X-Git-Url: http://git.megacz.com/?p=nestedvm.git;a=blobdiff_plain;f=src%2Forg%2Fibex%2Fnestedvm%2FUnixRuntime.java;h=e3afe98e3ae4e319fe310dfc36937603e3ced802;hp=bcac59bac5ee316faa468b30741b7a7e7e138c77;hb=119cb20e2b9d594032653c8464717b1420b6abc7;hpb=9a641039c47c2619982213501f49e1168fcdbda2

diff --git a/src/org/ibex/nestedvm/UnixRuntime.java b/src/org/ibex/nestedvm/UnixRuntime.java
index bcac59b..e3afe98 100644
--- a/src/org/ibex/nestedvm/UnixRuntime.java
+++ b/src/org/ibex/nestedvm/UnixRuntime.java
@@ -4,63 +4,40 @@ import org.ibex.nestedvm.util.*;
 import java.io.*;
 import java.util.*;
 
-// FEATURE: BusyBox's ASH doesn't like \r\n at the end of lines
-// is ash just broken or are many apps like this? if so workaround in nestedvm
+// FEATURE: vfork
 
-public abstract class UnixRuntime extends Runtime {
+public abstract class UnixRuntime extends Runtime implements Cloneable {
     /** The pid of this "process" */
     private int pid;
-    private int ppid;
-    protected int getPid() { return pid; }
+    private UnixRuntime parent;
+    public final int getPid() { return pid; }
     
-    /** processes filesystem */
-    private FS fs;
-    public FS getFS() { return fs; }
-    public void setFS(FS fs) {
-        if(state >= RUNNING) throw new IllegalStateException("Can't change fs while process is running");
-        this.fs = fs;
+    private static final GlobalState defaultGS = new GlobalState();
+    private GlobalState gs = defaultGS;
+    public void setGlobalState(GlobalState gs) {
+        if(state != STOPPED) throw new IllegalStateException("can't change GlobalState when running");
+        this.gs = gs;
     }
     
     /** proceses' current working directory - absolute path WITHOUT leading slash
         "" = root, "bin" = /bin "usr/bin" = /usr/bin */
     private String cwd;
     
-    /* Static stuff */
-    // FEATURE: Most of this is O(n) or worse - fix it
-    private final Object waitNotification = new Object();
-    private final static int MAX_TASKS = 256;
-    private final static UnixRuntime[] tasks = new UnixRuntime[MAX_TASKS];
-    private static int addTask(UnixRuntime rt) {
-        synchronized(tasks) {
-            for(int i=1;i<MAX_TASKS;i++) {
-                if(tasks[i] == null) {
-                    tasks[i] = rt;
-                    rt.pid = i;
-                    return i;
-                }
-            }
-            return -1;
-        }
-    }
-    private static void removeTask(UnixRuntime rt) {
-        synchronized(tasks) {
-            for(int i=1;i<MAX_TASKS;i++)
-                if(tasks[i] == rt) { tasks[i] = null; break; }
-        }
-    }
+    /** The runtime that should be run next when in state == EXECED */
+    private UnixRuntime execedRuntime;
+
+    private Object children; // used only for synchronizatin
+    private Vector activeChildren;
+    private Vector exitedChildren;
     
-    public UnixRuntime(int pageSize, int totalPages, boolean allowEmptyPages) {
-        super(pageSize,totalPages,allowEmptyPages);
-        
-        FS root = new HostFS();
-        FS dev = new DevFS();
-        MountPointFS mounts = new MountPointFS(root);
-        mounts.add("/dev",dev);
-        fs = mounts;
-        
+    protected UnixRuntime(int pageSize, int totalPages) {
+        super(pageSize,totalPages);
+                
         // FEATURE: Do the proper mangling for non-unix hosts
         String userdir = getSystemProperty("user.dir");
-        cwd = userdir != null && userdir.startsWith("/") && File.separatorChar == '/'  ? userdir.substring(1) : "";
+        cwd = 
+            userdir != null && userdir.startsWith("/") && File.separatorChar == '/' && getSystemProperty("nestedvm.root") == null
+            ? userdir.substring(1) : "";
     }
     
     // NOTE: getDisplayName() is a Java2 function
@@ -85,65 +62,74 @@ public abstract class UnixRuntime extends Runtime {
         return false;
     }
     
-    protected String[] createEnv(String[] extra) {
-        String[] defaults = new String[5];
+    String[] createEnv(String[] extra) {
+        String[] defaults = new String[6];
         int n=0;
         if(extra == null) extra = new String[0];
         if(!envHas("USER",extra) && getSystemProperty("user.name") != null)
             defaults[n++] = "USER=" + getSystemProperty("user.name");
-        if(!envHas("HOME",extra) && getSystemProperty("user.name") != null)
+        if(!envHas("HOME",extra) && getSystemProperty("user.home") != null)
             defaults[n++] = "HOME=" + getSystemProperty("user.home");
         if(!envHas("SHELL",extra)) defaults[n++] = "SHELL=/bin/sh";
         if(!envHas("TERM",extra))  defaults[n++] = "TERM=vt100";
         if(!envHas("TZ",extra))    defaults[n++] = "TZ=" + posixTZ();
+        if(!envHas("PATH",extra))  defaults[n++] = "PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/sbin:/usr/sbin:/sbin";
         String[] env = new String[extra.length+n];
         for(int i=0;i<n;i++) env[i] = defaults[i];
         for(int i=0;i<extra.length;i++) env[n++] = extra[i];
         return env;
     }
     
-    protected void _start() {
-        if(addTask(this) < 0) throw new Error("Task list full");
-    }
+    private static class ProcessTableFullExn extends RuntimeException { }
     
-    protected void _exit() {
-        synchronized(tasks) {
-            if(ppid == 0) removeTask(this);
-            for(int i=0;i<MAX_TASKS;i++) {
-                if(tasks[i] != null && tasks[i].ppid == pid) {
-                    if(tasks[i].state == DONE) removeTask(tasks[i]);
-                    else tasks[i].ppid = 0;
-                }
+    void _started() {
+        UnixRuntime[] tasks = gs.tasks;
+        synchronized(gs) {
+            if(pid != 0) {
+                if(tasks[pid] == null || tasks[pid].pid != pid) throw new Error("should never happen");
+            } else {
+                int newpid = -1;
+                int nextPID = gs.nextPID;
+                    for(int i=nextPID;i<tasks.length;i++) if(tasks[i] == null) { newpid = i; break; }
+                    if(newpid == -1) for(int i=1;i<nextPID;i++) if(tasks[i] == null) { newpid = i; break; }
+                    if(newpid == -1) throw new ProcessTableFullExn();
+                    pid = newpid;
+                gs.nextPID = newpid + 1;
             }
-            state = DONE;
-            if(ppid != 0) synchronized(tasks[ppid].waitNotification) { tasks[ppid].waitNotification.notify(); }
+            tasks[pid] = this;
         }
     }
-
-    protected int syscall(int syscall, int a, int b, int c, int d) {
+    
+    int _syscall(int syscall, int a, int b, int c, int d) throws ErrnoException, FaultException {
         switch(syscall) {
             case SYS_kill: return sys_kill(a,b);
             case SYS_fork: return sys_fork();
             case SYS_pipe: return sys_pipe(a);
             case SYS_dup2: return sys_dup2(a,b);
+            case SYS_dup: return sys_dup(a);
             case SYS_waitpid: return sys_waitpid(a,b,c);
             case SYS_stat: return sys_stat(a,b);
+            case SYS_lstat: return sys_lstat(a,b);
             case SYS_mkdir: return sys_mkdir(a,b);
             case SYS_getcwd: return sys_getcwd(a,b);
             case SYS_chdir: return sys_chdir(a);
-            case SYS_execve: return sys_execve(a,b.c);
+            case SYS_exec: return sys_exec(a,b,c);
+            case SYS_getdents: return sys_getdents(a,b,c,d);
+            case SYS_unlink: return sys_unlink(a);
+            case SYS_getppid: return sys_getppid();
 
