[Android] Define a baseline seccomp-bpf sandbox policy.

sandbox/linux/seccomp-bpf-helpers/baseline_policy_android.cc

+// Copyright (c) 2013 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 "sandbox/linux/seccomp-bpf-helpers/baseline_policy_android.h"
+
+#include <sys/types.h>
+
+#include "sandbox/linux/seccomp-bpf-helpers/syscall_sets.h"
+#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
+
+namespace sandbox {
+
+BaselinePolicyAndroid::BaselinePolicyAndroid()
+    : BaselinePolicy() {}
+
+BaselinePolicyAndroid::~BaselinePolicyAndroid() {}
+
+ErrorCode BaselinePolicyAndroid::EvaluateSyscall(SandboxBPF* sandbox,
+                                                 int sysno) const {
+  bool allowed = false;
+
+  switch (sysno) {
+    case __NR_open:

[jln (very slow on Chromium), 2014/03/07 01:30:30]

Very excited if this works!

We may want to experiment with having a "broker thread" in the browser, or a
better broker process model and broker out open afterwards.

[Robert Sesek, 2014/03/25 21:57:17]

Yes, this does work! This mostly appears to be reading data files in both the
apk and the system partition.

+
+    case __NR_uname:
+
+    case __NR_flock:
+    case __NR_sigaltstack:
+    case __NR_rt_sigtimedwait:
+    case __NR_mremap:
+    case __NR_ioctl:
+    case __NR_pread64:
+    case __NR_getpriority:
+    case __NR_setpriority:
+    case __NR_ugetrlimit:
+      allowed = true;
+      break;
+  }
+
+  if (allowed)
+    return ErrorCode(ErrorCode::ERR_ALLOWED);
+
+  return BaselinePolicy::EvaluateSyscall(sandbox, sysno);
+}
+
+}  // namespace sandbox