make grade 80/80 with comment

61810

Makefile

@@ -106,7 +106,7 @@ endif
 
 ifdef KCSAN
 CFLAGS += -DKCSAN
-KCSANFLAG = -fsanitize=thread
+KCSANFLAG = -fsanitize=thread -fno-inline
 endif
 
 # Disable PIE when possible (for Ubuntu 16.10 toolchain)
@@ -188,11 +188,6 @@ UPROGS=\
 	$U/_grind\
 	$U/_wc\
 	$U/_zombie\
-	$U/_sleep\
-	$U/_pingpong\
-	$U/_primes\
-	$U/_find\
-	$U/_xargs\
 
 
 

README

@@ -6,7 +6,7 @@ ACKNOWLEDGMENTS
 
 xv6 is inspired by John Lions's Commentary on UNIX 6th Edition (Peer
 to Peer Communications; ISBN: 1-57398-013-7; 1st edition (June 14,
-2000)).  See also https://pdos.csail.mit.edu/6.828/, which provides
+2000)).  See also https://pdos.csail.mit.edu/6.1810/, which provides
 pointers to on-line resources for v6.
 
 The following people have made contributions: Russ Cox (context switching,
@@ -14,29 +14,31 @@ locking), Cliff Frey (MP), Xiao Yu (MP), Nickolai Zeldovich, and Austin
 Clements.
 
 We are also grateful for the bug reports and patches contributed by
-Takahiro Aoyagi, Silas Boyd-Wickizer, Anton Burtsev, Ian Chen, Dan
-Cross, Cody Cutler, Mike CAT, Tej Chajed, Asami Doi, eyalz800, Nelson
-Elhage, Saar Ettinger, Alice Ferrazzi, Nathaniel Filardo, flespark,
-Peter Froehlich, Yakir Goaron, Shivam Handa, Matt Harvey, Bryan Henry,
-jaichenhengjie, Jim Huang, Matúš Jókay, Alexander Kapshuk, Anders
-Kaseorg, kehao95, Wolfgang Keller, Jungwoo Kim, Jonathan Kimmitt,
-Eddie Kohler, Vadim Kolontsov, Austin Liew, l0stman, Pavan
-Maddamsetti, Imbar Marinescu, Yandong Mao, Matan Shabtay, Hitoshi
-Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel Nider,
-OptimisticSide, Greg Price, Jude Rich, Ayan Shafqat, Eldar Sehayek,
-Yongming Shen, Fumiya Shigemitsu, Cam Tenny, tyfkda, Warren Toomey,
-Stephen Tu, Rafael Ubal, Amane Uehara, Pablo Ventura, Xi Wang, Keiichi
-Watanabe, Nicolas Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy
-Zheng, ZhUyU1997, and Zou Chang Wei.
+Takahiro Aoyagi, Silas Boyd-Wickizer, Anton Burtsev, carlclone, Ian
+Chen, Dan Cross, Cody Cutler, Mike CAT, Tej Chajed, Asami Doi,
+eyalz800, Nelson Elhage, Saar Ettinger, Alice Ferrazzi, Nathaniel
+Filardo, flespark, Peter Froehlich, Yakir Goaron, Shivam Handa, Matt
+Harvey, Bryan Henry, jaichenhengjie, Jim Huang, Matúš Jókay, John
+Jolly, Alexander Kapshuk, Anders Kaseorg, kehao95, Wolfgang Keller,
+Jungwoo Kim, Jonathan Kimmitt, Eddie Kohler, Vadim Kolontsov, Austin
+Liew, l0stman, Pavan Maddamsetti, Imbar Marinescu, Yandong Mao, Matan
+Shabtay, Hitoshi Mitake, Carmi Merimovich, Mark Morrissey, mtasm, Joel
+Nider, Hayato Ohhashi, OptimisticSide, Harry Porter, Greg Price, Jude
+Rich, segfault, Ayan Shafqat, Eldar Sehayek, Yongming Shen, Fumiya
+Shigemitsu, Cam Tenny, tyfkda, Warren Toomey, Stephen Tu, Rafael Ubal,
+Amane Uehara, Pablo Ventura, Xi Wang, WaheedHafez, Keiichi Watanabe,
+Nicolas Wolovick, wxdao, Grant Wu, Jindong Zhang, Icenowy Zheng,
+ZhUyU1997, and Zou Chang Wei.
+
 
 The code in the files that constitute xv6 is
-Copyright 2006-2020 Frans Kaashoek, Robert Morris, and Russ Cox.
+Copyright 2006-2022 Frans Kaashoek, Robert Morris, and Russ Cox.
 
 ERROR REPORTS
 
 Please send errors and suggestions to Frans Kaashoek and Robert Morris
 (kaashoek,rtm@mit.edu).  The main purpose of xv6 is as a teaching
-operating system for MIT's 6.S081, so we are more interested in
+operating system for MIT's 6.1810, so we are more interested in
 simplifications and clarifications than new features.
 
 BUILDING AND RUNNING XV6

conf/lab.mk

@@ -1 +1 @@
-LAB=util
+LAB=lock

grade-lab-lock

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+
+import re
+from gradelib import *
+
+r = Runner(save("xv6.out"))
+
+@test(0, "running kalloctest")
+def test_kalloctest():
+    r.run_qemu(shell_script([
+        'kalloctest'
+    ]), timeout=200)
+    
+@test(10, "kalloctest: test1", parent=test_kalloctest)
+def test_kalloctest_test1():
+    r.match('^test1 OK$')
+    
+@test(10, "kalloctest: test2", parent=test_kalloctest)
+def test_kalloctest_test2():
+    r.match('^test2 OK$')
+
+@test(10, "kalloctest: test3", parent=test_kalloctest)
+def test_kalloctest_test3():
+    r.match('^test3 OK$')
+
+@test(10, "kalloctest: sbrkmuch")
+def test_sbrkmuch():
+    r.run_qemu(shell_script([
+        'usertests sbrkmuch'
+    ]), timeout=90)
+    r.match('^ALL TESTS PASSED$')
+
+@test(0, "running bcachetest")
+def test_bcachetest():
+    r.run_qemu(shell_script([
+        'bcachetest'
+    ]), timeout=90)
+    
+@test(10, "bcachetest: test0", parent=test_bcachetest)
+def test_bcachetest_test0():
+    r.match('^test0: OK$')
+    
+@test(10, "bcachetest: test1", parent=test_bcachetest)
+def test_bcachetest_test1():
+    r.match('^test1 OK$')
+
+@test(19, "usertests")
+def test_usertests():
+    r.run_qemu(shell_script([
+        'usertests -q'
+    ]), timeout=300)
+    r.match('^ALL TESTS PASSED$')
+
+@test(1, "time")
+def test_time():
+    check_time()
+
+run_tests()

