diff --git a/xv6-public/Makefile b/xv6-public/Makefile
index 346f45c..de6e75c 100644
--- a/xv6-public/Makefile
+++ b/xv6-public/Makefile
@@ -188,6 +188,7 @@ UPROGS=\
 	_date\
 	_alarmtest\
 	_uthread\
+	_big\
 
 fs.img: mkfs README $(UPROGS)
 	./mkfs fs.img README $(UPROGS)
@@ -224,10 +225,12 @@ QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
 	then echo "-gdb tcp::$(GDBPORT)"; \
 	else echo "-s -p $(GDBPORT)"; fi)
 ifndef CPUS
-CPUS := 2
+CPUS := 1
 endif
+# QEMUEXTRA = -snapshot
 QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
 
+
 gdb:
 	gdb -x .gdbinit
 	
diff --git a/xv6-public/big b/xv6-public/big
new file mode 100644
index 0000000..3ed59db
Binary files /dev/null and b/xv6-public/big differ
diff --git a/xv6-public/big.c b/xv6-public/big.c
new file mode 100644
index 0000000..cecf1a0
--- /dev/null
+++ b/xv6-public/big.c
@@ -0,0 +1,53 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+#include "fcntl.h"
+
+int
+main()
+{
+  char buf[512];
+  int fd, i, sectors;
+
+  fd = open("big.file", O_CREATE | O_WRONLY);
+  if(fd < 0){
+    printf(2, "big: cannot open big.file for writing\n");
+    exit();
+  }
+
+  sectors = 0;
+  while(1){
+    *(int*)buf = sectors;
+    int cc = write(fd, buf, sizeof(buf));
+    if(cc <= 0)
+      break;
+    sectors++;
+	if (sectors % 100 == 0)
+		printf(2, ".");
+  }
+
+  printf(1, "\nwrote %d sectors\n", sectors);
+
+  close(fd);
+  fd = open("big.file", O_RDONLY);
+  if(fd < 0){
+    printf(2, "big: cannot re-open big.file for reading\n");
+    exit();
+  }
+  for(i = 0; i < sectors; i++){
+    int cc = read(fd, buf, sizeof(buf));
+    if(cc <= 0){
+      printf(2, "big: read error at sector %d\n", i);
+      exit();
+    }
+    if(*(int*)buf != i){
+      printf(2, "big: read the wrong data (%d) for sector %d\n",
+             *(int*)buf, i);
+      exit();
+    }
+  }
+
+  printf(1, "done; ok\n"); 
+
+  exit();
+}
diff --git a/xv6-public/file.h b/xv6-public/file.h
index 0990c82..eeb87cf 100644
--- a/xv6-public/file.h
+++ b/xv6-public/file.h
@@ -22,7 +22,7 @@ struct inode {
   short minor;
   short nlink;
   uint size;
-  uint addrs[NDIRECT+1];
+  uint addrs[NDIRECT+2];
 };
 
 // table mapping major device number to
diff --git a/xv6-public/fs.c b/xv6-public/fs.c
index feb59fe..1d527cd 100644
--- a/xv6-public/fs.c
+++ b/xv6-public/fs.c
@@ -375,18 +375,23 @@ bmap(struct inode *ip, uint bn)
 {
   uint addr, *a;
   struct buf *bp;
-
+  struct buf *bp2;
+  // 直接索引结点数目 bn= 0~10
   if(bn < NDIRECT){
+  	// 创建直接索引
     if((addr = ip->addrs[bn]) == 0)
       ip->addrs[bn] = addr = balloc(ip->dev);
     return addr;
   }
   bn -= NDIRECT;
-
+  
+  // #define NINDIRECT (BSIZE / sizeof(uint))  BSIZE = 512
   if(bn < NINDIRECT){
+  	// 一级索引
     // Load indirect block, allocating if necessary.
     if((addr = ip->addrs[NDIRECT]) == 0)
       ip->addrs[NDIRECT] = addr = balloc(ip->dev);
+	
     bp = bread(ip->dev, addr);
     a = (uint*)bp->data;
     if((addr = a[bn]) == 0){
@@ -397,6 +402,37 @@ bmap(struct inode *ip, uint bn)
     return addr;
   }
 
+  
+  bn -= NINDIRECT;
+  // 二级索引
+  if (bn < NDINDIRECT) {
+  	// 根结点
+    if((addr = ip->addrs[NDIRECT+1]) == 0)
+		ip->addrs[NDIRECT+1] = addr = balloc(ip->dev);
+
+	bp = bread(ip->dev, addr);
+    // 指向一级索引
+    a = (uint *)bp->data;
+    if ((addr = a[bn/NINDIRECT]) == 0) {
+       a[bn/NINDIRECT] = addr = balloc(ip->dev);
+	   log_write(bp);
+	}
+	
+	bp2 = bread(ip->dev, addr);
+	// 二级页表
+	a = (uint *)bp2->data;
+	if ((addr = a[bn%NINDIRECT]) == 0) {
+	  a[bn%NINDIRECT] = addr = balloc(ip->dev);
+      log_write(bp2);
+	}
+	
+	brelse(bp2);
+	brelse(bp);
+	return addr;
+	//
+  }
+
+  
   panic("bmap: out of range");
 }
 
diff --git a/xv6-public/fs.h b/xv6-public/fs.h
index 3214f1d..fb50385 100644
--- a/xv6-public/fs.h
+++ b/xv6-public/fs.h
@@ -21,9 +21,11 @@ struct superblock {
   uint bmapstart;    // Block number of first free map block
 };
 
-#define NDIRECT 12
+#define NDIRECT 11
 #define NINDIRECT (BSIZE / sizeof(uint))
-#define MAXFILE (NDIRECT + NINDIRECT)
+// DOUBLE INDIRECT
+#define NDINDIRECT (NINDIRECT * NINDIRECT)
+#define MAXFILE (NDIRECT + NINDIRECT + NDINDIRECT)
 
 // On-disk inode structure
 struct dinode {
@@ -32,7 +34,7 @@ struct dinode {
   short minor;          // Minor device number (T_DEV only)
   short nlink;          // Number of links to inode in file system
   uint size;            // Size of file (bytes)
-  uint addrs[NDIRECT+1];   // Data block addresses
+  uint addrs[NDIRECT+2];   // Data block addresses
 };
 
 // Inodes per block.
diff --git a/xv6-public/log.c b/xv6-public/log.c
index a64c0f6..62cb643 100644
--- a/xv6-public/log.c
+++ b/xv6-public/log.c
@@ -5,6 +5,10 @@
 #include "sleeplock.h"
 #include "fs.h"
 #include "buf.h"
+// -------------- hw11 crash added
+#include "mmu.h"
+#include "proc.h"
+
 
 // Simple logging that allows concurrent FS system calls.
 //
@@ -72,11 +76,11 @@ install_trans(void)
   int tail;
 
   for (tail = 0; tail < log.lh.n; tail++) {
-    struct buf *lbuf = bread(log.dev, log.start+tail+1); // read log block
+    // struct buf *lbuf = bread(log.dev, log.start+tail+1); // read log block
     struct buf *dbuf = bread(log.dev, log.lh.block[tail]); // read dst
-    memmove(dbuf->data, lbuf->data, BSIZE);  // copy block to dst
+    // memmove(dbuf->data, lbuf->data, BSIZE);  // copy block to dst
     bwrite(dbuf);  // write dst to disk
-    brelse(lbuf);
+    // brelse(lbuf);
     brelse(dbuf);
   }
 }
@@ -115,12 +119,14 @@ write_head(void)
 static void
 recover_from_log(void)
 {
-  read_head();
-  install_trans(); // if committed, copy from log to disk
+  read_head();		
+  cprintf("recovery: n=%d but ignoring\n", log.lh.n);
+  install_trans();
   log.lh.n = 0;
-  write_head(); // clear the log
+  write_head();
 }
 
+
 // called at the start of each FS system call.
