ass1.patch

diff --git a/Makefile b/Makefile
index 09d790c..dd5da0e 100644
--- a/Makefile
+++ b/Makefile
@@ -181,6 +181,11 @@ UPROGS=\
 	_usertests\
 	_wc\
 	_zombie\
+	_helloworld\
+	_memsizetest\
+	_checkPartC\
+	_policy\
+	_sanity\
 
 fs.img: mkfs README $(UPROGS)
 	./mkfs fs.img README $(UPROGS)
@@ -250,6 +255,7 @@ qemu-nox-gdb: fs.img xv6.img .gdbinit
 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\
+	helloworld.c memsizetest.c checkPartC.c policy.c sanity.c\
 	printf.c umalloc.c\
 	README dot-bochsrc *.pl toc.* runoff runoff1 runoff.list\
 	.gdbinit.tmpl gdbutil\
diff --git a/cat.c b/cat.c
index 5ddc820..e74de1a 100644
--- a/cat.c
+++ b/cat.c
@@ -12,12 +12,12 @@ cat(int fd)
   while((n = read(fd, buf, sizeof(buf))) > 0) {
     if (write(1, buf, n) != n) {
       printf(1, "cat: write error\n");
-      exit();
+      exit(1);
     }
   }
   if(n < 0){
     printf(1, "cat: read error\n");
-    exit();
+    exit(1);
   }
 }
 
@@ -28,16 +28,16 @@ main(int argc, char *argv[])
 
   if(argc <= 1){
     cat(0);
-    exit();
+    exit(0);
   }
 
   for(i = 1; i < argc; i++){
     if((fd = open(argv[i], 0)) < 0){
       printf(1, "cat: cannot open %s\n", argv[i]);
-      exit();
+      exit(1);
     }
     cat(fd);
     close(fd);
   }
-  exit();
+  exit(0);
 }
diff --git a/checkPartC.c b/checkPartC.c
new file mode 100644
index 0000000..fbd9567
--- /dev/null
+++ b/checkPartC.c
@@ -0,0 +1,29 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+int main(){
+	int pid;
+    printf(1, "Brachol & Nitz ###TEST### for PART3\n");
+    pid = fork();
+    if(pid < 0)
+    	printf(1, "ERROR forking ERROR\n");
+    if(pid == 0)
+    {
+    	char *str;
+    	printf(1, "HOLA IM A KID\n");
+    	memsize();
+    	str = (char *) malloc(2048);
+   		memsize();
+   		free(str);
+   		printf(1, "ADIOS IM A KID\n");
+    	exit(666);
+
+    }
+    int status;
+    wait(&status);
+    printf(1, "HOLA IM A FATHER\n");
+    memsize();
+    printf(1, "the status is: %d", status);
+    exit(0);
+  }
\ No newline at end of file
diff --git a/defs.h b/defs.h
index 82fb982..721c873 100644
--- a/defs.h
+++ b/defs.h
@@ -10,6 +10,13 @@ struct sleeplock;
 struct stat;
 struct superblock;
 
+struct perf {
+int ps_priority;
+int stime;
+int retime;
+int rtime;
+}perf;
+
 // bio.c
 void            binit(void);
 struct buf*     bread(uint, uint);
@@ -104,7 +111,7 @@ int             pipewrite(struct pipe*, char*, int);
 //PAGEBREAK: 16
 // proc.c
 int             cpuid(void);
-void            exit(void);
+void            exit(int);
 int             fork(void);
 int             growproc(int);
 int             kill(int);
@@ -117,9 +124,15 @@ void            sched(void);
 void            setproc(struct proc*);
 void            sleep(void*, struct spinlock*);
 void            userinit(void);
-int             wait(void);
+int             wait(int*);
 void            wakeup(void*);
 void            yield(void);
+void            memsize(void);
+int 			set_ps_priority(int);
+int 			policy(int);
+int 			set_cfs_priority(int);
+void			update_statistics(void);
+int 			proc_info(struct perf*);
 
 // swtch.S
 void            swtch(struct context**, struct context*);
@@ -188,3 +201,4 @@ void            clearpteu(pde_t *pgdir, char *uva);
 
 // number of elements in fixed-size array
 #define NELEM(x) (sizeof(x)/sizeof((x)[0]))
+int 			sched_type;
\ No newline at end of file
diff --git a/echo.c b/echo.c
index 806dee0..eed68a0 100644
--- a/echo.c
+++ b/echo.c
@@ -9,5 +9,5 @@ main(int argc, char *argv[])
 
   for(i = 1; i < argc; i++)
     printf(1, "%s%s", argv[i], i+1 < argc ? " " : "\n");
-  exit();
+  exit(0);
 }
diff --git a/forktest.c b/forktest.c
index 8bc984d..164d963 100644
--- a/forktest.c
+++ b/forktest.c
@@ -25,24 +25,24 @@ forktest(void)
     if(pid < 0)
       break;
     if(pid == 0)
-      exit();
+      exit(0);
   }
 
   if(n == N){
     printf(1, "fork claimed to work N times!\n", N);
-    exit();
+    exit(0);
   }
 
   for(; n > 0; n--){
-    if(wait() < 0){
+    if(wait(null) < 0){
       printf(1, "wait stopped early\n");
-      exit();
+      exit(1);
     }
   }
 
-  if(wait() != -1){
+  if(wait(null) != -1){
     printf(1, "wait got too many\n");
-    exit();
+    exit(1);
   }
 
   printf(1, "fork test OK\n");
@@ -52,5 +52,5 @@ int
 main(void)
 {
   forktest();
-  exit();
+  exit(0);
 }
diff --git a/grep.c b/grep.c
index adc4835..d354f2a 100644
--- a/grep.c
+++ b/grep.c
@@ -43,24 +43,24 @@ main(int argc, char *argv[])
 
   if(argc <= 1){
     printf(2, "usage: grep pattern [file ...]\n");
-    exit();
+    exit(1);
   }
   pattern = argv[1];
 
   if(argc <= 2){
     grep(pattern, 0);
-    exit();
+    exit(0);
   }
 
   for(i = 2; i < argc; i++){
     if((fd = open(argv[i], 0)) < 0){
       printf(1, "grep: cannot open %s\n", argv[i]);
-      exit();
+      exit(1);
     }
     grep(pattern, fd);
     close(fd);
   }
-  exit();
+  exit(0);
 }
 
 // Regexp matcher from Kernighan & Pike,
diff --git a/helloworld.c b/helloworld.c
new file mode 100755
index 0000000..9eb8004
--- /dev/null
+++ b/helloworld.c
@@ -0,0 +1,8 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+int main(){
+   printf(1, "Hello World XV6\n");
+   exit(0);
+  }
\ No newline at end of file
diff --git a/init.c b/init.c
index 046b551..7c93422 100644
--- a/init.c
+++ b/init.c
@@ -24,14 +24,14 @@ main(void)
     pid = fork();
     if(pid < 0){
       printf(1, "init: fork failed\n");
-      exit();
+      exit(1);
     }
     if(pid == 0){
       exec("sh", argv);
       printf(1, "init: exec sh failed\n");
-      exit();
+      exit(1);
     }
-    while((wpid=wait()) >= 0 && wpid != pid)
+    while((wpid=wait(null)) >= 0 && wpid != pid)
       printf(1, "zombie!\n");
   }
 }
diff --git a/kill.c b/kill.c
index 364f6af..875916c 100644
--- a/kill.c
+++ b/kill.c
@@ -9,9 +9,9 @@ main(int argc, char **argv)
 
   if(argc < 2){
     printf(2, "usage: kill pid...\n");
-    exit();
+    exit(1);
   }
   for(i=1; i<argc; i++)
     kill(atoi(argv[i]));
-  exit();
+  exit(0);
 }
diff --git a/ln.c b/ln.c
index cf8a64e..fb17c3b 100644
--- a/ln.c
+++ b/ln.c
@@ -7,9 +7,9 @@ main(int argc, char *argv[])
 {
   if(argc != 3){
     printf(2, "Usage: ln old new\n");
-    exit();
+    exit(1);
   }
   if(link(argv[1], argv[2]) < 0)
     printf(2, "link %s %s: failed\n", argv[1], argv[2]);
-  exit();
+  exit(0);
 }
diff --git a/ls.c b/ls.c
index 2862913..27742c2 100644
--- a/ls.c
+++ b/ls.c
@@ -77,9 +77,9 @@ main(int argc, char *argv[])
 
