X-Git-Url: http://git.megacz.com/?p=nestedvm.git;a=blobdiff_plain;f=src%2Forg%2Fibex%2Fnestedvm%2FUnixRuntime.java;h=051a50be063926a90b68c1f811487254a09ae4d2;hp=24a7967f0e598f0afc1d8a3cb4bb1fff044caf1b;hb=c59b7cfc7a6b67574d38c5c8eb7732bad37236b0;hpb=034a42fa65955289442614ef9914e5474fac62aa

diff --git a/src/org/ibex/nestedvm/UnixRuntime.java b/src/org/ibex/nestedvm/UnixRuntime.java
index 24a7967..051a50b 100644
--- a/src/org/ibex/nestedvm/UnixRuntime.java
+++ b/src/org/ibex/nestedvm/UnixRuntime.java
@@ -4,25 +4,19 @@ import org.ibex.nestedvm.util.*;
 import java.io.*;
 import java.util.*;
 
+// FEATURE: Remove System.{out,err}.printlns and throw Errors where applicable
+
 // 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: Throw ErrnoException and catch in syscall whereever possible 
-// (only in cases where we've already paid the price for a throw)
-
 public abstract class UnixRuntime extends Runtime implements Cloneable {
     /** The pid of this "process" */
     private int pid;
-    private int ppid;
+    private UnixRuntime parent;
     protected int getPid() { return pid; }
     
-    /** processes filesystem */
-    private FS fs;
-    public FS getFS() { return fs; }
-    public void setFS(FS fs) {
-        if(state != STOPPED) throw new IllegalStateException("Can't change fs while process is running");
-        this.fs = fs;
-    }
+    private static final GlobalState defaultGD = new GlobalState();
+    private GlobalState gd = defaultGD;
     
     /** proceses' current working directory - absolute path WITHOUT leading slash
         "" = root, "bin" = /bin "usr/bin" = /usr/bin */
@@ -30,40 +24,14 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
     
     /** The runtime that should be run next when in state == EXECED */
     private UnixRuntime execedRuntime;
-    
-    /* 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; }
-        }
-    }
+
+    private Object children; // used only for synchronizatin
+    private Vector activeChildren;
+    private Vector exitedChildren;
     
     public UnixRuntime(int pageSize, int totalPages) {
         super(pageSize,totalPages);
-        
-        FS root = new HostFS();
-        FS dev = new DevFS();
-        MountPointFS mounts = new MountPointFS(root);
-        mounts.add("/dev",dev);
-        fs = mounts;
-        
+                
         // FEATURE: Do the proper mangling for non-unix hosts
         String userdir = getSystemProperty("user.dir");
         cwd = userdir != null && userdir.startsWith("/") && File.separatorChar == '/'  ? userdir.substring(1) : "";
@@ -108,25 +76,27 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         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 == EXITED) removeTask(tasks[i]);
-                    else tasks[i].ppid = 0;
-                }
+    protected void _started() {
+        UnixRuntime[] tasks = gd.tasks;
+        synchronized(gd) {
+            if(pid != 0) {
+                if(tasks[pid] == null || tasks[pid].pid != pid) throw new Error("should never happen");
+            } else {
+                int newpid = -1;
+                int nextPID = gd.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;
+                gd.nextPID = newpid + 1;
             }
-            state = EXITED;
-            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();
@@ -134,22 +104,20 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
             case SYS_dup2: return sys_dup2(a,b);
             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);
 
-            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);
+    protected FD _open(String path, int flags, int mode) throws ErrnoException {
+        return gd.open(this,normalizePath(path),flags,mode);
     }
 
-    // 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.
@@ -178,45 +146,87 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         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 {
+        System.err.println("PID: " + this.pid + " is waiting on " + pid);
         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) {
+            System.err.println("WARNING: waitpid called with a pid of " + pid);
+            return -ECHILD;
+        }
+        boolean blocking = (options&WNOHANG)==0;
+        
+        if(pid !=-1 && (pid <= 0 || pid >= gd.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 == EXITED) {
-                            task = tasks[i];
-                            break;
-                        }
+                    if(exitedChildren.size() > 0) done = (UnixRuntime)exitedChildren.remove(exitedChildren.size() - 1);
+                } else if(pid > 0) {
+                    UnixRuntime t = gd.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 == EXITED) {
-                    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 {
+                    gd.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;
+    }
+    
+    
+    protected void _exited() {
+        if(children != null) synchronized(children) {
+            for(Enumeration e = exitedChildren.elements(); e.hasMoreElements(); ) {
+                UnixRuntime child = (UnixRuntime) e.nextElement();
+                    gd.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) {
+            gd.tasks[pid] = null;
+        } else {
+            synchronized(_parent.children) {
+                if(parent == null) {
+                    gd.tasks[pid] = null;
+                } else {
+                    parent.activeChildren.remove(this);
+                    parent.exitedChildren.add(this);
+                    parent.children.notify();
+                }
             }
         }
     }
     
     protected Object clone() throws CloneNotSupportedException {
     	    UnixRuntime r = (UnixRuntime) super.clone();
-        r.pid = r.ppid = 0;
+        r.pid = 0;
+        r.parent = null;
+        r.children = null;
+        r.activeChildren = r.exitedChildren = null;
         return r;
     }
 
