Android sandbox: workaround for restricted errno values.

sandbox/linux/seccomp-bpf/errorcode.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_ERRORCODE_H__
 #define SANDBOX_LINUX_SECCOMP_BPF_ERRORCODE_H__
 
 #include "sandbox/linux/seccomp-bpf/linux_seccomp.h"
 #include "sandbox/linux/seccomp-bpf/trap.h"
 
@@ skipping 16 matching lines @@
     // completely arbitrary. But we want to pick it so that is is unlikely
     // to be passed in accidentally, when the user intended to return an
     // "errno" (see below) value instead.
     ERR_ALLOWED   = 0x04000000,
 
     // Deny the system call with a particular "errno" value.
     // N.B.: It is also possible to return "0" here. That would normally
     //       indicate success, but it won't actually run the system call.
     //       This is very different from return ERR_ALLOWED.
     ERR_MIN_ERRNO = 0,
+    // TODO(markus): Android only supports errno up to 255
+    // (crbug.com/181647).
     ERR_MAX_ERRNO = 4095,
   };
 
   // While BPF filter programs always operate on 32bit quantities, the kernel
   // always sees system call arguments as 64bit values. This statement is true
   // no matter whether the host system is natively operating in 32bit or 64bit.
   // The BPF compiler hides the fact that BPF instructions cannot directly
   // access 64bit quantities. But policies are still advised to specify whether
   // a system call expects a 32bit or a 64bit quantity.
   enum ArgType {
@@ skipping 134 matching lines @@
   // 32bit field used for all possible types of ErrorCode values. This is
   // the value that uniquely identifies any ErrorCode and it (typically) can
   // be emitted directly into a BPF filter program.
   uint32_t err_;
 
 };
 
 }  // namespace
 
 #endif  // SANDBOX_LINUX_SECCOMP_BPF_ERRORCODE_H__