   if(argc < 2){
     ls(".");
-    exit();
+    exit(0);
   }
   for(i=1; i<argc; i++)
     ls(argv[i]);
-  exit();
+  exit(0);
 }
diff --git a/memsizetest.c b/memsizetest.c
new file mode 100644
index 0000000..eb12a55
--- /dev/null
+++ b/memsizetest.c
@@ -0,0 +1,17 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+
+int main(){
+   memsize();
+   char *str;
+
+   printf(1, "Allocating more memory\n");
+   str = (char *) malloc(2048);
+   memsize();
+   printf(1, "Freeing memory\n");
+   free(str);
+   memsize();
+   exit(0);
+ }
\ No newline at end of file
diff --git a/mkdir.c b/mkdir.c
index 6e4c954..2d90781 100644
--- a/mkdir.c
+++ b/mkdir.c
@@ -9,7 +9,7 @@ main(int argc, char *argv[])
 
   if(argc < 2){
     printf(2, "Usage: mkdir files...\n");
-    exit();
+    exit(1);
   }
 
   for(i = 1; i < argc; i++){
@@ -19,5 +19,5 @@ main(int argc, char *argv[])
     }
   }
 
-  exit();
+  exit(0);
 }
diff --git a/policy.c b/policy.c
new file mode 100644
index 0000000..9d705a1
--- /dev/null
+++ b/policy.c
@@ -0,0 +1,23 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+ int main (int argc, char *argv[]) {
+   const char *num_to_names[3];
+   num_to_names[0] = "Default";
+   num_to_names[1] = "Priority";
+   num_to_names[2] = "CFS";
+ 	if(argc!=2)
+   		printf(1, "Please provide input\n");
+   	else
+   	{
+   		int num;
+   		num = atoi(argv[1]);
+   		if(policy(num)==0)
+   			printf(1, "Policy has been successfully changed to - %s Policy\n", num_to_names[num]);
+   		else
+   			printf(1, "Error replacing policy, no such a policy number (%d)\n", num);
+
+   	}
+   exit(0);
+  }
\ No newline at end of file
diff --git a/proc.c b/proc.c
index 806b1b1..4646688 100644
--- a/proc.c
+++ b/proc.c
@@ -6,6 +6,9 @@
 #include "x86.h"
 #include "proc.h"
 #include "spinlock.h"
+#ifndef __LONG_LONG_MAX__
+#define __LONG_LONG_MAX__ 
+#endif
 
 struct {
   struct spinlock lock;
@@ -20,6 +23,54 @@ extern void trapret(void);
 
 static void wakeup1(void *chan);
 
+
+void 
+update_statistics(void){
+    struct proc *p;
+    acquire(&ptable.lock);  //DOC: sleeplock1
+   for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+      switch(p->state)
+      {
+        case RUNNING:
+          p->rtime = p->rtime + 1;
+          break;
+        case SLEEPING:
+          p->stime = p->stime + 1;
+          break;
+        case RUNNABLE:
+          p->retime = p->retime + 1;
+          break;
+        default:
+          break;
+      }
+    }
+    release(&ptable.lock);
+}
+
+int
+get_minimum_accumulator(void)
+{
+  struct proc *p;
+  long long cur_min = 0;
+  int at_least_one = 0;
+  for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
+  {
+    if(p->state == RUNNABLE || p->state == RUNNING)
+    {
+      if(at_least_one == 0)
+        cur_min = p->accumulator;
+      at_least_one = 1;
+      if(p->accumulator < cur_min)
+        cur_min = p->accumulator;
+    }
+  }
+   return cur_min;
+}
+int calculate_run_time_ratio(struct proc *p)
+{
+  return (p->rtime * p->decay_factor)/(p->rtime + p->stime + p->retime);
+}
+
 void
 pinit(void)
 {
@@ -88,7 +139,13 @@ allocproc(void)
 found:
   p->state = EMBRYO;
   p->pid = nextpid++;
-
+  //priority 
+  p->ps_priority = 5;
+  p->decay_factor = 1;
+  p->stime = 0;
+  p->retime = 0;
+  p->rtime = 0;
+  p->accumulator = get_minimum_accumulator();
   release(&ptable.lock);
 
   // Allocate kernel stack.
@@ -199,6 +256,7 @@ fork(void)
   np->sz = curproc->sz;
   np->parent = curproc;
   *np->tf = *curproc->tf;
+  np->decay_factor = curproc->decay_factor;
 
   // Clear %eax so that fork returns 0 in the child.
   np->tf->eax = 0;
@@ -225,7 +283,7 @@ fork(void)
 // An exited process remains in the zombie state
 // until its parent calls wait() to find out it exited.
 void
-exit(void)
+exit(int exit_status)
 {
   struct proc *curproc = myproc();
   struct proc *p;
@@ -246,6 +304,7 @@ exit(void)
   iput(curproc->cwd);
   end_op();
   curproc->cwd = 0;
+  curproc->exit_status = exit_status;
 
   acquire(&ptable.lock);
 
@@ -270,7 +329,7 @@ exit(void)
 // Wait for a child process to exit and return its pid.
 // Return -1 if this process has no children.
 int
-wait(void)
+wait(int *exit_status)
 {
   struct proc *p;
   int havekids, pid;
@@ -295,6 +354,8 @@ wait(void)
         p->name[0] = 0;
         p->killed = 0;
         p->state = UNUSED;
+        if (exit_status != null)
+          *exit_status = p->exit_status;
         release(&ptable.lock);
         return pid;
       }
@@ -311,6 +372,26 @@ wait(void)
   }
 }
 
+
+void
+scheduler_non_dependency_commands(struct proc *p, struct cpu *c)
+{
+          // Switch to chosen process.  It is the process's job
+          // to release ptable.lock and then reacquire it
+          // before jumping back to us.
+          c->proc = p;
+          switchuvm(p);
+          p->state = RUNNING;
+
+          swtch(&(c->scheduler), p->context);
+          switchkvm();
+          p->accumulator = p->accumulator + p->ps_priority;
+          // Process is done running for now.
+          // It should have changed its p->state before coming back.
+          c->proc = 0;
+}
+
+
 //PAGEBREAK: 42
 // Per-CPU process scheduler.
 // Each CPU calls scheduler() after setting itself up.
@@ -325,36 +406,62 @@ scheduler(void)
   struct proc *p;
   struct cpu *c = mycpu();
   c->proc = 0;
-  
+  sched_type = 0;
   for(;;){
-    // Enable interrupts on this processor.
-    sti();
-
-    // Loop over process table looking for process to run.
-    acquire(&ptable.lock);
-    for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
-      if(p->state != RUNNABLE)
-        continue;
-
-      // Switch to chosen process.  It is the process's job
-      // to release ptable.lock and then reacquire it
-      // before jumping back to us.
-      c->proc = p;
-      switchuvm(p);
-      p->state = RUNNING;
-
-      swtch(&(c->scheduler), p->context);
-      switchkvm();
-
-      // Process is done running for now.
-      // It should have changed its p->state before coming back.
-      c->proc = 0;
-    }
-    release(&ptable.lock);
+      // Enable interrupts on this processor.
+      sti();
+
+
+      // Loop over process table looking for process to run.
+      acquire(&ptable.lock);
+        if(sched_type == 0)
+        {
+          //round robin:
+          for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+            if(sched_type != 0)
+              break;
+            if(p->state != RUNNABLE)
+              continue;
+            scheduler_non_dependency_commands(p, c);
+          }
+        }
+        else if(sched_type == 1)
+        {
+          long long min_acc =__LONG_LONG_MAX__;
+          for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+            if(p->accumulator < min_acc && p->state == RUNNABLE)
+              min_acc = p->accumulator;
+          }
+          for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+            if(p->accumulator == min_acc && p->state == RUNNABLE)
+            {
+              scheduler_non_dependency_commands(p, c);
+              break;
+            }
+          }
+        }
+        else if(sched_type == 2)
+        {
+            int min_ratio = 2147483647;
+            for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+              if(calculate_run_time_ratio(p) < min_ratio && p->state == RUNNABLE)
+                min_ratio = calculate_run_time_ratio(p);
+          }
+            for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){
+              if(calculate_run_time_ratio(p) == min_ratio && p->state == RUNNABLE)
+              {
+                scheduler_non_dependency_commands(p, c);
+                break;
+              }
+            }
+        }
 