@@ -232,29 +242,37 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
             e.printStackTrace();
             return -ENOMEM;
         }
-        
-        int childPID = addTask(r);
-        if(childPID < 0) return -ENOMEM;
-        
-        r.ppid = pid;
+
+        r.parent = this;
+
+        try {
+            r._started();
+        } catch(ProcessTableFullExn e) {
+        	    return -ENOMEM;
+        }
+
+        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();
-                }
-            }
-        }.start();
+        new ForkedProcess(r);
         
-        return childPID;
+        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)); }
@@ -279,63 +297,40 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         return a;
     }
     
-    // FEATURE: call the syscall just "exec"
-    private int sys_execve(int cpath, int cargv, int cenvp) {
-        try {
-        	    return exec(normalizePath(cstring(cpath)),readStringArray(cargv),readStringArray(cenvp));
-        } catch(FaultException e) {
-            return -EFAULT;
-        }
+    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 path, String[] argv, String[] envp) {
-        final UnixRuntime r;
         
-        throw new Error("FIXME exec() not finished");
-        //Class klass = fs.getClass(path);
-        //if(klass != null) return exec(klass,argv,envp);
-        
-        /*try {
-             Seekable s = fs.getSeekable(path);
-             boolean elf = false;
-             boolean script = false;
-             switch(s.read()) {
-                case '\177': elf = s.read() == 'E' && s.read() == 'L' && s.read() == 'F'; break;
-                case '#': script = s.read() == '!';
-            }
-            s.close();
-            if(script) {
-                // FIXME #! support
-                throw new Error("FIXME can't exec scripts yet");
-                // append args, etc
-                // return exec(...)
-            } else if(elf) {
-                klass = fs.(path);
-                if(klass == null) return -ENOEXEC;
-                return exec(klass,argv,envp);
-            } else {
-            	    return -ENOEXEC;
+    private int exec(String normalizedPath, String[] argv, String[] envp) throws ErrnoException {
+        if(argv.length == 0) argv = new String[]{""};
+
+        Object o = gd.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;
             }
-        }*/
-        // FEATURE: Way too much overlap in the handling of ioexeptions everhwere
-        /*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; }*/
+        } 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(Class c, String[] argv, String[] envp) {
-        UnixRuntime r;
-        
-        try {
-        	    r = (UnixRuntime) c.newInstance();
-        } catch(Exception e) {
-        	    return -ENOMEM;
-        }
+    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;
@@ -343,12 +338,13 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         fds = null;
         closeOnExec = null;
         
+        r.gd = gd;
+        r.sm = sm;
         r.cwd = cwd;
-        r.fs = fs;
         r.pid = pid;
-        r.ppid = ppid;
+        r.parent = parent;
         r.start(argv,envp);
-        
+                
         state = EXECED;
         execedRuntime = r;
         
@@ -356,7 +352,7 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
     }
     
     // FEATURE: Use custom PipeFD - be sure to support PIPE_BUF of data
-    private int sys_pipe(int addr) {
+    private int sys_pipe(int addr) throws FaultException {
         PipedOutputStream writerStream = new PipedOutputStream();
         PipedInputStream readerStream;
         try {
@@ -391,107 +387,261 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         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_stat(int cstring, int addr) throws FaultException, ErrnoException {
+        FStat s = gd.stat(this,normalizePath(cstring(cstring)));
+        if(s == null) return -ENOENT;
+        return stat(s,addr);
     }
     
+    private int sys_lstat(int cstring, int addr) throws FaultException, ErrnoException {
+        FStat s = gd.lstat(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_mkdir(int cstring, int mode) throws FaultException, ErrnoException {
+        gd.mkdir(this,normalizePath(cstring(cstring)),mode);
+        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(gd.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 != STOPPED) 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();
+    
+    //  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 LSTAT = 3;
+        protected static final int MKDIR = 4;
+        
+        // Make this protected (need to fix _exit)
+        private final UnixRuntime[] tasks;
+        private int nextPID = 1;
+        
+        private final MP[][] mps = new MP[128][];
+        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) {
+            	    root = new HostFS();
+                addMount("/dev",new DevFS());
+            }
         }
-        cwd = dir;
-    }
         
