X-Git-Url: http://git.megacz.com/?p=nestedvm.git;a=blobdiff_plain;f=src%2Forg%2Fibex%2Fnestedvm%2FRuntime.java;h=2a91e3613ebda8733909fef05888a0aa83b9ce50;hp=bcbadd4d8bde15ef88351904e64b35c985e3a3a0;hb=b11e7c6c29f2b5f7b0828bf93eb741c4a30ec411;hpb=9a641039c47c2619982213501f49e1168fcdbda2

diff --git a/src/org/ibex/nestedvm/Runtime.java b/src/org/ibex/nestedvm/Runtime.java
index bcbadd4..2a91e36 100644
--- a/src/org/ibex/nestedvm/Runtime.java
+++ b/src/org/ibex/nestedvm/Runtime.java
@@ -1,3 +1,7 @@
+// Copyright 2000-2005 the Contributors, as shown in the revision logs.
+// Licensed under the Apache License 2.0 ("the License").
+// You may not use this file except in compliance with the License.
+
 // Copyright 2003 Brian Alliet
 // Based on org.xwt.imp.MIPS by Adam Megacz
 // Portions Copyright 2003 Adam Megacz
@@ -6,97 +10,86 @@ package org.ibex.nestedvm;
 
 import org.ibex.nestedvm.util.*;
 import java.io.*;
-import java.util.Arrays;
-
-// FEATURE: Look over the public API, make sure we're exposing a bare minimum
-// (we might make this an interface in the future)
 
-public abstract class Runtime implements UsermodeConstants,Registers {
-    /** Pages are 4k in size */
-    protected final int PAGE_SIZE;
-    protected final int PAGE_WORDS;
-    protected final int PAGE_SHIFT;
-    protected final int TOTAL_PAGES;
-    /** This is the upper limit of the pages allocated by the sbrk() syscall. */
-    protected final int BRK_LIMIT;
-    protected final int STACK_BOTTOM;
-
-    /** This is the maximum size of command line arguments */
-    public final static int ARGS_MAX = 1024*1024;
-    
-    /** True if we allow empty pages (_emptyPage) to exist in memory.
-       Empty pages are pages which are allocated by the program but do not contain any
-       data yet (they are all 0s). If empty pages are allowed subclasses must always
-       access main memory with the memRead and memWrite functions */
-    private final boolean allowEmptyPages;
-    /** the "empty page" */
-    private final static int[] _emptyPage = new int[0];
+public abstract class Runtime implements UsermodeConstants,Registers,Cloneable {
+    public static final String VERSION = "1.0";
     
-    protected final static boolean isEmptyPage(int[] page) { return page == _emptyPage; }
+    /** True to write useful diagnostic information to stderr when things go wrong */
+    final static boolean STDERR_DIAG = true;
     
-    /** Returns a new empty page (_emptyPage is empty pages are enabled or a new zero'd page) */
-    private final int[] emptyPage() { return allowEmptyPages ? _emptyPage : new int[PAGE_WORDS]; }
+    /** Number of bits to shift to get the page number (1<<<pageShift == pageSize) */
+    protected final int pageShift;
+    /** Bottom of region of memory allocated to the stack */
+    private final int stackBottom;
     
     /** Readable main memory pages */
-    protected final int[][] readPages;
+    protected int[][] readPages;
     /** Writable main memory pages.
         If the page is writable writePages[x] == readPages[x]; if not writePages[x] == null. */
-    protected final int[][] writePages;
+    protected int[][] writePages;
     
-    /** The current break between the heap and unallocated memory */
-    protected int brkAddr;
+    /** The address of the end of the heap */
+    private int heapEnd;
+    
+    /** Number of guard pages to keep between the stack and the heap */
+    private static final int STACK_GUARD_PAGES = 4;
+    
+    /** The last address the executable uses (other than the heap/stack) */
+    protected abstract int heapStart();
         
     /** The program's entry point */
-    protected int entryPoint;
+    protected abstract int entryPoint();
 
     /** The location of the _user_info block (or 0 is there is none) */
-    protected int userInfoBase;
-    protected int userInfoSize;
+    protected int userInfoBase() { return 0; }
+    protected int userInfoSize() { return 0; }
     
     /** The location of the global pointer */
-    protected int gp;
+    protected abstract int gp();
     
     /** When the process started */
     private long startTime;
     
-    /** State constant: There is no program loaded in memory */
-    public final static int UNINITIALIZED = 0; 
-    /**  Text/Data loaded in memory  */
-    public final static int INITIALIZED = 1;
     /** Program is executing instructions */
-    public final static int RUNNING = 2;
+    public final static int RUNNING = 0; // Horrible things will happen if this isn't 0
+    /**  Text/Data loaded in memory  */
+    public final static int STOPPED = 1;
     /** Prgram has been started but is paused */
-    public final static int PAUSED = 3;
+    public final static int PAUSED = 2;
     /** Program is executing a callJava() method */
-    public final static int CALLJAVA = 4;
+    public final static int CALLJAVA = 3;
     /** Program has exited (it cannot currently be restarted) */
-    public final static int DONE = 5;
-        
-    /** The current state (UNINITIALIZED, INITIALIZED, RUNNING, PAUSED, or DONE) */
-    protected int state = UNINITIALIZED;
+    public final static int EXITED = 4;
+    /** Program has executed a successful exec(), a new Runtime needs to be run (used by UnixRuntime) */
+    public final static int EXECED = 5;
+    
+    /** The current state */
+    protected int state = STOPPED;
     /** @see Runtime#state state */
     public final int getState() { return state; }
     
     /** The exit status if the process (only valid if state==DONE) 
         @see Runtime#state */
-    protected int exitStatus;
+    private int exitStatus;
     public ExecutionException exitException;
     
-    /** Maximum number of open file descriptors */
-    final static int OPEN_MAX = 256;
     /** Table containing all open file descriptors. (Entries are null if the fd is not in use */
-    FD[] fds  = new FD[OPEN_MAX];
+    FD[] fds; // package-private for UnixRuntime
+    boolean closeOnExec[];
+    
+    /** Pointer to a SecurityManager for this process */
+    SecurityManager sm;
+    public void setSecurityManager(SecurityManager sm) { this.sm = sm; }
     
     /** Pointer to a callback for the call_java syscall */
-    protected CallJavaCB callJavaCB;
+    private CallJavaCB callJavaCB;
     public void setCallJavaCB(CallJavaCB callJavaCB) { this.callJavaCB = callJavaCB; }
-    public CallJavaCB getCallJavaCB() { return callJavaCB; }
         
     /** Temporary buffer for read/write operations */
-    private byte[] _byteBuf = null;
+    private byte[] _byteBuf;
     /** Max size of temporary buffer
         @see Runtime#_byteBuf */
-    private final static int MAX_CHUNK = 15*1024*1024;
+    final static int MAX_CHUNK = 16*1024*1024 - 1024;
         
     /** Subclasses should actually execute program in this method. They should continue 
         executing until state != RUNNING. Only syscall() can modify state. It is safe 
@@ -105,63 +98,102 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     
     /** Subclasses should return the address of the symbol <i>symbol</i> or -1 it it doesn't exits in this method 
         This method is only required if the call() function is used */
-    protected int lookupSymbol(String symbol) { return -1; }
+    public int lookupSymbol(String symbol) { return -1; }
     
-    /** Subclasses should returns a CPUState object representing the cpu state */
-    protected abstract CPUState getCPUState();
+    /** Subclasses should populate a CPUState object representing the cpu state */
+    protected abstract void getCPUState(CPUState state);
     
     /** Subclasses should set the CPUState to the state held in <i>state</i> */
     protected abstract void setCPUState(CPUState state);
-
-    static void checkPageSize(int pageSize, int totalPages) throws IllegalArgumentException {
-        if(pageSize < 256) throw new IllegalArgumentException("pageSize too small");
-        if((pageSize&(pageSize-1)) != 0) throw new IllegalArgumentException("pageSize must be a power of two");
-        if((totalPages&(totalPages-1)) != 0) throw new IllegalArgumentException("totalPages must be a power of two");
-        if(totalPages != 1 && totalPages < 256) throw new IllegalArgumentException("totalPages too small");
-        if(totalPages * pageSize < 4*1024*1024) throw new IllegalArgumentException("total memory too small (" + totalPages + "*" + pageSize + ")");
+    
+    /** True to enabled a few hacks to better support the win32 console */
+    final static boolean win32Hacks;
+    
+    static {
+        String os = Platform.getProperty("os.name");
+        String prop = Platform.getProperty("nestedvm.win32hacks");
+        if(prop != null) { win32Hacks = Boolean.valueOf(prop).booleanValue(); }
+        else { win32Hacks = os != null && os.toLowerCase().indexOf("windows") != -1; }
+    }
+    
+    protected Object clone() throws CloneNotSupportedException {
+        Runtime r = (Runtime) super.clone();
+        r._byteBuf = null;
+        r.startTime = 0;
+        r.fds = new FD[OPEN_MAX];
+        for(int i=0;i<OPEN_MAX;i++) if(fds[i] != null) r.fds[i] = fds[i].dup();
+        int totalPages = writePages.length;
+        r.readPages = new int[totalPages][];
+        r.writePages = new int[totalPages][];
+        for(int i=0;i<totalPages;i++) {
+            if(readPages[i] == null) continue;
+            if(writePages[i] == null) r.readPages[i] = readPages[i];
+            else r.readPages[i] = r.writePages[i] = (int[])writePages[i].clone();
+        }
+        return r;
     }
     
-    protected Runtime(int pageSize, int totalPages, boolean allowEmptyPages) {
-        this.allowEmptyPages = allowEmptyPages;
-        
-        checkPageSize(pageSize,totalPages);
+    protected Runtime(int pageSize, int totalPages) { this(pageSize, totalPages,false); }
+    protected Runtime(int pageSize, int totalPages, boolean exec) {
+        if(pageSize <= 0) throw new IllegalArgumentException("pageSize <= 0");
+        if(totalPages <= 0) throw new IllegalArgumentException("totalPages <= 0");
+        if((pageSize&(pageSize-1)) != 0) throw new IllegalArgumentException("pageSize not a power of two");
+
+        int _pageShift = 0;
+        while(pageSize>>>_pageShift != 1) _pageShift++;
+        pageShift = _pageShift;
         