+        release(&ptable.lock);
   }
 }
 
+
+
 // Enter scheduler.  Must hold only ptable.lock
 // and have changed proc->state. Saves and restores
 // intena because intena is a property of this
@@ -461,7 +568,10 @@ wakeup1(void *chan)
 
   for(p = ptable.proc; p < &ptable.proc[NPROC]; p++)
     if(p->state == SLEEPING && p->chan == chan)
+    {
+      p->accumulator = get_minimum_accumulator();
       p->state = RUNNABLE;
+    }
 }
 
 // Wake up all processes sleeping on chan.
@@ -532,3 +642,53 @@ procdump(void)
     cprintf("\n");
   }
 }
+
+void
+memsize(void)
+{
+  cprintf("The process is using: %dB\n", myproc()->sz);
+}
+
+int
+set_ps_priority(int priority)
+{
+  if(priority < 1 || priority > 10)
+    return -1;
+  struct proc *curproc = myproc();
+  curproc->ps_priority = priority;
+  return 0;
+}
+
+
+
+int policy(int policy_num)
+{
+  if(policy_num<0 || policy_num>2)
+    return -1;
+  sched_type = policy_num;
+  return 0;
+}
+int
+set_cfs_priority(int priority)
+{
+  if(priority == 1)
+    myproc()->decay_factor = 0.75;
+  else if(priority == 2)
+    myproc()->decay_factor = 1.0;
+  else if(priority == 3)
+    myproc()->decay_factor = 1.25;
+  else
+    return -1;
+  return 0;
+
+}
+
+int
+proc_info(struct perf *p)
+{
+  p->ps_priority = myproc()->ps_priority;
+  p->stime = myproc()->stime;
+  p->retime = myproc()->retime;
+  p->rtime = myproc()->rtime;
+  return 0;
+}
diff --git a/proc.h b/proc.h
index 1647114..619b7b9 100644
--- a/proc.h
+++ b/proc.h
@@ -49,6 +49,14 @@ struct proc {
   struct file *ofile[NOFILE];  // Open files
   struct inode *cwd;           // Current directory
   char name[16];               // Process name (debugging)
+  int exit_status;             // Process exit status
+  long long accumulator;       // Process accumulator
+  double decay_factor;         // Process cfs priority
+  int ps_priority;             // Process ps priority
+  int stime;
+  int retime;
+  int rtime;
+
 };
 
 // Process memory is laid out contiguously, low addresses first:
diff --git a/rm.c b/rm.c
index 4fd33c8..1e6daec 100644
--- a/rm.c
+++ b/rm.c
@@ -9,7 +9,7 @@ main(int argc, char *argv[])
 
   if(argc < 2){
     printf(2, "Usage: rm files...\n");
-    exit();
+    exit(1);
   }
 
   for(i = 1; i < argc; i++){
@@ -19,5 +19,5 @@ main(int argc, char *argv[])
     }
   }
 
-  exit();
+  exit(0);
 }
diff --git a/sanity.c b/sanity.c
new file mode 100644
index 0000000..7e27842
--- /dev/null
+++ b/sanity.c
@@ -0,0 +1,67 @@
+#include "types.h"
+#include "stat.h"
+#include "user.h"
+
+void child_to_do(struct perf* p)
+{
+int i = 1000000;
+int dummy = 0;
+while(i--)
+{
+	printf(1, "");
+	dummy+=i;
+}
+proc_info(p);
+printf(1, "%d           %d            %d          %d         %d\n", getpid(), p->ps_priority, p->stime, p->retime, p->rtime);
+
+}
+
+int main(){
+	printf(1, "PID  #  PS_PRIORITY  #  STIME  #  RETIME  #  RTIME\n");
+	struct perf* p1_perf = (struct perf*)malloc(sizeof(struct perf));
+    struct perf* p2_perf = (struct perf*)malloc(sizeof(struct perf));
+    struct perf* p3_perf = (struct perf*)malloc(sizeof(struct perf));
+	int pid1;
+	int pid2;
+	int pid3;
+    pid1 = fork();
+    if(pid1 < 0)
+    	printf(1, "ERROR forking ERROR\n");
+    else if(pid1 == 0)
+    {	
+    	set_cfs_priority(3);
+       	set_ps_priority(10);
+    	child_to_do(p1_perf);
+    }
+    else
+    {
+    	pid2 = fork();
+    	if(pid2 < 0)
+    	printf(1, "ERROR forking ERROR\n");
+	    else if(pid2 == 0)
+	    {
+	    	set_cfs_priority(2);
+            set_ps_priority(5);
+	    	child_to_do(p2_perf);
+	    }
+	    else
+	    {
+	    	pid3 = fork();
+	    	if(pid3 < 0)
+			    printf(1, "ERROR forking ERROR\n");
+		    else if(pid3 == 0)
+		    {
+		    	set_cfs_priority(1);
+            	set_ps_priority(1);
+		    	child_to_do(p3_perf);
+		    }
+		    else
+		    {
+		    		    	wait(null);
+	    					wait(null);
+	    					wait(null);
+		    }
+	    }
+	}
+	exit(0);
+  }
diff --git a/sh.c b/sh.c
index 054bab9..1d8273c 100644
--- a/sh.c
+++ b/sh.c
@@ -65,7 +65,7 @@ runcmd(struct cmd *cmd)
   struct redircmd *rcmd;
 
   if(cmd == 0)
-    exit();
+    exit(0);
 
   switch(cmd->type){
   default:
@@ -74,7 +74,7 @@ runcmd(struct cmd *cmd)
   case EXEC:
     ecmd = (struct execcmd*)cmd;
     if(ecmd->argv[0] == 0)
-      exit();
+      exit(0);
     exec(ecmd->argv[0], ecmd->argv);
     printf(2, "exec %s failed\n", ecmd->argv[0]);
     break;
@@ -84,7 +84,7 @@ runcmd(struct cmd *cmd)
     close(rcmd->fd);
     if(open(rcmd->file, rcmd->mode) < 0){
       printf(2, "open %s failed\n", rcmd->file);
-      exit();
+      exit(1);
     }
     runcmd(rcmd->cmd);
     break;
@@ -93,7 +93,7 @@ runcmd(struct cmd *cmd)
     lcmd = (struct listcmd*)cmd;
     if(fork1() == 0)
       runcmd(lcmd->left);
-    wait();
+    wait(null);
     runcmd(lcmd->right);
     break;
 
@@ -117,8 +117,8 @@ runcmd(struct cmd *cmd)
     }
     close(p[0]);
     close(p[1]);
-    wait();
-    wait();
+    wait(null);
+    wait(null);
     break;
 
   case BACK:
@@ -127,7 +127,7 @@ runcmd(struct cmd *cmd)
       runcmd(bcmd->cmd);
     break;
   }
-  exit();
+  exit(0);
 }
 
 int
@@ -166,16 +166,16 @@ main(void)
     }
     if(fork1() == 0)
       runcmd(parsecmd(buf));
-    wait();
+    wait(null);
   }
-  exit();
+  exit(0);
 }
 
 void
 panic(char *s)
 {
   printf(2, "%s\n", s);
-  exit();
+  exit(0);
 }
 
 int
diff --git a/stressfs.c b/stressfs.c
index c0a4743..98e221e 100644
--- a/stressfs.c
+++ b/stressfs.c
@@ -43,7 +43,7 @@ main(int argc, char *argv[])
     read(fd, data, sizeof(data));
   close(fd);
 
-  wait();
+  wait(null);
 