-            default: return super.syscall(syscall,a,b,c,d);
+            default: return super._syscall(syscall,a,b,c,d);
         }
     }
     
-    protected FD open(String path, int flags, int mode) throws IOException {
-        return fs.open(normalizePath(path),flags,mode);
+    FD _open(String path, int flags, int mode) throws ErrnoException {
+        return gs.open(this,normalizePath(path),flags,mode);
+    }
+    
+    private int sys_getppid() {
+        return parent == null ? 1 : parent.pid;
     }
 
-    // FEATURE: Allow simple, broken signal delivery to other processes 
-    // (check if a signal was delivered before and after syscalls)
-    // FEATURE: Implement raise() in terms of call("raise",...) - kinda cheap, but it keeps the complexity in newlib
     /** The kill syscall.
        SIGSTOP, SIGTSTO, SIGTTIN, and SIGTTOUT pause the process.
        SIGCONT, SIGCHLD, SIGIO, and SIGWINCH are ignored.
@@ -166,140 +152,285 @@ public abstract class UnixRuntime extends Runtime {
             case 23: // SIGIO
             case 28: // SIGWINCH
                 break;
-            default: {
-                String msg = "Terminating on signal: " + signal + "\n";
-                exitStatus = 1;
-                state = DONE;
-                if(fds[2]==null) {
-                    System.out.print(msg);
-                } else {
-                    try {
-                        byte[] b = getBytes(msg); 
-                        fds[2].write(b,0,b.length);
-                    }
-                    catch(IOException e) { /* ignore */ }
-                }
-            }
+            default:
+                return syscall(SYS_exit,128+signal,0,0,0);
         }
         return 0;
     }
 
-    private int sys_waitpid(int pid, int statusAddr, int options) {
+    private int sys_waitpid(int pid, int statusAddr, int options) throws FaultException, ErrnoException {
         final int WNOHANG = 1;
         if((options & ~(WNOHANG)) != 0) return -EINVAL;
-        if(pid !=-1 && (pid <= 0 || pid >= MAX_TASKS)) return -ECHILD;
-        for(;;) {
-            synchronized(tasks) {
-                UnixRuntime task = null;
+        if(pid == 0 || pid < -1) {
+            if(STDERR_DIAG) System.err.println("WARNING: waitpid called with a pid of " + pid);
+            return -ECHILD;
+        }
+        boolean blocking = (options&WNOHANG)==0;
+        
+        if(pid !=-1 && (pid <= 0 || pid >= gs.tasks.length)) return -ECHILD;
+        if(children == null) return blocking ? -ECHILD : 0;
+        
+        UnixRuntime done = null;
+        
+        synchronized(children) {
+            for(;;) {
                 if(pid == -1) {
-                    for(int i=0;i<MAX_TASKS;i++) {
-                        if(tasks[i] != null && tasks[i].ppid == this.pid && tasks[i].state == DONE) {
-                            task = tasks[i];
-                            break;
-                        }
+                    if(exitedChildren.size() > 0) done = (UnixRuntime)exitedChildren.remove(exitedChildren.size() - 1);
+                } else if(pid > 0) {
+                    UnixRuntime t = gs.tasks[pid];
+                    if(t.parent != this) return -ECHILD;
+                    if(t.state == EXITED) {
+                        if(!exitedChildren.remove(t)) throw new Error("should never happen");
+                        done = t;
                     }
-                } else if(tasks[pid] != null && tasks[pid].ppid == this.pid && tasks[pid].state == DONE) {
-                    task = tasks[pid];
+                } else {
+                    // process group stuff, EINVAL returned above
+                        throw new Error("should never happen");
                 }
-                
-                if(task != null) {
-                    removeTask(task);
-                    try {
-                        if(statusAddr!=0) memWrite(statusAddr,task.exitStatus()<<8);
-                    } catch(FaultException e) {
-                        return -EFAULT;
-                    }
-
-                    return task.pid;
+                if(done == null) {
+                    if(!blocking) return 0;
+                    try { children.wait(); } catch(InterruptedException e) {}
+                    //System.err.println("waitpid woke up: " + exitedChildren.size());
+                } else {
+                    gs.tasks[done.pid] = null;
+                    break;
                 }
             }
-            if((options&WNOHANG)!=0) return 0;
-            synchronized(waitNotification) {
-                try { waitNotification.wait(); } catch(InterruptedException e) { /* ignore */ }
+        }
+        if(statusAddr!=0) memWrite(statusAddr,done.exitStatus()<<8);
+        return done.pid;
+    }
+    
+    
+    void _exited() {
+        if(children != null) synchronized(children) {
+            for(Enumeration e = exitedChildren.elements(); e.hasMoreElements(); ) {
+                UnixRuntime child = (UnixRuntime) e.nextElement();
+                gs.tasks[child.pid] = null;
+            }
+            exitedChildren.clear();
+            for(Enumeration e = activeChildren.elements(); e.hasMoreElements(); ) {
+                UnixRuntime child = (UnixRuntime) e.nextElement();
+                child.parent = null;
+            }
+            activeChildren.clear();
+        }
+        
+        UnixRuntime _parent = parent;
+        if(_parent == null) {
+            gs.tasks[pid] = null;
+        } else {
+            synchronized(_parent.children) {
+                if(parent == null) {
+                    gs.tasks[pid] = null;
+                } else {
+                    parent.activeChildren.remove(this);
+                    parent.exitedChildren.add(this);
+                    parent.children.notify();
+                }
             }
         }
     }
     
-    // FEATURE: Make this cleaner
-    // Great ugliness lies within.....
+    protected Object clone() throws CloneNotSupportedException {
+        UnixRuntime r = (UnixRuntime) super.clone();
+        r.pid = 0;
+        r.parent = null;
+        r.children = null;
+        r.activeChildren = r.exitedChildren = null;
+        return r;
+    }
+
     private int sys_fork() {
-        CPUState state = getCPUState();
+        CPUState state = new CPUState();
+        getCPUState(state);
         int sp = state.r[SP];
         final UnixRuntime r;
+        
         try {
-            r = (UnixRuntime) getClass().newInstance();
+            r = (UnixRuntime) clone();
         } catch(Exception e) {
-            System.err.println(e);
+            e.printStackTrace();
             return -ENOMEM;
         }
-        int child_pid = addTask(r);
-        if(child_pid < 0) return -ENOMEM;
-        
-        r.ppid = pid;
-        r.brkAddr = brkAddr;
-        r.fds = new FD[OPEN_MAX];
-        for(int i=0;i<OPEN_MAX;i++) if(fds[i] != null) r.fds[i] = fds[i].dup();
-        r.cwd = cwd;
-        r.fs = fs;
-        for(int i=0;i<TOTAL_PAGES;i++) {
-            if(readPages[i] == null) continue;
-            if(isEmptyPage(writePages[i])) {
-                r.readPages[i] = r.writePages[i] = writePages[i];
-            } else if(writePages[i] != null) {
-                r.readPages[i] = r.writePages[i] = new int[PAGE_WORDS];
-                if(STACK_BOTTOM == 0 || i*PAGE_SIZE < STACK_BOTTOM || i*PAGE_SIZE >= sp-PAGE_SIZE*2)
-                    System.arraycopy(writePages[i],0,r.writePages[i],0,PAGE_WORDS);
-            } else {
-                r.readPages[i] = r.readPages[i];
-            }
+
+        r.parent = this;
+
+        try {
+            r._started();
+        } catch(ProcessTableFullExn e) {
+            return -ENOMEM;
         }
-        state.r[V0] = 0;
-        state.pc += 4;
+
+        //System.err.println("fork " + pid + " -> " + r.pid + " tasks[" + r.pid + "] = " + gd.tasks[r.pid]);
+        if(children == null) {
+            children = new Object();
+            activeChildren = new Vector();
+            exitedChildren = new Vector();
+        }
+        activeChildren.add(r);
+        
+        state.r[V0] = 0; // return 0 to child
+        state.pc += 4; // skip over syscall instruction
         r.setCPUState(state);
         r.state = PAUSED;
         
