Linux Sandbox: Add support for SECCOMP_RET_TRACE.

sandbox/linux/seccomp-bpf/errorcode.cc

Index: sandbox/linux/seccomp-bpf/errorcode.cc
diff --git a/sandbox/linux/seccomp-bpf/errorcode.cc b/sandbox/linux/seccomp-bpf/errorcode.cc
index 648485282023247b26a7c85adb63ca885701542c..27a991a194c53ffb7d9984ffbc7f98d6122ba170 100644
--- a/sandbox/linux/seccomp-bpf/errorcode.cc
+++ b/sandbox/linux/seccomp-bpf/errorcode.cc
@@ -18,6 +18,11 @@ ErrorCode::ErrorCode(int 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");
   }
 }