-  exit();
+  exit(0);
 }
diff --git a/syscall.c b/syscall.c
index ee85261..1aafe08 100644
--- a/syscall.c
+++ b/syscall.c
@@ -103,6 +103,11 @@ extern int sys_unlink(void);
 extern int sys_wait(void);
 extern int sys_write(void);
 extern int sys_uptime(void);
+extern int sys_memsize(void);
+extern int sys_set_ps_priority(void);
+extern int sys_policy(void);
+extern int sys_set_cfs_priority(void);
+extern int sys_proc_info(void);
 
 static int (*syscalls[])(void) = {
 [SYS_fork]    sys_fork,
@@ -126,6 +131,11 @@ static int (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
+[SYS_memsize] sys_memsize,
+[SYS_set_ps_priority] sys_set_ps_priority,
+[SYS_policy] sys_policy,
+[SYS_set_cfs_priority] sys_set_cfs_priority,
+[SYS_proc_info] sys_proc_info,
 };
 
 void
@@ -143,3 +153,4 @@ syscall(void)
     curproc->tf->eax = -1;
   }
 }
+
diff --git a/syscall.h b/syscall.h
index bc5f356..6204115 100644
--- a/syscall.h
+++ b/syscall.h
@@ -20,3 +20,8 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
+#define SYS_memsize 22
+#define SYS_set_ps_priority 23
+#define SYS_policy 24
+#define SYS_set_cfs_priority 25
+#define SYS_proc_info 26
\ No newline at end of file
diff --git a/sysproc.c b/sysproc.c
index 0686d29..ac772da 100644
--- a/sysproc.c
+++ b/sysproc.c
@@ -16,14 +16,20 @@ sys_fork(void)
 int
 sys_exit(void)
 {
-  exit();
+  int exit_status;
+  if (argint(0, &exit_status) < 0)
+    return -1;
+  exit(exit_status);
   return 0;  // not reached
 }
 
 int
 sys_wait(void)
 {
-  return wait();
+  int *exit_status;
+  if (argptr(0, (char**)&exit_status, 4) < 0)
+    return -1;
+  return wait(exit_status);
 }
 
 int
@@ -89,3 +95,46 @@ sys_uptime(void)
   release(&tickslock);
   return xticks;
 }
+
+void
+sys_memsize(void)
+{
+  memsize();
+}
+
+int
+sys_set_ps_priority(void)
+{
+  int priority;
+
+  if(argint(0, &priority) < 0)
+    return -1;
+  return set_ps_priority(priority);
+}
+
+int
+sys_policy(void)
+{
+  int policy_num;
+  if(argint(0, &policy_num) < 0)
+    return -1;
+  return  policy(policy_num);
+}
+
+int
+sys_set_cfs_priority(void)
+{
+  int priority;
+  if(argint(0, &priority) < 0)
+    return -1;
+  return  set_cfs_priority(priority);
+}
+
+int
+sys_proc_info(void)
+{
+  struct perf *p;
+  if(argptr(0, (char**) &p, sizeof(perf))<0)
+    return -1;
+  return proc_info(p);
+}
\ No newline at end of file
diff --git a/trap.c b/trap.c
index 41c66eb..5f263a1 100644
--- a/trap.c
+++ b/trap.c
@@ -11,6 +11,7 @@
 // Interrupt descriptor table (shared by all CPUs).
 struct gatedesc idt[256];
 extern uint vectors[];  // in vectors.S: array of 256 entry pointers
+extern void update_statistics(void);
 struct spinlock tickslock;
 uint ticks;
 
@@ -38,11 +39,11 @@ trap(struct trapframe *tf)
 {
   if(tf->trapno == T_SYSCALL){
     if(myproc()->killed)
-      exit();
+      exit(0);
     myproc()->tf = tf;
     syscall();
     if(myproc()->killed)
-      exit();
+      exit(0);
     return;
   }
 
@@ -53,6 +54,7 @@ trap(struct trapframe *tf)
       ticks++;
       wakeup(&ticks);
       release(&tickslock);
+      update_statistics();
     }
     lapiceoi();
     break;
@@ -98,7 +100,7 @@ trap(struct trapframe *tf)
   // (If it is still executing in the kernel, let it keep running
   // until it gets to the regular system call return.)
   if(myproc() && myproc()->killed && (tf->cs&3) == DPL_USER)
-    exit();
+    exit(0);
 
   // Force process to give up CPU on clock tick.
   // If interrupts were on while locks held, would need to check nlock.
@@ -108,5 +110,5 @@ trap(struct trapframe *tf)
 
   // Check if the process has been killed since we yielded
   if(myproc() && myproc()->killed && (tf->cs&3) == DPL_USER)
-    exit();
+    exit(0);
 }
diff --git a/types.h b/types.h
index e4adf64..485f3b6 100644
--- a/types.h
+++ b/types.h
@@ -2,3 +2,4 @@ typedef unsigned int   uint;
 typedef unsigned short ushort;
 typedef unsigned char  uchar;
 typedef uint pde_t;
+#define null 0
diff --git a/user.h b/user.h
index 4f99c52..cc644af 100644
--- a/user.h
+++ b/user.h
@@ -1,10 +1,16 @@
 struct stat;
 struct rtcdate;
+struct perf {
+int ps_priority;
+int stime;
+int retime;
+int rtime;
+}perf;
 
 // system calls
 int fork(void);
-int exit(void) __attribute__((noreturn));
-int wait(void);
+int exit(int) __attribute__((noreturn));
+int wait(int*);
 int pipe(int*);
 int write(int, const void*, int);
 int read(int, void*, int);
@@ -23,6 +29,11 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
+void memsize(void);
+int set_ps_priority(int);
+int policy(int);
+int set_cfs_priority(int);
+int proc_info(struct perf*);
 
 // ulib.c
 int stat(const char*, struct stat*);
diff --git a/usertests.c b/usertests.c
index a1e97e7..979c5f7 100644
--- a/usertests.c
+++ b/usertests.c
@@ -21,19 +21,19 @@ iputtest(void)
 
   if(mkdir("iputdir") < 0){
     printf(stdout, "mkdir failed\n");
-    exit();
+    exit(1);
   }
   if(chdir("iputdir") < 0){
     printf(stdout, "chdir iputdir failed\n");
-    exit();
+    exit(1);
   }
   if(unlink("../iputdir") < 0){
     printf(stdout, "unlink ../iputdir failed\n");
-    exit();
+    exit(1);
   }
   if(chdir("/") < 0){
     printf(stdout, "chdir / failed\n");
-    exit();
+    exit(1);
   }
   printf(stdout, "iput test ok\n");
 }
@@ -49,24 +49,24 @@ exitiputtest(void)
   pid = fork();
   if(pid < 0){
     printf(stdout, "fork failed\n");
-    exit();
+    exit(1);
   }
   if(pid == 0){
     if(mkdir("iputdir") < 0){
       printf(stdout, "mkdir failed\n");
-      exit();
+      exit(1);
     }
     if(chdir("iputdir") < 0){
       printf(stdout, "child chdir failed\n");
-      exit();
+      exit(1);
     }
     if(unlink("../iputdir") < 0){
       printf(stdout, "unlink ../iputdir failed\n");
-      exit();
+      exit(1);
     }
-    exit();
+    exit(0);
   }
-  wait();
+  wait(null);
   printf(stdout, "exitiput test ok\n");
 }
 
@@ -89,27 +89,27 @@ openiputtest(void)
   printf(stdout, "openiput test\n");
   if(mkdir("oidir") < 0){
     printf(stdout, "mkdir oidir failed\n");
-    exit();
+    exit(1);
   }
   pid = fork();
   if(pid < 0){
     printf(stdout, "fork failed\n");
-    exit();
+    exit(1);
   }
   if(pid == 0){
     int fd = open("oidir", O_RDWR);
     if(fd >= 0){
       printf(stdout, "open directory for write succeeded\n");
-      exit();
+      exit(0);
     }
-    exit();
+    exit(0);
   }
   sleep(1);
   if(unlink("oidir") != 0){
     printf(stdout, "unlink failed\n");
-    exit();
+    exit(1);
   }
-  wait();
+  wait(null);
   printf(stdout, "openiput test ok\n");
 }
 