grade-lab-util

@@ -1,86 +0,0 @@
-#!/usr/bin/env python3
-
-import re
-from gradelib import *
-
-r = Runner(save("xv6.out"))
-
-@test(5, "sleep, no arguments")
-def test_sleep_no_args():
-    r.run_qemu(shell_script([
-        'sleep'
-    ]))
-    r.match(no=["exec .* failed", "$ sleep\n$"])
-
-@test(5, "sleep, returns")
-def test_sleep_no_args():
-    r.run_qemu(shell_script([
-        'sleep',
-        'echo OK'
-    ]))
-    r.match('^OK$', no=["exec .* failed", "$ sleep\n$"])
-
-@test(10, "sleep, makes syscall")
-def test_sleep():
-    r.run_qemu(shell_script([
-        'sleep 10',
-        'echo FAIL'
-    ]), stop_breakpoint('sys_sleep'))
-    r.match('\\$ sleep 10', no=['FAIL'])
-
-@test(20, "pingpong")
-def test_pingpong():
-    r.run_qemu(shell_script([
-        'pingpong', 'echo OK'
-    ]))
-    r.match('^\\d+: received ping$', '^\\d+: received pong$', '^OK$')
-
-@test(20, "primes")
-def test_primes():
-    r.run_qemu(shell_script([
-        'primes', 'echo OK'
-    ]))
-    args = ['prime %d' % i for i in [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31]]
-    args.append('^OK$')
-    r.match(*args)
-
-@test(10, "find, in current directory")
-def test_find_curdir():
-    fn = random_str()
-    r.run_qemu(shell_script([
-        'echo > %s' % fn,
-        'find . %s' % fn
-    ]))
-    r.match('./%s' % fn)
-
-@test(10, "find, recursive")
-def test_find_recursive():
-    needle = random_str()
-    dirs = [random_str() for _ in range(3)]
-    r.run_qemu(shell_script([
-        'mkdir %s' % dirs[0],
-        'echo > %s/%s' % (dirs[0], needle),
-        'mkdir %s/%s' % (dirs[0], dirs[1]),
-        'echo > %s/%s/%s' % (dirs[0], dirs[1], needle),
-        'mkdir %s' % dirs[2],
-        'echo > %s/%s' % (dirs[2], needle),
-        'find . %s' % needle
-    ]))
-    r.match('./%s/%s' % (dirs[0], needle),
-            './%s/%s/%s' % (dirs[0], dirs[1], needle),
-            './%s/%s' % (dirs[2], needle))
-
-@test(19, "xargs")
-def test_xargs():
-    r.run_qemu(shell_script([
-        'sh < xargstest.sh',
-        'echo DONE',
-    ], 'DONE'))
-    matches = re.findall("hello", r.qemu.output)
-    assert_equal(len(matches), 3, "Number of appearances of 'hello'")
-
-@test(1, "time")
-def test_time():
-    check_time()
-    
-run_tests()

kernel/bio.c

@@ -33,13 +33,34 @@ struct {
   struct buf head;
 } bcache;
 
+#define NLOCK_BUCKETS 13
+// #define ORIGINAL
+struct spinlock hash_locks[NLOCK_BUCKETS];
+static char lock_names [NLOCK_BUCKETS][20];
+
+struct hash_tbl {
+  struct buf* buf;
+  struct hash_tbl *next;
+} hash_tbl;
+
+struct hash_tbl* hash_entry[NLOCK_BUCKETS];
+struct hash_tbl hash_tbls[NBUF];
+
 void
 binit(void)
 {
   struct buf *b;
 
   initlock(&bcache.lock, "bcache");
-
+  for (int i = 0; i < NLOCK_BUCKETS; ++ i) {
+    snprintf(lock_names[i], 20, "bcache.lk%d", i);
+    initlock(&hash_locks[i], lock_names[i]);
+    hash_entry[i] = 0;
+  }
+  for (int i = 0; i < NBUF; ++ i) {
+    hash_tbls[i].buf = &bcache.buf[i];
+    hash_tbls[i].next = 0;
+  }
   // Create linked list of buffers
   bcache.head.prev = &bcache.head;
   bcache.head.next = &bcache.head;
@@ -58,12 +79,69 @@ binit(void)
 static struct buf*
 bget(uint dev, uint blockno)
 {
-  struct buf *b;
+  struct buf *b = 0;
 
+  // acquire(&bcache.lock);
+#ifndef ORIGINAL
+  int bucket = blockno % NLOCK_BUCKETS;
+  acquire(&hash_locks[bucket]);
+  struct hash_tbl* h = hash_entry[bucket];
+  struct hash_tbl* ph = 0;
+  while (h != 0) {
+    if (h->buf->dev == dev && h->buf->blockno == blockno) {
+      b = h->buf;
+      b->refcnt ++;
+      release(&hash_locks[bucket]);
+      // release(&bcache.lock);
+      acquiresleep(&b->lock);
+      return b;
+    }
+    h = h->next;
+  }
+  release(&hash_locks[bucket]); 
+  // release the unfound bucket, or there'll be deadlock
   acquire(&bcache.lock);
-
+  // after bcache.lock is aquired, only b->refcnt maybe out of our control
+  //    so, have to aquire hash_locks[victim_bucket] before test refcnt
+  for(int i = 0; i < NBUF; ++ i){
+    b = &bcache.buf[i];
+    int victim_bucket = b->blockno % NLOCK_BUCKETS;
+    acquire(&hash_locks[victim_bucket]);
+    if(b->refcnt == 0) {
+      b->dev = dev;
+      b->blockno = blockno;
+      b->valid = 0;
+      b->refcnt = 1;
+      // try to release hash entry from the old bucket
+      h = hash_entry[victim_bucket];
+      ph = 0;
+      while (h != 0) {
+        if (h->buf->dev == b->dev && h->buf->blockno == b->blockno) {
+          if (ph) ph->next = h->next;
+          else hash_entry[victim_bucket] = h->next;
+          break;
+        }
+        ph = h;
+        h = h->next;
+      }
+      release(&hash_locks[victim_bucket]);
+      release(&bcache.lock);
+      // this should avoid deadlock and meanwhile guard the hashtable
+      // because after b is set, the only thing we need is hashtable rather than buf attributes
+      h = &hash_tbls[i];
+      acquire(&hash_locks[bucket]);
+      h->next = hash_entry[bucket];
+      hash_entry[bucket] = h;
+      release(&hash_locks[bucket]);
+      acquiresleep(&b->lock);
+      return b;
+    }
+    release(&hash_locks[victim_bucket]);
+  }
+#else
   // Is the block already cached?
-  for(b = bcache.head.next; b != &bcache.head; b = b->next){
+  // for(b = bcache.head.next; b != &bcache.head; b = b->next){
+  for (b = &bcache.buf[0]; b < &bcache.buf[NBUF]; ++ b) {
     if(b->dev == dev && b->blockno == blockno){
       b->refcnt++;
       release(&bcache.lock);
@@ -74,7 +152,8 @@ bget(uint dev, uint blockno)
 
   // Not cached.
   // Recycle the least recently used (LRU) unused buffer.
-  for(b = bcache.head.prev; b != &bcache.head; b = b->prev){
+  // for(b = bcache.head.prev; b != &bcache.head; b = b->prev){
+  for(b = &bcache.buf[0]; b < &bcache.buf[NBUF]; ++ b){
     if(b->refcnt == 0) {
       b->dev = dev;
       b->blockno = blockno;
@@ -85,6 +164,7 @@ bget(uint dev, uint blockno)
       return b;
     }
   }
+#endif
   panic("bget: no buffers");
 }
 
@@ -121,19 +201,25 @@ brelse(struct buf *b)
 
   releasesleep(&b->lock);
 
-  acquire(&bcache.lock);
+// if you use bcache lock, test0 fails without doubt
+// the reason why this works is that, whenever b->refcnt is written or read
+//    its 'hash_locks[H(b->blockno)]' will always been locked
+// the reason why b->blockno is valid is that, only when refcnt==0 could this field be written
+//    but here it must be non-zero before lock aquired
+  int bucket = b->blockno % NLOCK_BUCKETS;
+  acquire(&hash_locks[bucket]);
   b->refcnt--;
-  if (b->refcnt == 0) {
-    // no one is waiting for it.
-    b->next->prev = b->prev;
-    b->prev->next = b->next;
-    b->next = bcache.head.next;
-    b->prev = &bcache.head;
-    bcache.head.next->prev = b;
-    bcache.head.next = b;
-  }
+  // if (b->refcnt == 0) {
+  //   // no one is waiting for it.
+  //   b->next->prev = b->prev;
+  //   b->prev->next = b->next;
+  //   b->next = bcache.head.next;
+  //   b->prev = &bcache.head;
+  //   bcache.head.next->prev = b;
+  //   bcache.head.next = b;
+  // }
   
