singrdk/base/Kernel/Singularity.Loader/Binder.sg

////////////////////////////////////////////////////////////////////////////////
//
//  Microsoft Research Singularity
//
//  Copyright (c) Microsoft Corporation.  All rights reserved.
//
//  File:   Binder.cs
//
//  Note:
///////////////////////////////////////////////////////////////////////////////

using System;
using System.Text;
using System.GCs;
using System.Collections;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Threading;

using Microsoft.SingSharp;
using Microsoft.Singularity.Channels;
using Microsoft.Singularity.Directory;
using Microsoft.Singularity.Init;
using Microsoft.Singularity.Io;
using Microsoft.Singularity.Loader;
using Microsoft.Singularity.Memory;
using Microsoft.Singularity.Scheduling;
using Microsoft.Singularity.Security;
using Microsoft.Singularity.V1.Types;
using Microsoft.Singularity.Xml;
using EndpointCoreImplementation = Microsoft.Singularity.Channels.EndpointCore;
using Allocation = Microsoft.Singularity.V1.Services.SharedHeapService.Allocation;

namespace Microsoft.Singularity.Loader
{
    [CLSCompliant(false)]
    public class Binder
    {
        private static TRef<DirectoryServiceContract.Imp:Start> nsRootRef;
        // the nameMap contains our full policy for how to resolve names
        private static SortedList! nameMap = new SortedList();

        private const int INITIALIZED = 0x42494e44;
        private static int initialized;
        private static bool redirectedRootRef;

        // Initialize the binder and naming policy.
        //
        // Should be called when still uniprocessor
        public static void Initialize(XmlNode! config)
        {
            if (!Initialized) {
                nameMap = new SortedList();

                lock (nameMap) {
                    // parse the namespaceConfig to set up the nameMap
                    foreach (XmlNode! rule in config.Children) {
                        if (rule.Name != NameXmlTag) {
                            continue;
                        }
                        string contract =
                            (!)rule.GetAttribute(ContractXmlAttribute, "");
                        string nsName =
                            rule.GetAttribute(NamePrefixXmlAttribute, "");
                        bool multiple =
                            rule.GetAttribute(AllowMultipleXmlAttribute, false);
                        int limit =
                            rule.GetAttribute(InstanceLimitXmlAttribute, -1);

#if VERBOSE
                        DebugStub.WriteLine("{0}: {1}", __arglist(contract, nsName));
#endif
                        assert nsName != null;
                        MapEntry e = new MapEntry(contract, nsName, multiple,
                                                  limit);
                        nameMap.Add(contract, e);
                    }
                }

                // cache a handle to the root name server for directory lookups.
                DirectoryServiceContract.Imp! rootNS = DirectoryService.NewClientEndpoint();
                nsRootRef = new TRef<DirectoryServiceContract.Imp:Start>(rootNS);
                initialized = INITIALIZED;

                DebugStub.Assert(redirectedRootRef == false);
                redirectedRootRef = false;
            }
        }

        //change the cached handle to point to the user-space directory service
        public static void RedirectRootRef()
        {
            DebugStub.Assert(Initialized);

            DebugStub.Print("Redirecting binder root ref\n");
            if(redirectedRootRef == true) {
                DebugStub.Print("Calling redirectRootRef twice?\n");
                DebugStub.Break();
            }

            DirectoryServiceContract.Imp! rootNS = DirectoryService.NewClientEndpoint();
            if (nsRootRef != null) {
                DirectoryServiceContract.Imp:Start oldRootNS = nsRootRef.Acquire();
                if(oldRootNS != null) {
                    delete oldRootNS;
                }
            }
            nsRootRef = new TRef<DirectoryServiceContract.Imp:Start>(rootNS);
            redirectedRootRef = true;
        }

        public static bool Initialized { get { return initialized == INITIALIZED; } }

        //
        // FindFileImage Extended.
        //

        public static IoMemory FindFileImage(string! file,
                                             DirectoryServiceContract.Imp:Ready! dirClient)
        {
            FileAttributesRecord fileAttributes;
            ErrorCode errorOut;

            long readSize = 1024 * 1024;
            Kernel.Waypoint(2500);

            bool ok = SdsUtils.GetAttributes(file,
                                    dirClient,
                                    out fileAttributes,
                                    out errorOut );
            if (!ok) return null;

            Kernel.Waypoint(2504);

