New NaCl zygote implementation 2

chrome/common/nacl_helper_linux.h

+// Copyright (c) 2011 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.
+
+// A mini-zygote specifically for Native Client.
+
+#ifndef CHROME_COMMON_NACL_HELPER_LINUX_H_
+#define CHROME_COMMON_NACL_HELPER_LINUX_H_
+#pragma once
+
+#define kNaClHelperStartupAck "NACLHELPER_OK"

[Evan Martin, 2011/06/24 18:57:33]

Why #define and not char[]?
Why no comments?

[Brad Chen, 2011/06/25 22:14:51]

I've added comments. The reason I'm not using the normal Chrome convention of in
a externs in a .h file and decl in a C file is that these constants need to be
referenced from two different executables (chrome and the nacl_helper) and there
is not an appropriate CC file shared between them. If you find the #defines a
problem I could add a data-only CC file.

See a related discussion with John here:
http://codereview.chromium.org/6995121/diff/33001/chrome/common/nacl_helper_l...
 
On 2011/06/24 18:57:33, Evan Martin wrote:

+#define kNaClForkRequest "NACLFORK"
+// kNaClBrowserDescriptor and kNaClSandboxDescriptor must match
+// content/browser/zygote_main_linux.cc kBrowserDescriptor and
+// kMagicSandboxIPCDescriptor.

[Evan Martin, 2011/06/24 18:57:33]

This will likely regress unless you either are very careful with comments in the
other code or (better) you make these share a header.

[Brad Chen, 2011/06/25 22:14:51]

I will add better comments to this file.

My first cut at this CL used a common header, however that tends to interfere
with the goals of isolating chrome/ from content/. I hate this sort of thing
too; it made it very hard to understand the zygote code and sandbox code in the
first place. Sadly kMagicSandboxIPCDescriptor is represented in other places
outside of zygote_main_linux.cc, so it's not just the nacl_helper that would
break if it changes. With NaCl in Chrome and the zygote in content the most
obvious ways to do this sort of thing are not an option.  

There are DCHECK()s in chrome/nacl/nacl_fork_delegate.cc that confirm that the
Browser and Sandbox descriptors have expected values.

On 2011/06/24 18:57:33, Evan Martin wrote:

+// We put the kNaClZygoteDescriptor on 3 together with the
+// kNaClBrowserDescriptor. They are never used at the same
+// time, and this prevents /dev/urandom from using the fd.
+#define kNaClBrowserDescriptor 3
+#define kNaClZygoteDescriptor 3
+#define kNaClSandboxDescriptor 5
+
+#define kNaClBrowserFDIndex 0
+#define kNaClDummyFDIndex 1
+#define kNaClParentFDIndex 2
+
+#endif  // CHROME_COMMON_NACL_HELPER_LINUX_H_