-  release(&bcache.lock);
+  release(&hash_locks[bucket]);
 }
 
 void

kernel/defs.h

@@ -8,6 +8,10 @@ struct spinlock;
 struct sleeplock;
 struct stat;
 struct superblock;
+#ifdef LAB_NET
+struct mbuf;
+struct sock;
+#endif
 
 // bio.c
 void            binit(void);
@@ -117,6 +121,10 @@ void            initlock(struct spinlock*, char*);
 void            release(struct spinlock*);
 void            push_off(void);
 void            pop_off(void);
+int             atomic_read4(int *addr);
+#ifdef LAB_LOCK
+void            freelock(struct spinlock*);
+#endif
 
 // sleeplock.c
 void            acquiresleep(struct sleeplock*);
@@ -187,3 +195,44 @@ void            virtio_disk_intr(void);
 
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))
+
+
+
+#ifdef LAB_PGTBL
+// vmcopyin.c
+int             copyin_new(pagetable_t, char *, uint64, uint64);
+int             copyinstr_new(pagetable_t, char *, uint64, uint64);
+#endif
+
+// stats.c
+void            statsinit(void);
+void            statsinc(void);
+
+// sprintf.c
+int             snprintf(char*, int, char*, ...);
+
+#ifdef KCSAN
+void            kcsaninit();
+#endif
+
+#ifdef LAB_NET
+// pci.c
+void            pci_init();
+
+// e1000.c
+void            e1000_init(uint32 *);
+void            e1000_intr(void);
+int             e1000_transmit(struct mbuf*);
+
+// net.c
+void            net_rx(struct mbuf*);
+void            net_tx_udp(struct mbuf*, uint32, uint16, uint16);
+
+// sysnet.c
+void            sockinit(void);
+int             sockalloc(struct file **, uint32, uint16, uint16);
+void            sockclose(struct sock *);
+int             sockread(struct sock *, uint64, int);
+int             sockwrite(struct sock *, uint64, int);
+void            sockrecvudp(struct mbuf*, uint32, uint16, uint16);
+#endif

kernel/file.h

@@ -1,10 +1,17 @@
 struct file {
+#ifdef LAB_NET
+  enum { FD_NONE, FD_PIPE, FD_INODE, FD_DEVICE, FD_SOCK } type;
+#else
   enum { FD_NONE, FD_PIPE, FD_INODE, FD_DEVICE } type;
+#endif
   int ref; // reference count
   char readable;
   char writable;
   struct pipe *pipe; // FD_PIPE
   struct inode *ip;  // FD_INODE and FD_DEVICE
+#ifdef LAB_NET
+  struct sock *sock; // FD_SOCK
+#endif
   uint off;          // FD_INODE
   short major;       // FD_DEVICE
 };
@@ -38,3 +45,4 @@ struct devsw {
 extern struct devsw devsw[];
 
 #define CONSOLE 1
+#define STATS   2

kernel/fs.c

@@ -295,11 +295,11 @@ ilock(struct inode *ip)
   struct buf *bp;
   struct dinode *dip;
 
-  if(ip == 0 || ip->ref < 1)
+  if(ip == 0 || atomic_read4(&ip->ref) < 1)
     panic("ilock");
 
   acquiresleep(&ip->lock);
-
+  
   if(ip->valid == 0){
     bp = bread(ip->dev, IBLOCK(ip->inum, sb));
     dip = (struct dinode*)bp->data + ip->inum%IPB;
@@ -320,7 +320,7 @@ ilock(struct inode *ip)
 void
 iunlock(struct inode *ip)
 {
-  if(ip == 0 || !holdingsleep(&ip->lock) || ip->ref < 1)
+  if(ip == 0 || !holdingsleep(&ip->lock) || atomic_read4(&ip->ref) < 1)
     panic("iunlock");
 
   releasesleep(&ip->lock);
@@ -416,7 +416,6 @@ bmap(struct inode *ip, uint bn)
     brelse(bp);
     return addr;
   }
-
   panic("bmap: out of range");
 }
 
@@ -447,7 +446,7 @@ itrunc(struct inode *ip)
     bfree(ip->dev, ip->addrs[NDIRECT]);
     ip->addrs[NDIRECT] = 0;
   }
-
+  
   ip->size = 0;
   iupdate(ip);
 }

kernel/kalloc.c

@@ -19,14 +19,19 @@ struct run {
 };
 
 struct {
-  struct spinlock lock;
-  struct run *freelist;
+  struct spinlock lock[NCPU];
+  struct run *freelist[NCPU];
 } kmem;
 
+static char kmem_lock_names [NCPU][10]; // ugly but have-to impl
+
 void
 kinit()
 {
-  initlock(&kmem.lock, "kmem");
+  for (int i = 0; i < NCPU; ++ i) {
+    snprintf(kmem_lock_names[i], NELEM(kmem_lock_names[0]), "kmem%d", i);
+    initlock(&kmem.lock[i], kmem_lock_names[i]);
+  }
   freerange(end, (void*)PHYSTOP);
 }
 
@@ -55,11 +60,13 @@ kfree(void *pa)
   memset(pa, 1, PGSIZE);
 
   r = (struct run*)pa;
-
-  acquire(&kmem.lock);
-  r->next = kmem.freelist;
-  kmem.freelist = r;
-  release(&kmem.lock);
+  push_off();
+  int _cpu = cpuid();
+  acquire(&kmem.lock[_cpu]);
+  r->next = kmem.freelist[_cpu];
+  kmem.freelist[_cpu] = r;
+  release(&kmem.lock[_cpu]);
+  pop_off();
 }
 
 // Allocate one 4096-byte page of physical memory.
@@ -69,13 +76,27 @@ void *
 kalloc(void)
 {
   struct run *r;
-
-  acquire(&kmem.lock);
-  r = kmem.freelist;
+  push_off();
+  int _cpu = cpuid();
+  acquire(&kmem.lock[_cpu]);
+  r = kmem.freelist[_cpu];
   if(r)
-    kmem.freelist = r->next;
-  release(&kmem.lock);
-
+    kmem.freelist[_cpu] = r->next;
+  else {
+    for (int i = 0, found = 0; i < NCPU && !found; ++ i) {
+      if (i != _cpu) {
+        acquire(&kmem.lock[i]);
+        if (kmem.freelist[i]) {
+          r = kmem.freelist[i];
+          kmem.freelist[i] = r->next;
+          found = 1;
+        }
+        release(&kmem.lock[i]);
+      }
+    }
+  }
+  release(&kmem.lock[_cpu]);
+  pop_off();
   if(r)
     memset((char*)r, 5, PGSIZE); // fill with junk
   return (void*)r;