 void
 begin_op(void)
@@ -189,6 +195,26 @@ write_log(void)
   }
 }
 
+/*
+void
+commit(void)
+{
+  int pid = myproc()->pid;
+  if (log.lh.n > 0) {
+    write_log();
+    write_head();
+    if(pid > 1)            // AAA
+      log.lh.block[0] = 0; // BBB
+    install_trans();
+    if(pid > 1)            // AAA
+      panic("commit mimicking crash"); // CCC
+    log.lh.n = 0; 
+    write_head();
+  }
+}
+*/
+
+
 static void
 commit()
 {
diff --git a/xv6-public/param.h b/xv6-public/param.h
index a7e90ef..fe38bfb 100644
--- a/xv6-public/param.h
+++ b/xv6-public/param.h
@@ -10,5 +10,5 @@
 #define MAXOPBLOCKS  10  // max # of blocks any FS op writes
 #define LOGSIZE      (MAXOPBLOCKS*3)  // max data blocks in on-disk log
 #define NBUF         (MAXOPBLOCKS*3)  // size of disk block cache
-#define FSSIZE       1000  // size of file system in blocks
+#define FSSIZE       20000  // size of file system in blocks
 
diff --git a/xv6-public/xv6.si4project/Backup/Makefile(3731) b/xv6-public/xv6.si4project/Backup/Makefile(3731)
new file mode 100644
index 0000000..e0d2379
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/Makefile(3731)
@@ -0,0 +1,297 @@
+OBJS = \
+	bio.o\
+	console.o\
+	exec.o\
+	file.o\
+	fs.o\
+	ide.o\
+	ioapic.o\
+	kalloc.o\
+	kbd.o\
+	lapic.o\
+	log.o\
+	main.o\
+	mp.o\
+	picirq.o\
+	pipe.o\
+	proc.o\
+	sleeplock.o\
+	spinlock.o\
+	string.o\
+	swtch.o\
+	syscall.o\
+	sysfile.o\
+	sysproc.o\
+	trapasm.o\
+	trap.o\
+	uart.o\
+	vectors.o\
+	vm.o\
+
+# Cross-compiling (e.g., on Mac OS X)
+# TOOLPREFIX = i386-jos-elf
+
+# Using native tools (e.g., on X86 Linux)
+#TOOLPREFIX = 
+
+# Try to infer the correct TOOLPREFIX if not set
+ifndef TOOLPREFIX
+TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \
+	then echo 'i386-jos-elf-'; \
+	elif objdump -i 2>&1 | grep 'elf32-i386' >/dev/null 2>&1; \
+	then echo ''; \
+	else echo "***" 1>&2; \
+	echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1>&2; \
+	echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2; \
+	echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2; \
+	echo "*** prefix other than 'i386-jos-elf-', set your TOOLPREFIX" 1>&2; \
+	echo "*** environment variable to that prefix and run 'make' again." 1>&2; \
+	echo "*** To turn off this error, run 'gmake TOOLPREFIX= ...'." 1>&2; \
+	echo "***" 1>&2; exit 1; fi)
+endif
+
+# If the makefile can't find QEMU, specify its path here
+# QEMU = qemu-system-i386
+
+# Try to infer the correct QEMU
+ifndef QEMU
+QEMU = $(shell if which qemu > /dev/null; \
+	then echo qemu; exit; \
+	elif which qemu-system-i386 > /dev/null; \
+	then echo qemu-system-i386; exit; \
+	elif which qemu-system-x86_64 > /dev/null; \
+	then echo qemu-system-x86_64; exit; \
+	else \
+	qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \
+	if test -x $$qemu; then echo $$qemu; exit; fi; fi; \
+	echo "***" 1>&2; \
+	echo "*** Error: Couldn't find a working QEMU executable." 1>&2; \
+	echo "*** Is the directory containing the qemu binary in your PATH" 1>&2; \
+	echo "*** or have you tried setting the QEMU variable in Makefile?" 1>&2; \
+	echo "***" 1>&2; exit 1)
+endif
+
+CC = $(TOOLPREFIX)gcc
+AS = $(TOOLPREFIX)gas
+LD = $(TOOLPREFIX)ld
+OBJCOPY = $(TOOLPREFIX)objcopy
+OBJDUMP = $(TOOLPREFIX)objdump
+CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
+CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
+ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
+# FreeBSD ld wants ``elf_i386_fbsd''
+LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2>/dev/null | head -n 1)
+
+# Disable PIE when possible (for Ubuntu 16.10 toolchain)
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]no-pie'),)
+CFLAGS += -fno-pie -no-pie
+endif
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]nopie'),)
+CFLAGS += -fno-pie -nopie
+endif
+
+xv6.img: bootblock kernel
+	dd if=/dev/zero of=xv6.img count=10000
+	dd if=bootblock of=xv6.img conv=notrunc
+	dd if=kernel of=xv6.img seek=1 conv=notrunc
+
+xv6memfs.img: bootblock kernelmemfs
+	dd if=/dev/zero of=xv6memfs.img count=10000
+	dd if=bootblock of=xv6memfs.img conv=notrunc
+	dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc
+
+bootblock: bootasm.S bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
+	$(OBJDUMP) -S bootblock.o > bootblock.asm
+	$(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
+	./sign.pl bootblock
+
+entryother: entryother.S
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7000 -o bootblockother.o entryother.o
+	$(OBJCOPY) -S -O binary -j .text bootblockother.o entryother
+	$(OBJDUMP) -S bootblockother.o > entryother.asm
+
+initcode: initcode.S
+	$(CC) $(CFLAGS) -nostdinc -I. -c initcode.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0 -o initcode.out initcode.o
+	$(OBJCOPY) -S -O binary initcode.out initcode
+	$(OBJDUMP) -S initcode.o > initcode.asm
+
+kernel: $(OBJS) entry.o entryother initcode kernel.ld
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
+	$(OBJDUMP) -S kernel > kernel.asm
+	$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
+
+_uthread: uthread.o uthread_switch.o
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _uthread uthread.o uthread_switch.o $(ULIB)
+	$(OBJDUMP) -S _uthread > uthread.asm
+
+# kernelmemfs is a copy of kernel that maintains the
+# disk image in memory instead of writing to a disk.
+# This is not so useful for testing persistent storage or
+# exploring disk buffering implementations, but it is
+# great for testing the kernel on real hardware without
+# needing a scratch disk.
+MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
+kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode kernel.ld fs.img
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernelmemfs entry.o  $(MEMFSOBJS) -b binary initcode entryother fs.img
+	$(OBJDUMP) -S kernelmemfs > kernelmemfs.asm
+	$(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym
+
+tags: $(OBJS) entryother.S _init
+	etags *.S *.c
+
+vectors.S: vectors.pl
+	./vectors.pl > vectors.S
+
+ULIB = ulib.o usys.o printf.o umalloc.o
+
+_%: %.o $(ULIB)
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^
+	$(OBJDUMP) -S $@ > $*.asm
+	$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym
+
+_forktest: forktest.o $(ULIB)
+	# forktest has less library code linked in - needs to be small
+	# in order to be able to max out the proc table.
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o
+	$(OBJDUMP) -S _forktest > forktest.asm
+
+mkfs: mkfs.c fs.h
+	gcc -Werror -Wall -o mkfs mkfs.c
+
+# Prevent deletion of intermediate files, e.g. cat.o, after first build, so
+# that disk image changes after first build are persistent until clean.  More
+# details:
+# http://www.gnu.org/software/make/manual/html_node/Chained-Rules.html
+.PRECIOUS: %.o
+
+UPROGS=\
+	_cat\
+	_echo\
+	_forktest\
+	_grep\
+	_init\
+	_kill\
+	_ln\
+	_ls\
+	_mkdir\
+	_rm\
+	_sh\
+	_stressfs\
+	_usertests\
+	_wc\
+	_zombie\
+	_date\
+	_alarmtest\
+	_uthread\
+
+fs.img: mkfs README $(UPROGS)
+	./mkfs fs.img README $(UPROGS)
+
+-include *.d
+
+clean: 
+	rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
+	*.o *.d *.asm *.sym vectors.S bootblock entryother \
+	initcode initcode.out kernel xv6.img fs.img kernelmemfs \
+	xv6memfs.img mkfs .gdbinit \
+	$(UPROGS)
+
+# make a printout
+FILES = $(shell grep -v '^\#' runoff.list)
+PRINT = runoff.list runoff.spec README toc.hdr toc.ftr $(FILES)
+
+xv6.pdf: $(PRINT)
+	./runoff
+	ls -l xv6.pdf
+
+print: xv6.pdf
+
+# run in emulators
+
+bochs : fs.img xv6.img
+	if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi
+	bochs -q
+
+# try to generate a unique GDB port
+GDBPORT = $(shell expr `id -u` % 5000 + 25000)
+# QEMU's gdb stub command line changed in 0.11
+QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
+	then echo "-gdb tcp::$(GDBPORT)"; \
+	else echo "-s -p $(GDBPORT)"; fi)
+ifndef CPUS
+CPUS := 1
+endif
+QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
+QEMUEXTRA = -snapshot
+
+gdb:
+	gdb -x .gdbinit
+	
+qemu: fs.img xv6.img
+	$(QEMU) -serial mon:stdio $(QEMUOPTS)
+
+qemu-memfs: xv6memfs.img
+	$(QEMU) -drive file=xv6memfs.img,index=0,media=disk,format=raw -smp $(CPUS) -m 256
+
+qemu-nox: fs.img xv6.img
+	$(QEMU) -nographic $(QEMUOPTS)
+
+.gdbinit: .gdbinit.tmpl
+	sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
+
+qemu-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB)
+
+qemu-nox-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
+
+# CUT HERE
+# prepare dist for students
+# after running make dist, probably want to
+# rename it to rev0 or rev1 or so on and then
+# check in that version.
+
+EXTRA=\
+	mkfs.c ulib.c user.h cat.c echo.c forktest.c grep.c kill.c\
+	ln.c ls.c mkdir.c rm.c stressfs.c usertests.c wc.c zombie.c\
+	printf.c umalloc.c\
+	README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\
+	.gdbinit.tmpl gdbutil\
+
+dist:
+	rm -rf dist
+	mkdir dist
+	for i in $(FILES); \
+	do \
+		grep -v PAGEBREAK $$i >dist/$$i; \
+	done
+	sed '/CUT HERE/,$$d' Makefile >dist/Makefile
+	echo >dist/runoff.spec
+	cp $(EXTRA) dist
+
+dist-test:
+	rm -rf dist
+	make dist
+	rm -rf dist-test
+	mkdir dist-test
+	cp dist/* dist-test
+	cd dist-test; $(MAKE) print
+	cd dist-test; $(MAKE) bochs || true
+	cd dist-test; $(MAKE) qemu
+
+# update this rule (change rev#) when it is time to
+# make a new revision.
