Decouple CodeGen from ErrorCode

sandbox/linux/seccomp-bpf/sandbox_bpf.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/sandbox_bpf.h"
 
 // Some headers on Android are missing cdefs: crbug.com/172337.
 // (We can't use OS_ANDROID here since build_config.h is not included).
 #if defined(ANDROID)
 #include <sys/cdefs.h>
@@ skipping 868 matching lines @@
   // this range object. If it is greater or equal, it might be inside.
   Ranges::const_iterator mid = start + (stop - start) / 2;
 
   // Sub-divide the list of ranges and continue recursively.
   Instruction* jf = AssembleJumpTable(gen, start, mid);
   Instruction* jt = AssembleJumpTable(gen, mid, stop);
   return gen->MakeInstruction(BPF_JMP + BPF_JGE + BPF_K, mid->from, jt, jf);
 }
 
 Instruction* SandboxBPF::RetExpression(CodeGen* gen, const ErrorCode& err) {
-  if (err.error_type_ == ErrorCode::ET_COND) {
+  switch (err.error_type()) {
+    case ErrorCode::ET_COND:
     return CondExpression(gen, err);

[rickyz (no longer on Chrome), 2014/09/16 22:36:46]

nit: fix indent

[mdempsky, 2014/09/16 22:41:30]

Oops, done.

-  } else {
-    return gen->MakeInstruction(BPF_RET + BPF_K, err);
+    case ErrorCode::ET_SIMPLE:
+    case ErrorCode::ET_TRAP:
+      return gen->MakeInstruction(BPF_RET + BPF_K, err.err());
+    default:
+      SANDBOX_DIE("ErrorCode is not suitable for returning from a BPF program");

[jln (very slow on Chromium), 2014/09/16 22:42:29]

Will this work with all compilers? I think there are cases where this is not
considered noreturn, so you may need to return NULL here.

[mdempsky, 2014/09/16 22:47:44]

I think so.  There are other functions in this file (e.g., BPFFailure) that call
SANDBOX_DIE() and don't have any return statements.

   }
 }
 
 Instruction* SandboxBPF::CondExpression(CodeGen* gen, const ErrorCode& cond) {
   // Sanity check that |cond| makes sense.
   if (cond.argno_ < 0 || cond.argno_ >= 6) {
     SANDBOX_DIE("sandbox_bpf: invalid argument number");
   }
   if (cond.width_ != ErrorCode::TP_32BIT &&
       cond.width_ != ErrorCode::TP_64BIT) {
@@ skipping 227 matching lines @@
   }
 }
 
 ErrorCode SandboxBPF::Kill(const char* msg) {
   return Trap(BPFFailure, const_cast<char*>(msg));
 }
 
 SandboxBPF::SandboxStatus SandboxBPF::status_ = STATUS_UNKNOWN;
 
 }  // namespace sandbox