-        new Thread() {
-            public void run() {
-                try {
-                    while(!r.execute());
-                } catch(Exception e) {
-                    System.err.println("Forked process threw exception: ");
-                    e.printStackTrace();
-                }
+        new ForkedProcess(r);
+        
+        return r.pid;
+    }
+    
+    public static final class ForkedProcess extends Thread {
+        private final UnixRuntime initial;
+        public ForkedProcess(UnixRuntime initial) { this.initial = initial; start(); }
+        public void run() { UnixRuntime.executeAndExec(initial); }
+    }
+    
+    public static int runAndExec(UnixRuntime r, String argv0, String[] rest) { return runAndExec(r,concatArgv(argv0,rest)); }
+    public static int runAndExec(UnixRuntime r, String[] argv) { r.start(argv); return executeAndExec(r); }
+    
+    public static int executeAndExec(UnixRuntime r) {
+        for(;;) {
+            for(;;) {
+                if(r.execute()) break;
+                if(STDERR_DIAG) System.err.println("WARNING: Pause requested while executing runAndExec()");
+            }
+            if(r.state != EXECED) return r.exitStatus();
+            r = r.execedRuntime;
+        }
+    }
+     
+    private String[] readStringArray(int addr) throws ReadFaultException {
+        int count = 0;
+        for(int p=addr;memRead(p) != 0;p+=4) count++;
+        String[] a = new String[count];
+        for(int i=0,p=addr;i<count;i++,p+=4) a[i] = cstring(memRead(p));
+        return a;
+    }
+    
+    private int sys_exec(int cpath, int cargv, int cenvp) throws ErrnoException, FaultException {
+        return exec(normalizePath(cstring(cpath)),readStringArray(cargv),readStringArray(cenvp));
+    }
+        
+    private int exec(String normalizedPath, String[] argv, String[] envp) throws ErrnoException {
+        if(argv.length == 0) argv = new String[]{""};
+
+        // NOTE: For this little hack to work nestedvm.root MUST be "."
+        /*try {
+            System.err.println("Execing normalized path: " + normalizedPath);
+            if(true) return exec(new Interpreter(normalizedPath),argv,envp);
+        } catch(IOException e) { throw new Error(e); }*/
+        
+        Object o = gs.exec(this,normalizedPath);
+        if(o == null) return -ENOENT;
+
+        if(o instanceof Class) {
+            Class c = (Class) o;
+            try {
+                return exec((UnixRuntime) c.newInstance(),argv,envp);
+            } catch(Exception e) {
+                e.printStackTrace();
+                return -ENOEXEC;
             }
-        }.start();
+        } else {
+            String[] command = (String[]) o;
+            String[] newArgv = new String[argv.length + command[1] != null ? 2 : 1];
+            int p = command[0].lastIndexOf('/');
+            newArgv[0] = p == -1 ? command[0] : command[0].substring(p+1);
+            p = 1;
+            if(command[1] != null) newArgv[p++] = command[1];
+            newArgv[p++] = "/" + normalizedPath;
+            for(int i=1;i<argv.length;i++) newArgv[p++] = argv[i];
+            return exec(command[0],newArgv,envp);
+        }
+    }
+    
+    private int exec(UnixRuntime r, String[] argv, String[] envp) {     
+        
+        //System.err.println("Execing " + r);
+        for(int i=0;i<OPEN_MAX;i++) if(closeOnExec[i]) closeFD(i);
+        r.fds = fds;
+        r.closeOnExec = closeOnExec;
+        // make sure this doesn't get messed with these since we didn't copy them
+        fds = null;
+        closeOnExec = null;
         
-        return child_pid;        
+        r.gs = gs;
+        r.sm = sm;
+        r.cwd = cwd;
+        r.pid = pid;
+        r.parent = parent;
+        r.start(argv,envp);
+                
+        state = EXECED;
+        execedRuntime = r;
+        
+        return 0;   
     }
+    
+    // FEATURE: Make sure fstat info is correct
+    // FEATURE: This could be faster if we did direct copies from each process' memory
+    // FEATURE: Check this logic one more time
+    public static class Pipe {
+        private final byte[] pipebuf = new byte[PIPE_BUF*4];
+        private int readPos;
+        private int writePos;
         
-    private int sys_execve(int cstring, int argv, int envp) {
-        /*
-        try {
-            String path = cstring(cstring);
-            FStat stat = fs.stat(path);
-            
-            
+        public final FD reader = new Reader();
+        public final FD writer = new Writer();
+        
+        public class Reader extends FD {
+            protected FStat _fstat() { return new FStat(); }
+            public int read(byte[] buf, int off, int len) throws ErrnoException {
+                if(len == 0) return 0;
+                synchronized(Pipe.this) {
+                    while(writePos != -1 && readPos == writePos) {
+                        try { Pipe.this.wait(); } catch(InterruptedException e) { /* ignore */ }
+                    }
+                    if(writePos == -1) return 0; // eof
+                    len = Math.min(len,writePos-readPos);
+                    System.arraycopy(pipebuf,readPos,buf,off,len);
+                    readPos += len;
+                    if(readPos == writePos) Pipe.this.notify();
+                    return len;
+                }
+            }
+            public void _close() { synchronized(Pipe.this) { readPos = -1; Pipe.this.notify(); } }
+        }
+        
+        public class Writer extends FD {   
+            protected FStat _fstat() { return new FStat(); }
+            public int write(byte[] buf, int off, int len) throws ErrnoException {
+                if(len == 0) return 0;
+                synchronized(Pipe.this) {
+                    if(readPos == -1) throw new ErrnoException(EPIPE);
+                    if(pipebuf.length - writePos < Math.min(len,PIPE_BUF)) {
+                        // not enough space to atomicly write the data
+                        while(readPos != -1 && readPos != writePos) {
+                            try { Pipe.this.wait(); } catch(InterruptedException e) { /* ignore */ }
+                        }
+                        if(readPos == -1) throw new ErrnoException(EPIPE);
+                        readPos = writePos = 0;
+                    }
+                    len = Math.min(len,pipebuf.length - writePos);
+                    System.arraycopy(buf,off,pipebuf,writePos,len);
+                    if(readPos == writePos) Pipe.this.notify();
+                    writePos += len;
+                    return len;
+                }
+            }
+            public void _close() { synchronized(Pipe.this) { writePos = -1; Pipe.this.notify(); } }
         }
-        catch(FaultException e) { return -EFAULT; }
-        catch(FileNotFoundException e) {  return -ENOENT; }
-        catch(IOException e) { return -EIO; }*/
-        throw new Error("FIXME - exec() isn't finished");
     }
-            
+    
     private int sys_pipe(int addr) {
-        PipedOutputStream writerStream = new PipedOutputStream();
-        PipedInputStream readerStream;
-        try {
-             readerStream = new PipedInputStream(writerStream);
-        } catch(IOException e) {
-            return -EIO;
-        }
-        FD reader = new InputStreamFD(readerStream);
-        FD writer = new OutputStreamFD(writerStream);
-        int fd1 = addFD(reader);
+        Pipe pipe = new Pipe();
+        
+        int fd1 = addFD(pipe.reader);
         if(fd1 < 0) return -ENFILE;
-        int fd2 = addFD(writer);
+        int fd2 = addFD(pipe.writer);
         if(fd2 < 0) { closeFD(fd1); return -ENFILE; }
+        
         try {
             memWrite(addr,fd1);
             memWrite(addr+4,fd2);
@@ -321,116 +452,304 @@ public abstract class UnixRuntime extends Runtime {
         return 0;
     }
     