+tar:
+	rm -rf /tmp/xv6
+	mkdir -p /tmp/xv6
+	cp dist/* dist/.gdbinit.tmpl /tmp/xv6
+	(cd /tmp; tar cf - xv6) | gzip >xv6-rev10.tar.gz  # the next one will be 10 (9/17)
+
+.PHONY: dist-test dist
diff --git a/xv6-public/xv6.si4project/Backup/Makefile(4513) b/xv6-public/xv6.si4project/Backup/Makefile(4513)
new file mode 100644
index 0000000..346f45c
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/Makefile(4513)
@@ -0,0 +1,296 @@
+OBJS = \
+	bio.o\
+	console.o\
+	exec.o\
+	file.o\
+	fs.o\
+	ide.o\
+	ioapic.o\
+	kalloc.o\
+	kbd.o\
+	lapic.o\
+	log.o\
+	main.o\
+	mp.o\
+	picirq.o\
+	pipe.o\
+	proc.o\
+	sleeplock.o\
+	spinlock.o\
+	string.o\
+	swtch.o\
+	syscall.o\
+	sysfile.o\
+	sysproc.o\
+	trapasm.o\
+	trap.o\
+	uart.o\
+	vectors.o\
+	vm.o\
+
+# Cross-compiling (e.g., on Mac OS X)
+# TOOLPREFIX = i386-jos-elf
+
+# Using native tools (e.g., on X86 Linux)
+#TOOLPREFIX = 
+
+# Try to infer the correct TOOLPREFIX if not set
+ifndef TOOLPREFIX
+TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \
+	then echo 'i386-jos-elf-'; \
+	elif objdump -i 2>&1 | grep 'elf32-i386' >/dev/null 2>&1; \
+	then echo ''; \
+	else echo "***" 1>&2; \
+	echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1>&2; \
+	echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2; \
+	echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2; \
+	echo "*** prefix other than 'i386-jos-elf-', set your TOOLPREFIX" 1>&2; \
+	echo "*** environment variable to that prefix and run 'make' again." 1>&2; \
+	echo "*** To turn off this error, run 'gmake TOOLPREFIX= ...'." 1>&2; \
+	echo "***" 1>&2; exit 1; fi)
+endif
+
+# If the makefile can't find QEMU, specify its path here
+# QEMU = qemu-system-i386
+
+# Try to infer the correct QEMU
+ifndef QEMU
+QEMU = $(shell if which qemu > /dev/null; \
+	then echo qemu; exit; \
+	elif which qemu-system-i386 > /dev/null; \
+	then echo qemu-system-i386; exit; \
+	elif which qemu-system-x86_64 > /dev/null; \
+	then echo qemu-system-x86_64; exit; \
+	else \
+	qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \
+	if test -x $$qemu; then echo $$qemu; exit; fi; fi; \
+	echo "***" 1>&2; \
+	echo "*** Error: Couldn't find a working QEMU executable." 1>&2; \
+	echo "*** Is the directory containing the qemu binary in your PATH" 1>&2; \
+	echo "*** or have you tried setting the QEMU variable in Makefile?" 1>&2; \
+	echo "***" 1>&2; exit 1)
+endif
+
+CC = $(TOOLPREFIX)gcc
+AS = $(TOOLPREFIX)gas
+LD = $(TOOLPREFIX)ld
+OBJCOPY = $(TOOLPREFIX)objcopy
+OBJDUMP = $(TOOLPREFIX)objdump
+CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
+CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
+ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
+# FreeBSD ld wants ``elf_i386_fbsd''
+LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2>/dev/null | head -n 1)
+
+# Disable PIE when possible (for Ubuntu 16.10 toolchain)
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]no-pie'),)
+CFLAGS += -fno-pie -no-pie
+endif
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]nopie'),)
+CFLAGS += -fno-pie -nopie
+endif
+
+xv6.img: bootblock kernel
+	dd if=/dev/zero of=xv6.img count=10000
+	dd if=bootblock of=xv6.img conv=notrunc
+	dd if=kernel of=xv6.img seek=1 conv=notrunc
+
+xv6memfs.img: bootblock kernelmemfs
+	dd if=/dev/zero of=xv6memfs.img count=10000
+	dd if=bootblock of=xv6memfs.img conv=notrunc
+	dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc
+
+bootblock: bootasm.S bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
+	$(OBJDUMP) -S bootblock.o > bootblock.asm
+	$(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
+	./sign.pl bootblock
+
+entryother: entryother.S
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7000 -o bootblockother.o entryother.o
+	$(OBJCOPY) -S -O binary -j .text bootblockother.o entryother
+	$(OBJDUMP) -S bootblockother.o > entryother.asm
+
+initcode: initcode.S
+	$(CC) $(CFLAGS) -nostdinc -I. -c initcode.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0 -o initcode.out initcode.o
+	$(OBJCOPY) -S -O binary initcode.out initcode
+	$(OBJDUMP) -S initcode.o > initcode.asm
+
+kernel: $(OBJS) entry.o entryother initcode kernel.ld
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
+	$(OBJDUMP) -S kernel > kernel.asm
+	$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
+
+_uthread: uthread.o uthread_switch.o
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _uthread uthread.o uthread_switch.o $(ULIB)
+	$(OBJDUMP) -S _uthread > uthread.asm
+
+# kernelmemfs is a copy of kernel that maintains the
+# disk image in memory instead of writing to a disk.
+# This is not so useful for testing persistent storage or
+# exploring disk buffering implementations, but it is
+# great for testing the kernel on real hardware without
+# needing a scratch disk.
+MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
+kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode kernel.ld fs.img
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernelmemfs entry.o  $(MEMFSOBJS) -b binary initcode entryother fs.img
+	$(OBJDUMP) -S kernelmemfs > kernelmemfs.asm
+	$(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym
+
+tags: $(OBJS) entryother.S _init
+	etags *.S *.c
+
+vectors.S: vectors.pl
+	./vectors.pl > vectors.S
+
+ULIB = ulib.o usys.o printf.o umalloc.o
+
+_%: %.o $(ULIB)
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^
+	$(OBJDUMP) -S $@ > $*.asm
+	$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym
+
+_forktest: forktest.o $(ULIB)
+	# forktest has less library code linked in - needs to be small
+	# in order to be able to max out the proc table.
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o
+	$(OBJDUMP) -S _forktest > forktest.asm
+
+mkfs: mkfs.c fs.h
+	gcc -Werror -Wall -o mkfs mkfs.c
+
+# Prevent deletion of intermediate files, e.g. cat.o, after first build, so
+# that disk image changes after first build are persistent until clean.  More
+# details:
+# http://www.gnu.org/software/make/manual/html_node/Chained-Rules.html
+.PRECIOUS: %.o
+
+UPROGS=\
+	_cat\
+	_echo\
+	_forktest\
+	_grep\
+	_init\
+	_kill\
+	_ln\
+	_ls\
+	_mkdir\
+	_rm\
+	_sh\
+	_stressfs\
+	_usertests\
+	_wc\
+	_zombie\
+	_date\
+	_alarmtest\
+	_uthread\
+
+fs.img: mkfs README $(UPROGS)
+	./mkfs fs.img README $(UPROGS)
+
+-include *.d
+
+clean: 
+	rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
+	*.o *.d *.asm *.sym vectors.S bootblock entryother \
+	initcode initcode.out kernel xv6.img fs.img kernelmemfs \
+	xv6memfs.img mkfs .gdbinit \
+	$(UPROGS)
+
+# make a printout
+FILES = $(shell grep -v '^\#' runoff.list)
+PRINT = runoff.list runoff.spec README toc.hdr toc.ftr $(FILES)
+
+xv6.pdf: $(PRINT)
+	./runoff
+	ls -l xv6.pdf
+
+print: xv6.pdf
+
+# run in emulators
+
+bochs : fs.img xv6.img
+	if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi
+	bochs -q
+
+# try to generate a unique GDB port
+GDBPORT = $(shell expr `id -u` % 5000 + 25000)
+# QEMU's gdb stub command line changed in 0.11
+QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
+	then echo "-gdb tcp::$(GDBPORT)"; \
+	else echo "-s -p $(GDBPORT)"; fi)
+ifndef CPUS
+CPUS := 2
+endif
+QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
+
+gdb:
+	gdb -x .gdbinit
+	
+qemu: fs.img xv6.img
+	$(QEMU) -serial mon:stdio $(QEMUOPTS)
+
+qemu-memfs: xv6memfs.img
+	$(QEMU) -drive file=xv6memfs.img,index=0,media=disk,format=raw -smp $(CPUS) -m 256
+
+qemu-nox: fs.img xv6.img
+	$(QEMU) -nographic $(QEMUOPTS)
+
+.gdbinit: .gdbinit.tmpl
+	sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
+
+qemu-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB)
+
+qemu-nox-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
+
+# CUT HERE
+# prepare dist for students
+# after running make dist, probably want to
+# rename it to rev0 or rev1 or so on and then
+# check in that version.
+
+EXTRA=\
+	mkfs.c ulib.c user.h cat.c echo.c forktest.c grep.c kill.c\
+	ln.c ls.c mkdir.c rm.c stressfs.c usertests.c wc.c zombie.c\
+	printf.c umalloc.c\
+	README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\
+	.gdbinit.tmpl gdbutil\
+
+dist:
+	rm -rf dist
+	mkdir dist
+	for i in $(FILES); \
+	do \
+		grep -v PAGEBREAK $$i >dist/$$i; \
+	done
+	sed '/CUT HERE/,$$d' Makefile >dist/Makefile
+	echo >dist/runoff.spec
+	cp $(EXTRA) dist
+
+dist-test:
+	rm -rf dist
+	make dist
+	rm -rf dist-test
+	mkdir dist-test
+	cp dist/* dist-test
+	cd dist-test; $(MAKE) print
+	cd dist-test; $(MAKE) bochs || true
+	cd dist-test; $(MAKE) qemu
+
+# update this rule (change rev#) when it is time to
+# make a new revision.
