Decouple Trap from ErrorCode

sandbox/linux/seccomp-bpf/trap.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_TRAP_H__
 #define SANDBOX_LINUX_SECCOMP_BPF_TRAP_H__
 
 #include <signal.h>
 #include <stdint.h>
 
 #include <map>
-#include <vector>
 
-#include "base/basictypes.h"
+#include "base/macros.h"
 #include "sandbox/sandbox_export.h"
 
 namespace sandbox {
 
-class ErrorCode;
+// This must match the kernel's seccomp_data structure.
+struct arch_seccomp_data {
+  int nr;
+  uint32_t arch;
+  uint64_t instruction_pointer;
+  uint64_t args[6];
+};
 
 // The Trap class allows a BPF filter program to branch out to user space by
 // raising a SIGSYS signal.
 // N.B.: This class does not perform any synchronization operations. If
 //   modifications are made to any of the traps, it is the caller's
 //   responsibility to ensure that this happens in a thread-safe fashion.
 //   Preferably, that means that no other threads should be running at that
 //   time. For the purposes of our sandbox, this assertion should always be
 //   true. Threads are incompatible with the seccomp sandbox anyway.
 class SANDBOX_EXPORT Trap {
@@ skipping 10 matching lines @@
   // In other words, it reports an error by returning an exit code in the
   // range -1..-4096. It should not set errno when reporting errors; on the
   // other hand, accidentally modifying errno is harmless and the changes will
   // be undone afterwards.
   typedef intptr_t (*TrapFnc)(const struct arch_seccomp_data& args, void* aux);
 
   // Registers a new trap handler and sets up the appropriate SIGSYS handler
   // as needed.
   // N.B.: This makes a permanent state change. Traps cannot be unregistered,
   //   as that would break existing BPF filters that are still active.
-  static ErrorCode MakeTrap(TrapFnc fnc, const void* aux, bool safe);
+  static uint16_t MakeTrap(TrapFnc fnc, const void* aux, bool safe);
 
   // Enables support for unsafe traps in the SIGSYS signal handler. This is a
   // one-way fuse. It works in conjunction with the BPF compiler emitting code
   // that unconditionally allows system calls, if they have a magic return
   // address (i.e. SandboxSyscall(-1)).
   // Once unsafe traps are enabled, the sandbox is essentially compromised.
   // But this is still a very useful feature for debugging purposes. Use with
   // care. This feature is availably only if enabled by the user (see above).
   // Returns "true", if unsafe traps were turned on.
   static bool EnableUnsafeTrapsInSigSysHandler();
 
-  // Returns the ErrorCode associate with a particular trap id.
-  static ErrorCode ErrorCodeFromTrapId(uint16_t id);
+  // Returns true if a safe trap handler is associated with a
+  // particular trap ID.
+  static bool IsSafeTrapId(uint16_t id);
 
  private:
   struct TrapKey {
+    TrapKey() : fnc(NULL), aux(NULL), safe(false) {}
     TrapKey(TrapFnc f, const void* a, bool s) : fnc(f), aux(a), safe(s) {}
     TrapFnc fnc;
     const void* aux;
     bool safe;
     bool operator<(const TrapKey&) const;
   };
   typedef std::map<TrapKey, uint16_t> TrapIds;
 
   // Our constructor is private. A shared global instance is created
   // automatically as needed.
@@ skipping 10 matching lines @@
   // It also gracefully deals with methods that should check for the singleton,
   // but avoid instantiating it, if it doesn't exist yet
   // (e.g. ErrorCodeFromTrapId()).
   static Trap* GetInstance();
   static void SigSysAction(int nr, siginfo_t* info, void* void_context);
 
   // Make sure that SigSys is not inlined in order to get slightly better crash
   // dumps.
   void SigSys(int nr, siginfo_t* info, void* void_context)
       __attribute__((noinline));
-  ErrorCode MakeTrapImpl(TrapFnc fnc, const void* aux, bool safe);
+  uint16_t MakeTrapImpl(TrapFnc fnc, const void* aux, bool safe);
   bool SandboxDebuggingAllowedByUser() const;
 
   // We have a global singleton that handles all of our SIGSYS traps. This
   // variable must never be deallocated after it has been set up initially, as
   // there is no way to reset in-kernel BPF filters that generate SIGSYS
   // events.
   static Trap* global_trap_;
 
   TrapIds trap_ids_;            // Maps from TrapKeys to numeric ids
-  ErrorCode* trap_array_;       // Array of ErrorCodes indexed by ids
+  TrapKey* trap_array_;         // Array of TrapKeys indexed by ids
   size_t trap_array_size_;      // Currently used size of array
   size_t trap_array_capacity_;  // Currently allocated capacity of array
   bool has_unsafe_traps_;       // Whether unsafe traps have been enabled
 
   // Copying and assigning is unimplemented. It doesn't make sense for a
   // singleton.
   DISALLOW_COPY_AND_ASSIGN(Trap);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SECCOMP_BPF_TRAP_H__