            // bind to file

            FileContract.Imp! fileClient;
            FileContract.Exp! fileServer;
            FileContract.NewChannel(out fileClient, out fileServer);

            Kernel.Waypoint(2505);
            ok = SdsUtils.Bind(file,dirClient,fileServer, out errorOut);
            if (!ok) {
                delete fileClient;
                return null;
            }
            Kernel.Waypoint(2506);
            fileClient.RecvSuccess();
            Kernel.Waypoint(2509);

            //  Now read file

            Kernel.Waypoint(2510);

            if (fileClient != null) {
                // allocate memory and read file
                IoMemory region = IoMemory.AllocateRealFixed((UIntPtr) fileAttributes.FileSize);
                if (region == null) {
                    delete fileClient;
                    return null;
                }

                byte[] in ExHeap buf = new[ExHeap] byte[readSize];
                long readOffset = 0;
                Kernel.Waypoint(2511);
                while (true) {
                    // invariant: we own the non-null buffer buf at the
                    //            loop head
                    //       and  we don't own the buffer at the loop exit.
                    //
                    Tracing.Log(Tracing.Debug,"FindImage pre SendRead");
                    Kernel.Waypoint(2512);
                    fileClient.SendRead(buf, 0, readOffset, readSize);
                    Kernel.Waypoint(2513);

                    switch receive {
                        case fileClient.AckRead(localbuf, bytesRead, error) :
                            Tracing.Log(Tracing.Debug,"FindImage Post SendRead");
                            Kernel.Waypoint(2514);
                            Bitter.ToIoMemory(localbuf, 0, (int)bytesRead,
                                              region, (int)readOffset);
                            Kernel.Waypoint(2515);
                            if (bytesRead == readSize) {
                                // see if there is more
                                readOffset += bytesRead;
                                buf = localbuf;
                                continue;
                            }
                            delete localbuf;
                            break;

                        case fileClient.ChannelClosed() :
                            break;
                        case unsatisfiable :
                            break;
                    }
                    // Get out of loop
                    break;
                }
                Kernel.Waypoint(2516);
                delete fileClient;
                Kernel.Waypoint(2517);
                return region;
            }
            return null;
        }

        private static DirectoryServiceContract.Imp:Ready openDir(string! filePath)
        {
            Kernel.Waypoint(2400);

            if (nsRootRef == null) {
                DebugStub.Break();
                return null;
            }
            DirectoryServiceContract.Imp:Start rootNS = nsRootRef.Acquire();
            if (rootNS == null) {
                DebugStub.Break();
                return null;
            }

            Kernel.Waypoint(2401);
            DirectoryServiceContract.Imp! dirClient;
            DirectoryServiceContract.Exp! dirServer;
            DirectoryServiceContract.NewChannel(
                out dirClient, out dirServer);

            ErrorCode errorCode;
            bool ok = SdsUtils.Bind(filePath, rootNS, dirServer, out errorCode);
            if (!ok) {
                nsRootRef.Release(rootNS);
                delete dirClient;
                return null;
            }

            Kernel.Waypoint(2403);
            dirClient.RecvSuccess();
            nsRootRef.Release(rootNS);
            Kernel.Waypoint(2404);

            return dirClient;
        }

        public static IoMemory GetSystemManifest()
        {
            return Resources.GetSystemManifest();
        }

        private static Manifest GetManifest(string! name,
                                            DirectoryServiceContract.Imp:Ready! dirEP,
                                            out string path)
        {
            Manifest manifest = null;
            path =  null;

            Tracing.Log(Tracing.Debug, "Binder.GetManifest: path={0}", name);
            try {
                Kernel.Waypoint(2300);
                IoMemory manifestMemory = FindFileImage(name,dirEP);
                Kernel.Waypoint(2301);
                if (manifestMemory != null) {
                    Kernel.Waypoint(2302);
                    manifest = new Manifest(manifestMemory);
                    path = manifest.Path;
                    Kernel.Waypoint(2303);
                    // Manifest consumes IoMemory in constructor
                    // and does not reference it later on.
                    IoMemory.Release(manifestMemory);
                    Kernel.Waypoint(2304);
                }
                else {
                    DebugStub.WriteLine(" no manifest! file={0}",__arglist(name));
                }
            }
            catch (Exception e) {
                DebugStub.WriteLine("Exception in GetManifest: {0}", __arglist(e.Message));
                Tracing.Log(Tracing.Debug, "Exception in GetManifest: {0}", e.Message);
            }