+tar:
+	rm -rf /tmp/xv6
+	mkdir -p /tmp/xv6
+	cp dist/* dist/.gdbinit.tmpl /tmp/xv6
+	(cd /tmp; tar cf - xv6) | gzip >xv6-rev10.tar.gz  # the next one will be 10 (9/17)
+
+.PHONY: dist-test dist
diff --git a/xv6-public/xv6.si4project/Backup/Makefile(7520) b/xv6-public/xv6.si4project/Backup/Makefile(7520)
new file mode 100644
index 0000000..ebfdfc9
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/Makefile(7520)
@@ -0,0 +1,299 @@
+OBJS = \
+	bio.o\
+	console.o\
+	exec.o\
+	file.o\
+	fs.o\
+	ide.o\
+	ioapic.o\
+	kalloc.o\
+	kbd.o\
+	lapic.o\
+	log.o\
+	main.o\
+	mp.o\
+	picirq.o\
+	pipe.o\
+	proc.o\
+	sleeplock.o\
+	spinlock.o\
+	string.o\
+	swtch.o\
+	syscall.o\
+	sysfile.o\
+	sysproc.o\
+	trapasm.o\
+	trap.o\
+	uart.o\
+	vectors.o\
+	vm.o\
+
+# Cross-compiling (e.g., on Mac OS X)
+# TOOLPREFIX = i386-jos-elf
+
+# Using native tools (e.g., on X86 Linux)
+#TOOLPREFIX = 
+
+# Try to infer the correct TOOLPREFIX if not set
+ifndef TOOLPREFIX
+TOOLPREFIX := $(shell if i386-jos-elf-objdump -i 2>&1 | grep '^elf32-i386$$' >/dev/null 2>&1; \
+	then echo 'i386-jos-elf-'; \
+	elif objdump -i 2>&1 | grep 'elf32-i386' >/dev/null 2>&1; \
+	then echo ''; \
+	else echo "***" 1>&2; \
+	echo "*** Error: Couldn't find an i386-*-elf version of GCC/binutils." 1>&2; \
+	echo "*** Is the directory with i386-jos-elf-gcc in your PATH?" 1>&2; \
+	echo "*** If your i386-*-elf toolchain is installed with a command" 1>&2; \
+	echo "*** prefix other than 'i386-jos-elf-', set your TOOLPREFIX" 1>&2; \
+	echo "*** environment variable to that prefix and run 'make' again." 1>&2; \
+	echo "*** To turn off this error, run 'gmake TOOLPREFIX= ...'." 1>&2; \
+	echo "***" 1>&2; exit 1; fi)
+endif
+
+# If the makefile can't find QEMU, specify its path here
+# QEMU = qemu-system-i386
+
+# Try to infer the correct QEMU
+ifndef QEMU
+QEMU = $(shell if which qemu > /dev/null; \
+	then echo qemu; exit; \
+	elif which qemu-system-i386 > /dev/null; \
+	then echo qemu-system-i386; exit; \
+	elif which qemu-system-x86_64 > /dev/null; \
+	then echo qemu-system-x86_64; exit; \
+	else \
+	qemu=/Applications/Q.app/Contents/MacOS/i386-softmmu.app/Contents/MacOS/i386-softmmu; \
+	if test -x $$qemu; then echo $$qemu; exit; fi; fi; \
+	echo "***" 1>&2; \
+	echo "*** Error: Couldn't find a working QEMU executable." 1>&2; \
+	echo "*** Is the directory containing the qemu binary in your PATH" 1>&2; \
+	echo "*** or have you tried setting the QEMU variable in Makefile?" 1>&2; \
+	echo "***" 1>&2; exit 1)
+endif
+
+CC = $(TOOLPREFIX)gcc
+AS = $(TOOLPREFIX)gas
+LD = $(TOOLPREFIX)ld
+OBJCOPY = $(TOOLPREFIX)objcopy
+OBJDUMP = $(TOOLPREFIX)objdump
+CFLAGS = -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer
+CFLAGS += $(shell $(CC) -fno-stack-protector -E -x c /dev/null >/dev/null 2>&1 && echo -fno-stack-protector)
+ASFLAGS = -m32 -gdwarf-2 -Wa,-divide
+# FreeBSD ld wants ``elf_i386_fbsd''
+LDFLAGS += -m $(shell $(LD) -V | grep elf_i386 2>/dev/null | head -n 1)
+
+# Disable PIE when possible (for Ubuntu 16.10 toolchain)
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]no-pie'),)
+CFLAGS += -fno-pie -no-pie
+endif
+ifneq ($(shell $(CC) -dumpspecs 2>/dev/null | grep -e '[^f]nopie'),)
+CFLAGS += -fno-pie -nopie
+endif
+
+xv6.img: bootblock kernel
+	dd if=/dev/zero of=xv6.img count=10000
+	dd if=bootblock of=xv6.img conv=notrunc
+	dd if=kernel of=xv6.img seek=1 conv=notrunc
+
+xv6memfs.img: bootblock kernelmemfs
+	dd if=/dev/zero of=xv6memfs.img count=10000
+	dd if=bootblock of=xv6memfs.img conv=notrunc
+	dd if=kernelmemfs of=xv6memfs.img seek=1 conv=notrunc
+
+bootblock: bootasm.S bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -O -nostdinc -I. -c bootmain.c
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c bootasm.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7C00 -o bootblock.o bootasm.o bootmain.o
+	$(OBJDUMP) -S bootblock.o > bootblock.asm
+	$(OBJCOPY) -S -O binary -j .text bootblock.o bootblock
+	./sign.pl bootblock
+
+entryother: entryother.S
+	$(CC) $(CFLAGS) -fno-pic -nostdinc -I. -c entryother.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0x7000 -o bootblockother.o entryother.o
+	$(OBJCOPY) -S -O binary -j .text bootblockother.o entryother
+	$(OBJDUMP) -S bootblockother.o > entryother.asm
+
+initcode: initcode.S
+	$(CC) $(CFLAGS) -nostdinc -I. -c initcode.S
+	$(LD) $(LDFLAGS) -N -e start -Ttext 0 -o initcode.out initcode.o
+	$(OBJCOPY) -S -O binary initcode.out initcode
+	$(OBJDUMP) -S initcode.o > initcode.asm
+
+kernel: $(OBJS) entry.o entryother initcode kernel.ld
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernel entry.o $(OBJS) -b binary initcode entryother
+	$(OBJDUMP) -S kernel > kernel.asm
+	$(OBJDUMP) -t kernel | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernel.sym
+
+_uthread: uthread.o uthread_switch.o
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _uthread uthread.o uthread_switch.o $(ULIB)
+	$(OBJDUMP) -S _uthread > uthread.asm
+
+# kernelmemfs is a copy of kernel that maintains the
+# disk image in memory instead of writing to a disk.
+# This is not so useful for testing persistent storage or
+# exploring disk buffering implementations, but it is
+# great for testing the kernel on real hardware without
+# needing a scratch disk.
+MEMFSOBJS = $(filter-out ide.o,$(OBJS)) memide.o
+kernelmemfs: $(MEMFSOBJS) entry.o entryother initcode kernel.ld fs.img
+	$(LD) $(LDFLAGS) -T kernel.ld -o kernelmemfs entry.o  $(MEMFSOBJS) -b binary initcode entryother fs.img
+	$(OBJDUMP) -S kernelmemfs > kernelmemfs.asm
+	$(OBJDUMP) -t kernelmemfs | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > kernelmemfs.sym
+
+tags: $(OBJS) entryother.S _init
+	etags *.S *.c
+
+vectors.S: vectors.pl
+	./vectors.pl > vectors.S
+
+ULIB = ulib.o usys.o printf.o umalloc.o
+
+_%: %.o $(ULIB)
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o $@ $^
+	$(OBJDUMP) -S $@ > $*.asm
+	$(OBJDUMP) -t $@ | sed '1,/SYMBOL TABLE/d; s/ .* / /; /^$$/d' > $*.sym
+
+_forktest: forktest.o $(ULIB)
+	# forktest has less library code linked in - needs to be small
+	# in order to be able to max out the proc table.