kernel/kcsan.c

@@ -0,0 +1,323 @@
+#include "types.h"
+#include "param.h"
+#include "memlayout.h"
+#include "spinlock.h"
+#include "riscv.h"
+#include "proc.h"
+#include "defs.h"
+
+//
+// Race detector using gcc's thread sanitizer. It delays all stores
+// and loads and monitors if any other CPU is using the same address.
+// If so, we have a race and print out the backtrace of the thread
+// that raced and the thread that set the watchpoint.
+//
+
+//
+// To run with kcsan:
+// make clean
+// make KCSAN=1 qemu
+//
+
+// The number of watch points.
+#define NWATCH (NCPU)
+
+// The number of cycles to delay stores, whatever that means on qemu.
+//#define DELAY_CYCLES 20000
+#define DELAY_CYCLES 200000
+
+#define MAXTRACE 20
+
+int
+trace(uint64 *trace, int maxtrace)
+{
+  uint64 i = 0;
+  
+  push_off();
+  
+  uint64 fp = r_fp();
+  uint64 ra, low = PGROUNDDOWN(fp) + 16, high = PGROUNDUP(fp);
+
+  while(!(fp & 7) && fp >= low && fp < high){
+    ra = *(uint64*)(fp - 8);
+    fp = *(uint64*)(fp - 16);
+    trace[i++] = ra;
+    if(i >= maxtrace)
+      break;
+  }
+
+  pop_off();
+  
+  return i;
+}
+
+struct watch {
+  uint64 addr;
+  int write;
+  int race;
+  uint64 trace[MAXTRACE];
+  int tracesz;
+};
+  
+struct {
+  struct spinlock lock;
+  struct watch points[NWATCH];
+  int on;
+} tsan;
+
+static struct watch*
+wp_lookup(uint64 addr)
+{
+  for(struct watch *w = &tsan.points[0]; w < &tsan.points[NWATCH]; w++) {
+    if(w->addr == addr) {
+      return w;
+    }
+  }
+  return 0;
+}
+
+static int
+wp_install(uint64 addr, int write)
+{
+  for(struct watch *w = &tsan.points[0]; w < &tsan.points[NWATCH]; w++) {
+    if(w->addr == 0) {
+      w->addr = addr;
+      w->write = write;
+      w->tracesz = trace(w->trace, MAXTRACE);
+      return 1;
+    }
+  }
+  panic("wp_install");
+  return 0;
+}
+
+static void
+wp_remove(uint64 addr)
+{
+  for(struct watch *w = &tsan.points[0]; w < &tsan.points[NWATCH]; w++) {
+    if(w->addr == addr) {
+      w->addr = 0;
+      w->tracesz = 0;
+      return;
+    }
+  }
+  panic("remove");
+}
+
+static void
+printtrace(uint64 *t, int n)
+{
+  int i;
+  
+  for(i = 0; i < n; i++) {
+    printf("%p\n", t[i]);
+  }
+}
+
+static void
+race(char *s, struct watch *w) {
+  uint64 t[MAXTRACE];
+  int n;
+  
+  n = trace(t, MAXTRACE);
+  printf("== race detected ==\n");
+  printf("backtrace for racing %s\n", s);
+  printtrace(t, n);
+  printf("backtrace for watchpoint:\n");
+  printtrace(w->trace, w->tracesz);
+  printf("==========\n");
+}
+
+// cycle counter
+static inline uint64
+r_cycle()
+{
+  uint64 x;
+  asm volatile("rdcycle %0" : "=r" (x) );
+  return x;
+}
+
+static void delay(void) __attribute__((noinline));
+static void delay() {
+  uint64 stop = r_cycle() + DELAY_CYCLES;
+  uint64 c = r_cycle();
+  while(c < stop) {
+    c = r_cycle();
+  }
+}
+
+static void
+kcsan_read(uint64 addr, int sz)
+{
+  struct watch *w;
+  
+  acquire(&tsan.lock);
+  if((w = wp_lookup(addr)) != 0) {
+    if(w->write) {
+      race("load", w);
+    }
+    release(&tsan.lock);
+    return;
+  }
+  release(&tsan.lock);
+}
+
+static void
+kcsan_write(uint64 addr, int sz)
+{
+  struct watch *w;
+  
+  acquire(&tsan.lock);
+  if((w = wp_lookup(addr)) != 0) {
+    race("store", w);
+    release(&tsan.lock);
+  }
+
+  // no watchpoint; try to install one
+  if(wp_install(addr, 1)) {
+
+    release(&tsan.lock);
+
+    // XXX maybe read value at addr before and after delay to catch
+    // races of unknown origins (e.g., device).
+
+    delay(); 
+
+    acquire(&tsan.lock);
+
+    wp_remove(addr);
+  }
+  release(&tsan.lock);
+}
+
+// tsan.on will only have effect with "make KCSAN=1"
+void
+kcsaninit(void)
+{
+  initlock(&tsan.lock, "tsan");
+  tsan.on = 1;
+  __sync_synchronize();
+}
+
+//
+// Calls inserted by compiler into kernel binary, except for this file.
+//
+
+void
+__tsan_init(void)
+{
+}
+
+void
+__tsan_read1(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  // kcsan_read(addr, 1);
+}
+
+void
+__tsan_read2(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  kcsan_read(addr, 2);
+}
+
+void
+__tsan_read4(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  kcsan_read(addr, 4);
+}
+
+void
+__tsan_read8(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  kcsan_read(addr, 8);
+}
+
+void
+__tsan_read_range(uint64 addr, uint64 size)
+{
+  if(!tsan.on)
+    return;
+  kcsan_read(addr, size);
+}
+
+void
+__tsan_write1(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  // kcsan_write(addr, 1);
+}
+
+void
+__tsan_write2(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  kcsan_write(addr, 2);
+}
+
+void
+__tsan_write4(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  kcsan_write(addr, 4);
+}
+
+void
+__tsan_write8(uint64 addr)
+{
+  if(!tsan.on)
+    return;
+  kcsan_write(addr, 8);
+}
+
+void
+__tsan_write_range(uint64 addr, uint64 size)
+{
+  if(!tsan.on)
+    return;
+  kcsan_write(addr, size);
+}
+
+void
+__tsan_atomic_thread_fence(int order)
+{
+  __sync_synchronize();
+}
+
+uint32
+__tsan_atomic32_load(uint *ptr, uint *val, int order)
+{
+  uint t;
+  __atomic_load(ptr, &t, __ATOMIC_SEQ_CST);
+  return t;
+}
+
+void
+__tsan_atomic32_store(uint *ptr, uint val, int order)
+{
+  __atomic_store(ptr, &val, __ATOMIC_SEQ_CST);
+}
+
+// We don't use this
+void
+__tsan_func_entry(uint64 pc)
+{
+}
+
+// We don't use this
+void
+__tsan_func_exit(void)
+{
+}
+
+

kernel/main.c

@@ -12,6 +12,9 @@ main()
 {
   if(cpuid() == 0){
     consoleinit();
+#if defined(LAB_LOCK)
+    statsinit();
+#endif
     printfinit();
     printf("\n");
     printf("xv6 kernel is booting\n");
@@ -28,11 +31,18 @@ main()
     iinit();         // inode table
     fileinit();      // file table
     virtio_disk_init(); // emulated hard disk
+#ifdef LAB_NET
+    pci_init();
+    sockinit();
+#endif    
     userinit();      // first user process
+#ifdef KCSAN
+    kcsaninit();
+#endif
     __sync_synchronize();
     started = 1;
   } else {
-    while(started == 0)
+    while(atomic_read4((int *) &started) == 0)
       ;
     __sync_synchronize();
     printf("hart %d starting\n", cpuid());

kernel/pipe.c

@@ -68,6 +68,9 @@ pipeclose(struct pipe *pi, int writable)
   }
   if(pi->readopen == 0 && pi->writeopen == 0){
     release(&pi->lock);
+#ifdef LAB_LOCK
+    freelock(&pi->lock);
+#endif    
     kfree((char*)pi);
   } else
     release(&pi->lock);

kernel/riscv.h

@@ -295,6 +295,14 @@ r_sp()
   return x;
 }
 
+static inline uint64
+r_fp()
+{
+  uint64 x;
+  asm volatile("mv %0, s0" : "=r" (x) );
+  return x;
+}
+
 // read and write tp, the thread pointer, which xv6 uses to hold
 // this core's hartid (core number), the index into cpus[].
 static inline uint64
@@ -344,6 +352,9 @@ typedef uint64 *pagetable_t; // 512 PTEs
 #define PTE_X (1L << 3)
 #define PTE_U (1L << 4) // user can access
 