            Kernel.Waypoint(2305);
            return manifest;
        }

        /// <summary>
        /// Loads the image of the corresponding application
        /// path has to be set to the actual path to the manifest
        /// (after resolution of symlinks)
        /// </summary>
        public static IoMemory LoadImage(Process parent,
                                         String! application,
                                         out Manifest outManifest)
        {
            Kernel.Waypoint(2000);
            application = (!)application.ToLower();
            string folderName = application;
            string appName = application;

            outManifest = null;

            // Open the directory containing the manifest and the executable
            // remove the ExecutableExtension (e.g. ".x86") if present
            if (application.EndsWith(DirectoryService.ExecutableExtension)) {
                const int extensionLength = DirectoryService.ExecutableExtensionLength;
                folderName =(!)application.Substring(0, application.Length - extensionLength);
                appName = folderName;
            }

            if (folderName.Length == 0) {
                // invalid application name
                Kernel.Waypoint(2001);
                return null;
            }

            // if the first character of the folder name is not "/",
            // then we will redirect to the init namespace.
            if (folderName[0] != '/') {
                appName = folderName;

                string        ns = DirectoryService.ExecutablesNamespace;
                StringBuilder sb = new StringBuilder(ns.Length +
                                                     appName.Length + 2);
                sb.Append("/");
                sb.Append(ns);
                sb.Append("/");
                sb.Append(appName);

                folderName = (!)sb.ToString();
            }
            else {
                // need to strip off all but last part.
                appName = folderName.Substring(folderName.LastIndexOf('/')+1);
            }

#if DEBUG
            DebugStub.WriteLine("Binder.LoadImage: application={0},folder={1},appName={2}",
                                __arglist (application,folderName,appName));
#endif

            Kernel.Waypoint(2002);
            DirectoryServiceContract.Imp:Ready dirEP = openDir(folderName);
            Kernel.Waypoint(2003);

            if (dirEP == null) {
                return null;
            }
            IoMemory result = null;
            // read the manifest
            Kernel.Waypoint(2004);
            string exePath;
            Manifest man = GetManifest(appName + DirectoryService.ManifestExtension, dirEP, out exePath);
            // set manifest out parameter. This is used by ProcessHandle.Create()
            // to get at the resources
            outManifest =  man;

            Kernel.Waypoint(2005);

            //DebugStub.Break();
            if (man != null) {
                Kernel.Waypoint(2006);
                if (exePath == null) {
                    delete dirEP;
                    return null; // calling contexts don't expect exceptions
                }
                // TODO: FIXFIX  the files in "/init" are being created in all lower case.
                // The files when built and their names in the manifest are case sensitive
                string exeName = exePath.ToLower();
                //DebugStub.WriteLine("Binder: path returned via manifest ={0}",
                //                    __arglist(exeName));
                result = Binder.FindFileImage(exeName,dirEP);
                //path = exeName;
                if (result == null) {
                    DebugStub.WriteLine("LoadImage not found: {0}",__arglist(exeName));
                }
                Kernel.Waypoint(2007);
            }
            else {
                delete dirEP;
                return null; // calling contexts don't expect exceptions
            }
            Kernel.Waypoint(2010);
            delete dirEP;
            return result;
        }

        // currently skips loading manifest, etc.
        public static IoMemory LoadRawImage(string! folderName,
                                            string! exeName)
        {
            // Open a directory service contract
            DirectoryServiceContract.Imp:Ready dirEP = openDir(folderName);
            if (dirEP == null) {
                DebugStub.WriteLine("LoadRawImage dirEP null [ERROR]");
                return null;
            }

            IoMemory result = null;

            // get file image
            result = Binder.FindFileImage(exeName,dirEP);
            if (result == null) {
                DebugStub.WriteLine("LoadRawImage {0} not found",
                                    __arglist(exeName));
            }
            delete dirEP;
            return result;
        }


        //////////////////////////////////////////////////////// Name Manager.
        //

        //////////////////////////////////////////////////////////////////////
        //