+	$(LD) $(LDFLAGS) -N -e main -Ttext 0 -o _forktest forktest.o ulib.o usys.o
+	$(OBJDUMP) -S _forktest > forktest.asm
+
+mkfs: mkfs.c fs.h
+	gcc -Werror -Wall -o mkfs mkfs.c
+
+# Prevent deletion of intermediate files, e.g. cat.o, after first build, so
+# that disk image changes after first build are persistent until clean.  More
+# details:
+# http://www.gnu.org/software/make/manual/html_node/Chained-Rules.html
+.PRECIOUS: %.o
+
+UPROGS=\
+	_cat\
+	_echo\
+	_forktest\
+	_grep\
+	_init\
+	_kill\
+	_ln\
+	_ls\
+	_mkdir\
+	_rm\
+	_sh\
+	_stressfs\
+	_usertests\
+	_wc\
+	_zombie\
+	_date\
+	_alarmtest\
+	_uthread\
+	_big\
+
+fs.img: mkfs README $(UPROGS)
+	./mkfs fs.img README $(UPROGS)
+
+-include *.d
+
+clean: 
+	rm -f *.tex *.dvi *.idx *.aux *.log *.ind *.ilg \
+	*.o *.d *.asm *.sym vectors.S bootblock entryother \
+	initcode initcode.out kernel xv6.img fs.img kernelmemfs \
+	xv6memfs.img mkfs .gdbinit \
+	$(UPROGS)
+
+# make a printout
+FILES = $(shell grep -v '^\#' runoff.list)
+PRINT = runoff.list runoff.spec README toc.hdr toc.ftr $(FILES)
+
+xv6.pdf: $(PRINT)
+	./runoff
+	ls -l xv6.pdf
+
+print: xv6.pdf
+
+# run in emulators
+
+bochs : fs.img xv6.img
+	if [ ! -e .bochsrc ]; then ln -s dot-bochsrc .bochsrc; fi
+	bochs -q
+
+# try to generate a unique GDB port
+GDBPORT = $(shell expr `id -u` % 5000 + 25000)
+# QEMU's gdb stub command line changed in 0.11
+QEMUGDB = $(shell if $(QEMU) -help | grep -q '^-gdb'; \
+	then echo "-gdb tcp::$(GDBPORT)"; \
+	else echo "-s -p $(GDBPORT)"; fi)
+ifndef CPUS
+CPUS := 1
+endif
+QEMUEXTRA = -snapshot
+QEMUOPTS = -drive file=fs.img,index=1,media=disk,format=raw -drive file=xv6.img,index=0,media=disk,format=raw -smp $(CPUS) -m 512 $(QEMUEXTRA)
+
+
+gdb:
+	gdb -x .gdbinit
+	
+qemu: fs.img xv6.img
+	$(QEMU) -serial mon:stdio $(QEMUOPTS)
+
+qemu-memfs: xv6memfs.img
+	$(QEMU) -drive file=xv6memfs.img,index=0,media=disk,format=raw -smp $(CPUS) -m 256
+
+qemu-nox: fs.img xv6.img
+	$(QEMU) -nographic $(QEMUOPTS)
+
+.gdbinit: .gdbinit.tmpl
+	sed "s/localhost:1234/localhost:$(GDBPORT)/" < $^ > $@
+
+qemu-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -serial mon:stdio $(QEMUOPTS) -S $(QEMUGDB)
+
+qemu-nox-gdb: fs.img xv6.img .gdbinit
+	@echo "*** Now run 'gdb'." 1>&2
+	$(QEMU) -nographic $(QEMUOPTS) -S $(QEMUGDB)
+
+# CUT HERE
+# prepare dist for students
+# after running make dist, probably want to
+# rename it to rev0 or rev1 or so on and then
+# check in that version.
+
+EXTRA=\
+	mkfs.c ulib.c user.h cat.c echo.c forktest.c grep.c kill.c\
+	ln.c ls.c mkdir.c rm.c stressfs.c usertests.c wc.c zombie.c\
+	printf.c umalloc.c\
+	README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\
+	.gdbinit.tmpl gdbutil\
+
+dist:
+	rm -rf dist
+	mkdir dist
+	for i in $(FILES); \
+	do \
+		grep -v PAGEBREAK $$i >dist/$$i; \
+	done
+	sed '/CUT HERE/,$$d' Makefile >dist/Makefile
+	echo >dist/runoff.spec
+	cp $(EXTRA) dist
+
+dist-test:
+	rm -rf dist
+	make dist
+	rm -rf dist-test
+	mkdir dist-test
+	cp dist/* dist-test
+	cd dist-test; $(MAKE) print
+	cd dist-test; $(MAKE) bochs || true
+	cd dist-test; $(MAKE) qemu
+
+# update this rule (change rev#) when it is time to
+# make a new revision.
+tar:
+	rm -rf /tmp/xv6
+	mkdir -p /tmp/xv6
+	cp dist/* dist/.gdbinit.tmpl /tmp/xv6
+	(cd /tmp; tar cf - xv6) | gzip >xv6-rev10.tar.gz  # the next one will be 10 (9/17)
+
+.PHONY: dist-test dist
diff --git a/xv6-public/xv6.si4project/Backup/big(6818).c b/xv6-public/xv6.si4project/Backup/big(6818).c
new file mode 100644
index 0000000..cecf1a0
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/big(6818).c
@@ -0,0 +1,53 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+#include "fcntl.h"
+
+int
+main()
+{
+  char buf[512];
+  int fd, i, sectors;
+
+  fd = open("big.file", O_CREATE | O_WRONLY);
+  if(fd < 0){
+    printf(2, "big: cannot open big.file for writing\n");
+    exit();
+  }
+
+  sectors = 0;
+  while(1){
+    *(int*)buf = sectors;
+    int cc = write(fd, buf, sizeof(buf));
+    if(cc <= 0)
+      break;
+    sectors++;
+	if (sectors % 100 == 0)
+		printf(2, ".");
+  }
+
+  printf(1, "\nwrote %d sectors\n", sectors);
+
+  close(fd);
+  fd = open("big.file", O_RDONLY);
+  if(fd < 0){
+    printf(2, "big: cannot re-open big.file for reading\n");
+    exit();
+  }
+  for(i = 0; i < sectors; i++){
+    int cc = read(fd, buf, sizeof(buf));
+    if(cc <= 0){
+      printf(2, "big: read error at sector %d\n", i);
+      exit();
+    }
+    if(*(int*)buf != i){
+      printf(2, "big: read the wrong data (%d) for sector %d\n",
+             *(int*)buf, i);
+      exit();
+    }
+  }
+
+  printf(1, "done; ok\n"); 
+
+  exit();
+}
diff --git a/xv6-public/xv6.si4project/Backup/file(5413).h b/xv6-public/xv6.si4project/Backup/file(5413).h
new file mode 100644
index 0000000..0990c82
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/file(5413).h
@@ -0,0 +1,37 @@
+struct file {
+  enum { FD_NONE, FD_PIPE, FD_INODE } type;
+  int ref; // reference count
+  char readable;
+  char writable;
+  struct pipe *pipe;
+  struct inode *ip;
+  uint off;
+};
+
+
+// in-memory copy of an inode
+struct inode {
+  uint dev;           // Device number
+  uint inum;          // Inode number
+  int ref;            // Reference count
+  struct sleeplock lock; // protects everything below here
+  int valid;          // inode has been read from disk?
+
+  short type;         // copy of disk inode
+  short major;
+  short minor;
+  short nlink;
+  uint size;
+  uint addrs[NDIRECT+1];
+};
+
+// table mapping major device number to
+// device functions
+struct devsw {
+  int (*read)(struct inode*, char*, int);
+  int (*write)(struct inode*, char*, int);
+};
+
+extern struct devsw devsw[];
+
+#define CONSOLE 1
diff --git a/xv6-public/xv6.si4project/Backup/fs(4986).c b/xv6-public/xv6.si4project/Backup/fs(4986).c
new file mode 100644
index 0000000..feb59fe
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/fs(4986).c
@@ -0,0 +1,671 @@
+// File system implementation.  Five layers:
+//   + Blocks: allocator for raw disk blocks.
+//   + Log: crash recovery for multi-step updates.
+//   + Files: inode allocator, reading, writing, metadata.
+//   + Directories: inode with special contents (list of other inodes!)
+//   + Names: paths like /usr/rtm/xv6/fs.c for convenient naming.
+//
+// This file contains the low-level file system manipulation
+// routines.  The (higher-level) system call implementations
+// are in sysfile.c.
+
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "stat.h"
+#include "mmu.h"
+#include "proc.h"
+#include "spinlock.h"
+#include "sleeplock.h"
+#include "fs.h"
+#include "buf.h"
+#include "file.h"
+
+#define min(a, b) ((a) < (b) ? (a) : (b))
+static void itrunc(struct inode*);
+// there should be one superblock per disk device, but we run with
+// only one device
+struct superblock sb; 
+
+// Read the super block.
+void
+readsb(int dev, struct superblock *sb)
+{
+  struct buf *bp;
+
+  bp = bread(dev, 1);
+  memmove(sb, bp->data, sizeof(*sb));
+  brelse(bp);
+}
+
+// Zero a block.
+static void
+bzero(int dev, int bno)
+{
+  struct buf *bp;
+
+  bp = bread(dev, bno);
+  memset(bp->data, 0, BSIZE);
+  log_write(bp);
+  brelse(bp);
+}
+
+// Blocks.
+
+// Allocate a zeroed disk block.
+static uint
+balloc(uint dev)
+{
+  int b, bi, m;
+  struct buf *bp;
+
+  bp = 0;
+  for(b = 0; b < sb.size; b += BPB){
+    bp = bread(dev, BBLOCK(b, sb));
+    for(bi = 0; bi < BPB && b + bi < sb.size; bi++){
+      m = 1 << (bi % 8);
+      if((bp->data[bi/8] & m) == 0){  // Is block free?
+        bp->data[bi/8] |= m;  // Mark block in use.
+        log_write(bp);
+        brelse(bp);
+        bzero(dev, b + bi);
+        return b + bi;
+      }
+    }
+    brelse(bp);
+  }
+  panic("balloc: out of blocks");
+}
+
+// Free a disk block.
+static void
+bfree(int dev, uint b)
+{
+  struct buf *bp;
+  int bi, m;
+
+  readsb(dev, &sb);
+  bp = bread(dev, BBLOCK(b, sb));
+  bi = b % BPB;
+  m = 1 << (bi % 8);
+  if((bp->data[bi/8] & m) == 0)
+    panic("freeing free block");
+  bp->data[bi/8] &= ~m;
+  log_write(bp);
+  brelse(bp);
+}
+
+// Inodes.
+//
+// An inode describes a single unnamed file.