-    private int sys_stat(int cstring, int addr) {
-        try {
-            String path = normalizePath(cstring(cstring));
-            return stat(fs.stat(path),addr);
-        }
-        catch(ErrnoException e) { return -e.errno; }
-        catch(FileNotFoundException e) {
-            if(e.getMessage() != null && e.getMessage().indexOf("Permission denied") >= 0) return -EACCES;
-            return -ENOENT;
-        }
-        catch(IOException e) { return -EIO; }
-        catch(FaultException e) { return -EFAULT; }
+    private int sys_dup(int oldd) {
+        if(oldd < 0 || oldd >= OPEN_MAX) return -EBADFD;
+        if(fds[oldd] == null) return -EBADFD;
+        FD fd = fds[oldd].dup();
+        int newd = addFD(fd);
+        if(newd < 0) { fd.close(); return -ENFILE; }
+        return newd;
     }
     
+    private int sys_stat(int cstring, int addr) throws FaultException, ErrnoException {
+        FStat s = gs.stat(this,normalizePath(cstring(cstring)));
+        if(s == null) return -ENOENT;
+        return stat(s,addr);
+    }
     
-    private int sys_mkdir(int cstring, int mode) {
-        try {
-            fs.mkdir(normalizePath(cstring(cstring)));
-            return 0;
-        }
-        catch(ErrnoException e) { return -e.errno; }
-        catch(FileNotFoundException e) { return -ENOENT; }
-        catch(IOException e) { return -EIO; }
-        catch(FaultException e) { return -EFAULT; }
+    private int sys_lstat(int cstring, int addr) throws FaultException, ErrnoException {
+        FStat s = gs.lstat(this,normalizePath(cstring(cstring)));
+        if(s == null) return -ENOENT;
+        return stat(s,addr);
+    }
+    
+    private int sys_mkdir(int cstring, int mode) throws FaultException, ErrnoException {
+        gs.mkdir(this,normalizePath(cstring(cstring)),mode);
+        return 0;
     }
    
+    private int sys_unlink(int cstring) throws FaultException, ErrnoException {
+        gs.unlink(this,normalizePath(cstring(cstring)));
+        return 0;
+    }
     
-    private int sys_getcwd(int addr, int size) {
+    private int sys_getcwd(int addr, int size) throws FaultException, ErrnoException {
         byte[] b = getBytes(cwd);
         if(size == 0) return -EINVAL;
         if(size < b.length+2) return -ERANGE;
-        try {
-            memset(addr,'/',1);
-            copyout(b,addr+1,b.length);
-            memset(addr+b.length+1,0,1);
-            return addr;
-        } catch(FaultException e) {
-            return -EFAULT;
-        }
+        memset(addr,'/',1);
+        copyout(b,addr+1,b.length);
+        memset(addr+b.length+1,0,1);
+        return addr;
     }
     