        // TODO: The namespace management code is all
        // below this comment, to include the fields in this
        // static class that are used.  this should make it much
        // easier to move this into a different module

        const string NameXmlTag = "name";
        const string NamePrefixXmlAttribute = "nsName";
        const string InstanceLimitXmlAttribute = "limit";
        const string AllowMultipleXmlAttribute = "allowMultiple";
        const string StartStatedIdXmlAttribute = "startStateId";
        const string EndpointClassName = "Microsoft.Singularity.Channels.Endpoint";
        const string ContractXmlAttribute = "contract";

        // we'll only put MapEntry objects in the nameMap; they
        // will be indexed by contractName
        private class MapEntry
        {
            public string contractName;
            public string! namespacePrefix;
            public bool appendInstance;
            public int instanceLimit;
            public int numInstances;

            public MapEntry(string contractName, string! namespacePrefix,
                            bool appendInstance, int instanceLimit)
            {
                // if we don't append the instance to the name, then we can't
                // ever have more than 1 instance.
                if (!appendInstance) {
                    this.instanceLimit = 1;
                }
                else {
                    this.instanceLimit = instanceLimit;
                }
                this.contractName = contractName;
                this.namespacePrefix = namespacePrefix;
                this.appendInstance = appendInstance;
                this.numInstances = 0;
            }
        }

        // to check dependencies, we need to be able to see if a
        // particular name has more instances than its limit
        public static bool IsServiceContractStartable(string contract)
        {
            // TODO: is this the right policy?  if we
            // don't understand this contract at all, then fail
            // by default
            lock (nameMap) {
                if (!nameMap.ContainsKey(contract)) {
                    return false;
                }

                MapEntry! e = (MapEntry!)nameMap[contract];
                // (-1 == no limit on the number of instances)
                return (e.instanceLimit == -1 ||
                        e.numInstances < e.instanceLimit);
            }
        }

        // we also need the ability to verify that an app who
        // needs a serviceprovider can get it; this lets us
        // check if the serviceprovider has started and claimed
        // a name:
        public static bool IsServiceContractAvailable(string contract)
        {
            lock (nameMap) {
                if (!nameMap.ContainsKey(contract)) {
                    return false;
                }

                MapEntry! e = (MapEntry!)nameMap[contract];
                return (e.numInstances != 0);
            }
        }

        private static bool AlreadyExists(string! name)
        {
            FileAttributesRecord far;
            ErrorCode ec;
            DirectoryServiceContract.Imp imp = DirectoryService.NewClientEndpoint();
            try {
                bool success = SdsUtils.GetAttributes(name, imp, out far, out ec);
                if (!success) {
                    DebugStub.Assert(ec == ErrorCode.NotFound);
                }
                return success;
            }
            finally {
                delete imp;
            }
        }

        // TODO: make this private and do the symlinks from this
        // class:  Warning - must fix VolMgr hack first!

        // This lets the system initializer indicate that a
        // particular contract instance has been claimed (it
        // does not create a contract!)  We need to return the
        // name so that IoSystem can create the symlinks
        public static string ClaimServiceContract(string contract)
        {
            lock (nameMap) {
                if (IsServiceContractStartable(contract)) {
                    MapEntry! e = (MapEntry!)nameMap[contract];
                    string prefix = e.namespacePrefix;
                    string publicName = prefix;

                    if (e.appendInstance) {
                        int n = e.numInstances;
                        publicName = prefix + n.ToString();
                        while (AlreadyExists(publicName)) {
                            n++;
                            publicName = prefix + n.ToString();
                        }

                        e.numInstances = n;
                    }
                    else {
                        e.numInstances++;
                    }

                    return publicName;
                }
                return null;
            }
        }

        // TODO: do we still need this now that we
        // have the wonderful and more generic method for doing
        // endpoints?  Attempt to bind a service provider
        // endpoint to the name nsName
        public static ServiceProviderContract.Exp!:Start
        BindServiceProvider(string! contract, string! nsName, out bool success,
                            out string! publicName)
        {
            // Create a ServiceProvider channel
            ServiceProviderContract.Imp! imp;
            ServiceProviderContract.Exp! sp;
            ServiceProviderContract.NewChannel(out imp, out sp);

            // Connect the service provider to the namespace.