+
+
+
 // shift a physical address to the right place for a PTE.
 #define PA2PTE(pa) ((((uint64)pa) >> 12) << 10)
 

kernel/spinlock.c

@@ -8,12 +8,52 @@
 #include "proc.h"
 #include "defs.h"
 
+#ifdef LAB_LOCK
+#define NLOCK 500
+
+static struct spinlock *locks[NLOCK];
+struct spinlock lock_locks;
+
+void
+freelock(struct spinlock *lk)
+{
+  acquire(&lock_locks);
+  int i;
+  for (i = 0; i < NLOCK; i++) {
+    if(locks[i] == lk) {
+      locks[i] = 0;
+      break;
+    }
+  }
+  release(&lock_locks);
+}
+
+static void
+findslot(struct spinlock *lk) {
+  acquire(&lock_locks);
+  int i;
+  for (i = 0; i < NLOCK; i++) {
+    if(locks[i] == 0) {
+      locks[i] = lk;
+      release(&lock_locks);
+      return;
+    }
+  }
+  panic("findslot");
+}
+#endif
+
 void
 initlock(struct spinlock *lk, char *name)
 {
   lk->name = name;
   lk->locked = 0;
   lk->cpu = 0;
+#ifdef LAB_LOCK
+  lk->nts = 0;
+  lk->n = 0;
+  findslot(lk);
+#endif  
 }
 
 // Acquire the lock.
@@ -25,12 +65,21 @@ acquire(struct spinlock *lk)
   if(holding(lk))
     panic("acquire");
 
+#ifdef LAB_LOCK
+    __sync_fetch_and_add(&(lk->n), 1);
+#endif      
+
   // On RISC-V, sync_lock_test_and_set turns into an atomic swap:
   //   a5 = 1
   //   s1 = &lk->locked
   //   amoswap.w.aq a5, a5, (s1)
-  while(__sync_lock_test_and_set(&lk->locked, 1) != 0)
-    ;
+  while(__sync_lock_test_and_set(&lk->locked, 1) != 0) {
+#ifdef LAB_LOCK
+    __sync_fetch_and_add(&(lk->nts), 1);
+#else
+   ;
+#endif
+  }
 
   // Tell the C compiler and the processor to not move loads or stores
   // past this point, to ensure that the critical section's memory
@@ -108,3 +157,61 @@ pop_off(void)
   if(c->noff == 0 && c->intena)
     intr_on();
 }
+
+// Read a shared 32-bit value without holding a lock
+int
+atomic_read4(int *addr) {
+  uint32 val;
+  __atomic_load(addr, &val, __ATOMIC_SEQ_CST);
+  return val;
+}
+
+#ifdef LAB_LOCK
+int
+snprint_lock(char *buf, int sz, struct spinlock *lk)
+{
+  int n = 0;
+  if(lk->n > 0) {
+    n = snprintf(buf, sz, "lock: %s: #test-and-set %d #acquire() %d\n",
+                 lk->name, lk->nts, lk->n);
+  }
+  return n;
+}
+
+int
+statslock(char *buf, int sz) {
+  int n;
+  int tot = 0;
+
+  acquire(&lock_locks);
+  n = snprintf(buf, sz, "--- lock kmem/bcache stats\n");
+  for(int i = 0; i < NLOCK; i++) {
+    if(locks[i] == 0)
+      break;
+    if(strncmp(locks[i]->name, "bcache", strlen("bcache")) == 0 ||
+       strncmp(locks[i]->name, "kmem", strlen("kmem")) == 0) {
+      tot += locks[i]->nts;
+      n += snprint_lock(buf +n, sz-n, locks[i]);
+    }
+  }
+  
+  n += snprintf(buf+n, sz-n, "--- top 5 contended locks:\n");
+  int last = 100000000;
+  // stupid way to compute top 5 contended locks
+  for(int t = 0; t < 5; t++) {
+    int top = 0;
+    for(int i = 0; i < NLOCK; i++) {
+      if(locks[i] == 0)
+        break;
+      if(locks[i]->nts > locks[top]->nts && locks[i]->nts < last) {
+        top = i;
+      }
+    }
+    n += snprint_lock(buf+n, sz-n, locks[top]);
+    last = locks[top]->nts;
+  }
+  n += snprintf(buf+n, sz-n, "tot= %d\n", tot);
+  release(&lock_locks);  
+  return n;
+}
+#endif

kernel/spinlock.h

@@ -5,5 +5,9 @@ struct spinlock {
   // For debugging:
   char *name;        // Name of lock.
   struct cpu *cpu;   // The cpu holding the lock.
+#ifdef LAB_LOCK
+  int nts;
+  int n;
+#endif
 };
 

kernel/sprintf.c

@@ -0,0 +1,91 @@
+#include <stdarg.h>
+
+#include "types.h"
+#include "param.h"
+#include "spinlock.h"
+#include "sleeplock.h"
+#include "fs.h"
+#include "file.h"
+#include "riscv.h"
+#include "defs.h"
+
+static char digits[] = "0123456789abcdef";
+
+static int
+sputc(char *s, char c)
+{
+  *s = c;
+  return 1;
+}
+
+static int
+sprintint(char *s, int xx, int base, int sign)
+{
+  char buf[16];
+  int i, n;
+  uint x;
+
+  if(sign && (sign = xx < 0))
+    x = -xx;
+  else
+    x = xx;
+
+  i = 0;
+  do {
+    buf[i++] = digits[x % base];
+  } while((x /= base) != 0);
+
+  if(sign)
+    buf[i++] = '-';
+
+  n = 0;
+  while(--i >= 0)
+    n += sputc(s+n, buf[i]);
+  return n;
+}
+
+int
+snprintf(char *buf, int sz, char *fmt, ...)
+{
+  va_list ap;
+  int i, c;
+  int off = 0;
+  char *s;
+
+  if (fmt == 0)
+    panic("null fmt");
+
+  va_start(ap, fmt);
+  for(i = 0; off < sz && (c = fmt[i] & 0xff) != 0; i++){
+    if(c != '%'){
+      off += sputc(buf+off, c);
+      continue;
+    }
+    c = fmt[++i] & 0xff;
+    if(c == 0)
+      break;
+    switch(c){
+    case 'd':
+      off += sprintint(buf+off, va_arg(ap, int), 10, 1);
+      break;
+    case 'x':
+      off += sprintint(buf+off, va_arg(ap, int), 16, 1);
+      break;
+    case 's':
+      if((s = va_arg(ap, char*)) == 0)
+        s = "(null)";
+      for(; *s && off < sz; s++)
+        off += sputc(buf+off, *s);
+      break;
+    case '%':
+      off += sputc(buf+off, '%');
+      break;
+    default:
+      // Print unknown % sequence to draw attention.
+      off += sputc(buf+off, '%');
+      off += sputc(buf+off, c);
+      break;
+    }
+  }
+  return off;
+}

kernel/start.c

@@ -38,6 +38,11 @@ start()
   w_mideleg(0xffff);
   w_sie(r_sie() | SIE_SEIE | SIE_STIE | SIE_SSIE);
 
