lab util grade 100

Makefile

@@ -188,7 +188,11 @@ UPROGS=\
 	$U/_grind\
 	$U/_wc\
 	$U/_zombie\
-	$U/_alarmtest\
+	$U/_sleep\
+	$U/_pingpong\
+	$U/_primes\
+	$U/_find\
+	$U/_xargs\
 
 
 

README

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

answers-traps.txt

@@ -1,33 +0,0 @@
-Q: Which registers contain arguments to functions? For example, which register holds 13 in main's call to printf?
-A: The base integer calling convention provides eight argument registers, a0-a7, the first two of which are also used to return values. Register a2 holds 13.
-
-Q: Where is the call to function f in the assembly code for main? Where is the call to g?
-A:  There is no call to function f for main, the value of f(8) (which is 12) is calculated at compile time and hard-coded into the executable.
-    The call to g is inlined into f, at address 0x14.
-
-Q: At what address is the function printf located?
-A:  The function printf is located at address 0x642.
-
-Q: What value is in the register ra just after the jalr to printf in main?
-A:  The address of the next instruction after return, aka 0x38.
-
-Q:
----
-Run the following code.
-
-	unsigned int i = 0x00646c72;
-	printf("H%x Wo%s", 57616, &i);
-      
-What is the output? Here's an ASCII table that maps bytes to characters.
-The output depends on that fact that the RISC-V is little-endian. If the RISC-V were instead big-endian what would you set i to in order to yield the same output? Would you need to change 57616 to a different value?
----
-A:  The output is, He110 World(with no whitespace or new line).
-    If big endian, the new i should be 0x726c6400; and there is no need to change 56716.
-
-Q:
----
-In the following code, what is going to be printed after 'y='? (note: the answer is not a specific value.) Why does this happen?
-	printf("x=%d y=%d", 3);
----
-A:  The value that register a2 holds when the caller calls printf. By default, the third argument passed to a procedure is stored in a2.
-

conf/lab.mk

@@ -1 +1 @@
-LAB=traps
+LAB=util

grade-lab-traps

@@ -1,74 +0,0 @@
-#!/usr/bin/env python3
-
-import os
-import re
-import subprocess
-from gradelib import *
-
-r = Runner(save("xv6.out"))
-
-@test(5, "answers-traps.txt")
-def test_answers():
-    # just a simple sanity check, will be graded manually
-    check_answers("answers-traps.txt")
-
-BACKTRACE_RE = r"^(0x000000008[0-9a-f]+)"
-
-def addr2line():
-    for f in ['riscv64-unknown-elf-addr2line', 'riscv64-linux-gnu-addr2line', 'addr2line', ]:
-        try:
-            devnull = open(os.devnull)
-            subprocess.Popen([f], stdout=devnull, stderr=devnull).communicate()
-            return f
-        except OSError:
-            continue
-    raise AssertionError('Cannot find the addr2line program')
-
-@test(10, "backtrace test")
-def test_backtracetest():
-    r.run_qemu(shell_script([
-        'bttest'
-    ]))
-    a2l = addr2line()
-    matches = re.findall(BACKTRACE_RE, r.qemu.output, re.MULTILINE)
-    assert_equal(len(matches), 3)
-    files = ['sysproc.c', 'syscall.c', 'trap.c']
-    for f, m in zip(files, matches):
-        result = subprocess.run([a2l, '-e', 'kernel/kernel', m], stdout=subprocess.PIPE)
-        if not f in result.stdout.decode("utf-8"):
-            raise AssertionError('Trace is incorrect; no %s' % f)
-
-@test(0, "running alarmtest")
-def test_alarmtest():
-    r.run_qemu(shell_script([
-        'alarmtest'
-    ]))
-
-@test(20, "alarmtest: test0", parent=test_alarmtest)
-def test_alarmtest_test0():
-    r.match('^test0 passed$')
-
-@test(20, "alarmtest: test1", parent=test_alarmtest)
-def test_alarmtest_test1():
-    r.match('^\\.?test1 passed$')
-
-@test(10, "alarmtest: test2", parent=test_alarmtest)
-def test_alarmtest_test2():
-    r.match('^\\.?test2 passed$')
-
-@test(10, "alarmtest: test3", parent=test_alarmtest)
-def test_alarmtest_test3():
-    r.match('^test3 passed$')
-
-@test(19, "usertests")
-def test_usertests():
-    r.run_qemu(shell_script([
-        'usertests -q'
-    ]), timeout=300)
-    r.match('^ALL TESTS PASSED$')
-
-@test(1, "time")
-def test_time():
-    check_time()
-
-run_tests()

grade-lab-util

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

kernel/defs.h

@@ -80,7 +80,6 @@ int             pipewrite(struct pipe*, uint64, int);
 void            printf(char*, ...);
 void            panic(char*) __attribute__((noreturn));
 void            printfinit(void);
-void            backtrace(void);
 