            // TODO: can we make nc a static field to avoid
            // re-allocating nc on every function call?
            DirectoryServiceContract.Imp nc =
                DirectoryService.NewClientEndpoint();

            success = false;
            try {
                nc.SendRegister((!)Bitter.FromString(nsName), imp);
                switch receive {
                    case nc.AckRegister():
                        success = true;
                        break;
                    case nc.NakRegister(rejected, error):
                        DebugStub.Break();
                        if (rejected != null) {
                            delete rejected;
                        }
                        break;
                    case unsatisfiable:
                        DebugStub.WriteLine("unable to register {0} with Nameservice",
                                            __arglist(nsName));
                        DebugStub.Break();
                        break;
                }
            }
            finally {
                delete nc;
            }

            if (success) {
                publicName = (!)ClaimServiceContract(contract);
            }
            else {
                publicName = "";
            }
            return sp;
        }

        public static void CreatePublicSymlink(string! publicName,
                                               string! nsName)
        {
            // TODO: this reveals a bug: the /dev
            // namespace isn't guaranteed to exist!  This code
            // force-creates it anyway:
            if (redirectedRootRef == true) {
                DirectoryServiceContract.Imp!:Ready nc = DirectoryService.NewClientEndpoint();
                ErrorCode error;
                if(!SdsUtils.CreateLink(publicName, nsName, nc, out error)) {
                    DebugStub.WriteLine("Binder.CreatePublicSymlink name {0} target {1} redirect==true failed.  Error {2}\n",__arglist(publicName, nsName, SdsUtils.ErrorCodeToString(error)));
                }

                FileAttributesRecord far;
                if (!SdsUtils.GetAttributes(publicName, nc, out far, out error)) {
                    DebugStub.WriteLine("Binder.CreatePublicSymlink name {0} redirect==true failed.  Error {1}\n",__arglist(publicName, SdsUtils.ErrorCodeToString(error)));
                }
                else {
                    DebugStub.Assert(far.Type == NodeType.SymLink);
                }

                delete nc;
            } else {
                int splitpoint = publicName.LastIndexOf('/');
                string directory =
                    publicName.Remove(splitpoint, publicName.Length - splitpoint);
                string endpoint = publicName.Remove(0, splitpoint + 1);

                DirNode! devFolder = (!)DirectoryService.FindDirectory(directory, true);
                DirectoryService.CreateSymbolicLink(devFolder, endpoint, nsName);
            }
        }

        // utility function for getting SystemTypes from strings
        // in the manifest
        private static SystemType GetEndpointType(XmlNode! metadata)
        {
            // everything must derive from Endpoint
            SystemType epBaseType = typeof(Channels.Endpoint).GetSystemType();

            // now traverse the metadata to the types, in order:
            foreach (XmlNode! child in metadata.Children) {
                string! name = (!)child.GetAttribute(NameXmlTag, "");

                long lower, upper;
                // TODO: the encoding of types will
                // change, and when it does, this will need to
                // change.  Right now, we create the type name
                // of foo.imp as foo+foo.imp (same for exp)
                // XXX now types are in line with CLR -- foo+exp
                if (name.EndsWith(".Exp")) {
                    name = name.Remove(name.Length - 4, 4) + "+Exp";
                }
                else if (name.EndsWith(".Imp")) {
                    name = name.Remove(name.Length - 4, 4) + "+Imp";
                }

                // get the hash for this type:
                System.RuntimeTypeHash.ComputeHash(name, out lower, out upper);

                // If this isn't the base of our derivation, get
                // the type
                if (name != EndpointClassName) {
                    epBaseType = SystemType.Register(name, lower, upper,
                                                     epBaseType);
                }
            }
            return epBaseType;
        }

        public static unsafe bool
        SetEndpoint(Process! process,
                    int      index,
                    [Claims] Endpoint * in ExHeap endpoint)
        {
            SharedHeap.Allocation * ep = (SharedHeap.Allocation *)endpoint;
            return process.SetEndpoint(index, ref ep);
        }


        ///
        /// This is factored into a separate method to limit the exposure of "unsafe" to code
        /// manipulating other resources, as the ownership checker is not checking methods marked
        /// unsafe.
        ///
        unsafe private static void
        CreateChannel(out Endpoint*! in ExHeap imp, out Endpoint*! in ExHeap exp, SystemType impType, SystemType expType, int initialState) {
            // Allocate each EndpointCore, with a default size
            // of 512 (512 is much bigger than we need, but we
            // don't have an exact number from the metadata yet)

            Allocation * impCore = (Allocation*)
                Microsoft.Singularity.V1.Services.EndpointCore.Allocate(
                    512, impType);