+#ifdef KCSAN
+  // allow supervisor to read cycle counter register
+  w_mcounteren(r_mcounteren()|0x3);
+#endif
+  
   // configure Physical Memory Protection to give supervisor mode
   // access to all of physical memory.
   w_pmpaddr0(0x3fffffffffffffull);

kernel/stats.c

@@ -0,0 +1,69 @@
+#include <stdarg.h>
+
+#include "types.h"
+#include "param.h"
+#include "spinlock.h"
+#include "sleeplock.h"
+#include "fs.h"
+#include "file.h"
+#include "riscv.h"
+#include "defs.h"
+
+#define BUFSZ 4096
+static struct {
+  struct spinlock lock;
+  char buf[BUFSZ];
+  int sz;
+  int off;
+} stats;
+
+int statscopyin(char*, int);
+int statslock(char*, int);
+  
+int
+statswrite(int user_src, uint64 src, int n)
+{
+  return -1;
+}
+
+int
+statsread(int user_dst, uint64 dst, int n)
+{
+  int m;
+
+  acquire(&stats.lock);
+
+  if(stats.sz == 0) {
+#ifdef LAB_PGTBL
+    stats.sz = statscopyin(stats.buf, BUFSZ);
+#endif
+#ifdef LAB_LOCK
+    stats.sz = statslock(stats.buf, BUFSZ);
+#endif
+  }
+  m = stats.sz - stats.off;
+
+  if (m > 0) {
+    if(m > n)
+      m  = n;
+    if(either_copyout(user_dst, dst, stats.buf+stats.off, m) != -1) {
+      stats.off += m;
+    }
+  } else {
+    m = -1;
+    stats.sz = 0;
+    stats.off = 0;
+  }
+  release(&stats.lock);
+  return m;
+}
+
+void
+statsinit(void)
+{
+  initlock(&stats.lock, "stats");
+
+  devsw[STATS].read = statsread;
+  devsw[STATS].write = statswrite;
+}
+

kernel/sysproc.c

@@ -55,6 +55,8 @@ sys_sleep(void)
   uint ticks0;
 
   argint(0, &n);
+  if(n < 0)
+    n = 0;
   acquire(&tickslock);
   ticks0 = ticks;
   while(ticks - ticks0 < n){

time.txt

@@ -1 +1 @@
-6
+9

user/bcachetest.c

@@ -0,0 +1,189 @@
+#include "kernel/fcntl.h"
+#include "kernel/param.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/riscv.h"
+#include "kernel/fs.h"
+#include "user/user.h"
+
+void test0();
+void test1();
+
+#define SZ 4096
+char buf[SZ];
+
+int
+main(int argc, char *argv[])
+{
+  test0();
+  test1();
+  exit(0);
+}
+
+void
+createfile(char *file, int nblock)
+{
+  int fd;
+  char buf[BSIZE];
+  int i;
+  
+  fd = open(file, O_CREATE | O_RDWR);
+  if(fd < 0){
+    printf("createfile %s failed\n", file);
+    exit(-1);
+  }
+  for(i = 0; i < nblock; i++) {
+    if(write(fd, buf, sizeof(buf)) != sizeof(buf)) {
+      printf("write %s failed\n", file);
+      exit(-1);
+    }
+  }
+  close(fd);
+}
+
+void
+readfile(char *file, int nbytes, int inc)
+{
+  char buf[BSIZE];
+  int fd;
+  int i;
+
+  if(inc > BSIZE) {
+    printf("readfile: inc too large\n");
+    exit(-1);
+  }
+  if ((fd = open(file, O_RDONLY)) < 0) {
+    printf("readfile open %s failed\n", file);
+    exit(-1);
+  }
+  for (i = 0; i < nbytes; i += inc) {
+    if(read(fd, buf, inc) != inc) {
+      printf("read %s failed for block %d (%d)\n", file, i, nbytes);
+      exit(-1);
+    }
+  }
+  close(fd);
+}
+
+int ntas(int print)
+{
+  int n;
+  char *c;
+
+  if (statistics(buf, SZ) <= 0) {
+    fprintf(2, "ntas: no stats\n");
+  }
+  c = strchr(buf, '=');
+  n = atoi(c+2);
+  if(print)
+    printf("%s", buf);
+  return n;
+}
+
+// Test reading small files concurrently
+void
+test0()
+{
+  char file[2];
+  char dir[2];
+  enum { N = 10, NCHILD = 3 };
+  int m, n;
+
+  dir[0] = '0';
+  dir[1] = '\0';
+  file[0] = 'F';
+  file[1] = '\0';
+
+  printf("start test0\n");
+  for(int i = 0; i < NCHILD; i++){
+    dir[0] = '0' + i;
+    mkdir(dir);
+    if (chdir(dir) < 0) {
+      printf("chdir failed\n");
+      exit(1);
+    }
+    unlink(file);
+    createfile(file, N);
+    if (chdir("..") < 0) {
+      printf("chdir failed\n");
+      exit(1);
+    }
+  }
+  m = ntas(0);
+  for(int i = 0; i < NCHILD; i++){
+    dir[0] = '0' + i;
+    int pid = fork();
+    if(pid < 0){
+      printf("fork failed");
+      exit(-1);
+    }
+    if(pid == 0){
+      if (chdir(dir) < 0) {
+        printf("chdir failed\n");
+        exit(1);
+      }
+
+      readfile(file, N*BSIZE, 1);
+
+      exit(0);
+    }
+  }
+
+  for(int i = 0; i < NCHILD; i++){
+    wait(0);
+  }
+  printf("test0 results:\n");
+  n = ntas(1);
+  if (n-m < 500)
+    printf("test0: OK\n");
+  else
+    printf("test0: FAIL\n");
+}
+
+// Test bcache evictions by reading a large file concurrently
+void test1()
+{
+  char file[3];
+  enum { N = 200, BIG=100, NCHILD=2 };
+  
+  printf("start test1\n");
+  file[0] = 'B';
+  file[2] = '\0';
+  for(int i = 0; i < NCHILD; i++){
+    file[1] = '0' + i;
+    unlink(file);
+    if (i == 0) {
+      createfile(file, BIG);
+    } else {
+      createfile(file, 1);
+    }
+  }
+  for(int i = 0; i < NCHILD; i++){
+    file[1] = '0' + i;
+    int pid = fork();
+    if(pid < 0){
+      printf("fork failed");
+      exit(-1);
+    }
+    if(pid == 0){
+      if (i==0) {
+        for (i = 0; i < N; i++) {
+          readfile(file, BIG*BSIZE, BSIZE);
+        }
+        unlink(file);
+        exit(0);
+      } else {
+        for (i = 0; i < N*20; i++) {
+          readfile(file, 1, BSIZE);
+        }
+        unlink(file);
+      }
+      exit(0);
+    }
+  }
+
+  for(int i = 0; i < NCHILD; i++){
+    wait(0);
+  }
+  printf("test1 OK\n");
+}

user/cat.c

@@ -1,5 +1,6 @@
 #include "kernel/types.h"
 #include "kernel/stat.h"
+#include "kernel/fcntl.h"
 #include "user/user.h"
 
