[MIPS] Add seccomp bpf support

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/basictypes.h"
 #include "sandbox/linux/seccomp-bpf/linux_seccomp.h"
 
 namespace sandbox {
 
 uint32_t SyscallIterator::Next() {
   if (done_) {
     return num_;
   }
 
   uint32_t val;
   do {
+#if defined(__mips__) && (_MIPS_SIM == _MIPS_SIM_ABI32)
+    // |num_| has been initialized to 4000, which we assume is also MIN_SYSCALL.
+    // This is true for Mips O32 ABI.
+    COMPILE_ASSERT(MIN_SYSCALL == __NR_Linux, min_syscall_should_be_4000);
+#else
     // |num_| has been initialized to 0, which we assume is also MIN_SYSCALL.
     // This true for supported architectures (Intel and ARM EABI).
     COMPILE_ASSERT(MIN_SYSCALL == 0u, min_syscall_should_always_be_zero);
+#endif
     val = num_;
 
+    // The syscall iterator always starts at zero.
+    // If zero is not a valid system call, iterator first returns MIN_SYSCALL -1
+    // before continuing to iterate.
+    if (num_ == 0 && MIN_SYSCALL != num_) {
+      num_ = MIN_SYSCALL - 1;
     // 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.
-    if (num_ <= MAX_PUBLIC_SYSCALL) {
+    } else if (num_ <= MAX_PUBLIC_SYSCALL) {
       if (invalid_only_ && num_ < MAX_PUBLIC_SYSCALL) {
         num_ = MAX_PUBLIC_SYSCALL;
       } else {
         ++num_;
       }
 #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.
     } else if (num_ < MIN_PRIVATE_SYSCALL - 1) {
@@ skipping 46 matching lines @@
 #if defined(__arm__) && (defined(__thumb__) || defined(__ARM_EABI__))
 bool SyscallIterator::IsArmPrivate(uint32_t num) {
   return (num >= MIN_PRIVATE_SYSCALL && num <= MAX_PRIVATE_SYSCALL) ||
          (num >= MIN_GHOST_SYSCALL && num <= MAX_SYSCALL);
 }
 #else
 bool SyscallIterator::IsArmPrivate(uint32_t) { return false; }
 #endif
 
 }  // namespace sandbox