+// The inode disk structure holds metadata: the file's type,
+// its size, the number of links referring to it, and the
+// list of blocks holding the file's content.
+//
+// The inodes are laid out sequentially on disk at
+// sb.startinode. Each inode has a number, indicating its
+// position on the disk.
+//
+// The kernel keeps a cache of in-use inodes in memory
+// to provide a place for synchronizing access
+// to inodes used by multiple processes. The cached
+// inodes include book-keeping information that is
+// not stored on disk: ip->ref and ip->valid.
+//
+// An inode and its in-memory representation go through a
+// sequence of states before they can be used by the
+// rest of the file system code.
+//
+// * Allocation: an inode is allocated if its type (on disk)
+//   is non-zero. ialloc() allocates, and iput() frees if
+//   the reference and link counts have fallen to zero.
+//
+// * Referencing in cache: an entry in the inode cache
+//   is free if ip->ref is zero. Otherwise ip->ref tracks
+//   the number of in-memory pointers to the entry (open
+//   files and current directories). iget() finds or
+//   creates a cache entry and increments its ref; iput()
+//   decrements ref.
+//
+// * Valid: the information (type, size, &c) in an inode
+//   cache entry is only correct when ip->valid is 1.
+//   ilock() reads the inode from
+//   the disk and sets ip->valid, while iput() clears
+//   ip->valid if ip->ref has fallen to zero.
+//
+// * Locked: file system code may only examine and modify
+//   the information in an inode and its content if it
+//   has first locked the inode.
+//
+// Thus a typical sequence is:
+//   ip = iget(dev, inum)
+//   ilock(ip)
+//   ... examine and modify ip->xxx ...
+//   iunlock(ip)
+//   iput(ip)
+//
+// ilock() is separate from iget() so that system calls can
+// get a long-term reference to an inode (as for an open file)
+// and only lock it for short periods (e.g., in read()).
+// The separation also helps avoid deadlock and races during
+// pathname lookup. iget() increments ip->ref so that the inode
+// stays cached and pointers to it remain valid.
+//
+// Many internal file system functions expect the caller to
+// have locked the inodes involved; this lets callers create
+// multi-step atomic operations.
+//
+// The icache.lock spin-lock protects the allocation of icache
+// entries. Since ip->ref indicates whether an entry is free,
+// and ip->dev and ip->inum indicate which i-node an entry
+// holds, one must hold icache.lock while using any of those fields.
+//
+// An ip->lock sleep-lock protects all ip-> fields other than ref,
+// dev, and inum.  One must hold ip->lock in order to
+// read or write that inode's ip->valid, ip->size, ip->type, &c.
+
+struct {
+  struct spinlock lock;
+  struct inode inode[NINODE];
+} icache;
+
+void
+iinit(int dev)
+{
+  int i = 0;
+  
+  initlock(&icache.lock, "icache");
+  for(i = 0; i < NINODE; i++) {
+    initsleeplock(&icache.inode[i].lock, "inode");
+  }
+
+  readsb(dev, &sb);
+  cprintf("sb: size %d nblocks %d ninodes %d nlog %d logstart %d\
+ inodestart %d bmap start %d\n", sb.size, sb.nblocks,
+          sb.ninodes, sb.nlog, sb.logstart, sb.inodestart,
+          sb.bmapstart);
+}
+
+static struct inode* iget(uint dev, uint inum);
+
+//PAGEBREAK!
+// Allocate an inode on device dev.
+// Mark it as allocated by  giving it type type.
+// Returns an unlocked but allocated and referenced inode.
+struct inode*
+ialloc(uint dev, short type)
+{
+  int inum;
+  struct buf *bp;
+  struct dinode *dip;
+
+  for(inum = 1; inum < sb.ninodes; inum++){
+    bp = bread(dev, IBLOCK(inum, sb));
+    dip = (struct dinode*)bp->data + inum%IPB;
+    if(dip->type == 0){  // a free inode
+      memset(dip, 0, sizeof(*dip));
+      dip->type = type;
+      log_write(bp);   // mark it allocated on the disk
+      brelse(bp);
+      return iget(dev, inum);
+    }
+    brelse(bp);
+  }
+  panic("ialloc: no inodes");
+}
+
+// Copy a modified in-memory inode to disk.
+// Must be called after every change to an ip->xxx field
+// that lives on disk, since i-node cache is write-through.
+// Caller must hold ip->lock.
+void
+iupdate(struct inode *ip)
+{
+  struct buf *bp;
+  struct dinode *dip;
+
+  bp = bread(ip->dev, IBLOCK(ip->inum, sb));
+  dip = (struct dinode*)bp->data + ip->inum%IPB;
+  dip->type = ip->type;
+  dip->major = ip->major;
+  dip->minor = ip->minor;
+  dip->nlink = ip->nlink;
+  dip->size = ip->size;
+  memmove(dip->addrs, ip->addrs, sizeof(ip->addrs));
+  log_write(bp);
+  brelse(bp);
+}
+
+// Find the inode with number inum on device dev
+// and return the in-memory copy. Does not lock
+// the inode and does not read it from disk.
+static struct inode*
+iget(uint dev, uint inum)
+{
+  struct inode *ip, *empty;
+
+  acquire(&icache.lock);
+
+  // Is the inode already cached?
+  empty = 0;
+  for(ip = &icache.inode[0]; ip < &icache.inode[NINODE]; ip++){
+    if(ip->ref > 0 && ip->dev == dev && ip->inum == inum){
+      ip->ref++;
+      release(&icache.lock);
+      return ip;
+    }
+    if(empty == 0 && ip->ref == 0)    // Remember empty slot.
+      empty = ip;
+  }
+
+  // Recycle an inode cache entry.
+  if(empty == 0)
+    panic("iget: no inodes");
+
+  ip = empty;
+  ip->dev = dev;
+  ip->inum = inum;
+  ip->ref = 1;
+  ip->valid = 0;
+  release(&icache.lock);
+
+  return ip;
+}
+
+// Increment reference count for ip.
+// Returns ip to enable ip = idup(ip1) idiom.
+struct inode*
+idup(struct inode *ip)
+{
+  acquire(&icache.lock);
+  ip->ref++;
+  release(&icache.lock);
+  return ip;
+}
+
+// Lock the given inode.
+// Reads the inode from disk if necessary.
+void
+ilock(struct inode *ip)
+{
+  struct buf *bp;
+  struct dinode *dip;
+
+  if(ip == 0 || 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;
+    ip->type = dip->type;
+    ip->major = dip->major;
+    ip->minor = dip->minor;
+    ip->nlink = dip->nlink;
+    ip->size = dip->size;
+    memmove(ip->addrs, dip->addrs, sizeof(ip->addrs));
+    brelse(bp);
+    ip->valid = 1;
+    if(ip->type == 0)
+      panic("ilock: no type");
+  }
+}
+
+// Unlock the given inode.
+void
+iunlock(struct inode *ip)
+{
+  if(ip == 0 || !holdingsleep(&ip->lock) || ip->ref < 1)
+    panic("iunlock");
+
+  releasesleep(&ip->lock);
+}
+
+// Drop a reference to an in-memory inode.
+// If that was the last reference, the inode cache entry can
+// be recycled.
+// If that was the last reference and the inode has no links
+// to it, free the inode (and its content) on disk.
+// All calls to iput() must be inside a transaction in
+// case it has to free the inode.
+void
+iput(struct inode *ip)
+{
+  acquiresleep(&ip->lock);
+  if(ip->valid && ip->nlink == 0){
+    acquire(&icache.lock);
+    int r = ip->ref;
+    release(&icache.lock);
+    if(r == 1){
+      // inode has no links and no other references: truncate and free.
+      itrunc(ip);
+      ip->type = 0;
+      iupdate(ip);
+      ip->valid = 0;
+    }
+  }
+  releasesleep(&ip->lock);
+
+  acquire(&icache.lock);
+  ip->ref--;
+  release(&icache.lock);
+}
+
+// Common idiom: unlock, then put.
+void
+iunlockput(struct inode *ip)
+{
+  iunlock(ip);
+  iput(ip);
+}
+
+//PAGEBREAK!
+// Inode content
+//
+// The content (data) associated with each inode is stored
+// in blocks on the disk. The first NDIRECT block numbers
+// are listed in ip->addrs[].  The next NINDIRECT blocks are
+// listed in block ip->addrs[NDIRECT].
+
+// Return the disk block address of the nth block in inode ip.
+// If there is no such block, bmap allocates one.
+static uint
+bmap(struct inode *ip, uint bn)
+{
+  uint addr, *a;
+  struct buf *bp;
+
+  if(bn < NDIRECT){
+    if((addr = ip->addrs[bn]) == 0)
+      ip->addrs[bn] = addr = balloc(ip->dev);
+    return addr;
+  }
+  bn -= NDIRECT;
+
+  if(bn < NINDIRECT){
+    // Load indirect block, allocating if necessary.
+    if((addr = ip->addrs[NDIRECT]) == 0)
+      ip->addrs[NDIRECT] = addr = balloc(ip->dev);
+    bp = bread(ip->dev, addr);
+    a = (uint*)bp->data;
+    if((addr = a[bn]) == 0){
+      a[bn] = addr = balloc(ip->dev);
+      log_write(bp);
+    }
+    brelse(bp);
+    return addr;
+  }
+
+  panic("bmap: out of range");
+}
+
+// Truncate inode (discard contents).
+// Only called when the inode has no links
+// to it (no directory entries referring to it)
+// and has no in-memory reference to it (is
+// not an open file or current directory).