@@ -124,13 +124,13 @@ opentest(void)
   fd = open("echo", 0);
   if(fd < 0){
     printf(stdout, "open echo failed!\n");
-    exit();
+    exit(1);
   }
   close(fd);
   fd = open("doesnotexist", 0);
   if(fd >= 0){
     printf(stdout, "open doesnotexist succeeded!\n");
-    exit();
+    exit(0);
   }
   printf(stdout, "open test ok\n");
 }
@@ -147,16 +147,16 @@ writetest(void)
     printf(stdout, "creat small succeeded; ok\n");
   } else {
     printf(stdout, "error: creat small failed!\n");
-    exit();
+    exit(1);
   }
   for(i = 0; i < 100; i++){
     if(write(fd, "aaaaaaaaaa", 10) != 10){
       printf(stdout, "error: write aa %d new file failed\n", i);
-      exit();
+      exit(1);
     }
     if(write(fd, "bbbbbbbbbb", 10) != 10){
       printf(stdout, "error: write bb %d new file failed\n", i);
-      exit();
+      exit(1);
     }
   }
   printf(stdout, "writes ok\n");
@@ -166,20 +166,20 @@ writetest(void)
     printf(stdout, "open small succeeded ok\n");
   } else {
     printf(stdout, "error: open small failed!\n");
-    exit();
+    exit(0);
   }
   i = read(fd, buf, 2000);
   if(i == 2000){
     printf(stdout, "read succeeded ok\n");
   } else {
     printf(stdout, "read failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
   if(unlink("small") < 0){
     printf(stdout, "unlink small failed\n");
-    exit();
+    exit(1);
   }
   printf(stdout, "small file test ok\n");
 }
@@ -194,14 +194,14 @@ writetest1(void)
   fd = open("big", O_CREATE|O_RDWR);
   if(fd < 0){
     printf(stdout, "error: creat big failed!\n");
-    exit();
+    exit(1);
   }
 
   for(i = 0; i < MAXFILE; i++){
     ((int*)buf)[0] = i;
     if(write(fd, buf, 512) != 512){
       printf(stdout, "error: write big file failed\n", i);
-      exit();
+      exit(1);
     }
   }
 
@@ -210,7 +210,7 @@ writetest1(void)
   fd = open("big", O_RDONLY);
   if(fd < 0){
     printf(stdout, "error: open big failed!\n");
-    exit();
+    exit(1);
   }
 
   n = 0;
@@ -219,24 +219,24 @@ writetest1(void)
     if(i == 0){
       if(n == MAXFILE - 1){
         printf(stdout, "read only %d blocks from big", n);
-        exit();
+        exit(1);
       }
       break;
     } else if(i != 512){
       printf(stdout, "read failed %d\n", i);
-      exit();
+      exit(1);
     }
     if(((int*)buf)[0] != n){
       printf(stdout, "read content of block %d is %d\n",
              n, ((int*)buf)[0]);
-      exit();
+      exit(0);
     }
     n++;
   }
   close(fd);
   if(unlink("big") < 0){
     printf(stdout, "unlink big failed\n");
-    exit();
+    exit(1);
   }
   printf(stdout, "big files ok\n");
 }
@@ -270,22 +270,22 @@ void dirtest(void)
 
   if(mkdir("dir0") < 0){
     printf(stdout, "mkdir failed\n");
-    exit();
+    exit(1);
   }
 
   if(chdir("dir0") < 0){
     printf(stdout, "chdir dir0 failed\n");
-    exit();
+    exit(1);
   }
 
   if(chdir("..") < 0){
     printf(stdout, "chdir .. failed\n");
-    exit();
+    exit(1);
   }
 
   if(unlink("dir0") < 0){
     printf(stdout, "unlink dir0 failed\n");
-    exit();
+    exit(1);
   }
   printf(stdout, "mkdir test ok\n");
 }
@@ -296,7 +296,7 @@ exectest(void)
   printf(stdout, "exec test\n");
   if(exec("echo", echoargv) < 0){
     printf(stdout, "exec echo failed\n");
-    exit();
+    exit(1);
   }
 }
 
@@ -310,7 +310,7 @@ pipe1(void)
 
   if(pipe(fds) != 0){
     printf(1, "pipe() failed\n");
-    exit();
+    exit(1);
   }
   pid = fork();
   seq = 0;
@@ -321,10 +321,10 @@ pipe1(void)
         buf[i] = seq++;
       if(write(fds[1], buf, 1033) != 1033){
         printf(1, "pipe1 oops 1\n");
-        exit();
+        exit(1);
       }
     }
-    exit();
+    exit(0);
   } else if(pid > 0){
     close(fds[1]);
     total = 0;
@@ -343,13 +343,13 @@ pipe1(void)
     }
     if(total != 5 * 1033){
       printf(1, "pipe1 oops 3 total %d\n", total);
-      exit();
+      exit(1);
     }
     close(fds[0]);
-    wait();
+    wait(null);
   } else {
     printf(1, "fork() failed\n");
-    exit();
+    exit(1);
   }
   printf(1, "pipe1 ok\n");
 }
@@ -394,9 +394,9 @@ preempt(void)
   kill(pid2);
   kill(pid3);
   printf(1, "wait... ");
-  wait();
-  wait();
-  wait();
+  wait(null);
+  wait(null);
+  wait(null);
   printf(1, "preempt ok\n");
 }
 
@@ -413,12 +413,12 @@ exitwait(void)
       return;
     }
     if(pid){
-      if(wait() != pid){
+      if(wait(null) != pid){
         printf(1, "wait wrong pid\n");
         return;
       }
     } else {
-      exit();
+      exit(0);
     }
   }
   printf(1, "exitwait ok\n");
@@ -447,13 +447,13 @@ mem(void)
     if(m1 == 0){
       printf(1, "couldn't allocate mem?!!\n");
       kill(ppid);
-      exit();
+      exit(1);
     }
     free(m1);
     printf(1, "mem ok\n");
-    exit();
+    exit(0);
   } else {
-    wait();
+    wait(null);
   }
 }
 
@@ -484,9 +484,9 @@ sharedfd(void)
     }
   }
   if(pid == 0)
-    exit();
+    exit(0);
   else
-    wait();
+    wait(null);
   close(fd);
   fd = open("sharedfd", 0);
   if(fd < 0){
@@ -508,7 +508,7 @@ sharedfd(void)
     printf(1, "sharedfd ok\n");
   } else {
     printf(1, "sharedfd oops %d %d\n", nc, np);
-    exit();
+    exit(1);
   }
 }
 
@@ -530,29 +530,29 @@ fourfiles(void)
     pid = fork();
     if(pid < 0){
       printf(1, "fork failed\n");
-      exit();
+      exit(1);
     }
 
     if(pid == 0){
       fd = open(fname, O_CREATE | O_RDWR);
       if(fd < 0){
         printf(1, "create failed\n");
-        exit();
+        exit(1);
       }
 
       memset(buf, '0'+pi, 512);
       for(i = 0; i < 12; i++){
         if((n = write(fd, buf, 500)) != 500){
           printf(1, "write failed %d\n", n);
-          exit();
+          exit(1);
         }
       }
-      exit();
+      exit(0);
     }
   }
 
   for(pi = 0; pi < 4; pi++){
-    wait();
+    wait(null);
   }
 
   for(i = 0; i < 2; i++){
@@ -563,7 +563,7 @@ fourfiles(void)
       for(j = 0; j < n; j++){
         if(buf[j] != '0'+i){
           printf(1, "wrong char\n");
-          exit();
+          exit(1);
         }
       }
       total += n;
@@ -571,7 +571,7 @@ fourfiles(void)
     close(fd);
     if(total != 12*500){
       printf(1, "wrong length %d\n", total);
-      exit();
+      exit(1);
     }
     unlink(fname);
   }
@@ -593,7 +593,7 @@ createdelete(void)
     pid = fork();
     if(pid < 0){
       printf(1, "fork failed\n");
-      exit();
+      exit(1);
     }
 
     if(pid == 0){
@@ -604,23 +604,23 @@ createdelete(void)
         fd = open(name, O_CREATE | O_RDWR);
         if(fd < 0){
           printf(1, "create failed\n");
-          exit();
+          exit(1);
         }
         close(fd);
         if(i > 0 && (i % 2 ) == 0){
           name[1] = '0' + (i / 2);
           if(unlink(name) < 0){
             printf(1, "unlink failed\n");
-            exit();
+            exit(1);
           }
         }
       }
-      exit();
+      exit(0);
     }
   }
 
   for(pi = 0; pi < 4; pi++){
-    wait();
+    wait(null);
   }
 
   name[0] = name[1] = name[2] = 0;
@@ -631,10 +631,10 @@ createdelete(void)
       fd = open(name, 0);
       if((i == 0 || i >= N/2) && fd < 0){
         printf(1, "oops createdelete %s didn't exist\n", name);
-        exit();
+        exit(1);
       } else if((i >= 1 && i < N/2) && fd >= 0){
         printf(1, "oops createdelete %s did exist\n", name);
-        exit();
+        exit(1);
       }
       if(fd >= 0)
         close(fd);
@@ -662,7 +662,7 @@ unlinkread(void)
   fd = open("unlinkread", O_CREATE | O_RDWR);
   if(fd < 0){
     printf(1, "create unlinkread failed\n");
-    exit();
+    exit(1);
   }
   write(fd, "hello", 5);
   close(fd);
@@ -670,11 +670,11 @@ unlinkread(void)
   fd = open("unlinkread", O_RDWR);
   if(fd < 0){
     printf(1, "open unlinkread failed\n");
-    exit();
+    exit(1);
   }
   if(unlink("unlinkread") != 0){
     printf(1, "unlink unlinkread failed\n");
-    exit();
+    exit(1);
   }
 