 char buf[512];
@@ -32,7 +33,7 @@ main(int argc, char *argv[])
   }
 
   for(i = 1; i < argc; i++){
-    if((fd = open(argv[i], 0)) < 0){
+    if((fd = open(argv[i], O_RDONLY)) < 0){
       fprintf(2, "cat: cannot open %s\n", argv[i]);
       exit(1);
     }

user/find.c

@@ -1,74 +0,0 @@
-#include "kernel/types.h"
-#include "user/user.h"
-#include "kernel/stat.h"
-#include "kernel/fs.h"
-
-int fmtname(const char *path) {
-  int p;
-  for(p=strlen(path); p >= 0 && *(path + p) != '/'; p--);
-  p++;
-  return p;
-}
-
-void find(const char *path, const char* target) {
-    char buf[512], *p;
-    int fd;
-    struct dirent de;
-    struct stat st;
-    if((fd = open(path, 0)) < 0){
-        fprintf(2, "find: cannot open %s\n", path);
-        return;
-    }
-
-    if(fstat(fd, &st) < 0){
-        fprintf(2, "find: cannot stat %s\n", path);
-        close(fd);
-        return;
-    }
-
-    switch(st.type){
-    case T_DEVICE:
-    case T_FILE:
-        if (strcmp(path + fmtname(path), target) == 0) {
-            printf("%s\n", path);
-        }
-        break;
-
-    case T_DIR:
-        if (strcmp(path + fmtname(path), target) == 0) {
-            printf("%s\n", path);
-        }
-        if(strlen(path) + 1 + DIRSIZ + 1 > sizeof buf){
-            printf("find: path too long\n");
-            break;
-        }
-        strcpy(buf, path);
-        p = buf+strlen(buf);
-        *p++ = '/';
-        while(read(fd, &de, sizeof(de)) == sizeof(de)){
-            if(de.inum == 0)
-                continue;
-            if (strcmp(de.name, ".") == 0 || strcmp(de.name, "..") == 0)
-                continue;
-            memmove(p, de.name, DIRSIZ);
-            p[DIRSIZ] = 0;
-            if(stat(buf, &st) < 0){
-                printf("find: cannot stat %s\n", buf);
-                continue;
-            }
-            find(buf, target);
-        }
-        break;
-    }
-    close(fd);
-}
-
-int main(int argc, char** argv) {
-    if (argc != 3) {
-        printf("\x1b[31mInvalid arguments\x1b[0m\n");
-        printf("\x1b[32musage\x1b[0m: find <base directory> <file name to find>\n");
-        exit(0);
-    }
-    find(argv[1], argv[2]);
-    exit(0);
-}

user/grep.c

@@ -2,6 +2,7 @@
 
 #include "kernel/types.h"
 #include "kernel/stat.h"
+#include "kernel/fcntl.h"
 #include "user/user.h"
 
 char buf[1024];
@@ -51,7 +52,7 @@ main(int argc, char *argv[])
   }
 
   for(i = 2; i < argc; i++){
-    if((fd = open(argv[i], 0)) < 0){
+    if((fd = open(argv[i], O_RDONLY)) < 0){
       printf("grep: cannot open %s\n", argv[i]);
       exit(1);
     }

user/init.c

@@ -18,6 +18,7 @@ main(void)
 
   if(open("console", O_RDWR) < 0){
     mknod("console", CONSOLE, 0);
+    mknod("statistics", STATS, 0);
     open("console", O_RDWR);
   }
   dup(0);  // stdout

user/kalloctest.c

@@ -0,0 +1,161 @@
+#include "kernel/param.h"
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/riscv.h"
+#include "kernel/memlayout.h"
+#include "kernel/fcntl.h"
+#include "user/user.h"
+
+#define NCHILD 2
+#define N 100000
+#define SZ 4096
+
+void test1(void);
+void test2(void);
+void test3(void);
+char buf[SZ];
+
+int
+main(int argc, char *argv[])
+{
+  test1();
+  test2();
+  test3();
+  exit(0);
+}
+
+int ntas(int print)
+{
+  int n;
+  char *c;
+
+  if (statistics(buf, SZ) <= 0) {
+    fprintf(2, "ntas: no stats\n");
+  }
+  c = strchr(buf, '=');
+  n = atoi(c+2);
+  if(print)
+    printf("%s", buf);
+  return n;
+}
+
+// Test concurrent kallocs and kfrees
+void test1(void)
+{
+  void *a, *a1;
+  int n, m;
+  printf("start test1\n");  
+  m = ntas(0);
+  for(int i = 0; i < NCHILD; i++){
+    int pid = fork();
+    if(pid < 0){
+      printf("fork failed");
+      exit(-1);
+    }
+    if(pid == 0){
+      for(i = 0; i < N; i++) {
+        a = sbrk(4096);
+        *(int *)(a+4) = 1;
+        a1 = sbrk(-4096);
+        if (a1 != a + 4096) {
+          printf("wrong sbrk\n");
+          exit(-1);
+        }
+      }
+      exit(-1);
+    }
+  }
+
+  for(int i = 0; i < NCHILD; i++){
+    wait(0);
+  }
+  printf("test1 results:\n");
+  n = ntas(1);
+  if(n-m < 10) 
+    printf("test1 OK\n");
+  else
+    printf("test1 FAIL\n");
+}
+
+//
+// countfree() from usertests.c
+//
+int
+countfree()
+{
+  uint64 sz0 = (uint64)sbrk(0);
+  int n = 0;
+
+  while(1){
+    uint64 a = (uint64) sbrk(4096);
+    if(a == 0xffffffffffffffff){
+      break;
+    }
+    // modify the memory to make sure it's really allocated.
+    *(char *)(a + 4096 - 1) = 1;
+    n += 1;
+  }
+  sbrk(-((uint64)sbrk(0) - sz0));
+  return n;
+}
+
+// Test stealing
+void test2() {
+  int free0 = countfree();
+  int free1;
+  int n = (PHYSTOP-KERNBASE)/PGSIZE;
+  printf("start test2\n");  
+  printf("total free number of pages: %d (out of %d)\n", free0, n);
+  if(n - free0 > 1000) {
+    printf("test2 FAILED: cannot allocate enough memory");
+    exit(-1);
+  }
+  for (int i = 0; i < 50; i++) {
+    free1 = countfree();
+    if(i % 10 == 9)
+      printf(".");
+    if(free1 != free0) {
+      printf("test2 FAIL: losing pages\n");
+      exit(-1);
+    }
+  }
+  printf("\ntest2 OK\n");  
+}
+
+// Test concurrent kalloc/kfree and stealing
+void test3(void)
+{
+  void *a, *a1;
+  printf("start test3\n");  
+  for(int i = 0; i < NCHILD; i++){
+    int pid = fork();
+    if(pid < 0){
+      printf("fork failed");
+      exit(-1);
+    }
+    if(pid == 0){
+      if (i == 0) {
+        for(i = 0; i < N; i++) {
+          a = sbrk(4096);
+          *(int *)(a+4) = 1;
+          a1 = sbrk(-4096);
+          if (a1 != a + 4096) {
+            printf("wrong sbrk\n");
+            exit(-1);
+          }
+        }
+        printf("child done %d\n", i);
+        exit(0);
+      } else {
+        countfree();
+        printf("child done %d\n", i);
+        exit(0);
+      }
+    }
+  }
+
+  for(int i = 0; i < NCHILD; i++){
+    wait(0);
+  }
+  printf("test3 OK\n");
+}

user/ls.c

@@ -2,6 +2,7 @@
 #include "kernel/stat.h"
 #include "user/user.h"
 #include "kernel/fs.h"
+#include "kernel/fcntl.h"
 
 char*
 fmtname(char *path)
@@ -30,7 +31,7 @@ ls(char *path)
   struct dirent de;
   struct stat st;
 