-    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); }
+        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);
+            }
+        }
         
-        protected static final int OPEN = 1;
-        protected static final int STAT = 2;
-        protected static final int MKDIR = 3;
+        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);
+            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 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(path.equals("/")) { root = fs; return; }
+            path = path.substring(1);
+            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 synchronized void removeMount(String path) {
+            if(getMount(path) == null) throw new IllegalArgumentException("mount point doesn't exist");
+            if(!path.startsWith("/")) throw new IllegalArgumentException("Mount point doesn't start with a /");
+            if(path.equals("/")) { root = null; return; }
+            path = path.substring(1);
+            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;
+        }
+        
+        private Object fsop(int op, UnixRuntime r, String path, int arg1, int arg2) throws ErrnoException {
+            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(path.startsWith(mp.path) && (pl == mpl || (pl < mpl && path.charAt(mpl) == '/')))
+                        	    return dispatch(mp.fs,op,r,pl == mpl ? "" : path.substring(mpl+1),arg1,arg2);
+                    }
+                }
+            }
+            return dispatch(root,op,r,path,arg1,arg2);
+        }
         
-        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");
-        		}
+        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;
+                default: throw new Error("should never happen");
+            }
         }
         
-        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); }
+        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); }
+        
+        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 {
+            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 Error("zero length file");
+                
+                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) {
+                    throw new ErrnoException(ENOEXEC);
+                } catch(IOException e) {
+                	    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 {
 		// FEATURE: inode stuff
         // FEATURE: Implement whatever is needed to get newlib's opendir and friends to work - that patch is a pain
-        protected static FD directoryFD(String[] files, int hashCode) throws IOException {
+        protected static FD directoryFD(String[] files, int hashCode)  {
             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);
+            try {
+            	    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);
+                }
+            } catch(IOException e) {
+            	    return null;
             }
             final byte[] data = bos.toByteArray();
             return new SeekableFD(new Seekable.ByteArray(data,false),RD_ONLY) {
@@ -501,6 +651,14 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
                 }; }
             };
         }
+
+        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;
     }
         
     private String normalizePath(String path) {
@@ -545,76 +703,22 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         //System.err.println("normalize: " + path + " -> " + new String(out,0,outp) + " (cwd: " + cwd + ")");
         return new String(out,0,outp);
     }
+         
+    // FEATURE: override Runtime.hostFStat to add executable type checking
+    // hostFStat
+    /*             try {
+                FileInputStream fis = new FileInputStream(f);
+                switch(fis.read()) {
+                    case '\177': _executable = fis.read() == 'E' && fis.read() == 'L' && fis.read() == 'F'; break;
+                    case '#': _executable = fis.read() == '!';
+                }
+                fis.close();
+            } catch(IOException e) { }
+    */
+
+    // FEATURE: inode stuff
+    FD hostFSDirFD(File f) { return FS.directoryFD(f.list(),f.hashCode()); }
     
-    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 synchronized 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 synchronized 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 synchronized 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);
-                 }
-            }
-            return root.op(op,path,arg1,arg2);
-        }
-    }
-        
     public static class HostFS extends FS {
         protected File root;
         public File getRoot() { return root; }
@@ -627,7 +731,7 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
             return f;
         }
         
-        File hostFile(String path) {
+        private File hostFile(String path) {
             char sep = File.separatorChar;
             if(sep != '/') {
                 char buf[] = path.toCharArray();
@@ -646,37 +750,21 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         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);
         }
         
-        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);
         }
         
-        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();
@@ -685,80 +773,78 @@ public abstract class UnixRuntime extends Runtime implements Cloneable {
         }
     }
         
-    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(); }
-    };    
-    
-    // FIXME: Support /dev/fd (need to have syscalls pass along Runtime instance)
     public static class DevFS extends FS {
-        public FD _open(String path, int mode, int flags) throws IOException {
+        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 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/")) {
+            if(path.startsWith("fd/")) {
                 int n;
                 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++; 
+                for(int i=0;i<OPEN_MAX;i++) if(r.fds[i] != null) count++; 
                 String[] files = new String[count];
                 count = 0;
-                for(int i=0;i<OPEN_MAX;i++) if(fds[i] != null) files[count++] = Integer.toString(i);
+                for(int i=0;i<OPEN_MAX;i++) if(r.fds[i] != null) files[count++] = Integer.toString(i);
                 return directoryFD(files,hashCode());
-            }*/
+            }
             if(path.equals("")) {
                 String[] files = { "null", "zero", "fd" };
                 return directoryFD(files,hashCode());
             }
-            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/")) {
+            if(path.startsWith("fd/")) {
                 int n;
                 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();
             }
             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(EACCES); }
     }
 }