+static void
+itrunc(struct inode *ip)
+{
+  int i, j;
+  struct buf *bp;
+  uint *a;
+
+  for(i = 0; i < NDIRECT; i++){
+    if(ip->addrs[i]){
+      bfree(ip->dev, ip->addrs[i]);
+      ip->addrs[i] = 0;
+    }
+  }
+
+  if(ip->addrs[NDIRECT]){
+    bp = bread(ip->dev, ip->addrs[NDIRECT]);
+    a = (uint*)bp->data;
+    for(j = 0; j < NINDIRECT; j++){
+      if(a[j])
+        bfree(ip->dev, a[j]);
+    }
+    brelse(bp);
+    bfree(ip->dev, ip->addrs[NDIRECT]);
+    ip->addrs[NDIRECT] = 0;
+  }
+
+  ip->size = 0;
+  iupdate(ip);
+}
+
+// Copy stat information from inode.
+// Caller must hold ip->lock.
+void
+stati(struct inode *ip, struct stat *st)
+{
+  st->dev = ip->dev;
+  st->ino = ip->inum;
+  st->type = ip->type;
+  st->nlink = ip->nlink;
+  st->size = ip->size;
+}
+
+//PAGEBREAK!
+// Read data from inode.
+// Caller must hold ip->lock.
+int
+readi(struct inode *ip, char *dst, uint off, uint n)
+{
+  uint tot, m;
+  struct buf *bp;
+
+  if(ip->type == T_DEV){
+    if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].read)
+      return -1;
+    return devsw[ip->major].read(ip, dst, n);
+  }
+
+  if(off > ip->size || off + n < off)
+    return -1;
+  if(off + n > ip->size)
+    n = ip->size - off;
+
+  for(tot=0; tot<n; tot+=m, off+=m, dst+=m){
+    bp = bread(ip->dev, bmap(ip, off/BSIZE));
+    m = min(n - tot, BSIZE - off%BSIZE);
+    memmove(dst, bp->data + off%BSIZE, m);
+    brelse(bp);
+  }
+  return n;
+}
+
+// PAGEBREAK!
+// Write data to inode.
+// Caller must hold ip->lock.
+int
+writei(struct inode *ip, char *src, uint off, uint n)
+{
+  uint tot, m;
+  struct buf *bp;
+
+  if(ip->type == T_DEV){
+    if(ip->major < 0 || ip->major >= NDEV || !devsw[ip->major].write)
+      return -1;
+    return devsw[ip->major].write(ip, src, n);
+  }
+
+  if(off > ip->size || off + n < off)
+    return -1;
+  if(off + n > MAXFILE*BSIZE)
+    return -1;
+
+  for(tot=0; tot<n; tot+=m, off+=m, src+=m){
+    bp = bread(ip->dev, bmap(ip, off/BSIZE));
+    m = min(n - tot, BSIZE - off%BSIZE);
+    memmove(bp->data + off%BSIZE, src, m);
+    log_write(bp);
+    brelse(bp);
+  }
+
+  if(n > 0 && off > ip->size){
+    ip->size = off;
+    iupdate(ip);
+  }
+  return n;
+}
+
+//PAGEBREAK!
+// Directories
+
+int
+namecmp(const char *s, const char *t)
+{
+  return strncmp(s, t, DIRSIZ);
+}
+
+// Look for a directory entry in a directory.
+// If found, set *poff to byte offset of entry.
+struct inode*
+dirlookup(struct inode *dp, char *name, uint *poff)
+{
+  uint off, inum;
+  struct dirent de;
+
+  if(dp->type != T_DIR)
+    panic("dirlookup not DIR");
+
+  for(off = 0; off < dp->size; off += sizeof(de)){
+    if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
+      panic("dirlookup read");
+    if(de.inum == 0)
+      continue;
+    if(namecmp(name, de.name) == 0){
+      // entry matches path element
+      if(poff)
+        *poff = off;
+      inum = de.inum;
+      return iget(dp->dev, inum);
+    }
+  }
+
+  return 0;
+}
+
+// Write a new directory entry (name, inum) into the directory dp.
+int
+dirlink(struct inode *dp, char *name, uint inum)
+{
+  int off;
+  struct dirent de;
+  struct inode *ip;
+
+  // Check that name is not present.
+  if((ip = dirlookup(dp, name, 0)) != 0){
+    iput(ip);
+    return -1;
+  }
+
+  // Look for an empty dirent.
+  for(off = 0; off < dp->size; off += sizeof(de)){
+    if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
+      panic("dirlink read");
+    if(de.inum == 0)
+      break;
+  }
+
+  strncpy(de.name, name, DIRSIZ);
+  de.inum = inum;
+  if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de))
+    panic("dirlink");
+
+  return 0;
+}
+
+//PAGEBREAK!
+// Paths
+
+// Copy the next path element from path into name.
+// Return a pointer to the element following the copied one.
+// The returned path has no leading slashes,
+// so the caller can check *path=='\0' to see if the name is the last one.
+// If no name to remove, return 0.
+//
+// Examples:
+//   skipelem("a/bb/c", name) = "bb/c", setting name = "a"
+//   skipelem("///a//bb", name) = "bb", setting name = "a"
+//   skipelem("a", name) = "", setting name = "a"
+//   skipelem("", name) = skipelem("////", name) = 0
+//
+static char*
+skipelem(char *path, char *name)
+{
+  char *s;
+  int len;
+
+  while(*path == '/')
+    path++;
+  if(*path == 0)
+    return 0;
+  s = path;
+  while(*path != '/' && *path != 0)
+    path++;
+  len = path - s;
+  if(len >= DIRSIZ)
+    memmove(name, s, DIRSIZ);
+  else {
+    memmove(name, s, len);
+    name[len] = 0;
+  }
+  while(*path == '/')
+    path++;
+  return path;
+}
+
+// Look up and return the inode for a path name.
+// If parent != 0, return the inode for the parent and copy the final
+// path element into name, which must have room for DIRSIZ bytes.
+// Must be called inside a transaction since it calls iput().
+static struct inode*
+namex(char *path, int nameiparent, char *name)
+{
+  struct inode *ip, *next;
+
+  if(*path == '/')
+    ip = iget(ROOTDEV, ROOTINO);
+  else
+    ip = idup(myproc()->cwd);
+
+  while((path = skipelem(path, name)) != 0){
+    ilock(ip);
+    if(ip->type != T_DIR){
+      iunlockput(ip);
+      return 0;
+    }
+    if(nameiparent && *path == '\0'){
+      // Stop one level early.
+      iunlock(ip);
+      return ip;
+    }
+    if((next = dirlookup(ip, name, 0)) == 0){
+      iunlockput(ip);
+      return 0;
+    }
+    iunlockput(ip);
+    ip = next;
+  }
+  if(nameiparent){
+    iput(ip);
+    return 0;
+  }
+  return ip;
+}
+
+struct inode*
+namei(char *path)
+{
+  char name[DIRSIZ];
+  return namex(path, 0, name);
+}
+
+struct inode*
+nameiparent(char *path, char *name)
+{
+  return namex(path, 1, name);
+}
diff --git a/xv6-public/xv6.si4project/Backup/fs(5757).h b/xv6-public/xv6.si4project/Backup/fs(5757).h
new file mode 100644
index 0000000..3214f1d
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/fs(5757).h
@@ -0,0 +1,57 @@
+// On-disk file system format.
+// Both the kernel and user programs use this header file.
+
+
+#define ROOTINO 1  // root i-number
+#define BSIZE 512  // block size
+
+// Disk layout:
+// [ boot block | super block | log | inode blocks |
+//                                          free bit map | data blocks]
+//
+// mkfs computes the super block and builds an initial file system. The
+// super block describes the disk layout:
+struct superblock {
+  uint size;         // Size of file system image (blocks)
+  uint nblocks;      // Number of data blocks
+  uint ninodes;      // Number of inodes.
+  uint nlog;         // Number of log blocks
+  uint logstart;     // Block number of first log block
+  uint inodestart;   // Block number of first inode block
+  uint bmapstart;    // Block number of first free map block
+};
+
+#define NDIRECT 12
+#define NINDIRECT (BSIZE / sizeof(uint))
+#define MAXFILE (NDIRECT + NINDIRECT)
+
+// On-disk inode structure
+struct dinode {
+  short type;           // File type
+  short major;          // Major device number (T_DEV only)
+  short minor;          // Minor device number (T_DEV only)
+  short nlink;          // Number of links to inode in file system
+  uint size;            // Size of file (bytes)
+  uint addrs[NDIRECT+1];   // Data block addresses
+};
+
+// Inodes per block.
+#define IPB           (BSIZE / sizeof(struct dinode))
+
+// Block containing inode i
+#define IBLOCK(i, sb)     ((i) / IPB + sb.inodestart)
+
+// Bitmap bits per block
+#define BPB           (BSIZE*8)
+
+// Block of free map containing bit for block b
+#define BBLOCK(b, sb) (b/BPB + sb.bmapstart)
+
+// Directory is a file containing a sequence of dirent structures.
+#define DIRSIZ 14
+
+struct dirent {
+  ushort inum;
+  char name[DIRSIZ];
+};
+
diff --git a/xv6-public/xv6.si4project/Backup/log(5899).c b/xv6-public/xv6.si4project/Backup/log(5899).c
new file mode 100644
index 0000000..a64c0f6
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/log(5899).c
@@ -0,0 +1,234 @@
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "spinlock.h"
+#include "sleeplock.h"
+#include "fs.h"
+#include "buf.h"
+
+// Simple logging that allows concurrent FS system calls.