-    private int sys_chdir(int addr) {
-        try {
-            String path = normalizePath(cstring(addr));
-            System.err.println("Chdir: " + cstring(addr) + " -> " + path + " pwd: " + cwd);
-            if(fs.stat(path).type() != FStat.S_IFDIR) return -ENOTDIR;
-            cwd = path;
-            System.err.println("Now: [" + cwd + "]");
-            return 0;
-        }
-        catch(ErrnoException e) { return -e.errno; }
-        catch(FileNotFoundException e) { return -ENOENT; }
-        catch(IOException e) { return -EIO; }
-        catch(FaultException e) { return -EFAULT; }
+    private int sys_chdir(int addr) throws ErrnoException, FaultException {
+        String path = normalizePath(cstring(addr));
+        //System.err.println("Chdir: " + cstring(addr) + " -> " + path + " pwd: " + cwd);
+        if(gs.stat(this,path).type() != FStat.S_IFDIR) return -ENOTDIR;
+        cwd = path;
+        //System.err.println("Now: [" + cwd + "]");
+        return 0;
     }
-
-    public void chdir(String dir) throws FileNotFoundException {
-        if(state >= RUNNING) throw new IllegalStateException("Can't chdir while process is running");
-        try {
-            dir = normalizePath(dir);
-            if(fs.stat(dir).type() != FStat.S_IFDIR) throw new FileNotFoundException();
-        } catch(IOException e) {
-            throw new FileNotFoundException();
-        }
-        cwd = dir;
+    
+    private int sys_getdents(int fdn, int addr, int count, int seekptr) throws FaultException, ErrnoException {
+        count = Math.min(count,MAX_CHUNK);
+        if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
+        if(fds[fdn] == null) return -EBADFD;
+        byte[] buf = byteBuf(count);
+        int n = fds[fdn].getdents(buf,0,count);
+        copyout(buf,addr,n);
+        return n;
     }
-        
-    public abstract static class FS {
-        protected FD _open(String path, int flags, int mode) throws IOException { return null; }
-        protected FStat _stat(String path) throws IOException { return null; }
-        protected void _mkdir(String path) throws IOException { throw new ErrnoException(EROFS); }
-        
+    
+    //  FEATURE: Run through the fork/wait stuff one more time
+    public static class GlobalState {    
         protected static final int OPEN = 1;
         protected static final int STAT = 2;
-        protected static final int MKDIR = 3;
-        
-        protected Object op(int op, String path, int arg1, int arg2) throws IOException {
-        		switch(op) {
-        			case OPEN: return _open(path,arg1,arg2);
-        			case STAT: return _stat(path);
-        			case MKDIR: _mkdir(path); return null;
-        			default: throw new IllegalArgumentException("Unknown FS OP");
-        		}
-        }
-        
-        public final FD open(String path, int flags, int mode) throws IOException { return (FD) op(OPEN,path,flags,mode); }
-        public final FStat stat(String path) throws IOException { return (FStat) op(STAT,path,0,0); }
-        public final void mkdir(String path) throws IOException { op(MKDIR,path,0,0); }
-		
-		// FIXME: inode stuff
-        protected static FD directoryFD(String[] files, int hashCode) throws IOException {
-            ByteArrayOutputStream bos = new ByteArrayOutputStream();
-            DataOutputStream dos = new DataOutputStream(bos);
-            for(int i=0;i<files.length;i++) {
-                byte[] b = getBytes(files[i]);
-                int inode = (files[i].hashCode() ^ hashCode) & 0xfffff;
-                dos.writeInt(inode);
-                dos.writeInt(b.length);
-                dos.write(b,0,b.length);
+        protected static final int LSTAT = 3;
+        protected static final int MKDIR = 4;
+        protected static final int UNLINK = 5;
+        
+        final UnixRuntime[] tasks;
+        int nextPID = 1;
+        
+        private MP[] mps = new MP[0];
+        private FS root;
+        
+        public GlobalState() { this(255); }
+        public GlobalState(int maxProcs) { this(maxProcs,true); }
+        public GlobalState(int maxProcs, boolean defaultMounts) {
+            tasks = new UnixRuntime[maxProcs+1];
+            if(defaultMounts) {
+                addMount("/",new HostFS());
+                addMount("/dev",new DevFS());
             }
-            final byte[] data = bos.toByteArray();
-            return new SeekableFD(new Seekable.ByteArray(data,false),RD_ONLY) {
-                protected FStat _fstat() { return  new FStat() {
-                    public int length() { return data.length; }
-                    public int type() { return S_IFDIR; }
-                }; }
-            };
         }
+        
+        private static class MP {
+            public MP(String path, FS fs) { this.path = path; this.fs = fs; }
+            public String path;
+            public FS fs;
+            public int compareTo(Object o) {
+                if(!(o instanceof MP)) return 1;
+                return -path.compareTo(((MP)o).path);
+            }
+        }
+        
+        public synchronized FS getMount(String path) {
+            if(!path.startsWith("/")) throw new IllegalArgumentException("Mount point doesn't start with a /");
+            if(path.equals("/")) return root;
+            path  = path.substring(1);
+            for(int i=0;i<mps.length;i++)
+                if(mps[i].path.equals(path)) return mps[i].fs;
+            return null;
+        }
+        
+        public synchronized void addMount(String path, FS fs) {
+            if(getMount(path) != null) throw new IllegalArgumentException("mount point already exists");
+            if(!path.startsWith("/")) throw new IllegalArgumentException("Mount point doesn't start with a /");
+            
+            if(fs.owner != null) fs.owner.removeMount(fs);
+            fs.owner = this;
+            
+            if(path.equals("/")) { root = fs; fs.devno = 1; return; }
+            path = path.substring(1);
+            int oldLength = mps.length;
+            MP[] newMPS = new MP[oldLength + 1];
+            if(oldLength != 0) System.arraycopy(mps,0,newMPS,0,oldLength);
+            newMPS[oldLength] = new MP(path,fs);
+            Arrays.sort(newMPS);
+            mps = newMPS;
+            int highdevno = 0;
+            for(int i=0;i<mps.length;i++) highdevno = max(highdevno,mps[i].fs.devno);
+            fs.devno = highdevno + 2;
+        }
+        
+        public synchronized void removeMount(FS fs) {
+            for(int i=0;i<mps.length;i++) if(mps[i].fs == fs) { removeMount(i); return; }
+            throw new IllegalArgumentException("mount point doesn't exist");
+        }
+        
+        public synchronized void removeMount(String path) {
+            if(!path.startsWith("/")) throw new IllegalArgumentException("Mount point doesn't start with a /");
+            if(path.equals("/")) {
+                removeMount(-1);
+            } else {
+                path = path.substring(1);
+                int p;
+                for(p=0;p<mps.length;p++) if(mps[p].path.equals(path)) break;
+                if(p == mps.length) throw new IllegalArgumentException("mount point doesn't exist");
+                removeMount(p);
+            }
+        }
+        
+        private void removeMount(int index) {
+            if(index == -1) { root.owner = null; root = null; return; }
+            MP[] newMPS = new MP[mps.length - 1];
+            System.arraycopy(mps,0,newMPS,0,index);
+            System.arraycopy(mps,0,newMPS,index,mps.length-index-1);
+            mps = newMPS;
+        }
+        
+        private Object fsop(int op, UnixRuntime r, String normalizedPath, int arg1, int arg2) throws ErrnoException {
+            int pl = normalizedPath.length();
+            if(pl != 0) {
+                MP[] list;
+                synchronized(this) { list = mps; }
+                for(int i=0;i<list.length;i++) {
+                    MP mp = list[i];
+                    int mpl = mp.path.length();
+                    if(normalizedPath.startsWith(mp.path) && (pl == mpl || (pl < mpl && normalizedPath.charAt(mpl) == '/')))
+                        return dispatch(mp.fs,op,r,pl == mpl ? "" : normalizedPath.substring(mpl+1),arg1,arg2);
+                }
+            }
+            return dispatch(root,op,r,normalizedPath,arg1,arg2);
+        }
+        
+        private static Object dispatch(FS fs, int op, UnixRuntime r, String path, int arg1, int arg2) throws ErrnoException {
+            switch(op) {
+                case OPEN: return fs.open(r,path,arg1,arg2);
+                case STAT: return fs.stat(r,path);
+                case LSTAT: return fs.lstat(r,path);
+                case MKDIR: fs.mkdir(r,path,arg1); return null;
+                case UNLINK: fs.unlink(r,path); return null;
+                default: throw new Error("should never happen");
+            }
+        }
+        
+        public final FD open(UnixRuntime r, String path, int flags, int mode) throws ErrnoException { return (FD) fsop(OPEN,r,path,flags,mode); }
+        public final FStat stat(UnixRuntime r, String path) throws ErrnoException { return (FStat) fsop(STAT,r,path,0,0); }
+        public final FStat lstat(UnixRuntime r, String path) throws ErrnoException { return (FStat) fsop(LSTAT,r,path,0,0); }
+        public final void mkdir(UnixRuntime r, String path, int mode) throws ErrnoException { fsop(MKDIR,r,path,mode,0); }
+        public final void unlink(UnixRuntime r, String path) throws ErrnoException { fsop(UNLINK,r,path,0,0); }
+        
+        private Hashtable execCache = new Hashtable();
+        private static class CacheEnt {
+            public final long time;
+            public final long size;
+            public final Object o;
+            public CacheEnt(long time, long size, Object o) { this.time = time; this.size = size; this.o = o; }
+        }
+
+        public synchronized Object exec(UnixRuntime r, String path) throws ErrnoException {
+            // FIXME: Hideous hack to make a standalone busybox possible
+            if(path.equals("bin/busybox") && r.getClass().getName().endsWith("BusyBox"))
+                return r.getClass();
+            FStat fstat = stat(r,path);
+            if(fstat == null) return null;
+            long mtime = fstat.mtime();
+            long size = fstat.size();
+            CacheEnt ent = (CacheEnt) execCache.get(path);
+            if(ent != null) {
+                //System.err.println("Found cached entry for " + path);
+                if(ent.time == mtime && ent.size == size) return ent.o;
+                //System.err.println("Cache was out of date");
+                execCache.remove(path);
+            }
+            FD fd = open(r,path,RD_ONLY,0);
+            if(fd == null) return null;
+            Seekable s = fd.seekable();
+            
+            String[] command  = null;
+
+            if(s == null) throw new ErrnoException(EACCES);
+            byte[] buf = new byte[4096];
+            
+            try {
+                int n = s.read(buf,0,buf.length);
+                if(n == -1) throw new ErrnoException(ENOEXEC);
+                
+                switch(buf[0]) {
+                    case '\177': // possible ELF
+                        if(n < 4 && s.tryReadFully(buf,n,4-n) != 4-n) throw new ErrnoException(ENOEXEC);
+                        if(buf[1] != 'E' || buf[2] != 'L' || buf[3] != 'F') throw new ErrnoException(ENOEXEC);
+                        break;
+                    case '#':
+                        if(n == 1) {
+                            int n2 = s.read(buf,1,buf.length-1);
+                            if(n2 == -1) throw new ErrnoException(ENOEXEC);
+                            n += n2;
+                        }
+                        if(buf[1] != '!') throw new ErrnoException(ENOEXEC);
+                        int p = 2;
+                        n -= 2;
+                        OUTER: for(;;) {
+                            for(int i=p;i<p+n;i++) if(buf[i] == '\n') { p = i; break OUTER; }
+                            p += n;
+                            if(p == buf.length) break OUTER;
+                            n = s.read(buf,p,buf.length-p);
+                        }
+                        command = new String[2];
+                        int arg;
+                        for(arg=2;arg<p;arg++) if(buf[arg] == ' ') break;
+                        if(arg < p) {
+                            int cmdEnd = arg;
+                            while(arg < p && buf[arg] == ' ') arg++;
+                            command[0] = new String(buf,2,cmdEnd);
+                            command[1] = arg < p ? new String(buf,arg,p-arg) : null;
+                        } else {
+                            command[0] = new String(buf,2,p-2);
+                        }
+                        //System.err.println("command[0]: " + command[0] + " command[1]: " + command[1]);
+                        break;
+                    default:
+                        throw new ErrnoException(ENOEXEC);
+                }
+            } catch(IOException e) {
+                fd.close();
+                throw new ErrnoException(EIO);
+            }
+                        
+            if(command == null) {
+                // its an elf binary
+                try {
+                    s.seek(0);
+                    Class c = RuntimeCompiler.compile(s);
+                    //System.err.println("Compile succeeded: " + c);
+                    ent = new CacheEnt(mtime,size,c);
+                } catch(Compiler.Exn e) {
+                    if(STDERR_DIAG) e.printStackTrace();
+                    throw new ErrnoException(ENOEXEC);
+                } catch(IOException e) {
+                    if(STDERR_DIAG) e.printStackTrace();
+                    throw new ErrnoException(EIO);
+                }
+            } else {
+                ent = new CacheEnt(mtime,size,command);
+            }
+            
+            fd.close();
+            
+            execCache.put(path,ent);
+            return ent.o;
+        }
+    }
+    
+    public abstract static class FS {
+        GlobalState owner;
+        int devno;
+        
+        public FStat lstat(UnixRuntime r, String path) throws ErrnoException { return stat(r,path); }
+
+        // If this returns null it'll be truned into an ENOENT
+        public abstract FD open(UnixRuntime r, String path, int flags, int mode) throws ErrnoException;
+        // If this returns null it'll be turned into an ENOENT
+        public abstract FStat stat(UnixRuntime r, String path) throws ErrnoException;
+        public abstract void mkdir(UnixRuntime r, String path, int mode) throws ErrnoException;
+        public abstract void unlink(UnixRuntime r, String path) throws ErrnoException;
     }
         