-        PAGE_SIZE = pageSize;
-        PAGE_WORDS = pageSize>>>2;
-        int pageShift = 0;
-        while(pageSize>>>pageShift != 1) pageShift++;
-        PAGE_SHIFT = pageShift;
+        int heapStart = heapStart();
+        int totalMemory = totalPages * pageSize;
+        int stackSize = max(totalMemory/512,ARG_MAX+65536);
+        int stackPages = 0;
+        if(totalPages > 1) {
+            stackSize = max(stackSize,pageSize);
+            stackSize = (stackSize + pageSize - 1) & ~(pageSize-1);
+            stackPages = stackSize >>> pageShift;
+            heapStart = (heapStart + pageSize - 1) & ~(pageSize-1);
+            if(stackPages + STACK_GUARD_PAGES + (heapStart >>> pageShift) >= totalPages)
+                throw new IllegalArgumentException("total pages too small");
+        } else {
+            if(pageSize < heapStart + stackSize) throw new IllegalArgumentException("total memory too small");
+            heapStart = (heapStart + 4095) & ~4096;
+        }
         
-        TOTAL_PAGES = totalPages;
+        stackBottom = totalMemory - stackSize;
+        heapEnd = heapStart;
         
-        readPages = new int[TOTAL_PAGES][];
-        writePages = new int[TOTAL_PAGES][];
+        readPages = new int[totalPages][];
+        writePages = new int[totalPages][];
         
-        if(TOTAL_PAGES == 1) {
-            readPages[0] = writePages[0] = new int[PAGE_WORDS];
-            BRK_LIMIT = STACK_BOTTOM = 0;
+        if(totalPages == 1) {
+            readPages[0] = writePages[0] = new int[pageSize>>2];
         } else {
-            int stackPages = max(TOTAL_PAGES>>>8,(1024*1024)>>>PAGE_SHIFT);
-            STACK_BOTTOM = (TOTAL_PAGES - stackPages) * PAGE_SIZE;
-            // leave some unmapped pages between the stack and the heap
-            BRK_LIMIT = STACK_BOTTOM - 4*PAGE_SIZE;
-        
-            for(int i=0;i<stackPages;i++)
-                readPages[TOTAL_PAGES-1-i] = writePages[TOTAL_PAGES-1-i] = emptyPage();
+            for(int i=(stackBottom >>> pageShift);i<writePages.length;i++) {
+                readPages[i] = writePages[i] = new int[pageSize>>2];
+            }
         }
+
+        if(!exec) {
+            fds = new FD[OPEN_MAX];
+            closeOnExec = new boolean[OPEN_MAX];
         
-        addFD(new StdinFD(System.in));
-        addFD(new StdoutFD(System.out));
-        addFD(new StdoutFD(System.err));
+            InputStream stdin = win32Hacks ? new Win32ConsoleIS(System.in) : System.in;
+            addFD(new TerminalFD(stdin));
+            addFD(new TerminalFD(System.out));
+            addFD(new TerminalFD(System.err));
+        }
     }
     
     /** Copy everything from <i>src</i> to <i>addr</i> initializing uninitialized pages if required. 
        Newly initalized pages will be marked read-only if <i>ro</i> is set */
     protected final void initPages(int[] src, int addr, boolean ro) {
+        int pageWords = (1<<pageShift)>>>2;
+        int pageMask = (1<<pageShift) - 1;
+        
         for(int i=0;i<src.length;) {
-            int page = addr >>> PAGE_SHIFT;
-            int start = (addr&(PAGE_SIZE-1))>>2;
-            int elements = min(PAGE_WORDS-start,src.length-i);
+            int page = addr >>> pageShift;
+            int start = (addr&pageMask)>>2;
+            int elements = min(pageWords-start,src.length-i);
             if(readPages[page]==null) {
                 initPage(page,ro);
             } else if(!ro) {
@@ -175,12 +207,15 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     
     /** Initialize <i>words</i> of pages starting at <i>addr</i> to 0 */
     protected final void clearPages(int addr, int words) {
+        int pageWords = (1<<pageShift)>>>2;
+        int pageMask = (1<<pageShift) - 1;
+
         for(int i=0;i<words;) {
-            int page = addr >>> PAGE_SHIFT;
-            int start = (addr&(PAGE_SIZE-1))>>2;
-            int elements = min(PAGE_WORDS-start,words-i);
+            int page = addr >>> pageShift;
+            int start = (addr&pageMask)>>2;
+            int elements = min(pageWords-start,words-i);
             if(readPages[page]==null) {
-                readPages[page] = writePages[page] = emptyPage();
+                readPages[page] = writePages[page] = new int[pageWords];
             } else {
                 if(writePages[page] == null) writePages[page] = readPages[page];
                 for(int j=start;j<start+elements;j++) writePages[page][j] = 0;
@@ -193,6 +228,9 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     /** Copies <i>length</i> bytes from the processes memory space starting at
         <i>addr</i> INTO a java byte array <i>a</i> */
     public final void copyin(int addr, byte[] buf, int count) throws ReadFaultException {
+        int pageWords = (1<<pageShift)>>>2;
+        int pageMask = pageWords - 1;
+
         int x=0;
         if(count == 0) return;
         if((addr&3)!=0) {
@@ -208,16 +246,14 @@ public abstract class Runtime implements UsermodeConstants,Registers {
             int c = count>>>2;
             int a = addr>>>2;
             while(c != 0) {
-                int[] page = readPages[a >>> (PAGE_SHIFT-2)];
+                int[] page = readPages[a >>> (pageShift-2)];
                 if(page == null) throw new ReadFaultException(a<<2);
-                int index = a&(PAGE_WORDS-1);
-                int n = min(c,PAGE_WORDS-index);
-                if(page != _emptyPage) {
-                    for(int i=0;i<n;i++,x+=4) {
-                        int word = page[index+i];
-                        buf[x+0] = (byte)((word>>>24)&0xff); buf[x+1] = (byte)((word>>>16)&0xff);
-                        buf[x+2] = (byte)((word>>> 8)&0xff); buf[x+3] = (byte)((word>>> 0)&0xff);                        
-                    }
+                int index = a&pageMask;
+                int n = min(c,pageWords-index);
+                for(int i=0;i<n;i++,x+=4) {
+                    int word = page[index+i];
+                    buf[x+0] = (byte)((word>>>24)&0xff); buf[x+1] = (byte)((word>>>16)&0xff);
+                    buf[x+2] = (byte)((word>>> 8)&0xff); buf[x+3] = (byte)((word>>> 0)&0xff);                        
                 }
                 a += n; c -=n;
             }
@@ -236,6 +272,9 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     /** Copies <i>length</i> bytes OUT OF the java array <i>a</i> into the processes memory
         space at <i>addr</i> */
     public final void copyout(byte[] buf, int addr, int count) throws FaultException {
+        int pageWords = (1<<pageShift)>>>2;
+        int pageWordMask = pageWords - 1;
+        
         int x=0;
         if(count == 0) return;
         if((addr&3)!=0) {
@@ -248,21 +287,22 @@ public abstract class Runtime implements UsermodeConstants,Registers {
             memWrite(addr&~3,word);
             addr += x;
         }
+
         if((count&~3) != 0) {
             int c = count>>>2;
             int a = addr>>>2;
             while(c != 0) {
-                int[] page = writePages[a >>> (PAGE_SHIFT-2)];
+                int[] page = writePages[a >>> (pageShift-2)];
                 if(page == null) throw new WriteFaultException(a<<2);
-                if(page == _emptyPage) page = initPage(a >>> (PAGE_SHIFT-2));
-                int index = a&(PAGE_WORDS-1);
-                int n = min(c,PAGE_WORDS-index);
+                int index = a&pageWordMask;
+                int n = min(c,pageWords-index);
                 for(int i=0;i<n;i++,x+=4)
                     page[index+i] = ((buf[x+0]&0xff)<<24)|((buf[x+1]&0xff)<<16)|((buf[x+2]&0xff)<<8)|((buf[x+3]&0xff)<<0);
                 a += n; c -=n;
             }
             addr = a<<2; count&=3;
         }
+
         if(count != 0) {
             int word = memRead(addr);
             switch(count) {
@@ -275,25 +315,22 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     }
     
     public final void memcpy(int dst, int src, int count) throws FaultException {
+        int pageWords = (1<<pageShift)>>>2;
+        int pageWordMask = pageWords - 1;
         if((dst&3) == 0 && (src&3)==0) {
             if((count&~3) != 0) {
                 int c = count>>2;
                 int s = src>>>2;
                 int d = dst>>>2;
                 while(c != 0) {
-                    int[] srcPage = readPages[s>>>(PAGE_SHIFT-2)];
+                    int[] srcPage = readPages[s>>>(pageShift-2)];
                     if(srcPage == null) throw new ReadFaultException(s<<2);
-                    int[] dstPage = writePages[d>>>(PAGE_SHIFT-2)];
+                    int[] dstPage = writePages[d>>>(pageShift-2)];
                     if(dstPage == null) throw new WriteFaultException(d<<2);
-                    int srcIndex = (s&(PAGE_WORDS-1));
-                    int dstIndex = (d&(PAGE_WORDS-1));
-                    int n = min(c,PAGE_WORDS-max(srcIndex,dstIndex));
-                    if(srcPage != _emptyPage) {
-                        if(dstPage == _emptyPage) dstPage = initPage(d>>>(PAGE_SHIFT-2));
-                        System.arraycopy(srcPage,srcIndex,dstPage,dstIndex,n);
-                    } else if(srcPage == _emptyPage && dstPage != _emptyPage) {
-                        Arrays.fill(dstPage,dstIndex,dstIndex+n,0);
-                    }
+                    int srcIndex = s&pageWordMask;
+                    int dstIndex = d&pageWordMask;
+                    int n = min(c,pageWords-max(srcIndex,dstIndex));
+                    System.arraycopy(srcPage,srcIndex,dstPage,dstIndex,n);
                     s += n; d += n; c -= n;
                 }
                 src = s<<2; dst = d<<2; count&=3;
@@ -319,6 +356,9 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     }
     