   fd1 = open("unlinkread", O_CREATE | O_RDWR);
@@ -683,15 +683,15 @@ unlinkread(void)
 
   if(read(fd, buf, sizeof(buf)) != 5){
     printf(1, "unlinkread read failed");
-    exit();
+    exit(1);
   }
   if(buf[0] != 'h'){
     printf(1, "unlinkread wrong data\n");
-    exit();
+    exit(1);
   }
   if(write(fd, buf, 10) != 10){
     printf(1, "unlinkread write failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
   unlink("unlinkread");
@@ -711,50 +711,50 @@ linktest(void)
   fd = open("lf1", O_CREATE|O_RDWR);
   if(fd < 0){
     printf(1, "create lf1 failed\n");
-    exit();
+    exit(1);
   }
   if(write(fd, "hello", 5) != 5){
     printf(1, "write lf1 failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
   if(link("lf1", "lf2") < 0){
     printf(1, "link lf1 lf2 failed\n");
-    exit();
+    exit(1);
   }
   unlink("lf1");
 
   if(open("lf1", 0) >= 0){
     printf(1, "unlinked lf1 but it is still there!\n");
-    exit();
+    exit(1);
   }
 
   fd = open("lf2", 0);
   if(fd < 0){
     printf(1, "open lf2 failed\n");
-    exit();
+    exit(1);
   }
   if(read(fd, buf, sizeof(buf)) != 5){
     printf(1, "read lf2 failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
   if(link("lf2", "lf2") >= 0){
     printf(1, "link lf2 lf2 succeeded! oops\n");
-    exit();
+    exit(1);
   }
 
   unlink("lf2");
   if(link("lf2", "lf1") >= 0){
     printf(1, "link non-existant succeeded! oops\n");
-    exit();
+    exit(1);
   }
 
   if(link(".", "lf1") >= 0){
     printf(1, "link . lf1 succeeded! oops\n");
-    exit();
+    exit(1);
   }
 
   printf(1, "linktest ok\n");
@@ -787,14 +787,14 @@ concreate(void)
       fd = open(file, O_CREATE | O_RDWR);
       if(fd < 0){
         printf(1, "concreate create %s failed\n", file);
-        exit();
+        exit(1);
       }
       close(fd);
     }
     if(pid == 0)
-      exit();
+      exit(0);
     else
-      wait();
+      wait(null);
   }
 
   memset(fa, 0, sizeof(fa));
@@ -807,11 +807,11 @@ concreate(void)
       i = de.name[1] - '0';
       if(i < 0 || i >= sizeof(fa)){
         printf(1, "concreate weird file %s\n", de.name);
-        exit();
+        exit(1);
       }
       if(fa[i]){
         printf(1, "concreate duplicate file %s\n", de.name);
-        exit();
+        exit(1);
       }
       fa[i] = 1;
       n++;
@@ -821,7 +821,7 @@ concreate(void)
 
   if(n != 40){
     printf(1, "concreate not enough files in directory listing\n");
-    exit();
+    exit(1);
   }
 
   for(i = 0; i < 40; i++){
@@ -829,7 +829,7 @@ concreate(void)
     pid = fork();
     if(pid < 0){
       printf(1, "fork failed\n");
-      exit();
+      exit(1);
     }
     if(((i % 3) == 0 && pid == 0) ||
        ((i % 3) == 1 && pid != 0)){
@@ -844,9 +844,9 @@ concreate(void)
       unlink(file);
     }
     if(pid == 0)
-      exit();
+      exit(0);
     else
-      wait();
+      wait(null);
   }
 
   printf(1, "concreate ok\n");
@@ -865,7 +865,7 @@ linkunlink()
   pid = fork();
   if(pid < 0){
     printf(1, "fork failed\n");
-    exit();
+    exit(1);
   }
 
   unsigned int x = (pid ? 1 : 97);
@@ -881,9 +881,9 @@ linkunlink()
   }
 
   if(pid)
-    wait();
+    wait(null);
   else
-    exit();
+    exit(0);
 
   printf(1, "linkunlink ok\n");
 }
@@ -901,7 +901,7 @@ bigdir(void)
   fd = open("bd", O_CREATE);
   if(fd < 0){
     printf(1, "bigdir create failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
@@ -912,7 +912,7 @@ bigdir(void)
     name[3] = '\0';
     if(link("bd", name) != 0){
       printf(1, "bigdir link failed\n");
-      exit();
+      exit(1);
     }
   }
 
@@ -924,7 +924,7 @@ bigdir(void)
     name[3] = '\0';
     if(unlink(name) != 0){
       printf(1, "bigdir unlink failed");
-      exit();
+      exit(1);
     }
   }
 
@@ -941,31 +941,31 @@ subdir(void)
   unlink("ff");
   if(mkdir("dd") != 0){
     printf(1, "subdir mkdir dd failed\n");
-    exit();
+    exit(1);
   }
 
   fd = open("dd/ff", O_CREATE | O_RDWR);
   if(fd < 0){
     printf(1, "create dd/ff failed\n");
-    exit();
+    exit(1);
   }
   write(fd, "ff", 2);
   close(fd);
 
   if(unlink("dd") >= 0){
     printf(1, "unlink dd (non-empty dir) succeeded!\n");
-    exit();
+    exit(1);
   }
 
   if(mkdir("/dd/dd") != 0){
     printf(1, "subdir mkdir dd/dd failed\n");
-    exit();
+    exit(1);
   }
 
   fd = open("dd/dd/ff", O_CREATE | O_RDWR);
   if(fd < 0){
     printf(1, "create dd/dd/ff failed\n");
-    exit();
+    exit(1);
   }
   write(fd, "FF", 2);
   close(fd);
@@ -973,142 +973,142 @@ subdir(void)
   fd = open("dd/dd/../ff", 0);
   if(fd < 0){
     printf(1, "open dd/dd/../ff failed\n");
-    exit();
+    exit(1);
   }
   cc = read(fd, buf, sizeof(buf));
   if(cc != 2 || buf[0] != 'f'){
     printf(1, "dd/dd/../ff wrong content\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
   if(link("dd/dd/ff", "dd/dd/ffff") != 0){
     printf(1, "link dd/dd/ff dd/dd/ffff failed\n");
-    exit();
+    exit(1);
   }
 
   if(unlink("dd/dd/ff") != 0){
     printf(1, "unlink dd/dd/ff failed\n");
-    exit();
+    exit(1);
   }
   if(open("dd/dd/ff", O_RDONLY) >= 0){
     printf(1, "open (unlinked) dd/dd/ff succeeded\n");
-    exit();
+    exit(0);
   }
 
   if(chdir("dd") != 0){
     printf(1, "chdir dd failed\n");
-    exit();
+    exit(1);
   }
   if(chdir("dd/../../dd") != 0){
     printf(1, "chdir dd/../../dd failed\n");
-    exit();
+    exit(1);
   }
   if(chdir("dd/../../../dd") != 0){
     printf(1, "chdir dd/../../dd failed\n");
-    exit();
+    exit(1);
   }
   if(chdir("./..") != 0){
     printf(1, "chdir ./.. failed\n");
-    exit();
+    exit(1);
   }
 
   fd = open("dd/dd/ffff", 0);
   if(fd < 0){
     printf(1, "open dd/dd/ffff failed\n");
-    exit();
+    exit(1);
   }
   if(read(fd, buf, sizeof(buf)) != 2){
     printf(1, "read dd/dd/ffff wrong len\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
   if(open("dd/dd/ff", O_RDONLY) >= 0){
     printf(1, "open (unlinked) dd/dd/ff succeeded!\n");
-    exit();
+    exit(0);
   }
 