-  if((fd = open(path, 0)) < 0){
+  if((fd = open(path, O_RDONLY)) < 0){
     fprintf(2, "ls: cannot open %s\n", path);
     return;
   }

user/pingpong.c

@@ -1,27 +0,0 @@
-#include "kernel/types.h"
-#include "user/user.h"
-
-int main(int argc, char** argv) {
-    int p[2]; // hell, read from p[0] and write to p[1] no matter in pa/ch
-    if (pipe(p) == -1) exit(1);
-    uint8 senddata[] = {0xAC};
-    uint8 recvdata[] = {0};
-    int pid = fork();
-    if (pid == 0) {
-        // child
-        if (read(p[0], recvdata, 1) != 1) printf("error child read\n");
-        close(p[0]);
-        printf("%d: received ping\n", getpid());
-        if (write(p[1], senddata, 1) != 1) printf("error child write\n");
-        close(p[1]);
-        exit(0);
-    }
-    else {
-        if (write(p[1], senddata, 1) != 1) printf("error parent write\n");
-        close(p[1]);
-        if (read(p[0], recvdata, 1) != 1) printf("error parent read\n");
-        printf("%d: received pong\n", getpid());
-        close(p[0]);
-        exit(0);
-    }
-}

user/primes.c

@@ -1,51 +0,0 @@
-#include "kernel/types.h"
-#include "user/user.h"
-
-void pipeline(int leftfd) {
-    int pipefd[2];
-    int p; read(leftfd, &p, sizeof(p));
-    printf("prime %d\n", p);
-    int n; 
-    int has_right = 0;
-    while (read(leftfd, &n, sizeof(n)) > 0) {
-        if (n % p != 0) {
-            if (!has_right) {
-                has_right = 1;
-                pipe(pipefd);
-                if (fork() == 0) {
-                    close(pipefd[1]);
-                    pipeline(pipefd[0]);
-                } else {
-                    close(pipefd[0]);
-                }
-            }
-            write(pipefd[1], &n, sizeof(n));
-        }
-    }
-    close(leftfd);
-    if (has_right) {
-        close(pipefd[1]);
-        while(wait(0) != -1);
-    }
-    exit(0);
-}
-
-int main(int argc, char** argv) {
-    int pipefd[2];
-    pipe(pipefd);
-    int pid = fork();
-    if (pid != 0) {
-        close(pipefd[0]); // no need to read in the feeding proc
-        for (int i = 2; i <= 35; ++ i) {
-            write(pipefd[1], &i, sizeof(i));
-        }
-        close(pipefd[1]);
-        while(wait(0) != -1);
-        exit(0);
-    }
-    else {
-        close(pipefd[1]);  // pipeline proc will have its own write pipe
-        pipeline(pipefd[0]);
-    }
-    exit(0);
-}

user/sleep.c

@@ -1,17 +0,0 @@
-#include "kernel/types.h"
-#include "user/user.h"
-
-int main(int argc, char** argv) {
-    if (argc != 2) {
-        printf("\x1b[31mUnexpected argument\x1b[0m\n");
-        printf("usage: sleep <ticks>\n");
-        exit(0);
-    }
-    int ticks = atoi(argv[1]);
-    int ret = sleep(ticks);
-    if (ret) {
-        printf("\x1b[31mFailed to sleep\x1b[0m\n");
-        exit(-1);
-    }
-    exit(0);
-}

user/statistics.c

@@ -0,0 +1,24 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/fcntl.h"
+#include "user/user.h"
+
+int
+statistics(void *buf, int sz)
+{
+  int fd, i, n;
+  
+  fd = open("statistics", O_RDONLY);
+  if(fd < 0) {
+      fprintf(2, "stats: open failed\n");
+      exit(1);
+  }
+  for (i = 0; i < sz; ) {
+    if ((n = read(fd, buf+i, sz-i)) < 0) {
+      break;
+    }
+    i += n;
+  }
+  close(fd);
+  return i;
+}

user/stats.c

@@ -0,0 +1,24 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/fcntl.h"
+#include "user/user.h"
+
+#define SZ 4096
+char buf[SZ];
+
+int
+main(void)
+{
+  int i, n;
+  
+  while (1) {
+    n = statistics(buf, SZ);
+    for (i = 0; i < n; i++) {
+      write(1, buf+i, 1);
+    }
+    if (n != SZ)
+      break;
+  }
+
+  exit(0);
+}

user/user.h

@@ -22,6 +22,14 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+#ifdef LAB_NET
+int connect(uint32, uint16, uint16);
+#endif
+#ifdef LAB_PGTBL
+int pgaccess(void *base, int len, void *mask);
+// usyscall region
+int ugetpid(void);
+#endif
 
 // ulib.c
 int stat(const char*, struct stat*);
@@ -39,3 +47,4 @@ void free(void*);
 int atoi(const char*);
 int memcmp(const void *, const void *, uint);
 void *memcpy(void *, const void *, uint);
+int statistics(void*, int);

user/wc.c

@@ -1,5 +1,6 @@
 #include "kernel/types.h"
 #include "kernel/stat.h"
+#include "kernel/fcntl.h"
 #include "user/user.h"
 
 char buf[512];
@@ -43,7 +44,7 @@ main(int argc, char *argv[])
   }
 
   for(i = 1; i < argc; i++){
-    if((fd = open(argv[i], 0)) < 0){
+    if((fd = open(argv[i], O_RDONLY)) < 0){
       printf("wc: cannot open %s\n", argv[i]);
       exit(1);
     }

user/xargs.c

@@ -1,59 +0,0 @@
-#include "kernel/param.h"
-#include "kernel/types.h"
-#include "user/user.h"
-
-static inline int is_ws(const char ch) {
-    return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r';
-}
-
-int main(int argc, char** argv) {
-    int STDIN = 0;
-    char linebuf[1024];
-    char* p = linebuf;
-    char* _argv[MAXARG];
-    while (read(STDIN, p, 1) > 0) {
-        if (*p == '\n') {
-            int i;
-            int in_ws = 1;
-            for (i = 0; i < argc - 1; ++i) {
-                _argv[i] = argv[i + 1];
-            }
-            for (char* p0 = linebuf; p0 <= p; ++p0) {
-                if (is_ws(*p0)) {
-                    if (!in_ws) {
-                        in_ws = 1;
-                        i++;
-                    }
-                    *p0 = '\0';
-                } else if (in_ws) {
-                    in_ws = 0;
-                    _argv[i] = p0;
-                }
-                if (i >= MAXARG) {
-                    printf("warning: too many arguments");
-                    break;
-                }
-            }
-            *p = '\0';
-            _argv[i] = 0;
-            // for (int j = 0; j < i; ++ j) {
-            //     printf("%s\n", _argv[j]);
-            // }
-            if (fork() == 0) {
-                exec(_argv[0], _argv);
-                exit(0);
-            } else {
-                p = linebuf;
-                while (wait(0) != -1)
-                    ;
-            }
-        } else {
-            p++;
-            if (p >= linebuf + sizeof(linebuf)) {
-                printf("line buffer exceeded\n");
-                exit(0);
-            }
-        }
-    }
-    exit(0);
-}

user/xargstest.sh

@@ -1,6 +0,0 @@
-mkdir a
-echo hello > a/b
-mkdir c
-echo hello > c/b
-echo hello > b
-find . b | xargs grep hello