+    // FEATURE: chroot support in here
     private String normalizePath(String path) {
         boolean absolute = path.startsWith("/");
         int cwdl = cwd.length();
@@ -445,15 +764,15 @@ public abstract class UnixRuntime extends Runtime {
         if(absolute) {
             do { inp++; } while(in[inp] == '/');
         } else if(cwdl != 0) {
-            	cwd.getChars(0,cwdl,out,0);
-            	outp = cwdl;
+            cwd.getChars(0,cwdl,out,0);
+            outp = cwdl;
         }
             
         path.getChars(0,path.length(),in,0);
         while(in[inp] != 0) {
-            if(inp != 0) {
-            	    if(in[inp] != '/') { out[outp++] = in[inp++]; continue; }
-            	    while(in[inp] == '/') inp++;
+            if(inp != 0 || cwdl==0) {
+                if(in[inp] != '/') { out[outp++] = in[inp++]; continue; }
+                while(in[inp] == '/') inp++;
             }
             if(in[inp] == '\0') continue;
             if(in[inp] != '.') { out[outp++] = '/'; out[outp++] = in[inp++]; continue; }
@@ -462,10 +781,11 @@ public abstract class UnixRuntime extends Runtime {
                 inp += 2;
                 if(outp > 0) outp--;
                 while(outp > 0 && out[outp] != '/') outp--;
-                System.err.println("After ..: " + new String(out,0,outp));
+                //System.err.println("After ..: " + new String(out,0,outp));
                 continue;
             }
             inp++;
+            out[outp++] = '/';
             out[outp++] = '.';
         }
         if(outp > 0 && out[outp-1] == '/') outp--;
@@ -473,170 +793,60 @@ public abstract class UnixRuntime extends Runtime {
         return new String(out,0,outp);
     }
     
-    // FIXME: This is probably still buggy
-    // FEATURE: Remove some of the "should never happen checks"
-    /*protected static String cleanupPath(String p) throws ErrnoException {
-        if(p.length() == 0) throw new ErrnoException(ENOENT);
-        if(needsCleanup(p)) {
-            char[] in = p.toCharArray();
-            char[] out;
-            int outp ;
-            if(in[0] == '/') {
-                out = new char[in.length];
-                outp = 0;
-            } else {
-                out = new char[cwd.length() + in.length + 1];
-                outp = cwd.length();
-                for(int i=0;i<outp;i++) out[i] = cwd.charAt(i);
-                if(outp == 0 || out[0] != '/') throw new Error("should never happen");
-            }
-            int inLength = in.length;
-            int inp = 0;
-            while(inp<inLength) {
-                if(inp == 0 || in[inp] == '/') {
-                    while(inp < inLength && in[inp] == '/') inp++;
-                    if(inp == inLength) break;
-                    if(in[inp] == '.') {
-                        if(inp+1 == inLength) break;
-                        if(in[inp+1] == '.' && (inp+2 == inLength || in[inp+2] == '/')) {
-                            inp+=2;
-                            if(outp == 0) continue;
-                            do { outp--; } while(outp > 0 && out[outp] != '/');
-                        } else if(in[inp+1] == '/') {
-                            inp++;
-                        } else {
-                            out[outp++] = '/';
-                        }
-                    } else {
-                        out[outp++] = '/';
-                        out[outp++] = in[inp++];
-                    }
-                } else {
-                    out[outp++] = in[inp++];
-                }
-            }
-            if(outp == 0) out[outp++] = '/';
-            return new String(out,0,outp);
-        } else {
-            if(p.startsWith("/")) return p;
-            StringBuffer sb = new StringBuffer(cwd);
-            if(!cwd.equals("/")) sb.append('/');
-            return sb.append(p).toString();
-        }
-    }*/
-    
-    public static class MountPointFS extends FS {
-        private static class MP {
-            public MP(String path, FS fs) { this.path = path; this.fs = fs; }
-            public String path;
-            public FS fs;
-            public int compareTo(Object o) {
-                if(!(o instanceof MP)) return 1;
-                return -path.compareTo(((MP)o).path);
-            }
-        }
-        private final MP[][] mps = new MP[128][];
-        private final FS root;
-        public MountPointFS(FS root) { this.root = root; }
-        
-        private static String fixup(String path) {
-            if(!path.startsWith("/")) throw new IllegalArgumentException("Mount point doesn't start with a /");
-            path = path.substring(1);
-            if(path.length() == 0) throw new IllegalArgumentException("Zero length mount point path");
-            return path;
-        }
-        public FS get(String path) {
-            path = fixup(path);
-            int f = path.charAt(0) & 0x7f;
-            for(int i=0;mps[f] != null && i < mps[f].length;i++)
-                if(mps[f][i].path.equals(path)) return mps[f][i].fs;
-            return null;
-        }
-        
-        public void add(String path, FS fs) {
-            if(get(path) != null) throw new IllegalArgumentException("mount point already exists");
-            path = fixup(path);
-            int f = path.charAt(0) & 0x7f;
-            int oldLength = mps[f] == null ? 0 : mps[f].length;
-            MP[] newList = new MP[oldLength + 1];
-            if(oldLength != 0) System.arraycopy(mps[f],0,newList,0,oldLength);
-            newList[oldLength] = new MP(path,fs);
-            Arrays.sort(newList);
-            mps[f] = newList;
-        }
-        
-        public void remove(String path) {
-            path = fixup(path);
-            if(get(path) == null) throw new IllegalArgumentException("mount point doesn't exist");
-            int f = path.charAt(0) & 0x7f;
-            MP[] oldList = mps[f];
-            MP[] newList = new MP[oldList.length - 1];
-            int p = 0;
-            for(p=0;p<oldList.length;p++) if(oldList[p].path.equals(path)) break;
-            if(p == oldList.length) throw new Error("should never happen");
-            System.arraycopy(oldList,0,newList,0,p);
-            System.arraycopy(oldList,0,newList,p,oldList.length-p-1);
-            mps[f] = newList;
-        }
-        
-        protected Object op(int op, String path, int arg1, int arg2) throws IOException {
-            int pl = path.length();
-            if(pl != 0) {
-            	    MP[] list = mps[path.charAt(0) & 0x7f];
-            	    if(list != null) for(int i=0;i<list.length;i++) {
-            	    	    	MP mp = list[i];
-            	    	    	int mpl = mp.path.length();
-            	    	    	if(pl == mpl || (pl < mpl && path.charAt(mpl) == '/'))
-            	    	    	return mp.fs.op(op,pl == mpl ? "" : path.substring(mpl+1),arg1,arg2);
-                 }
+    FStat hostFStat(final File f, Object data) {
+        boolean e = false;
+        try {
+            FileInputStream fis = new FileInputStream(f);
+            switch(fis.read()) {
+                case '\177': e = fis.read() == 'E' && fis.read() == 'L' && fis.read() == 'F'; break;
+                case '#': e = fis.read() == '!';
             }
-            return root.op(op,path,arg1,arg2);
-        }
+            fis.close();
+        } catch(IOException e2) { } 
+        HostFS fs = (HostFS) data;
+        final int inode = fs.inodes.get(f.getAbsolutePath());
+        final int devno = fs.devno;
+        return new HostFStat(f,e) {
+            public int inode() { return inode; }
+            public int dev() { return devno; }
+        };
+    }
+
+    FD hostFSDirFD(File f, Object _fs) {
+        HostFS fs = (HostFS) _fs;
+        return fs.new HostDirFD(f);
     }
-    
-    // FEATURE: Probably should make this more general - support mountpoints, etc
-    /*public class UnixOverlayFS extends FS {
-        private final FS root;
-        private final FS dev = new DevFS();
-        public UnixOverlayFS(FS root) {
-            this.root = root;
-        }
-        private String devPath(String path) {
-            if(path.startsWith("/dev")) {
-                if(path.length() == 4) return "/";
-                if(path.charAt(4) == '/') return path.substring(4);
-            }
-            return null;
-        }
-        public FD open(String path, int flags, int mode) throws IOException{
-            String dp = devPath(path);
-            return dp == null ? root.open(path,flags,mode) : dev.open(dp,flags,mode);
-        }
-        public FStat stat(String path) throws IOException {
-            String dp = devPath(path);
-            return dp == null ? root.stat(path) : dev.stat(dp);
-        }
-        public void mkdir(String path) throws IOException {
-            String dp = devPath(path);
-            if(dp == null) root.mkdir(path);
-            else dev.mkdir(dp);
-        }
-    }*/
     
