Update from chromium 62675d9fb31fb8cedc40f68e78e8445a74f362e7

sandbox/linux/seccomp-bpf/syscall_iterator.cc

+// 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.
+
+#include "sandbox/linux/seccomp-bpf/syscall_iterator.h"
+
+#include "base/logging.h"
+#include "base/macros.h"
+#include "sandbox/linux/seccomp-bpf/linux_seccomp.h"
+
+namespace sandbox {
+
+namespace {
+
+#if defined(__mips__) && (_MIPS_SIM == _MIPS_SIM_ABI32)
+// This is true for Mips O32 ABI.
+COMPILE_ASSERT(MIN_SYSCALL == __NR_Linux, min_syscall_should_be_4000);
+#else
+// This true for supported architectures (Intel and ARM EABI).
+COMPILE_ASSERT(MIN_SYSCALL == 0u, min_syscall_should_always_be_zero);
+#endif
+
+// SyscallRange represents an inclusive range of system call numbers.
+struct SyscallRange {
+  uint32_t first;
+  uint32_t last;
+};
+
+const SyscallRange kValidSyscallRanges[] = {
+    // First we iterate up to MAX_PUBLIC_SYSCALL, which is equal to MAX_SYSCALL
+    // on Intel architectures, but leaves room for private syscalls on ARM.
+    {MIN_SYSCALL, MAX_PUBLIC_SYSCALL},
+#if defined(__arm__)
+    // ARM EABI includes "ARM private" system calls starting at
+    // MIN_PRIVATE_SYSCALL, and a "ghost syscall private to the kernel" at
+    // MIN_GHOST_SYSCALL.
+    {MIN_PRIVATE_SYSCALL, MAX_PRIVATE_SYSCALL},
+    {MIN_GHOST_SYSCALL, MAX_SYSCALL},
+#endif
+};
+
+// NextSyscall returns the next system call in the specified system
+// call set after |cur|, or 0 if no such system call exists.
+uint32_t NextSyscall(uint32_t cur, bool invalid_only) {
+  for (const SyscallRange& range : kValidSyscallRanges) {
+    if (range.first > 0 && cur < range.first - 1) {
+      return range.first - 1;
+    }
+    if (cur <= range.last) {
+      if (invalid_only) {
+        return range.last + 1;
+      }
+      return cur + 1;
+    }
+  }
+
+  // BPF programs only ever operate on unsigned quantities. So, that's how
+  // we iterate; we return values from 0..0xFFFFFFFFu. But there are places,
+  // where the kernel might interpret system call numbers as signed
+  // quantities, so the boundaries between signed and unsigned values are
+  // potential problem cases. We want to explicitly return these values from
+  // our iterator.
+  if (cur < 0x7FFFFFFFu)
+    return 0x7FFFFFFFu;
+  if (cur < 0x80000000u)
+    return 0x80000000u;
+
+  if (cur < 0xFFFFFFFFu)
+    return 0xFFFFFFFFu;
+  return 0;
+}
+
+}  // namespace
+
+SyscallSet::Iterator SyscallSet::begin() const {
+  return Iterator(set_, false);
+}
+
+SyscallSet::Iterator SyscallSet::end() const {
+  return Iterator(set_, true);
+}
+
+bool SyscallSet::IsValid(uint32_t num) {
+  for (const SyscallRange& range : kValidSyscallRanges) {
+    if (num >= range.first && num <= range.last) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool operator==(const SyscallSet& lhs, const SyscallSet& rhs) {
+  return (lhs.set_ == rhs.set_);
+}
+
+SyscallSet::Iterator::Iterator(Set set, bool done)
+    : set_(set), done_(done), num_(0) {
+  if (set_ == Set::INVALID_ONLY && !done_ && IsValid(num_)) {
+    ++*this;
+  }
+}
+
+uint32_t SyscallSet::Iterator::operator*() const {
+  DCHECK(!done_);
+  return num_;
+}
+
+SyscallSet::Iterator& SyscallSet::Iterator::operator++() {
+  DCHECK(!done_);
+
+  num_ = NextSyscall(num_, set_ == Set::INVALID_ONLY);
+  if (num_ == 0) {
+    done_ = true;
+  }
+
+  return *this;
+}
+
+bool operator==(const SyscallSet::Iterator& lhs,
+                const SyscallSet::Iterator& rhs) {
+  DCHECK(lhs.set_ == rhs.set_);
+  return (lhs.done_ == rhs.done_) && (lhs.num_ == rhs.num_);
+}
+
+bool operator!=(const SyscallSet::Iterator& lhs,
+                const SyscallSet::Iterator& rhs) {
+  return !(lhs == rhs);
+}
+
+}  // namespace sandbox