 // proc.c
 int             cpuid(void);

kernel/printf.c

@@ -122,7 +122,6 @@ panic(char *s)
   printf("panic: ");
   printf(s);
   printf("\n");
-  backtrace();
   panicked = 1; // freeze uart output from other CPUs
   for(;;)
     ;
@@ -134,14 +133,3 @@ printfinit(void)
   initlock(&pr.lock, "pr");
   pr.locking = 1;
 }
-
-void backtrace(void)
-{
-  printf("backtrace:\n");
-  uint64 fp = r_fp();
-  uint64 fp_pg = PGROUNDDOWN(fp);
-  while (PGROUNDDOWN(fp) == fp_pg) {
-    printf("%p\n", (*(uint64*)(fp-8)));
-    fp = *(uint64*)(fp-16);
-  }
-}

kernel/proc.c

@@ -131,11 +131,6 @@ found:
     release(&p->lock);
     return 0;
   }
-  if((p->trapframe1 = (struct trapframe *)kalloc()) == 0){
-    freeproc(p);
-    release(&p->lock);
-    return 0;
-  }
 
   // An empty user page table.
   p->pagetable = proc_pagetable(p);
@@ -150,8 +145,6 @@ found:
   memset(&p->context, 0, sizeof(p->context));
   p->context.ra = (uint64)forkret;
   p->context.sp = p->kstack + PGSIZE;
-  p->alarm_hdlr = 0;
-  p->alarm_intrv = p->alarm_ticks = 0;
 
   return p;
 }
@@ -165,9 +158,6 @@ freeproc(struct proc *p)
   if(p->trapframe)
     kfree((void*)p->trapframe);
   p->trapframe = 0;
-  if(p->trapframe1)
-    kfree((void*)p->trapframe1);
-  p->trapframe1 = 0;
   if(p->pagetable)
     proc_freepagetable(p->pagetable, p->sz);
   p->pagetable = 0;

kernel/proc.h

@@ -100,12 +100,8 @@ struct proc {
   uint64 sz;                   // Size of process memory (bytes)
   pagetable_t pagetable;       // User page table
   struct trapframe *trapframe; // data page for trampoline.S
-  struct trapframe *trapframe1; // data page for trampoline.S
   struct context context;      // swtch() here to run process
   struct file *ofile[NOFILE];  // Open files
   struct inode *cwd;           // Current directory
-  int alarm_intrv;             // alarm interval
-  uint64 alarm_hdlr;            // alarm handler
-  int alarm_ticks;             // ticks after last alarm
   char name[16];               // Process name (debugging)
 };

kernel/riscv.h

@@ -319,14 +319,6 @@ r_ra()
   return x;
 }
 
-static inline uint64
-r_fp()
-{
-  uint64 x;
-  asm volatile("mv %0, s0" : "=r" (x) );
-  return x;
-}
-
 // flush the TLB.
 static inline void
 sfence_vma()

kernel/syscall.c

@@ -101,8 +101,6 @@ extern uint64 sys_unlink(void);
 extern uint64 sys_link(void);
 extern uint64 sys_mkdir(void);
 extern uint64 sys_close(void);
-extern uint64 sys_sigalarm(void);
-extern uint64 sys_sigreturn(void);
 
 // An array mapping syscall numbers from syscall.h
 // to the function that handles the system call.
@@ -128,8 +126,6 @@ static uint64 (*syscalls[])(void) = {
 [SYS_link]    sys_link,
 [SYS_mkdir]   sys_mkdir,
 [SYS_close]   sys_close,
-[SYS_sigalarm]   sys_sigalarm,
-[SYS_sigreturn]   sys_sigreturn,
 };
 
 void

kernel/syscall.h

@@ -20,5 +20,3 @@
 #define SYS_link   19
 #define SYS_mkdir  20
 #define SYS_close  21
-#define SYS_sigalarm    22
-#define SYS_sigreturn   23

kernel/sysproc.c

@@ -55,9 +55,6 @@ sys_sleep(void)
   uint ticks0;
 
   argint(0, &n);
-  if(n < 0)
-    n = 0;
-  backtrace();
   acquire(&tickslock);
   ticks0 = ticks;
   while(ticks - ticks0 < n){
@@ -92,28 +89,3 @@ sys_uptime(void)
   release(&tickslock);
   return xticks;
 }
-
-uint64
-sys_sigalarm(void)
-{
-  int interval;
-  uint64 hdlr;
-  argint(0, &interval); 
-  argaddr(1, &hdlr);
-  struct proc* p = myproc();
-
-  p->alarm_ticks = 0;
-  p->alarm_intrv = interval;
-  p->alarm_hdlr = hdlr;
-
-  return 0;
-}
-
-uint64
-sys_sigreturn(void)
-{
-  struct proc* p = myproc();
-  memmove(p->trapframe, p->trapframe1, sizeof(struct trapframe));
-  p->alarm_ticks = 0;
-  return p->trapframe->a0;
-}