     public static class HostFS extends FS {
+        InodeCache inodes = new InodeCache(4000);
         protected File root;
         public File getRoot() { return root; }
         
         private static File hostRootDir() {
+            if(getSystemProperty("nestedvm.root") != null) {
+                File f = new File(getSystemProperty("nestedvm.root"));
+                if(f.isDirectory()) return f;
+                // fall through to case below
+            }
             String cwd = getSystemProperty("user.dir");
             File f = new File(cwd != null ? cwd : ".");
+            if(!f.exists()) throw new Error("Couldn't get File for cwd");
             f = new File(f.getAbsolutePath());
             while(f.getParent() != null) f = new File(f.getParent());
             return f;
         }
         
         private File hostFile(String path) {
-            if(File.separatorChar != '/') path = path.replace('/',File.separatorChar);
+            char sep = File.separatorChar;
+            if(sep != '/') {
+                char buf[] = path.toCharArray();
+                for(int i=0;i<buf.length;i++) {
+                    char c = buf[i];
+                    if(c == '/') buf[i] = sep;
+                    else if(c == sep) buf[i] = '/';
+                }
+                path = new String(buf);
+            }
             return new File(root,path);
         }
         
@@ -645,70 +855,147 @@ public abstract class UnixRuntime extends Runtime {
         public HostFS(File root) { this.root = root; }
         
         
-        // FEATURE: This shares a lot with Runtime.open
-        // NOTE: createNewFile is a Java2 function
-        public FD _open(String path, int flags, int mode) throws IOException {
+        public FD open(UnixRuntime r, String path, int flags, int mode) throws ErrnoException {
             final File f = hostFile(path);
-            if(f.isDirectory()) {
-                if((flags&3)!=RD_ONLY) throw new ErrnoException(EACCES);
-                return directoryFD(f.list(),path.hashCode());
-            }
-            if((flags & (O_EXCL|O_CREAT)) == (O_EXCL|O_CREAT))
-                if(!f.createNewFile()) throw new ErrnoException(EEXIST);
-            if((flags&O_CREAT) == 0 && !f.exists())
-                return null;
-            final Seekable.File sf = new Seekable.File(f,(flags&3)!=RD_ONLY);
-            if((flags&O_TRUNC)!=0) sf.setLength(0);
-            return new SeekableFD(sf,mode) {
-                protected FStat _fstat() { return new HostFStat(f) {
-                    public int size() {
-                        try { return sf.length(); } catch(IOException e) { return 0; }
-                    }
-                };}
-            };
+            return r.hostFSOpen(f,flags,mode,this);
+        }
+        
+        public void unlink(UnixRuntime r, String path) throws ErrnoException {
+            File f = hostFile(path);
+            if(r.sm != null && !r.sm.allowUnlink(f)) throw new ErrnoException(EPERM);
+            if(!f.exists()) throw new ErrnoException(ENOENT);
+            if(!f.delete()) throw new ErrnoException(EPERM);
         }
         
-        public FStat _stat(String path) throws FileNotFoundException {
+        public FStat stat(UnixRuntime r, String path) throws ErrnoException {
             File f = hostFile(path);
-            if(!f.exists()) throw new FileNotFoundException();
-            return new HostFStat(f);
+            if(r.sm != null && !r.sm.allowStat(f)) throw new ErrnoException(EACCES);
+            if(!f.exists()) return null;
+            return r.hostFStat(f,this);
         }
         
-        public void _mkdir(String path) throws IOException {
+        public void mkdir(UnixRuntime r, String path, int mode) throws ErrnoException {
             File f = hostFile(path);
+            if(r.sm != null && !r.sm.allowWrite(f)) throw new ErrnoException(EACCES);
             if(f.exists() && f.isDirectory()) throw new ErrnoException(EEXIST);
             if(f.exists()) throw new ErrnoException(ENOTDIR);
             File parent = f.getParentFile();
             if(parent!=null && (!parent.exists() || !parent.isDirectory())) throw new ErrnoException(ENOTDIR);
             if(!f.mkdir()) throw new ErrnoException(EIO);            
         }
+        
+        public class HostDirFD extends DirFD {
+            private final File f;
+            private final File[] children;
+            public HostDirFD(File f) { this.f = f; children = f.listFiles(); }
+            public int size() { return children.length; }
+            public String name(int n) { return children[n].getName(); }
+            public int inode(int n) { return inodes.get(children[n].getAbsolutePath()); }
+            public int parentInode() {
+                File parent = f.getParentFile();
+                return parent == null ? -1 : inodes.get(parent.getAbsolutePath());
+            }
+            public int myInode() { return inodes.get(f.getAbsolutePath()); }
+            public int myDev() { return devno; } 
+        }
+    }
+    
+    private static void putInt(byte[] buf, int off, int n) {
+        buf[off+0] = (byte)((n>>>24)&0xff);
+        buf[off+1] = (byte)((n>>>16)&0xff);
+        buf[off+2] = (byte)((n>>> 8)&0xff);
+        buf[off+3] = (byte)((n>>> 0)&0xff);
+    }
+    
+    public static abstract class DirFD extends FD {
+        private int pos = -2;
+        
+        protected abstract int size();
+        protected abstract String name(int n);
+        protected abstract int inode(int n);
+        protected abstract int myDev();
+        protected int parentInode() { return -1; }
+        protected int myInode() { return -1; }
+        
+        public int getdents(byte[] buf, int off, int len) {
+            int ooff = off;
+            int ino;
+            int reclen;
+            OUTER: for(;len > 0 && pos < size();pos++){
+                switch(pos) {
+                    case -2:
+                    case -1:
+                        ino = pos == -1 ? parentInode() : myInode();
+                        if(ino == -1) continue;
+                        reclen = 9 + (pos == -1 ? 2 : 1);
+                        if(reclen > len) break OUTER;
+                        buf[off+8] = '.';
+                        if(pos == -1) buf[off+9] = '.';
+                        break;
+                    default: {
+                        String f = name(pos);
+                        byte[] fb = getBytes(f);
+                        reclen = fb.length + 9;
+                        if(reclen > len) break OUTER;
+                        ino = inode(pos);
+                        System.arraycopy(fb,0,buf,off+8,fb.length);
+                    }
+                }
+                buf[off+reclen-1] = 0; // null terminate
+                reclen = (reclen + 3) & ~3; // add padding
+                putInt(buf,off,reclen);
+                putInt(buf,off+4,ino);
+                off += reclen;
+                len -= reclen;    
+            }
+            return off-ooff;
+        }
+        
+        protected FStat _fstat() {
+            return new FStat() { 
+                public int type() { return S_IFDIR; }
+                public int inode() { return myInode(); }
+                public int dev() { return myDev(); }
+            };
+        }
     }
         