     public final void memset(int addr, int ch, int count) throws FaultException {
+        int pageWords = (1<<pageShift)>>>2;
+        int pageWordMask = pageWords - 1;
+        
         int fourBytes = ((ch&0xff)<<24)|((ch&0xff)<<16)|((ch&0xff)<<8)|((ch&0xff)<<0);
         if((addr&3)!=0) {
             int word = memRead(addr&~3);
@@ -334,14 +374,12 @@ public abstract class Runtime implements UsermodeConstants,Registers {
             int c = count>>2;
             int a = addr>>>2;
             while(c != 0) {
-                int[] page = readPages[a>>>(PAGE_SHIFT-2)];
+                int[] page = readPages[a>>>(pageShift-2)];
                 if(page == null) throw new WriteFaultException(a<<2);
-                int index = (a&(PAGE_WORDS-1));
-                int n = min(c,PAGE_WORDS-index);
-                if(page != _emptyPage || ch != 0) {
-                    if(page == _emptyPage) page = initPage(a>>>(PAGE_SHIFT-2));
-                    Arrays.fill(page,index,index+n,fourBytes);
-                }
+                int index = a&pageWordMask;
+                int n = min(c,pageWords-index);
+                /* Arrays.fill(page,index,index+n,fourBytes);*/
+                for(int i=index;i<index+n;i++) page[i] = fourBytes;
                 a += n; c -= n;
             }
             addr = a<<2; count&=3;
@@ -364,16 +402,13 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     }
        
     protected final int unsafeMemRead(int addr) throws ReadFaultException {
-        int page = addr >>> PAGE_SHIFT;
-        int entry = (addr >>> 2) & (PAGE_WORDS-1);
+        int page = addr >>> pageShift;
+        int entry = (addr&(1<<pageShift) - 1)>>2;
         try {
             return readPages[page][entry];
         } catch(ArrayIndexOutOfBoundsException e) {
-            if(page < 0) throw e; // should never happen
-            if(page >= readPages.length) throw new ReadFaultException(addr);
-            if(readPages[page] != _emptyPage) throw e; // should never happen
-            initPage(page);
-            return 0;
+            if(page < 0 || page >= readPages.length) throw new ReadFaultException(addr);
+            throw e; // should never happen
         } catch(NullPointerException e) {
             throw new ReadFaultException(addr);
         }
@@ -386,16 +421,13 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     }
     
     protected final void unsafeMemWrite(int addr, int value) throws WriteFaultException {
-        int page = addr >>> PAGE_SHIFT;
-        int entry = (addr>>>2)&(PAGE_WORDS-1);
+        int page = addr >>> pageShift;
+        int entry = (addr&(1<<pageShift) - 1)>>2;
         try {
             writePages[page][entry] = value;
         } catch(ArrayIndexOutOfBoundsException e) {
-            if(page < 0) throw e;// should never happen
-            if(page >= writePages.length) throw new WriteFaultException(addr);
-            if(readPages[page] != _emptyPage) throw e; // should never happen
-            initPage(page);
-            writePages[page][entry] = value;
+            if(page < 0 || page >= writePages.length) throw new WriteFaultException(addr);
+            throw e; // should never happen
         } catch(NullPointerException e) {
             throw new WriteFaultException(addr);
         }
@@ -405,7 +437,7 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     private final int[] initPage(int page) { return initPage(page,false); }
     /** Created a new non-empty page at page number <i>page</i>. If <i>ro</i> is set the page will be read-only */
     private final int[] initPage(int page, boolean ro) {
-        int[] buf = new int[PAGE_WORDS];
+        int[] buf = new int[(1<<pageShift)>>>2];
         writePages[page] = ro ? null : buf;
         readPages[page] = buf;
         return buf;
@@ -414,15 +446,14 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     /** Returns the exit status of the process. (only valid if state == DONE) 
         @see Runtime#state */
     public final int exitStatus() {
-        if(state != DONE) throw new IllegalStateException("exitStatus() called in an inappropriate state");
+        if(state != EXITED) throw new IllegalStateException("exitStatus() called in an inappropriate state");
         return exitStatus;
     }
         
-    private int addStringArray(String[] strings, int topAddr) {
+    private int addStringArray(String[] strings, int topAddr) throws FaultException {
         int count = strings.length;
         int total = 0; /* null last table entry  */
         for(int i=0;i<count;i++) total += strings[i].length() + 1;
-        if(total >= ARGS_MAX) throw new IllegalArgumentException("arguments/environ too big");
         total += (count+1)*4;
         int start = (topAddr - total)&~3;
         int addr = start + (count+1)*4;
@@ -441,13 +472,12 @@ public abstract class Runtime implements UsermodeConstants,Registers {
                 addr += 4;
             }
         } catch(FaultException e) {
-            // should never happen
-            throw new Error(e.toString());
+            throw new RuntimeException(e.toString());
         }
         return start;
     }
     
-    protected String[] createEnv(String[] extra) { if(extra == null) extra = new String[0]; return extra; }
+    String[] createEnv(String[] extra) { if(extra == null) extra = new String[0]; return extra; }
     
     /** Sets word number <i>index</i> in the _user_info table to <i>word</i>
      * The user_info table is a chunk of memory in the program's memory defined by the
@@ -455,19 +485,19 @@ public abstract class Runtime implements UsermodeConstants,Registers {
      * and location of the user_info table from the ELF symbol table. setUserInfo and
      * getUserInfo are used to modify the words in the user_info table. */
     public void setUserInfo(int index, int word) {
-        if(index < 0 || index >= userInfoSize/4) throw new IndexOutOfBoundsException("setUserInfo called with index >= " + (userInfoSize/4));
+        if(index < 0 || index >= userInfoSize()/4) throw new IndexOutOfBoundsException("setUserInfo called with index >= " + (userInfoSize()/4));
         try {
-            memWrite(userInfoBase+index*4,word);
-        } catch(FaultException e) { throw new Error("should never happen: " + e); }
+            memWrite(userInfoBase()+index*4,word);
+        } catch(FaultException e) { throw new RuntimeException(e.toString()); }
     }
     
     /** Returns the word in the _user_info table entry <i>index</i>
         @see Runtime#setUserInfo(int,int) setUserInfo */
     public int getUserInfo(int index) {
-        if(index < 0 || index >= userInfoSize/4) throw new IndexOutOfBoundsException("setUserInfo called with index >= " + (userInfoSize/4));
+        if(index < 0 || index >= userInfoSize()/4) throw new IndexOutOfBoundsException("setUserInfo called with index >= " + (userInfoSize()/4));
         try {
-            return memRead(userInfoBase+index*4);
-        } catch(FaultException e) { throw new Error("should never happen: " + e); }
+            return memRead(userInfoBase()+index*4);
+        } catch(FaultException e) { throw new RuntimeException(e.toString()); }
     }
     
     /** Calls _execute() (subclass's execute()) and catches exceptions */
@@ -475,13 +505,12 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         try {
             _execute();
         } catch(FaultException e) {
-            e.printStackTrace();
-            sys_exit(128+11); // SIGSEGV
+            if(STDERR_DIAG) e.printStackTrace();
+            exit(128+11,true); // SIGSEGV
             exitException = e;
         } catch(ExecutionException e) {
-            e.printStackTrace();
-            System.err.println(e);
-            sys_exit(128+4); // SIGILL
+            if(STDERR_DIAG) e.printStackTrace();
+            exit(128+4,true); // SIGILL
             exitException = e;
         }
     }
@@ -492,17 +521,20 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         if(startTime == 0) startTime = System.currentTimeMillis();
         state = RUNNING;
         __execute();
-        if(state != PAUSED && state != DONE) throw new IllegalStateException("execute() ended up in an inappropriate state (" + state + ")");
-        return state == DONE;
+        if(state != PAUSED && state != EXITED && state != EXECED)
+            throw new IllegalStateException("execute() ended up in an inappropriate state (" + state + ")");
+        return state != PAUSED;
     }
     
-    public final int run() { return run(null); }
-    public final int run(String argv0, String[] rest) {
-        String[] args = new String[rest.length+1];
-        System.arraycopy(rest,0,args,1,rest.length);
-        args[0] = argv0;
-        return run(args);
+    static String[] concatArgv(String argv0, String[] rest) {
+        String[] argv = new String[rest.length+1];
+        System.arraycopy(rest,0,argv,1,rest.length);
+        argv[0] = argv0;
+        return argv;
     }
+    
+    public final int run() { return run(null); }
+    public final int run(String argv0, String[] rest) { return run(concatArgv(argv0,rest)); }
     public final int run(String[] args) { return run(args,null); }
     
     /** Runs the process until it exits and returns the exit status.
@@ -511,10 +543,10 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         start(args,env);
         for(;;) {
             if(execute()) break;
-            System.err.println("WARNING: Pause requested while executing run()");
-            try { Thread.sleep(500); } catch(InterruptedException e) { /* noop */ }
+            if(STDERR_DIAG) System.err.println("WARNING: Pause requested while executing run()");
         }
-        return exitStatus();
+        if(state == EXECED && STDERR_DIAG) System.err.println("WARNING: Process exec()ed while being run under run()");
+        return state == EXITED ? exitStatus() : 0;
     }
 
     public final void start() { start(null); }
@@ -522,125 +554,177 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     
     /** Initializes the process and prepairs it to be executed with execute() */
     public final void start(String[] args, String[] environ)  {
-        int sp, argsAddr, envAddr;
-        if(state != INITIALIZED) throw new IllegalStateException("start() called in inappropriate state");
-
+        int top, sp, argsAddr, envAddr;
+        if(state != STOPPED) throw new IllegalStateException("start() called in inappropriate state");
         if(args == null) args = new String[]{getClass().getName()};
         
