Fuchsia requires the ability to sandbox Isolates w.r.t. file IO.
When a new Isolate starts, Fuchsia will pass the Isolate an object
called a namespace. We can translate the namespace object into a
file descriptor suitable for passing to the *at() family of
POSIX file system calls. The file system calls will then
have visibility only into the specified namespace.
We also plumb Namespaces through on all the other platforms as well to
make the change easier to test and so that in the future we can
implement e.g. per-isolate cwds.
This change adds a new internal class to dart:io called _Namespace,
which is implemented in a patch file. See:
sdk/lib/io/namespace_impl.dart
runtime/bin/namespace_patch.dart
The embedder can set up a non-default namespace by calling
_Namespace._setupNamespace during Isolate setup.
Instances of _Namespace have a native field that holds a pointer
to a native Namespace object. See:
runtime/bin/namespace.h
Calls from e.g. file_impl.dart are now also passed a
_Namespace object. The implementations in e.g. file.cc and
file_linux.cc then extract the namespace, and use it to compute a
file descriptor and path suitable for passing to e.g. openat().
related US-313
R=asiva@google.com, rmacnak@google.com
Review-Url: https://codereview.chromium.org/3007703002 .
Zach Anderson