Linux Sandbox: Add support for SECCOMP_RET_TRACE.

sandbox/linux/seccomp-bpf/errorcode.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/die.h"
 #include "sandbox/linux/seccomp-bpf/errorcode.h"
 
 namespace sandbox {
 
 ErrorCode::ErrorCode(int err) {
   switch (err) {
     case ERR_ALLOWED:
       err_ = SECCOMP_RET_ALLOW;
       error_type_ = ET_SIMPLE;
       break;
     case ERR_MIN_ERRNO... ERR_MAX_ERRNO:
       err_ = SECCOMP_RET_ERRNO + err;
       error_type_ = ET_SIMPLE;
       break;
     default:
+      if (err & ERR_TRACE) {

[jln (very slow on Chromium), 2014/05/20 03:02:10]

We should also check that the rest of |err| does indeed fit in
SECCCOMP_RET_DATA.

Maybe simply add a nested: "if (err & ~SECCOMP_RET_DATA) break;" ?

Or add it to the original "if" if you think it's readable.

[rickyz (Google), 2014/05/20 22:34:01]

I changed the condition to (err & ~SECCOMP_RET_DATA) == ERR_TRACE.

+        err_ = SECCOMP_RET_TRACE + (err & SECCOMP_RET_DATA);
+        error_type_ = ET_SIMPLE;
+        break;
+      }
       SANDBOX_DIE("Invalid use of ErrorCode object");
   }
 }
 
 ErrorCode::ErrorCode(Trap::TrapFnc fnc, const void* aux, bool safe, uint16_t id)
     : error_type_(ET_TRAP),
       fnc_(fnc),
       aux_(const_cast<void*>(aux)),
       safe_(safe),
       err_(SECCOMP_RET_TRAP + id) {}
@@ skipping 64 matching lines @@
       } else {
         return false;
       }
     } else {
       SANDBOX_DIE("Corrupted ErrorCode");
     }
   }
 }
 
 }  // namespace sandbox