-        sp = TOTAL_PAGES*PAGE_SIZE-512;
-        sp = argsAddr = addStringArray(args,sp);
-        sp = envAddr = addStringArray(createEnv(environ),sp);
+        sp = top = writePages.length*(1<<pageShift);
+        try {
+            sp = argsAddr = addStringArray(args,sp);
+            sp = envAddr = addStringArray(createEnv(environ),sp);
+        } catch(FaultException e) {
+            throw new IllegalArgumentException("args/environ too big");
+        }
         sp &= ~15;
-        
+        if(top - sp > ARG_MAX) throw new IllegalArgumentException("args/environ too big");
+
+        // HACK: heapStart() isn't always available when the constructor
+        // is run and this sometimes doesn't get initialized
+        if(heapEnd == 0) {
+            heapEnd = heapStart();
+            if(heapEnd == 0) throw new Error("heapEnd == 0");
+            int pageSize = writePages.length == 1 ? 4096 : (1<<pageShift);
+            heapEnd = (heapEnd + pageSize - 1) & ~(pageSize-1);
+        }
+
         CPUState cpuState = new CPUState();
         cpuState.r[A0] = argsAddr;
         cpuState.r[A1] = envAddr;
         cpuState.r[SP] = sp;
         cpuState.r[RA] = 0xdeadbeef;
-        cpuState.r[GP] = gp;
-        cpuState.pc = entryPoint;
+        cpuState.r[GP] = gp();
+        cpuState.pc = entryPoint();
         setCPUState(cpuState);
-                
+        
         state = PAUSED;
         
-        _start();
+        _started();        
     }
-    
+
+    public final void stop() {
+        if (state != RUNNING && state != PAUSED) throw new IllegalStateException("stop() called in inappropriate state");
+        exit(0, false);
+    }
+
     /** Hook for subclasses to do their own startup */
-    protected void _start() { /* noop */ }
+    void _started() {  }
     
-    // FEATURE: call() that accepts an Object[] array and automatically allocates strings/arrays/etc on the stack
-    public final int call(String sym) throws CallException { return call(sym,0,0,0,0,0,0,0); }
-    public final int call(String sym, int a0) throws CallException  { return call(sym,a0,0,0,0,0,0,0); }
-    public final int call(String sym, int a0, int a1) throws CallException  { return call(sym,a0,a1,0,0,0,0,0); }
-    public final int call(String sym, int a0, int a1, int a2) throws CallException  { return call(sym,a0,a1,a2,0,0,0,0); }
-    public final int call(String sym, int a0, int a1, int a2, int a3) throws CallException  { return call(sym,a0,a1,a2,a3,0,0,0); }
-    public final int call(String sym, int a0, int a1, int a2, int a3, int a4) throws CallException  { return call(sym,a0,a1,a2,a3,a4,0,0); }
-    public final int call(String sym, int a0, int a1, int a2, int a3, int a4, int a5) throws CallException  { return call(sym,a0,a1,a2,a3,a4,a5,0); }
+    public final int call(String sym, Object[] args) throws CallException, FaultException {
+        if(state != PAUSED && state != CALLJAVA) throw new IllegalStateException("call() called in inappropriate state");
+        if(args.length > 7) throw new IllegalArgumentException("args.length > 7");
+        CPUState state = new CPUState();
+        getCPUState(state);
+        
+        int sp = state.r[SP];
+        int[] ia = new int[args.length];
+        for(int i=0;i<args.length;i++) {
+            Object o = args[i];
+            byte[] buf = null;
+            if(o instanceof String) {
+                buf = getBytes((String)o);
+            } else if(o instanceof byte[]) {
+                buf = (byte[]) o;
+            } else if(o instanceof Number) {
+                ia[i] = ((Number)o).intValue();
+            }
+            if(buf != null) {
+                sp -= buf.length;
+                copyout(buf,sp,buf.length);
+                ia[i] = sp;
+            }
+        }
+        int oldSP = state.r[SP];
+        if(oldSP == sp) return call(sym,ia);
+        
+        state.r[SP] = sp;
+        setCPUState(state);
+        int ret = call(sym,ia);
+        state.r[SP] = oldSP;
+        setCPUState(state);
+        return ret;
+    }
+    
+    public final int call(String sym) throws CallException { return call(sym,new int[]{}); }
+    public final int call(String sym, int a0) throws CallException  { return call(sym,new int[]{a0}); }
+    public final int call(String sym, int a0, int a1) throws CallException  { return call(sym,new int[]{a0,a1}); }
     
     /** Calls a function in the process with the given arguments */
-    public final int call(String sym, int a0, int a1, int a2, int a3, int a4, int a5, int a6) throws CallException {
+    public final int call(String sym, int[] args) throws CallException {
         int func = lookupSymbol(sym);
         if(func == -1) throw new CallException(sym + " not found");
         int helper = lookupSymbol("_call_helper");
         if(helper == -1) throw new CallException("_call_helper not found");
-        return call(helper,func,a0,a1,a2,a3,a4,a5,a6);
+        return call(helper,func,args);
     }
     
     /** Executes the code at <i>addr</i> in the process setting A0-A3 and S0-S3 to the given arguments
         and returns the contents of V1 when the the pause syscall is invoked */
-    public final int call(int addr, int a0, int a1, int a2, int a3, int s0, int s1, int s2, int s3) {
+    //public final int call(int addr, int a0, int a1, int a2, int a3, int s0, int s1, int s2, int s3) {
+    public final int call(int addr, int a0, int[] rest) throws CallException {
+        if(rest.length > 7) throw new IllegalArgumentException("rest.length > 7");
         if(state != PAUSED && state != CALLJAVA) throw new IllegalStateException("call() called in inappropriate state");
         int oldState = state;
-        CPUState saved = getCPUState();
-        CPUState cpustate = new CPUState();
-        cpustate.r[SP] = saved.r[SP]&~15;
+        CPUState saved = new CPUState();        
+        getCPUState(saved);
+        CPUState cpustate = saved.dup();
+        
+        cpustate.r[SP] = cpustate.r[SP]&~15;
         cpustate.r[RA] = 0xdeadbeef;
         cpustate.r[A0] = a0;
-        cpustate.r[A1] = a1;
-        cpustate.r[A2] = a2;
-        cpustate.r[A3] = a3;
-        cpustate.r[S0] = s0;
-        cpustate.r[S1] = s1;
-        cpustate.r[S2] = s2;
-        cpustate.r[S3] = s3;
-        cpustate.r[GP] = gp;
+        switch(rest.length) {            
+            case 7: cpustate.r[S3] = rest[6];
+            case 6: cpustate.r[S2] = rest[5];
+            case 5: cpustate.r[S1] = rest[4];
+            case 4: cpustate.r[S0] = rest[3];
+            case 3: cpustate.r[A3] = rest[2];
+            case 2: cpustate.r[A2] = rest[1];
+            case 1: cpustate.r[A1] = rest[0];
+        }
         cpustate.pc = addr;
         
         state = RUNNING;
 
         setCPUState(cpustate);
         __execute();
-        cpustate = getCPUState();
+        getCPUState(cpustate);
         setCPUState(saved);
 
-        if(state != PAUSED)
-            System.out.println("WARNING: Process exit()ed while servicing a call() request");
-        else
-            state = oldState;
+        if(state != PAUSED) throw new CallException("Process exit()ed while servicing a call() request");
+        state = oldState;
         
         return cpustate.r[V1];
     }
-    
-    /** Determines if the process can access <i>fileName</i>. The default implementation simply logs 
-        the request and allows it */
-    protected boolean allowFileAccess(String fileName, boolean write) {
-        //System.err.println("Allowing " + (write?"write":"read-only") + " access to " + fileName);
-        return true;
-    }
-    
+        
     /** Allocated an entry in the FileDescriptor table for <i>fd</i> and returns the number.
         Returns -1 if the table is full. This can be used by subclasses to use custom file
         descriptors */
-    public int addFD(FD fd) {
+    public final int addFD(FD fd) {
+        if(state == EXITED || state == EXECED) throw new IllegalStateException("addFD called in inappropriate state");
         int i;
         for(i=0;i<OPEN_MAX;i++) if(fds[i] == null) break;
         if(i==OPEN_MAX) return -1;
         fds[i] = fd;
+        closeOnExec[i] = false;
         return i;
     }
 
+    /** Hooks for subclasses before and after the process closes an FD */
+    void _preCloseFD(FD fd) {  }
+    void _postCloseFD(FD fd) {  }
+
     /** Closes file descriptor <i>fdn</i> and removes it from the file descriptor table */
-    public boolean closeFD(int fdn) {
+    public final boolean closeFD(int fdn) {
+        if(state == EXITED || state == EXECED) throw new IllegalStateException("closeFD called in inappropriate state");
         if(fdn < 0 || fdn >= OPEN_MAX) return false;
         if(fds[fdn] == null) return false;
+        _preCloseFD(fds[fdn]);
         fds[fdn].close();
+        _postCloseFD(fds[fdn]);
         fds[fdn] = null;        
         return true;
     }
     
     /** Duplicates the file descriptor <i>fdn</i> and returns the new fs */
-    public int dupFD(int fdn) {
-    		int i;
-    		if(fdn < 0 || fdn >= OPEN_MAX) return -1;
-    		if(fds[fdn] == null) return -1;
-    		for(i=0;i<OPEN_MAX;i++) if(fds[i] == null) break;
+    public final int dupFD(int fdn) {
+        int i;
+        if(fdn < 0 || fdn >= OPEN_MAX) return -1;
+        if(fds[fdn] == null) return -1;
+        for(i=0;i<OPEN_MAX;i++) if(fds[i] == null) break;
         if(i==OPEN_MAX) return -1;
         fds[i] = fds[fdn].dup();
         return i;
     }
 