            Allocation *expCore = (Allocation*)
                Microsoft.Singularity.V1.Services.EndpointCore.Allocate(
                    512, expType);

            if (impCore == null || expCore == null) {
                throw new ApplicationException("SharedHeap.Allocate returned null");
            }

            // set the start state of each endpoint via Initialize()
            Endpoint*! in ExHeap impEp = (Endpoint* in ExHeap) impCore;
            Endpoint*! in ExHeap expEp = (Endpoint* in ExHeap) expCore;

            impEp->Initialize(initialState);
            expEp->Initialize(initialState);

            // connect the endpoints
            Microsoft.Singularity.Channels.Endpoint.Connect(impEp, expEp);

            // return the endpoints
            imp = impEp;
            exp = expEp;
        }

        public static bool
        BindToService(Process!   process,
                      SystemType impType,
                      SystemType expType,
                      string     contract,
                      int        initialState,
                      int        index)
        {
            if (contract == null) return false;

            Endpoint* in ExHeap! impEp;
            Endpoint* in ExHeap! expEp;
            CreateChannel(out impEp, out expEp, impType, expType, initialState);

            // Now we need to use policy to get the name for binding the exp,
            // and we need to cast the exp Endpoint as a ServiceContract
            ServiceContract.Exp exp = expEp as ServiceContract.Exp;
            if (exp == null) {
                // The channel contract does not derive from ServiceContract.
                // This error can be induced by user-mode apps, so the kernel
                // needs to guard against it.
                DebugStub.WriteLine("Binder.BindToService: The channel allocated does not derive from ServiceContract.");
                DebugStub.WriteLine("Binder.BindToService: The BindToService request will fail.");
                delete expEp;
                delete impEp;
                return false;
            }

            // TODO: this should be a static field
            DirectoryServiceContract.Imp nc =
                DirectoryService.NewClientEndpoint();
            try {
                lock (nameMap) {
                    if (LockedAttachFirstInstance(nc, contract, exp)) {
                        // TODO: Do the Success hand shake here

                        // Wire the client endpoint directly into
                        // the target process to simplifies the
                        // security checks.
                        SetEndpoint(process, index, impEp);
                        return true;
                    }
                }
            }
            finally {
                delete nc;
            }
            delete impEp;
            return false;
        }

        // requires nameMap be locked on entry.
        private static bool
        LockedAttachFirstInstance(DirectoryServiceContract.Imp! nc,
                                  string contract,
                                  [Claims] ServiceContract.Exp! exp)
        {
            // TODO: for now, we only attach to the first instance:
            MapEntry! e;
            try {
                e = (MapEntry!)nameMap[contract];
            }
            catch (Exception e) {
                DebugStub.WriteLine("Loader.BindToService tried to index {0}",
                                    __arglist(contract));
                DebugStub.WriteLine("Loader.BindToService exception:{0}",
                                    __arglist(e.Message));
                return false;
            }

            string name = e.namespacePrefix;
            if (e.appendInstance) {
                name += "0";
            }

            ErrorCode errorOut;
            // Do the bind and return the result:
            if (SdsUtils.Bind(name, nc, exp, out errorOut)) {
                return true;
            }
            DebugStub.WriteLine("Locked instance binding to name {0} failed error {1}\n",
                                __arglist(name, SdsUtils.ErrorCodeToString(errorOut)));
            // TODO: FIXFIX what should be done if this bind fails?
            // should the process even allowed to be started?
            //DebugStub.Break();
            return false;
        }

        // Attempt to bind an endpoint to a service provider.  We are going to
        // assume that the serviceprovider has already been started
        // This relies on some clever tricks based on the implementation
        // of the Sing# compiler.
        public static bool BindServiceUser(Process! process,
                                           int index,
                                           string! contract,
                                           XmlNode! metadata)
        {
            // get the metadata for both sides of the channel
            XmlNode! impNode = (!)metadata.GetChild("imp");
            XmlNode! expNode = (!)metadata.GetChild("exp");

            // get the initial state as an integer
            int initialState = metadata.GetAttribute(StartStatedIdXmlAttribute, 0);

            // now get the SystemType of each endpoint's type (we don't actually
            // know the type in the kernel, but we can discern it using the
            // fullname from the metadata)
            SystemType impType = GetEndpointType(impNode);
            SystemType expType = GetEndpointType(expNode);

            return BindToService(process, impType, expType, contract, initialState, index);
        }
    }
}