Add a platform-specific syscall number iterator.

sandbox/linux/seccomp-bpf/syscall_iterator.h

+// Copyright (c) 2012 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.
+
+#ifndef SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_ITERATOR_H__
+#define SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_ITERATOR_H__
+
+#include <stdint.h>
+
+#include <base/logging.h>
+
+namespace playground2 {
+
+// Iterates over the entire system call range from 0..0xFFFFFFFFu. This
+// iterator is aware of how system calls look like and will skip quickly
+// over ranges that can't contain system calls. It iterates more slowly
+// whenever it reaches a range that is potentially problematic. And it
+// iterates over individual values whenever it is in the normal range for
+// system calls (typically MIN_SYSCALL..MAX_SYSCALL).
+// If |invalid_only| is true, the iterator will only return invalid
+// syscall numbers, but will still skip quickly over invalid ranges.
+//
+// Example usage:
+//   for (SyscallIterator iter(false); !iter.Done(); ) {
+//     uint32_t sysnum = iter.Next();
+//     // Do something with sysnum.
+//   }
+//
+// TODO(markus): Make this a classic C++ iterator.
+class SyscallIterator {
+ public:
+  explicit SyscallIterator(bool invalid_only)
+      : invalid_only_(invalid_only),

[jln (very slow on Chromium), 2012/10/13 02:44:22]

Style: You misread my previous comment. Colon should be indented 4 spaces, the
rest of the initializers should be indented below other initializers.

[Jorge Lucangeli Obes, 2012/10/13 04:45:42]

I'm not sure what's wrong in this case. The colon is indented 4 spaces, and then
the initializers are aligned, e.g.
http://code.google.com/searchframe#OAMlx_jo-ck/src/base/observer_list.h&type=...

+        done_(false),
+        num_(MIN_SYSCALL) {
+    CHECK_EQ(MIN_SYSCALL, 0u);

[jln (very slow on Chromium), 2012/10/13 02:44:22]

This needs to be localized where you are actually making this assumption, in the
implementation.

[Jorge Lucangeli Obes, 2012/10/13 04:45:42]

Done.

+  }
+
+  bool Done() const { return done_; }
+  uint32_t Next();
+  static bool IsValid(uint32_t num);
+
+ private:
+  static bool IsArmPrivate(uint32_t num);
+
+  bool     invalid_only_;
+  bool     done_;
+  uint32_t num_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyscallIterator);
+};
+
+}  // namespace

[jln (very slow on Chromium), 2012/10/13 02:44:22]

Style: namespace playground2

[Jorge Lucangeli Obes, 2012/10/13 04:45:42]

Done.

+
+#endif  // SANDBOX_LINUX_SECCOMP_BPF_SYSCALL_ITERATOR_H__
+