-    // FEATURE: These should be pulled in from UsermodeConstants but fcntl.h is hard to parse
     public static final int RD_ONLY = 0;
     public static final int WR_ONLY = 1;
     public static final int RDWR = 2;
@@ -650,89 +734,101 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     public static final int O_APPEND = 0x0008;
     public static final int O_TRUNC = 0x0400;
     public static final int O_NONBLOCK = 0x4000;
+    public static final int O_NOCTTY = 0x8000;
     
-    // FEATURE: Lots of duplicate code between this and UnixRuntime.HostFS.open()
-    protected FD open(String path, int flags, int mode) throws IOException {
-        final File f = new File(path);
-        // NOTE: createNewFile is a Java2 function
-        if((flags & (O_EXCL|O_CREAT)) == (O_EXCL|O_CREAT))
-            if(!f.createNewFile()) throw new ErrnoException(EEXIST);
-        if(!f.exists() && (flags&O_CREAT) == 0) return null;
-        if(f.isDirectory()) return null;
-        final Seekable.File sf = new Seekable.File(path,mode!=RD_ONLY);
-        if((flags&O_TRUNC)!=0) sf.setLength(0);
-        return new SeekableFD(sf,flags) {
-            protected FStat _fstat() { return new HostFStat(f) {
-                public int size() {
-                    try { return sf.length(); } catch(IOException e) { return 0; }
-                }
-            };}
-        };
-    }
     
-    /** The open syscall */
-    private int sys_open(int addr, int flags, int mode) {
-        if((flags & O_NONBLOCK) != 0) {
-            System.err.println("WARNING: O_NONBLOCK not supported");
-            return -EOPNOTSUPP;
+    FD hostFSOpen(final File f, int flags, int mode, final Object data) throws ErrnoException {
+        if((flags & ~(3|O_CREAT|O_EXCL|O_APPEND|O_TRUNC)) != 0) {
+            if(STDERR_DIAG)
+                System.err.println("WARNING: Unsupported flags passed to open(\"" + f + "\"): " + toHex(flags & ~(3|O_CREAT|O_EXCL|O_APPEND|O_TRUNC)));
+            throw new ErrnoException(ENOTSUP);
         }
+        boolean write = (flags&3) != RD_ONLY;
 
-        try {
-            FD fd = open(cstring(addr),flags,mode);
-            if(fd == null) return -ENOENT;
-            int fdn = addFD(fd);
-            if(fdn == -1) {
-                fd.close();
-                return -ENFILE;
+        if(sm != null && !(write ? sm.allowWrite(f) : sm.allowRead(f))) throw new ErrnoException(EACCES);
+        
+        if((flags & (O_EXCL|O_CREAT)) == (O_EXCL|O_CREAT)) {
+            try {
+                if(!Platform.atomicCreateFile(f)) throw new ErrnoException(EEXIST);
+            } catch(IOException e) {
+                throw new ErrnoException(EIO);
             }
-            return fdn;
+        } else if(!f.exists()) {
+            if((flags&O_CREAT)==0) return null;
+        } else if(f.isDirectory()) {
+            return hostFSDirFD(f,data);
         }
-        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; }
+        
+        final Seekable.File sf;
+        try {
+            sf = new Seekable.File(f,write,(flags & O_TRUNC) != 0);
+        } catch(FileNotFoundException e) {
+            if(e.getMessage() != null && e.getMessage().indexOf("Permission denied") >= 0) throw new ErrnoException(EACCES);
+            return null;
+        } catch(IOException e) { throw new ErrnoException(EIO); }
+        
+        return new SeekableFD(sf,flags) { protected FStat _fstat() { return hostFStat(f,sf,data); } };
+    }
+    
+    FStat hostFStat(File f, Seekable.File sf, Object data) { return new HostFStat(f,sf); }
+    
+    FD hostFSDirFD(File f, Object data) { return null; }
+    
+    FD _open(String path, int flags, int mode) throws ErrnoException {
+        return hostFSOpen(new File(path),flags,mode,null);
+    }
+    
+    /** The open syscall */
+    private int sys_open(int addr, int flags, int mode) throws ErrnoException, FaultException {
+        String name = cstring(addr);
+        
+        // HACK: TeX, or GPC, or something really sucks
+        if(name.length() == 1024 && getClass().getName().equals("tests.TeX")) name = name.trim();
+        
+        flags &= ~O_NOCTTY; // this is meaningless under nestedvm
+        FD fd = _open(name,flags,mode);
+        if(fd == null) return -ENOENT;
+        int fdn = addFD(fd);
+        if(fdn == -1) { fd.close(); return -ENFILE; }
+        return fdn;
     }
 
     /** The write syscall */
-    private int sys_write(int fdn, int addr, int count) {
+    
+    private int sys_write(int fdn, int addr, int count) throws FaultException, ErrnoException {
         count = Math.min(count,MAX_CHUNK);
         if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
-        if(fds[fdn] == null || !fds[fdn].writable()) return -EBADFD;
+        if(fds[fdn] == null) return -EBADFD;
+        byte[] buf = byteBuf(count);
+        copyin(addr,buf,count);
         try {
-            byte[] buf = byteBuf(count);
-            copyin(addr,buf,count);
             return fds[fdn].write(buf,0,count);
-        } catch(FaultException e) {
-            System.err.println(e);
-            return -EFAULT;
-        } catch(IOException e) {
-            // FEATURE: We should support signals and send a SIGPIPE
-            if(e.getMessage().equals("Pipe closed")) return sys_exit(128+13);
-            System.err.println(e);
-            return -EIO;
+        } catch(ErrnoException e) {
+            if(e.errno == EPIPE) sys_exit(128+13);
+            throw e;
         }
     }
 
     /** The read syscall */
-    private int sys_read(int fdn, int addr, int count) {
+    private int sys_read(int fdn, int addr, int count) throws FaultException, ErrnoException {
         count = Math.min(count,MAX_CHUNK);
         if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
-        if(fds[fdn] == null || !fds[fdn].readable()) return -EBADFD;
-        try {
-            byte[] buf = byteBuf(count);
-            int n = fds[fdn].read(buf,0,count);
-            copyout(buf,addr,n);
-            return n;
-        } catch(FaultException e) {
-            System.err.println(e);
-            return -EFAULT;
-        } catch(IOException e) {
-            System.err.println(e);
-            return -EIO;
-        }
+        if(fds[fdn] == null) return -EBADFD;
+        byte[] buf = byteBuf(count);
+        int n = fds[fdn].read(buf,0,count);
+        copyout(buf,addr,n);
+        return n;
+    }
+
+    /** The ftruncate syscall */
+    private int sys_ftruncate(int fdn, long length) {
+      if (fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
+      if (fds[fdn] == null) return -EBADFD;
+
+      Seekable seekable = fds[fdn].seekable();
+      if (length < 0 || seekable == null) return -EINVAL;
+      try { seekable.resize(length); } catch (IOException e) { return -EIO; }
+      return 0;
     }
     
     /** The close syscall */
@@ -742,45 +838,36 @@ public abstract class Runtime implements UsermodeConstants,Registers {
 
     
     /** The seek syscall */
-    private int sys_lseek(int fdn, int offset, int whence) {
+    private int sys_lseek(int fdn, int offset, int whence) throws ErrnoException {
         if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
         if(fds[fdn] == null) return -EBADFD;
         if(whence != SEEK_SET && whence !=  SEEK_CUR && whence !=  SEEK_END) return -EINVAL;
-        try {
-            int n = fds[fdn].seek(offset,whence);
-            return n < 0 ? -ESPIPE : n;
-        } catch(IOException e) {
-            return -ESPIPE;
-        }
+        int n = fds[fdn].seek(offset,whence);
+        return n < 0 ? -ESPIPE : n;
     }
     
     /** The stat/fstat syscall helper */
-    int stat(FStat fs, int addr) {
-        try {
-            memWrite(addr+0,(fs.dev()<<16)|(fs.inode()&0xffff)); // st_dev (top 16), // st_ino (bottom 16)
-            memWrite(addr+4,((fs.type()&0xf000))|(fs.mode()&0xfff)); // st_mode
-            memWrite(addr+8,1<<16); // st_nlink (top 16) // st_uid (bottom 16)
-            memWrite(addr+12,0); // st_gid (top 16) // st_rdev (bottom 16)
-            memWrite(addr+16,fs.size()); // st_size
-            memWrite(addr+20,fs.atime()); // st_atime
-            // memWrite(addr+24,0) // st_spare1
-            memWrite(addr+28,fs.mtime()); // st_mtime
-            // memWrite(addr+32,0) // st_spare2
-            memWrite(addr+36,fs.ctime()); // st_ctime
-            // memWrite(addr+40,0) // st_spare3
-            memWrite(addr+44,fs.blksize()); // st_bklsize;
-            memWrite(addr+48,fs.blocks()); // st_blocks
-            // memWrite(addr+52,0) // st_spare4[0]
-            // memWrite(addr+56,0) // st_spare4[1]
-        } catch(FaultException e) {
-            System.err.println(e);
-            return -EFAULT;
-        }
+    int stat(FStat fs, int addr) throws FaultException {
+        memWrite(addr+0,(fs.dev()<<16)|(fs.inode()&0xffff)); // st_dev (top 16), // st_ino (bottom 16)
+        memWrite(addr+4,((fs.type()&0xf000))|(fs.mode()&0xfff)); // st_mode
+        memWrite(addr+8,fs.nlink()<<16|fs.uid()&0xffff); // st_nlink (top 16) // st_uid (bottom 16)
+        memWrite(addr+12,fs.gid()<<16|0); // st_gid (top 16) // st_rdev (bottom 16)
+        memWrite(addr+16,fs.size()); // st_size
+        memWrite(addr+20,fs.atime()); // st_atime
+        // memWrite(addr+24,0) // st_spare1
+        memWrite(addr+28,fs.mtime()); // st_mtime
+        // memWrite(addr+32,0) // st_spare2
+        memWrite(addr+36,fs.ctime()); // st_ctime
+        // memWrite(addr+40,0) // st_spare3
+        memWrite(addr+44,fs.blksize()); // st_bklsize;
+        memWrite(addr+48,fs.blocks()); // st_blocks
+        // memWrite(addr+52,0) // st_spare4[0]
+        // memWrite(addr+56,0) // st_spare4[1]
         return 0;
     }
     