   if(open("dd/ff/ff", O_CREATE|O_RDWR) >= 0){
     printf(1, "create dd/ff/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(open("dd/xx/ff", O_CREATE|O_RDWR) >= 0){
     printf(1, "create dd/xx/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(open("dd", O_CREATE) >= 0){
     printf(1, "create dd succeeded!\n");
-    exit();
+    exit(0);
   }
   if(open("dd", O_RDWR) >= 0){
     printf(1, "open dd rdwr succeeded!\n");
-    exit();
+    exit(0);
   }
   if(open("dd", O_WRONLY) >= 0){
     printf(1, "open dd wronly succeeded!\n");
-    exit();
+    exit(0);
   }
   if(link("dd/ff/ff", "dd/dd/xx") == 0){
     printf(1, "link dd/ff/ff dd/dd/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   if(link("dd/xx/ff", "dd/dd/xx") == 0){
     printf(1, "link dd/xx/ff dd/dd/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   if(link("dd/ff", "dd/dd/ffff") == 0){
     printf(1, "link dd/ff dd/dd/ffff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(mkdir("dd/ff/ff") == 0){
     printf(1, "mkdir dd/ff/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(mkdir("dd/xx/ff") == 0){
     printf(1, "mkdir dd/xx/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(mkdir("dd/dd/ffff") == 0){
     printf(1, "mkdir dd/dd/ffff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dd/xx/ff") == 0){
     printf(1, "unlink dd/xx/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dd/ff/ff") == 0){
     printf(1, "unlink dd/ff/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(chdir("dd/ff") == 0){
     printf(1, "chdir dd/ff succeeded!\n");
-    exit();
+    exit(0);
   }
   if(chdir("dd/xx") == 0){
     printf(1, "chdir dd/xx succeeded!\n");
-    exit();
+    exit(0);
   }
 
   if(unlink("dd/dd/ffff") != 0){
     printf(1, "unlink dd/dd/ff failed\n");
-    exit();
+    exit(1);
   }
   if(unlink("dd/ff") != 0){
     printf(1, "unlink dd/ff failed\n");
-    exit();
+    exit(1);
   }
   if(unlink("dd") == 0){
     printf(1, "unlink non-empty dd succeeded!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dd/dd") < 0){
     printf(1, "unlink dd/dd failed\n");
-    exit();
+    exit(1);
   }
   if(unlink("dd") < 0){
     printf(1, "unlink dd failed\n");
-    exit();
+    exit(1);
   }
 
   printf(1, "subdir ok\n");
@@ -1127,14 +1127,14 @@ bigwrite(void)
     fd = open("bigwrite", O_CREATE | O_RDWR);
     if(fd < 0){
       printf(1, "cannot create bigwrite\n");
-      exit();
+      exit(1);
     }
     int i;
     for(i = 0; i < 2; i++){
       int cc = write(fd, buf, sz);
       if(cc != sz){
         printf(1, "write(%d) ret %d\n", sz, cc);
-        exit();
+        exit(1);
       }
     }
     close(fd);
@@ -1155,13 +1155,13 @@ bigfile(void)
   fd = open("bigfile", O_CREATE | O_RDWR);
   if(fd < 0){
     printf(1, "cannot create bigfile");
-    exit();
+    exit(1);
   }
   for(i = 0; i < 20; i++){
     memset(buf, i, 600);
     if(write(fd, buf, 600) != 600){
       printf(1, "write bigfile failed\n");
-      exit();
+      exit(1);
     }
   }
   close(fd);
@@ -1169,31 +1169,31 @@ bigfile(void)
   fd = open("bigfile", 0);
   if(fd < 0){
     printf(1, "cannot open bigfile\n");
-    exit();
+    exit(1);
   }
   total = 0;
   for(i = 0; ; i++){
     cc = read(fd, buf, 300);
     if(cc < 0){
       printf(1, "read bigfile failed\n");
-      exit();
+      exit(1);
     }
     if(cc == 0)
       break;
     if(cc != 300){
       printf(1, "short read bigfile\n");
-      exit();
+      exit(1);
     }
     if(buf[0] != i/2 || buf[299] != i/2){
       printf(1, "read bigfile wrong data\n");
-      exit();
+      exit(1);
     }
     total += cc;
   }
   close(fd);
   if(total != 20*600){
     printf(1, "read bigfile wrong total\n");
-    exit();
+    exit(1);
   }
   unlink("bigfile");
 
@@ -1210,32 +1210,32 @@ fourteen(void)
 
   if(mkdir("12345678901234") != 0){
     printf(1, "mkdir 12345678901234 failed\n");
-    exit();
+    exit(1);
   }
   if(mkdir("12345678901234/123456789012345") != 0){
     printf(1, "mkdir 12345678901234/123456789012345 failed\n");
-    exit();
+    exit(1);
   }
   fd = open("123456789012345/123456789012345/123456789012345", O_CREATE);
   if(fd < 0){
     printf(1, "create 123456789012345/123456789012345/123456789012345 failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
   fd = open("12345678901234/12345678901234/12345678901234", 0);
   if(fd < 0){
     printf(1, "open 12345678901234/12345678901234/12345678901234 failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
 
   if(mkdir("12345678901234/12345678901234") == 0){
     printf(1, "mkdir 12345678901234/12345678901234 succeeded!\n");
-    exit();
+    exit(0);
   }
   if(mkdir("123456789012345/12345678901234") == 0){
     printf(1, "mkdir 12345678901234/123456789012345 succeeded!\n");
-    exit();
+    exit(0);
   }
 
   printf(1, "fourteen ok\n");
@@ -1247,35 +1247,35 @@ rmdot(void)
   printf(1, "rmdot test\n");
   if(mkdir("dots") != 0){
     printf(1, "mkdir dots failed\n");
-    exit();
+    exit(1);
   }
   if(chdir("dots") != 0){
     printf(1, "chdir dots failed\n");
-    exit();
+    exit(1);
   }
   if(unlink(".") == 0){
     printf(1, "rm . worked!\n");
-    exit();
+    exit(0);
   }
   if(unlink("..") == 0){
     printf(1, "rm .. worked!\n");
-    exit();
+    exit(0);
   }
   if(chdir("/") != 0){
     printf(1, "chdir / failed\n");
-    exit();
+    exit(1);
   }
   if(unlink("dots/.") == 0){
     printf(1, "unlink dots/. worked!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dots/..") == 0){
     printf(1, "unlink dots/.. worked!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dots") != 0){
     printf(1, "unlink dots failed!\n");
-    exit();
+    exit(1);
   }
   printf(1, "rmdot ok\n");
 }
@@ -1290,49 +1290,49 @@ dirfile(void)
   fd = open("dirfile", O_CREATE);
   if(fd < 0){
     printf(1, "create dirfile failed\n");
-    exit();
+    exit(1);
   }
   close(fd);
   if(chdir("dirfile") == 0){
     printf(1, "chdir dirfile succeeded!\n");
-    exit();
+    exit(0);
   }
   fd = open("dirfile/xx", 0);
   if(fd >= 0){
     printf(1, "create dirfile/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   fd = open("dirfile/xx", O_CREATE);
   if(fd >= 0){
     printf(1, "create dirfile/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   if(mkdir("dirfile/xx") == 0){
     printf(1, "mkdir dirfile/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dirfile/xx") == 0){
     printf(1, "unlink dirfile/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   if(link("README", "dirfile/xx") == 0){
     printf(1, "link to dirfile/xx succeeded!\n");
-    exit();
+    exit(0);
   }
   if(unlink("dirfile") != 0){
     printf(1, "unlink dirfile failed!\n");
-    exit();
+    exit(1);
   }
 
   fd = open(".", O_RDWR);
   if(fd >= 0){
     printf(1, "open . for writing succeeded!\n");
-    exit();
+    exit(0);
   }
   fd = open(".", 0);
   if(write(fd, "x", 1) > 0){
     printf(1, "write . succeeded!\n");
-    exit();
+    exit(0);
   }
   close(fd);
 
@@ -1351,11 +1351,11 @@ iref(void)
   for(i = 0; i < 50 + 1; i++){
     if(mkdir("irefd") != 0){
       printf(1, "mkdir irefd failed\n");
-      exit();
+      exit(1);
     }
     if(chdir("irefd") != 0){
       printf(1, "chdir irefd failed\n");
-      exit();
+      exit(1);
     }
 
     mkdir("");
@@ -1388,24 +1388,24 @@ forktest(void)
     if(pid < 0)
       break;
     if(pid == 0)
-      exit();
+      exit(0);
   }
 
   if(n == 1000){
     printf(1, "fork claimed to work 1000 times!\n");
-    exit();
+    exit(0);
   }
 
   for(; n > 0; n--){
-    if(wait() < 0){
+    if(wait(null) < 0){
       printf(1, "wait stopped early\n");
-      exit();
+      exit(0);
     }
   }
 