+//
+// A log transaction contains the updates of multiple FS system
+// calls. The logging system only commits when there are
+// no FS system calls active. Thus there is never
+// any reasoning required about whether a commit might
+// write an uncommitted system call's updates to disk.
+//
+// A system call should call begin_op()/end_op() to mark
+// its start and end. Usually begin_op() just increments
+// the count of in-progress FS system calls and returns.
+// But if it thinks the log is close to running out, it
+// sleeps until the last outstanding end_op() commits.
+//
+// The log is a physical re-do log containing disk blocks.
+// The on-disk log format:
+//   header block, containing block #s for block A, B, C, ...
+//   block A
+//   block B
+//   block C
+//   ...
+// Log appends are synchronous.
+
+// Contents of the header block, used for both the on-disk header block
+// and to keep track in memory of logged block# before commit.
+struct logheader {
+  int n;
+  int block[LOGSIZE];
+};
+
+struct log {
+  struct spinlock lock;
+  int start;
+  int size;
+  int outstanding; // how many FS sys calls are executing.
+  int committing;  // in commit(), please wait.
+  int dev;
+  struct logheader lh;
+};
+struct log log;
+
+static void recover_from_log(void);
+static void commit();
+
+void
+initlog(int dev)
+{
+  if (sizeof(struct logheader) >= BSIZE)
+    panic("initlog: too big logheader");
+
+  struct superblock sb;
+  initlock(&log.lock, "log");
+  readsb(dev, &sb);
+  log.start = sb.logstart;
+  log.size = sb.nlog;
+  log.dev = dev;
+  recover_from_log();
+}
+
+// Copy committed blocks from log to their home location
+static void
+install_trans(void)
+{
+  int tail;
+
+  for (tail = 0; tail < log.lh.n; tail++) {
+    struct buf *lbuf = bread(log.dev, log.start+tail+1); // read log block
+    struct buf *dbuf = bread(log.dev, log.lh.block[tail]); // read dst
+    memmove(dbuf->data, lbuf->data, BSIZE);  // copy block to dst
+    bwrite(dbuf);  // write dst to disk
+    brelse(lbuf);
+    brelse(dbuf);
+  }
+}
+
+// Read the log header from disk into the in-memory log header
+static void
+read_head(void)
+{
+  struct buf *buf = bread(log.dev, log.start);
+  struct logheader *lh = (struct logheader *) (buf->data);
+  int i;
+  log.lh.n = lh->n;
+  for (i = 0; i < log.lh.n; i++) {
+    log.lh.block[i] = lh->block[i];
+  }
+  brelse(buf);
+}
+
+// Write in-memory log header to disk.
+// This is the true point at which the
+// current transaction commits.
+static void
+write_head(void)
+{
+  struct buf *buf = bread(log.dev, log.start);
+  struct logheader *hb = (struct logheader *) (buf->data);
+  int i;
+  hb->n = log.lh.n;
+  for (i = 0; i < log.lh.n; i++) {
+    hb->block[i] = log.lh.block[i];
+  }
+  bwrite(buf);
+  brelse(buf);
+}
+
+static void
+recover_from_log(void)
+{
+  read_head();
+  install_trans(); // if committed, copy from log to disk
+  log.lh.n = 0;
+  write_head(); // clear the log
+}
+
+// called at the start of each FS system call.
+void
+begin_op(void)
+{
+  acquire(&log.lock);
+  while(1){
+    if(log.committing){
+      sleep(&log, &log.lock);
+    } else if(log.lh.n + (log.outstanding+1)*MAXOPBLOCKS > LOGSIZE){
+      // this op might exhaust log space; wait for commit.
+      sleep(&log, &log.lock);
+    } else {
+      log.outstanding += 1;
+      release(&log.lock);
+      break;
+    }
+  }
+}
+
+// called at the end of each FS system call.
+// commits if this was the last outstanding operation.
+void
+end_op(void)
+{
+  int do_commit = 0;
+
+  acquire(&log.lock);
+  log.outstanding -= 1;
+  if(log.committing)
+    panic("log.committing");
+  if(log.outstanding == 0){
+    do_commit = 1;
+    log.committing = 1;
+  } else {
+    // begin_op() may be waiting for log space,
+    // and decrementing log.outstanding has decreased
+    // the amount of reserved space.
+    wakeup(&log);
+  }
+  release(&log.lock);
+
+  if(do_commit){
+    // call commit w/o holding locks, since not allowed
+    // to sleep with locks.
+    commit();
+    acquire(&log.lock);
+    log.committing = 0;
+    wakeup(&log);
+    release(&log.lock);
+  }
+}
+
+// Copy modified blocks from cache to log.
+static void
+write_log(void)
+{
+  int tail;
+
+  for (tail = 0; tail < log.lh.n; tail++) {
+    struct buf *to = bread(log.dev, log.start+tail+1); // log block
+    struct buf *from = bread(log.dev, log.lh.block[tail]); // cache block
+    memmove(to->data, from->data, BSIZE);
+    bwrite(to);  // write the log
+    brelse(from);
+    brelse(to);
+  }
+}
+
+static void
+commit()
+{
+  if (log.lh.n > 0) {
+    write_log();     // Write modified blocks from cache to log
+    write_head();    // Write header to disk -- the real commit
+    install_trans(); // Now install writes to home locations
+    log.lh.n = 0;
+    write_head();    // Erase the transaction from the log
+  }
+}
+
+// Caller has modified b->data and is done with the buffer.
+// Record the block number and pin in the cache with B_DIRTY.
+// commit()/write_log() will do the disk write.
+//
+// log_write() replaces bwrite(); a typical use is:
+//   bp = bread(...)
+//   modify bp->data[]
+//   log_write(bp)
+//   brelse(bp)
+void
+log_write(struct buf *b)
+{
+  int i;
+
+  if (log.lh.n >= LOGSIZE || log.lh.n >= log.size - 1)
+    panic("too big a transaction");
+  if (log.outstanding < 1)
+    panic("log_write outside of trans");
+
+  acquire(&log.lock);
+  for (i = 0; i < log.lh.n; i++) {
+    if (log.lh.block[i] == b->blockno)   // log absorbtion
+      break;
+  }
+  log.lh.block[i] = b->blockno;
+  if (i == log.lh.n)
+    log.lh.n++;
+  b->flags |= B_DIRTY; // prevent eviction
+  release(&log.lock);
+}
+
diff --git a/xv6-public/xv6.si4project/Backup/param(1678).h b/xv6-public/xv6.si4project/Backup/param(1678).h
new file mode 100644
index 0000000..a7e90ef
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/param(1678).h
@@ -0,0 +1,14 @@
+#define NPROC        64  // maximum number of processes
+#define KSTACKSIZE 4096  // size of per-process kernel stack
+#define NCPU          8  // maximum number of CPUs
+#define NOFILE       16  // open files per process
+#define NFILE       100  // open files per system
+#define NINODE       50  // maximum number of active i-nodes
+#define NDEV         10  // maximum major device number
+#define ROOTDEV       1  // device number of file system root disk
+#define MAXARG       32  // max exec arguments
+#define MAXOPBLOCKS  10  // max # of blocks any FS op writes
+#define LOGSIZE      (MAXOPBLOCKS*3)  // max data blocks in on-disk log
+#define NBUF         (MAXOPBLOCKS*3)  // size of disk block cache
+#define FSSIZE       1000  // size of file system in blocks
+
diff --git a/xv6-public/xv6.si4project/Backup/param(8017).h b/xv6-public/xv6.si4project/Backup/param(8017).h
new file mode 100644
index 0000000..fe38bfb
--- /dev/null
+++ b/xv6-public/xv6.si4project/Backup/param(8017).h
@@ -0,0 +1,14 @@
+#define NPROC        64  // maximum number of processes
+#define KSTACKSIZE 4096  // size of per-process kernel stack
+#define NCPU          8  // maximum number of CPUs
+#define NOFILE       16  // open files per process
+#define NFILE       100  // open files per system
+#define NINODE       50  // maximum number of active i-nodes
+#define NDEV         10  // maximum major device number
+#define ROOTDEV       1  // device number of file system root disk
+#define MAXARG       32  // max exec arguments
+#define MAXOPBLOCKS  10  // max # of blocks any FS op writes
+#define LOGSIZE      (MAXOPBLOCKS*3)  // max data blocks in on-disk log
+#define NBUF         (MAXOPBLOCKS*3)  // size of disk block cache
+#define FSSIZE       20000  // size of file system in blocks
+
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diff --git a/xv6-public/xv6.si4project/cache/parse/log.c.sisc b/xv6-public/xv6.si4project/cache/parse/log.c.sisc
index d74c5cd..53e59ad 100644
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diff --git a/xv6-public/xv6.si4project/cache/parse/param.h.sisc b/xv6-public/xv6.si4project/cache/parse/param.h.sisc
index dae8fa1..06cdf34 100644
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diff --git a/xv6-public/xv6.si4project/xv6.SearchResults b/xv6-public/xv6.si4project/xv6.SearchResults
index 77b88b3..f9a31df 100644
--- a/xv6-public/xv6.si4project/xv6.SearchResults
+++ b/xv6-public/xv6.si4project/xv6.SearchResults
@@ -1,4 +1 @@
----- sys_write Matches (3 in 2 files) ----
-syscall.c line 104 : extern int sys_write(void);
-syscall.c line 126 : [SYS_write]   sys_write,
-sysfile.c line 83 : sys_write(void)
+---- commit(); Matches (0 in 0 files) ----
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