     /** The fstat syscall */
-    private int sys_fstat(int fdn, int addr) {
+    private int sys_fstat(int fdn, int addr) throws FaultException {
         if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
         if(fds[fdn] == null) return -EBADFD;
         return stat(fds[fdn].fstat(),addr);
@@ -792,17 +879,13 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     long tv_usec;
     };
     */
-    private int sys_gettimeofday(int timevalAddr, int timezoneAddr) {
+    private int sys_gettimeofday(int timevalAddr, int timezoneAddr) throws FaultException {
         long now = System.currentTimeMillis();
         int tv_sec = (int)(now / 1000);
         int tv_usec = (int)((now%1000)*1000);
-        try {
-            memWrite(timevalAddr+0,tv_sec);
-            memWrite(timevalAddr+4,tv_usec);
-            return 0;
-        } catch(FaultException e) {
-            return -EFAULT;
-        }
+        memWrite(timevalAddr+0,tv_sec);
+        memWrite(timevalAddr+4,tv_usec);
+        return 0;
     }
     
     private int sys_sleep(int sec) {
@@ -846,46 +929,43 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     private int sys_sysconf(int n) {
         switch(n) {
             case _SC_CLK_TCK: return 1000;
+            case _SC_PAGESIZE: return  writePages.length == 1 ? 4096 : (1<<pageShift);
+            case _SC_PHYS_PAGES: return writePages.length == 1 ? (1<<pageShift)/4096 : writePages.length;
             default:
-                System.err.println("WARNING: Attempted to use unknown sysconf key: " + n);
+                if(STDERR_DIAG) System.err.println("WARNING: Attempted to use unknown sysconf key: " + n);
                 return -EINVAL;
         }
     }
     
     /** The sbrk syscall. This can also be used by subclasses to allocate memory.
         <i>incr</i> is how much to increase the break by */
-    public int sbrk(int incr) {
+    public final int sbrk(int incr) {
         if(incr < 0) return -ENOMEM;
-        if(incr==0) return brkAddr;
+        if(incr==0) return heapEnd;
         incr = (incr+3)&~3;
-        int oldBrk = brkAddr;
-        int newBrk = oldBrk + incr;
-        if(TOTAL_PAGES == 1) {
-            CPUState state = getCPUState();
-            if(newBrk >= state.r[SP] - 65536) {
-                System.err.println("WARNING: brk too close to stack pointer");
-                return -ENOMEM;
-            }
-        } else if(newBrk >= BRK_LIMIT) {
-            System.err.println("WARNING: Hit BRK_LIMIT");
-            return -ENOMEM;
-        }
-        if(TOTAL_PAGES != 1) {
+        int oldEnd = heapEnd;
+        int newEnd = oldEnd + incr;
+        if(newEnd >= stackBottom) return -ENOMEM;
+        
+        if(writePages.length > 1) {
+            int pageMask = (1<<pageShift) - 1;
+            int pageWords = (1<<pageShift) >>> 2;
+            int start = (oldEnd + pageMask) >>> pageShift;
+            int end = (newEnd + pageMask) >>> pageShift;
             try {
-                for(int i=(oldBrk+PAGE_SIZE-1)>>>PAGE_SHIFT;i<((newBrk+PAGE_SIZE-1)>>>PAGE_SHIFT);i++)
-                    readPages[i] = writePages[i] = emptyPage();
+                for(int i=start;i<end;i++) readPages[i] = writePages[i] = new int[pageWords];
             } catch(OutOfMemoryError e) {
-                System.err.println("WARNING: Caught OOM Exception in sbrk: " + e);
+                if(STDERR_DIAG) System.err.println("WARNING: Caught OOM Exception in sbrk: " + e);
                 return -ENOMEM;
             }
         }
-        brkAddr = newBrk;
-        return oldBrk;
+        heapEnd = newEnd;
+        return oldEnd;
     }
 
     /** The getpid syscall */
     private int sys_getpid() { return getPid(); }
-    protected int getPid() { return 1; }
+    int getPid() { return 1; }
     
     public static interface CallJavaCB { public int call(int a, int b, int c, int d); }
     
@@ -893,12 +973,19 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         if(state != RUNNING) throw new IllegalStateException("wound up calling sys_calljava while not in RUNNING");
         if(callJavaCB != null) {
             state = CALLJAVA;
-            int ret = callJavaCB.call(a,b,c,d);
+            int ret;
+            try {
+                ret = callJavaCB.call(a,b,c,d);
+            } catch(RuntimeException e) {
+                System.err.println("Error while executing callJavaCB");
+                e.printStackTrace();
+                ret = 0;
+            }
             state = RUNNING;
             return ret;
         } else {
-        		System.err.println("WARNING: calljava syscall invoked without a calljava callback set");
-        		return 0;
+            if(STDERR_DIAG) System.err.println("WARNING: calljava syscall invoked without a calljava callback set");
+            return 0;
         }
     }
         
@@ -907,27 +994,30 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         return 0;
     }
     
-    private int sys_getpagesize() { return TOTAL_PAGES == 1 ? 4096 : PAGE_SIZE; }
+    private int sys_getpagesize() { return writePages.length == 1 ? 4096 : (1<<pageShift); }
     
-    private int sys_isatty(int fdn) {
-        if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
-        if(fds[fdn] == null) return -EBADFD;
-        return fds[fdn].isatty() ? 1 : 0;
+    /** Hook for subclasses to do something when the process exits  */
+    void _exited() {  }
+    
+    void exit(int status, boolean fromSignal) {
+        if(fromSignal && fds[2] != null) {
+            try {
+                byte[] msg = getBytes("Process exited on signal " + (status - 128) + "\n");
+                fds[2].write(msg,0,msg.length);
+            } catch(ErrnoException e) { }
+        }
+        exitStatus = status;
+        for(int i=0;i<fds.length;i++) if(fds[i] != null) closeFD(i);
+        state = EXITED;
+        _exited();
     }
-
     
-    /** Hook for subclasses to do something when the process exits (MUST set state = DONE) */
-    protected void _exit() { state = DONE; }
     private int sys_exit(int status) {
-        exitStatus = status;
-        for(int i=0;i<fds.length;i++) if(fds[i] != null) sys_close(i);
-        _exit();
+        exit(status,false);
         return 0;
     }
        
-    private int sys_fcntl(int fdn, int cmd, int arg) {
-        final int F_DUPFD = 0;
-        final int F_GETFL = 3;
+    final int sys_fcntl(int fdn, int cmd, int arg) throws FaultException {
         int i;
             
         if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
@@ -940,24 +1030,64 @@ public abstract class Runtime implements UsermodeConstants,Registers {
                 for(i=arg;i<OPEN_MAX;i++) if(fds[i]==null) break;
                 if(i==OPEN_MAX) return -EMFILE;
                 fds[i] = fd.dup();
-                return 0;
+                return i;
             case F_GETFL:
-                int flags = 0;
-                if(fd.writable() && fd.readable())  flags = 2;
-                else if(fd.writable()) flags = 1;
-                return flags;
+                return fd.flags();
+            case F_SETFD:
+                closeOnExec[fdn] = arg != 0;
+                return 0;
+            case F_GETFD:
+                return closeOnExec[fdn] ? 1 : 0;
+            case F_GETLK:
+            case F_SETLK:
+                if(STDERR_DIAG) System.err.println("WARNING: file locking requires UnixRuntime");
+                return -ENOSYS;
             default:
-                System.err.println("WARNING: Unknown fcntl command: " + cmd);
+                if(STDERR_DIAG) System.err.println("WARNING: Unknown fcntl command: " + cmd);
                 return -ENOSYS;
         }
     }
-            
+
+    final int fsync(int fdn) {
+        if(fdn < 0 || fdn >= OPEN_MAX) return -EBADFD;
+        if(fds[fdn] == null) return -EBADFD;
+        FD fd = fds[fdn];
+
+        Seekable s = fd.seekable();
+        if (s == null) return -EINVAL;
+
+        try {
+            s.sync();
+            return 0;
+        } catch (IOException e) {
+            return -EIO;
+        }
+    }
+
     /** The syscall dispatcher.
         The should be called by subclasses when the syscall instruction is invoked.
         <i>syscall</i> should be the contents of V0 and <i>a</i>, <i>b</i>, <i>c</i>, and <i>d</i> should be 
         the contenst of A0, A1, A2, and A3. The call MAY change the state
         @see Runtime#state state */
-    protected int syscall(int syscall, int a, int b, int c, int d) {
+    protected final int syscall(int syscall, int a, int b, int c, int d, int e, int f) {
+        try {
+            int n = _syscall(syscall,a,b,c,d,e,f);
+            //if(n<0) throw new ErrnoException(-n);
+            return n;
+        } catch(ErrnoException ex) {
+            //System.err.println("While executing syscall: " + syscall + ":");
+            //if(syscall == SYS_open) try { System.err.println("Failed to open " + cstring(a) + " errno " + ex.errno); } catch(Exception e2) { }
+            //ex.printStackTrace();
+            return -ex.errno;
+        } catch(FaultException ex) {
+            return -EFAULT;
+        } catch(RuntimeException ex) {
+            ex.printStackTrace();
+            throw new Error("Internal Error in _syscall()");
+        }
+    }
+    
+    int _syscall(int syscall, int a, int b, int c, int d, int e, int f) throws ErrnoException, FaultException {
         switch(syscall) {
             case SYS_null: return 0;
             case SYS_exit: return sys_exit(a);
@@ -969,15 +1099,23 @@ public abstract class Runtime implements UsermodeConstants,Registers {
             case SYS_close: return sys_close(a);
             case SYS_read: return sys_read(a,b,c);
             case SYS_lseek: return sys_lseek(a,b,c);
+            case SYS_ftruncate: return sys_ftruncate(a,b);
             case SYS_getpid: return sys_getpid();
             case SYS_calljava: return sys_calljava(a,b,c,d);
             case SYS_gettimeofday: return sys_gettimeofday(a,b);
             case SYS_sleep: return sys_sleep(a);
             case SYS_times: return sys_times(a);
             case SYS_getpagesize: return sys_getpagesize();
-            case SYS_isatty: return sys_isatty(a);
             case SYS_fcntl: return sys_fcntl(a,b,c);
             case SYS_sysconf: return sys_sysconf(a);
+            case SYS_getuid: return sys_getuid();
+            case SYS_geteuid: return sys_geteuid();
+            case SYS_getgid: return sys_getgid();
+            case SYS_getegid: return sys_getegid();
+            
+            case SYS_fsync: return fsync(a);
+            case SYS_memcpy: memcpy(a,b,c); return a;
+            case SYS_memset: memset(a,b,c); return a;
 