-  if(wait() != -1){
+  if(wait(null) != -1){
     printf(1, "wait got too many\n");
-    exit();
+    exit(1);
   }
 
   printf(1, "fork test OK\n");
@@ -1428,7 +1428,7 @@ sbrktest(void)
     b = sbrk(1);
     if(b != a){
       printf(stdout, "sbrk test failed %d %x %x\n", i, a, b);
-      exit();
+      exit(1);
     }
     *b = 1;
     a = b + 1;
@@ -1436,17 +1436,17 @@ sbrktest(void)
   pid = fork();
   if(pid < 0){
     printf(stdout, "sbrk test fork failed\n");
-    exit();
+    exit(1);
   }
   c = sbrk(1);
   c = sbrk(1);
   if(c != a + 1){
     printf(stdout, "sbrk test failed post-fork\n");
-    exit();
+    exit(1);
   }
   if(pid == 0)
-    exit();
-  wait();
+    exit(0);
+  wait(null);
 
   // can one grow address space to something big?
 #define BIG (100*1024*1024)
@@ -1455,7 +1455,7 @@ sbrktest(void)
   p = sbrk(amt);
   if (p != a) {
     printf(stdout, "sbrk test failed to grow big address space; enough phys mem?\n");
-    exit();
+    exit(1);
   }
   lastaddr = (char*) (BIG-1);
   *lastaddr = 99;
@@ -1465,12 +1465,12 @@ sbrktest(void)
   c = sbrk(-4096);
   if(c == (char*)0xffffffff){
     printf(stdout, "sbrk could not deallocate\n");
-    exit();
+    exit(1);
   }
   c = sbrk(0);
   if(c != a - 4096){
     printf(stdout, "sbrk deallocation produced wrong address, a %x c %x\n", a, c);
-    exit();
+    exit(1);
   }
 
   // can one re-allocate that page?
@@ -1478,19 +1478,19 @@ sbrktest(void)
   c = sbrk(4096);
   if(c != a || sbrk(0) != a + 4096){
     printf(stdout, "sbrk re-allocation failed, a %x c %x\n", a, c);
-    exit();
+    exit(1);
   }
   if(*lastaddr == 99){
     // should be zero
     printf(stdout, "sbrk de-allocation didn't really deallocate\n");
-    exit();
+    exit(1);
   }
 
   a = sbrk(0);
   c = sbrk(-(sbrk(0) - oldbrk));
   if(c != a){
     printf(stdout, "sbrk downsize failed, a %x c %x\n", a, c);
-    exit();
+    exit(1);
   }
 
   // can we read the kernel's memory?
@@ -1499,21 +1499,21 @@ sbrktest(void)
     pid = fork();
     if(pid < 0){
       printf(stdout, "fork failed\n");
-      exit();
+      exit(1);
     }
     if(pid == 0){
       printf(stdout, "oops could read %x = %x\n", a, *a);
       kill(ppid);
-      exit();
+      exit(1);
     }
-    wait();
+    wait(null);
   }
 
   // if we run the system out of memory, does it clean up the last
   // failed allocation?
   if(pipe(fds) != 0){
     printf(1, "pipe() failed\n");
-    exit();
+    exit(1);
   }
   for(i = 0; i < sizeof(pids)/sizeof(pids[0]); i++){
     if((pids[i] = fork()) == 0){
@@ -1533,11 +1533,11 @@ sbrktest(void)
     if(pids[i] == -1)
       continue;
     kill(pids[i]);
-    wait();
+    wait(null);
   }
   if(c == (char*)0xffffffff){
     printf(stdout, "failed sbrk leaked memory\n");
-    exit();
+    exit(1);
   }
 
   if(sbrk(0) > oldbrk)
@@ -1572,17 +1572,17 @@ validatetest(void)
     if((pid = fork()) == 0){
       // try to crash the kernel by passing in a badly placed integer
       validateint((int*)p);
-      exit();
+      exit(0);
     }
     sleep(0);
     sleep(0);
     kill(pid);
-    wait();
+    wait(null);
 
     // try to crash the kernel by passing in a bad string pointer
     if(link("nosuchfile", (char*)p) != -1){
       printf(stdout, "link should not succeed\n");
-      exit();
+      exit(1);
     }
   }
 
@@ -1600,7 +1600,7 @@ bsstest(void)
   for(i = 0; i < sizeof(uninit); i++){
     if(uninit[i] != '\0'){
       printf(stdout, "bss test failed\n");
-      exit();
+      exit(1);
     }
   }
   printf(stdout, "bss test ok\n");
@@ -1627,16 +1627,16 @@ bigargtest(void)
     printf(stdout, "bigarg test ok\n");
     fd = open("bigarg-ok", O_CREATE);
     close(fd);
-    exit();
+    exit(0);
   } else if(pid < 0){
     printf(stdout, "bigargtest: fork failed\n");
-    exit();
+    exit(0);
   }
-  wait();
+  wait(null);
   fd = open("bigarg-ok", 0);
   if(fd < 0){
     printf(stdout, "bigarg test failed!\n");
-    exit();
+    exit(1);
   }
   close(fd);
   unlink("bigarg-ok");
@@ -1715,12 +1715,12 @@ uio()
     port = RTC_DATA;
     asm volatile("inb %1,%0" : "=a" (val) : "d" (port));
     printf(1, "uio: uio succeeded; test FAILED\n");
-    exit();
+    exit(1);
   } else if(pid < 0){
     printf (1, "fork failed\n");
-    exit();
+    exit(1);
   }
-  wait();
+  wait(null);
   printf(1, "uio test done\n");
 }
 
@@ -1730,7 +1730,7 @@ void argptest()
   fd = open("init", O_RDONLY);
   if (fd < 0) {
     printf(2, "open failed\n");
-    exit();
+    exit(1);
   }
   read(fd, sbrk(0) - 1, -1);
   close(fd);
@@ -1752,7 +1752,7 @@ main(int argc, char *argv[])
 
   if(open("usertests.ran", 0) >= 0){
     printf(1, "already ran user tests -- rebuild fs.img\n");
-    exit();
+    exit(1);
   }
   close(open("usertests.ran", O_CREATE));
 
@@ -1799,5 +1799,5 @@ main(int argc, char *argv[])
 
   exectest();
 
-  exit();
+  exit(0);
 }
diff --git a/usys.S b/usys.S
index 8bfd8a1..f275550 100644
--- a/usys.S
+++ b/usys.S
@@ -29,3 +29,8 @@ SYSCALL(getpid)
 SYSCALL(sbrk)
 SYSCALL(sleep)
 SYSCALL(uptime)
+SYSCALL(memsize)
+SYSCALL(set_ps_priority)
+SYSCALL(policy)
+SYSCALL(set_cfs_priority)
+SYSCALL(proc_info)
\ No newline at end of file
diff --git a/wc.c b/wc.c
index d6a54df..549a3e8 100644
--- a/wc.c
+++ b/wc.c
@@ -27,7 +27,7 @@ wc(int fd, char *name)
   }
   if(n < 0){
     printf(1, "wc: read error\n");
-    exit();
+    exit(1);
   }
   printf(1, "%d %d %d %s\n", l, w, c, name);
 }
@@ -39,16 +39,16 @@ main(int argc, char *argv[])
 
   if(argc <= 1){
     wc(0, "");
-    exit();
+    exit(0);
   }
 
   for(i = 1; i < argc; i++){
     if((fd = open(argv[i], 0)) < 0){
       printf(1, "wc: cannot open %s\n", argv[i]);
-      exit();
+      exit(1);
     }
     wc(fd, argv[i]);
     close(fd);
   }
-  exit();
+  exit(0);
 }
diff --git a/zombie.c b/zombie.c
index ee817da..c96b92d 100644
--- a/zombie.c
+++ b/zombie.c
@@ -10,5 +10,5 @@ main(void)
 {
   if(fork() > 0)
     sleep(5);  // Let child exit before parent.
-  exit();
+  exit(0);
 }