-    private static class DevFStat extends FStat {
-        public int dev() { return 1; }
-        public int mode() { return 0666; }
-        public int type() { return S_IFCHR; }
-        public int nlink() { return 1; }
-    }
-    private static FD devZeroFD = new FD() {
-        public boolean readable() { return true; }
-        public boolean writable() { return true; }
-        public int read(byte[] a, int off, int length) { Arrays.fill(a,off,off+length,(byte)0); return length; }
-        public int write(byte[] a, int off, int length) { return length; }
-        public int seek(int n, int whence) { return 0; }
-        public FStat _fstat() { return new DevFStat(); }
-    };
-    private static FD devNullFD = new FD() {
-        public boolean readable() { return true; }
-        public boolean writable() { return true; }
-        public int read(byte[] a, int off, int length) { return 0; }
-        public int write(byte[] a, int off, int length) { return length; }
-        public int seek(int n, int whence) { return 0; }
-        public FStat _fstat() { return new DevFStat(); }
-    };    
-    
-    public class DevFS extends FS {
-        public FD _open(String path, int mode, int flags) throws IOException {
+    public static class DevFS extends FS {
+        private static final int ROOT_INODE = 1;
+        private static final int NULL_INODE = 2;
+        private static final int ZERO_INODE = 3;
+        private static final int FD_INODE = 4;
+        private static final int FD_INODES = 32;
+        
+        private class DevFStat extends FStat {
+            public int dev() { return devno; }
+            public int mode() { return 0666; }
+            public int type() { return S_IFCHR; }
+            public int nlink() { return 1; }
+        }
+        
+        private abstract class DevDirFD extends DirFD {
+            public int myDev() { return devno; }
+        }
+        
+        private FD devZeroFD = new FD() {
+            public boolean readable() { return true; }
+            public boolean writable() { return true; }
+            public int read(byte[] a, int off, int length) { Arrays.fill(a,off,off+length,(byte)0); return length; }
+            public int write(byte[] a, int off, int length) { return length; }
+            public int seek(int n, int whence) { return 0; }
+            public FStat _fstat() { return new DevFStat(){ public int inode() { return ZERO_INODE; } }; }
+        };
+        private FD devNullFD = new FD() {
+            public boolean readable() { return true; }
+            public boolean writable() { return true; }
+            public int read(byte[] a, int off, int length) { return 0; }
+            public int write(byte[] a, int off, int length) { return length; }
+            public int seek(int n, int whence) { return 0; }
+            public FStat _fstat() { return new DevFStat(){ public int inode() { return NULL_INODE; } }; }
+        }; 
+        
+        public FD open(UnixRuntime r, String path, int mode, int flags) throws ErrnoException {
             if(path.equals("null")) return devNullFD;
             if(path.equals("zero")) return devZeroFD;
             if(path.startsWith("fd/")) {
@@ -716,28 +1003,55 @@ public abstract class UnixRuntime extends Runtime {
                 try {
                     n = Integer.parseInt(path.substring(4));
                 } catch(NumberFormatException e) {
-                    throw new FileNotFoundException();
+                    return null;
                 }
-                if(n < 0 || n >= OPEN_MAX) throw new FileNotFoundException();
-                if(fds[n] == null) throw new FileNotFoundException();
-                return fds[n].dup();
+                if(n < 0 || n >= OPEN_MAX) return null;
+                if(r.fds[n] == null) return null;
+                return r.fds[n].dup();
             }
             if(path.equals("fd")) {
                 int count=0;
-                for(int i=0;i<OPEN_MAX;i++) if(fds[i] != null) count++; 
-                String[] files = new String[count];
+                for(int i=0;i<OPEN_MAX;i++) if(r.fds[i] != null) { count++; }
+                final int[] files = new int[count];
                 count = 0;
-                for(int i=0;i<OPEN_MAX;i++) if(fds[i] != null) files[count++] = Integer.toString(i);
-                return directoryFD(files,hashCode());
+                for(int i=0;i<OPEN_MAX;i++) if(r.fds[i] != null) files[count++] = i;
+                return new DevDirFD() {
+                    public int myInode() { return FD_INODE; }
+                    public int parentInode() { return ROOT_INODE; }
+                    public int inode(int n) { return FD_INODES + n; }
+                    public String name(int n) { return Integer.toString(files[n]); }
+                    public int size() { return files.length; }
+                };
             }
             if(path.equals("")) {
-                String[] files = { "null", "zero", "fd" };
-                return directoryFD(files,hashCode());
+                return new DevDirFD() {
+                    public int myInode() { return ROOT_INODE; }
+                    // FEATURE: Get the real parent inode somehow
+                    public int parentInode() { return -1; }
+                    public int inode(int n) {
+                        switch(n) {
+                            case 0: return NULL_INODE;
+                            case 1: return ZERO_INODE;
+                            case 2: return FD_INODE;
+                            default: return -1;
+                        }
+                    }
+                    
+                    public String name(int n) {
+                        switch(n) {
+                            case 0: return "null";
+                            case 1: return "zero";
+                            case 2: return "fd";
+                            default: return null;
+                        }
+                    }
+                    public int size() { return 3; }
+                };
             }
-            throw new FileNotFoundException();
+            return null;
         }
         
-        public FStat _stat(String path) throws IOException {
+        public FStat stat(UnixRuntime r,String path) throws ErrnoException {
             if(path.equals("null")) return devNullFD.fstat();
             if(path.equals("zero")) return devZeroFD.fstat();            
             if(path.startsWith("fd/")) {
@@ -745,17 +1059,19 @@ public abstract class UnixRuntime extends Runtime {
                 try {
                     n = Integer.parseInt(path.substring(4));
                 } catch(NumberFormatException e) {
-                    throw new FileNotFoundException();
+                    return null;
                 }
-                if(n < 0 || n >= OPEN_MAX) throw new FileNotFoundException();
-                if(fds[n] == null) throw new FileNotFoundException();
-                return fds[n].fstat();
+                if(n < 0 || n >= OPEN_MAX) return null;
+                if(r.fds[n] == null) return null;
+                return r.fds[n].fstat();
             }
+            // FEATURE: inode stuff
             if(path.equals("fd")) return new FStat() { public int type() { return S_IFDIR; } public int mode() { return 0444; }};
             if(path.equals("")) return new FStat() { public int type() { return S_IFDIR; } public int mode() { return 0444; }};
-            throw new FileNotFoundException();
+            return null;
         }
         
-        public void _mkdir(String path) throws IOException { throw new ErrnoException(EACCES); }
-    }
+        public void mkdir(UnixRuntime r, String path, int mode) throws ErrnoException { throw new ErrnoException(EROFS); }
+        public void unlink(UnixRuntime r, String path) throws ErrnoException { throw new ErrnoException(EROFS); }
+    }    
 }