             case SYS_kill:
             case SYS_fork:
@@ -988,14 +1126,19 @@ public abstract class Runtime implements UsermodeConstants,Registers {
             case SYS_mkdir:
             case SYS_getcwd:
             case SYS_chdir:
-                System.err.println("Attempted to use a UnixRuntime syscall in Runtime (" + syscall + ")");
+                if(STDERR_DIAG) System.err.println("Attempted to use a UnixRuntime syscall in Runtime (" + syscall + ")");
                 return -ENOSYS;
             default:
-                System.err.println("Attempted to use unknown syscall: " + syscall);
+                if(STDERR_DIAG) System.err.println("Attempted to use unknown syscall: " + syscall);
                 return -ENOSYS;
         }
     }
     
+    private int sys_getuid() { return 0; }
+    private int sys_geteuid() { return 0; }
+    private int sys_getgid() { return 0; }
+    private int sys_getegid() { return 0; }
+    
     public int xmalloc(int size) { int p=malloc(size); if(p==0) throw new RuntimeException("malloc() failed"); return p; }
     public int xrealloc(int addr,int newsize) { int p=realloc(addr,newsize); if(p==0) throw new RuntimeException("realloc() failed"); return p; }
     public int realloc(int addr, int newsize) { try { return call("realloc",addr,newsize); } catch(CallException e) { return 0; } }
@@ -1019,9 +1162,38 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         }
         return addr;
     }
-    
+
+    // TODO: less memory copying (custom utf-8 reader)
+    //       or at least roll strlen() into copyin()
+    public final String utfstring(int addr) throws ReadFaultException {
+        if (addr == 0) return null;
+
+        // determine length
+        int i=addr;
+        for(int word = 1; word != 0; i++) {
+            word = memRead(i&~3);
+            switch(i&3) {
+                case 0: word = (word>>>24)&0xff; break;
+                case 1: word = (word>>>16)&0xff; break;
+                case 2: word = (word>>> 8)&0xff; break;
+                case 3: word = (word>>> 0)&0xff; break;
+            }
+        }
+        if (i > addr) i--; // do not count null
+
+        byte[] bytes = new byte[i-addr];
+        copyin(addr, bytes, bytes.length);
+
+        try {
+            return new String(bytes, "UTF-8");
+        } catch (UnsupportedEncodingException e) {
+            throw new RuntimeException(e); // should never happen with UTF-8
+        }
+    }
+
     /** Helper function to read a cstring from main memory */
-    public String cstring(int addr) throws ReadFaultException {
+    public final String cstring(int addr) throws ReadFaultException {
+        if (addr == 0) return null;
         StringBuffer sb = new StringBuffer();
         for(;;) {
             int word = memRead(addr&~3);
@@ -1037,22 +1209,28 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     /** File Descriptor class */
     public static abstract class FD {
         private int refCount = 1;
-    
-        /** returns true if the fd is readable */
-        public boolean readable() { return false; }
-        /** returns true if the fd is writable */
-        public boolean writable() { return false; }
+        private String normalizedPath = null;
+        private boolean deleteOnClose = false;
+
+        public void setNormalizedPath(String path) { normalizedPath = path; }
+        public String getNormalizedPath() { return normalizedPath; }
+
+        public void markDeleteOnClose() { deleteOnClose = true; }
+        public boolean isMarkedForDeleteOnClose() { return deleteOnClose; }
         
         /** Read some bytes. Should return the number of bytes read, 0 on EOF, or throw an IOException on error */
-        public int read(byte[] a, int off, int length) throws IOException { throw new IOException("no definition"); }
+        public int read(byte[] a, int off, int length) throws ErrnoException { throw new ErrnoException(EBADFD); }
         /** Write. Should return the number of bytes written or throw an IOException on error */
-        public int write(byte[] a, int off, int length) throws IOException { throw new IOException("no definition"); }
+        public int write(byte[] a, int off, int length) throws ErrnoException { throw new ErrnoException(EBADFD); }
 
         /** Seek in the filedescriptor. Whence is SEEK_SET, SEEK_CUR, or SEEK_END. Should return -1 on error or the new position. */
-        public int seek(int n, int whence)  throws IOException  { return -1; }
+        public int seek(int n, int whence)  throws ErrnoException  { return -1; }
         
-        /** Should return true if this is a tty */
-        public boolean isatty() { return false; }
+        public int getdents(byte[] a, int off, int length) throws ErrnoException { throw new ErrnoException(EBADFD); }
+        
+        /** Return a Seekable object representing this file descriptor (can be read only) 
+            This is required for exec() */
+        Seekable seekable() { return null; }
         
         private FStat cachedFStat = null;
         public final FStat fstat() {
@@ -1061,6 +1239,7 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         }
         
         protected abstract FStat _fstat();
+        public abstract int  flags();
         
         /** Closes the fd */
         public final void close() { if(--refCount==0) _close(); }
@@ -1073,80 +1252,152 @@ public abstract class Runtime implements UsermodeConstants,Registers {
     public abstract static class SeekableFD extends FD {
         private final int flags;
         private final Seekable data;
-        public boolean readable() { return (flags&3) != WR_ONLY; }
-        public boolean writable() { return (flags&3) != RD_ONLY; }
         
         SeekableFD(Seekable data, int flags) { this.data = data; this.flags = flags; }
         
         protected abstract FStat _fstat();
+        public int flags() { return flags; }
 
-        public int seek(int n, int whence) throws IOException {
-            switch(whence) {
-                case SEEK_SET: break;
-                case SEEK_CUR: n += data.pos(); break;
-                case SEEK_END: n += data.length(); break;
-                default: return -1;
+        Seekable seekable() { return data; }
+        
+        public int seek(int n, int whence) throws ErrnoException {
+            try {
+                switch(whence) {
+                        case SEEK_SET: break;
+                        case SEEK_CUR: n += data.pos(); break;
+                        case SEEK_END: n += data.length(); break;
+                        default: return -1;
+                }
+                data.seek(n);
+                return n;
+            } catch(IOException e) {
+                throw new ErrnoException(ESPIPE);
             }
-            data.seek(n);
-            return n;
         }
         
-        public int write(byte[] a, int off, int length) throws IOException {
+        public int write(byte[] a, int off, int length) throws ErrnoException {
+            if((flags&3) == RD_ONLY) throw new ErrnoException(EBADFD);
             // NOTE: There is race condition here but we can't fix it in pure java
             if((flags&O_APPEND) != 0) seek(0,SEEK_END);
-            return data.write(a,off,length);
+            try {
+                return data.write(a,off,length);
+            } catch(IOException e) {
+                throw new ErrnoException(EIO);
+            }
         }
         
-        public int read(byte[] a, int off, int length) throws IOException {
-            int n = data.read(a,off,length);
-            return n < 0 ? 0 : n;
+        public int read(byte[] a, int off, int length) throws ErrnoException {
+            if((flags&3) == WR_ONLY) throw new ErrnoException(EBADFD);
+            try {
+                int n = data.read(a,off,length);
+                return n < 0 ? 0 : n;
+            } catch(IOException e) {
+                throw new ErrnoException(EIO);
+            }
         }
         
         protected void _close() { try { data.close(); } catch(IOException e) { /*ignore*/ } }        
     }
     
-    public static class OutputStreamFD extends FD {
-        private OutputStream os;
-        public boolean writable() { return true; }
-        public OutputStreamFD(OutputStream os) { this.os = os; }
-        public int write(byte[] a, int off, int length) throws IOException { os.write(a,off,length); return length; }
-        public void _close() { try { os.close(); } catch(IOException e) { /*ignore*/ }  }
-        public FStat _fstat() { return new FStat(); }
-    }
-    
-    public static class InputStreamFD extends FD {
-        private InputStream is;
-        public boolean readable() { return true; }
-        public InputStreamFD(InputStream is) { this.is = is; }
-        public int read(byte[] a, int off, int length) throws IOException { int n = is.read(a,off,length); return n < 0 ? 0 : n; }
-        public void _close() { try { is.close(); } catch(IOException e) { /*ignore*/ } }
-        public FStat _fstat() { return new FStat(); }
+    public static class InputOutputStreamFD extends FD {
+        private final InputStream is;
+        private final OutputStream os;
+        
+        public InputOutputStreamFD(InputStream is) { this(is,null); }
+        public InputOutputStreamFD(OutputStream os) { this(null,os); }
+        public InputOutputStreamFD(InputStream is, OutputStream os) {
+            this.is = is;
+            this.os = os;
+            if(is == null && os == null) throw new IllegalArgumentException("at least one stream must be supplied");
+        }
+        
+        public int flags() {
+            if(is != null && os != null) return O_RDWR;
+            if(is != null) return O_RDONLY;
+            if(os != null) return O_WRONLY;
+            throw new Error("should never happen");
+        }
+        
+        public void _close() {
+            if(is != null) try { is.close(); } catch(IOException e) { /*ignore*/ }
+            if(os != null) try { os.close(); } catch(IOException e) { /*ignore*/ }
+        }
+        
+        public int read(byte[] a, int off, int length) throws ErrnoException {
+            if(is == null) return super.read(a,off,length);
+            try {
+                int n = is.read(a,off,length);
+                return n < 0 ? 0 : n;
+            } catch(IOException e) {
+                throw new ErrnoException(EIO);
+            }
+        }    
+        
+        public int write(byte[] a, int off, int length) throws ErrnoException {
+            if(os == null) return super.write(a,off,length);
+            try {
+                os.write(a,off,length);
+                return length;
+            } catch(IOException e) {
+                throw new ErrnoException(EIO);
+            }
+        }
+        
+        public FStat _fstat() { return new SocketFStat(); }
     }
     
