DetectSeccompSupport_ResultPrctl,
+                        OnDetectPrctl)
+    IPC_MESSAGE_HANDLER(ChromeUtilityHostMsg_DetectSeccompSupport_ResultSyscall,
+                        OnDetectSyscall)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+  return handled;
+}
+
+void SeccompSupportDetector::OnDetectPrctl(bool prctl_supported) {
+  prctl_detected_ = true;
+
+  UMA_HISTOGRAM_ENUMERATION("Android.SeccompStatus.Prctl",
+                            prctl_supported ? SUPPORTED : NOT_SUPPORTED,
+                            LAST_STATUS);
+}
+
+void SeccompSupportDetector::OnDetectSyscall(bool syscall_supported) {
+  DCHECK(prctl_detected_);
+
+  UMA_HISTOGRAM_ENUMERATION("Android.SeccompStatus.Syscall",
+                            syscall_supported ? SUPPORTED : NOT_SUPPORTED,
+                            LAST_STATUS);
+
+  // The utility process will shutdown after this, and this object will
+  // be deleted when the UtilityProcessHost releases its reference.
+}