-    protected static class StdinFD extends InputStreamFD {
-        public StdinFD(InputStream is) { super(is); }
+    static class TerminalFD extends InputOutputStreamFD {
+        public TerminalFD(InputStream is) { this(is,null); }
+        public TerminalFD(OutputStream os) { this(null,os); }
+        public TerminalFD(InputStream is, OutputStream os) { super(is,os); }
         public void _close() { /* noop */ }
-        public FStat _fstat() { return new FStat() { public int type() { return S_IFCHR; } }; }
-        public boolean isatty() { return true; }
-    }
-    protected static class StdoutFD extends OutputStreamFD {
-        public StdoutFD(OutputStream os) { super(os); }
-        public void _close() { /* noop */ }
-        public FStat _fstat() { return new FStat() { public int type() { return S_IFCHR; } }; }
-        public boolean isatty() { return true; }
+        public FStat _fstat() { return new SocketFStat() { public int type() { return S_IFCHR; } public int mode() { return 0600; } }; }
+    }
+    
+    // This is pretty inefficient but it is only used for reading from the console on win32
+    static class Win32ConsoleIS extends InputStream {
+        private int pushedBack = -1;
+        private final InputStream parent;
+        public Win32ConsoleIS(InputStream parent) { this.parent = parent; }
+        public int read() throws IOException {
+            if(pushedBack != -1) { int c = pushedBack; pushedBack = -1; return c; }
+            int c = parent.read();
+            if(c == '\r' && (c = parent.read()) != '\n') { pushedBack = c; return '\r'; }
+            return c;
+        }
+        public int read(byte[] buf, int pos, int len) throws IOException {
+            boolean pb = false;
+            if(pushedBack != -1 && len > 0) {
+                buf[0] = (byte) pushedBack;
+                pushedBack = -1;
+                pos++; len--; pb = true;
+            }
+            int n = parent.read(buf,pos,len);
+            if(n == -1) return pb ? 1 : -1;
+            for(int i=0;i<n;i++) {
+                if(buf[pos+i] == '\r') {
+                    if(i==n-1) {
+                        int c = parent.read();
+                        if(c == '\n') buf[pos+i] = '\n';
+                        else pushedBack = c;
+                    } else if(buf[pos+i+1] == '\n') {
+                        System.arraycopy(buf,pos+i+1,buf,pos+i,len-i-1);
+                        n--;
+                    }
+                }
+            }
+            return n + (pb ? 1 : 0);
+        }
     }
     
-    public static class FStat {
-        public static final int S_IFIFO = 0010000;
-        public static final int S_IFCHR = 0020000;
-        public static final int S_IFDIR = 0040000;
-        public static final int S_IFREG = 0100000;
+    public abstract static class FStat {
+        public static final int S_IFIFO =  0010000;
+        public static final int S_IFCHR =  0020000;
+        public static final int S_IFDIR =  0040000;
+        public static final int S_IFREG =  0100000;
+        public static final int S_IFSOCK = 0140000;
         
-        public int dev() { return -1; }
-        // FEATURE: inode numbers are calculated inconsistently throught the runtime
-        public int inode() { return hashCode() & 0xfffff; }
         public int mode() { return 0; }
-        public int type() { return S_IFIFO; }
         public int nlink() { return 0; }
         public int uid() { return 0; }
         public int gid() { return 0; }
@@ -1156,27 +1407,31 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         public int ctime() { return 0; }
         public int blksize() { return 512; }
         public int blocks() { return (size()+blksize()-1)/blksize(); }        
+        
+        public abstract int dev();
+        public abstract int type();
+        public abstract int inode();
     }
     
-    protected static class HostFStat extends FStat {
+    public static class SocketFStat extends FStat {
+        public int dev() { return -1; }
+        public int type() { return S_IFSOCK; }
+        public int inode() { return hashCode() & 0x7fff; }
+    }
+    
+    static class HostFStat extends FStat {
         private final File f;
+        private final Seekable.File sf;
         private final boolean executable; 
-        public HostFStat(File f) {
+        public HostFStat(File f, Seekable.File sf) { this(f,sf,false); }
+        public HostFStat(File f, boolean executable) {this(f,null,executable);}
+        public HostFStat(File f, Seekable.File sf, boolean executable) {
             this.f = f;
-            boolean _executable = false;
-            // FEATURE: This might be too expensive
-            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) { /* ignore */ }
-            executable = _executable;
+            this.sf = sf;
+            this.executable = executable;
         }
         public int dev() { return 1; }
-        public int inode() { return f.getName().hashCode() & 0xffff; }
+        public int inode() { return f.getAbsolutePath().hashCode() & 0x7fff; }
         public int type() { return f.isDirectory() ? S_IFDIR : S_IFREG; }
         public int nlink() { return 1; }
         public int mode() {
@@ -1187,20 +1442,28 @@ public abstract class Runtime implements UsermodeConstants,Registers {
             if(f.canWrite()) mode |= 0222;
             return mode;
         }
-        public int size() { return (int) f.length(); }
-        public int mtime() { return (int)(f.lastModified()/1000); }
+        public int size() {
+          try {
+            return sf != null ? (int)sf.length() : (int)f.length();
+          } catch (Exception x) {
+            return (int)f.length();
+          }
+        }
+        public int mtime() { return (int)(f.lastModified()/1000); }        
     }
     
     // Exceptions
-    public class ReadFaultException extends FaultException {
+    public static class ReadFaultException extends FaultException {
         public ReadFaultException(int addr) { super(addr); }
     }
-    public class WriteFaultException extends FaultException {
+    public static class WriteFaultException extends FaultException {
         public WriteFaultException(int addr) { super(addr); }
     }
-    public abstract class FaultException extends ExecutionException {
-        public int addr;
-        public FaultException(int addr) { super("fault at: " + toHex(addr)); this.addr = addr; }
+    public static class FaultException extends ExecutionException {
+        public final int addr;
+        public final RuntimeException cause;
+        public FaultException(int addr) { super("fault at: " + toHex(addr)); this.addr = addr; cause = null; }
+        public FaultException(RuntimeException e) { super(e.toString()); addr = -1; cause = e; }
     }
     public static class ExecutionException extends Exception {
         private String message = "(null)";
@@ -1214,7 +1477,7 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         public CallException(String s) { super(s); }
     }
     
-    protected static class ErrnoException extends IOException {
+    protected static class ErrnoException extends Exception {
         public int errno;
         public ErrnoException(int errno) { super("Errno: " + errno); this.errno = errno; }
     }
@@ -1229,31 +1492,43 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         public int hi, lo;
         public int fcsr;
         public int pc;
+        
+        public CPUState dup() {
+            CPUState c = new CPUState();
+            c.hi = hi;
+            c.lo = lo;
+            c.fcsr = fcsr;
+            c.pc = pc;
+            for(int i=0;i<32;i++) {
+                    c.r[i] = r[i];
+                c.f[i] = f[i];
+            }
+            return c;
+        }
+    }
+    
+    public static class SecurityManager {
+        public boolean allowRead(File f) { return true; }
+        public boolean allowWrite(File f) { return true; }
+        public boolean allowStat(File f) { return true; }
+        public boolean allowUnlink(File f) { return true; }
     }
     
     // Null pointer check helper function
     protected final void nullPointerCheck(int addr) throws ExecutionException {
-        if(TOTAL_PAGES==1 ? addr < 65536 : (addr>>>PAGE_SHIFT) < 16)
+        if(addr < 65536)
             throw new ExecutionException("Attempted to dereference a null pointer " + toHex(addr));
     }
     
     // Utility functions
-    private byte[] byteBuf(int size) {
+    byte[] byteBuf(int size) {
         if(_byteBuf==null) _byteBuf = new byte[size];
         else if(_byteBuf.length < size)
             _byteBuf = new byte[min(max(_byteBuf.length*2,size),MAX_CHUNK)];
         return _byteBuf;
     }
     
-    protected static String getSystemProperty(String key) {
-        try {
-            return System.getProperty(key);
-        } catch(SecurityException e) {
-            return null;
-        }
-    }
-    
-    /** Decode an packed string.. FEATURE: document this better */
+    /** Decode a packed string */
     protected static final int[] decodeData(String s, int words) {
         if(s.length() % 8 != 0) throw new IllegalArgumentException("string length must be a multiple of 8");
         if((s.length() / 8) * 7 < words*4) throw new IllegalArgumentException("string isn't big enough");
@@ -1270,15 +1545,22 @@ public abstract class Runtime implements UsermodeConstants,Registers {
         return buf;
     }
     
-    protected static byte[] getBytes(String s) {
+    static byte[] getBytes(String s) {
         try {
-            return s.getBytes("ISO-8859-1");
+            return s.getBytes("UTF-8");
         } catch(UnsupportedEncodingException e) {
             return null; // should never happen
         }
     }
     
-    protected final static String toHex(int n) { return "0x" + Long.toString(n & 0xffffffffL, 16); }
-    protected final static int min(int a, int b) { return a < b ? a : b; }
-    protected final static int max(int a, int b) { return a > b ? a : b; }
+    static byte[] getNullTerminatedBytes(String s) {
+        byte[] buf1 = getBytes(s);
+        byte[] buf2 = new byte[buf1.length+1];
+        System.arraycopy(buf1,0,buf2,0,buf1.length);
+        return buf2;
+    }
+    
+    final static String toHex(int n) { return "0x" + Long.toString(n & 0xffffffffL, 16); }
+    final static int min(int a, int b) { return a < b ? a : b; }
+    final static int max(int a, int b) { return a > b ? a : b; }
 }