kernel/trap.c

@@ -67,18 +67,6 @@ usertrap(void)
     syscall();
   } else if((which_dev = devintr()) != 0){
     // ok
-    if (which_dev == 2) {
-      acquire(&p->lock);
-      if (p->alarm_intrv) {
-        if (p->alarm_ticks <= p->alarm_intrv)
-          p->alarm_ticks ++;
-        if (p->alarm_intrv == p->alarm_ticks) {
-          memmove(p->trapframe1, p->trapframe, sizeof(struct trapframe));
-          p->trapframe->epc = p->alarm_hdlr;
-        }
-      }
-      release(&p->lock);
-    }
   } else {
     printf("usertrap(): unexpected scause %p pid=%d\n", r_scause(), p->pid);
     printf("            sepc=%p stval=%p\n", r_sepc(), r_stval());

time.txt

@@ -1 +1 @@
-4
+6

user/alarmtest.c

@@ -1,193 +0,0 @@
-//
-// test program for the alarm lab.
-// you can modify this file for testing,
-// but please make sure your kernel
-// modifications pass the original
-// versions of these tests.
-//
-
-#include "kernel/param.h"
-#include "kernel/types.h"
-#include "kernel/stat.h"
-#include "kernel/riscv.h"
-#include "user/user.h"
-
-void test0();
-void test1();
-void test2();
-void test3();
-void periodic();
-void slow_handler();
-void dummy_handler();
-
-int
-main(int argc, char *argv[])
-{
-  test0();
-  test1();
-  test2();
-  test3();
-  exit(0);
-}
-
-volatile static int count;
-
-void
-periodic()
-{
-  count = count + 1;
-  printf("alarm!\n");
-  sigreturn();
-}
-
-// tests whether the kernel calls
-// the alarm handler even a single time.
-void
-test0()
-{
-  int i;
-  printf("test0 start\n");
-  count = 0;
-  sigalarm(2, periodic);
-  for(i = 0; i < 1000*500000; i++){
-    if((i % 1000000) == 0)
-      write(2, ".", 1);
-    if(count > 0)
-      break;
-  }
-  sigalarm(0, 0);
-  if(count > 0){
-    printf("test0 passed\n");
-  } else {
-    printf("\ntest0 failed: the kernel never called the alarm handler\n");
-  }
-}
-
-void __attribute__ ((noinline)) foo(int i, int *j) {
-  if((i % 2500000) == 0) {
-    write(2, ".", 1);
-  }
-  *j += 1;
-}
-
-//
-// tests that the kernel calls the handler multiple times.
-//
-// tests that, when the handler returns, it returns to
-// the point in the program where the timer interrupt
-// occurred, with all registers holding the same values they
-// held when the interrupt occurred.
-//
-void
-test1()
-{
-  int i;
-  int j;
-
-  printf("test1 start\n");
-  count = 0;
-  j = 0;
-  sigalarm(2, periodic);
-  for(i = 0; i < 500000000; i++){
-    if(count >= 10)
-      break;
-    foo(i, &j);
-  }
-  if(count < 10){
-    printf("\ntest1 failed: too few calls to the handler\n");
-  } else if(i != j){
-    // the loop should have called foo() i times, and foo() should
-    // have incremented j once per call, so j should equal i.
-    // once possible source of errors is that the handler may
-    // return somewhere other than where the timer interrupt
-    // occurred; another is that that registers may not be
-    // restored correctly, causing i or j or the address ofj
-    // to get an incorrect value.
-    printf("\ntest1 failed: foo() executed fewer times than it was called\n");
-  } else {
-    printf("test1 passed\n");
-  }
-}
-
-//
-// tests that kernel does not allow reentrant alarm calls.
-void
-test2()
-{
-  int i;
-  int pid;
-  int status;
-
-  printf("test2 start\n");
-  if ((pid = fork()) < 0) {
-    printf("test2: fork failed\n");
-  }
-  if (pid == 0) {
-    count = 0;
-    sigalarm(2, slow_handler);
-    for(i = 0; i < 1000*500000; i++){
-      if((i % 1000000) == 0)
-        write(2, ".", 1);
-      if(count > 0)
-        break;
-    }
-    if (count == 0) {
-      printf("\ntest2 failed: alarm not called\n");
-      exit(1);
-    }
-    exit(0);
-  }
-  wait(&status);
-  if (status == 0) {
-    printf("test2 passed\n");
-  }
-}
-
-void
-slow_handler()
-{
-  count++;
-  printf("alarm!\n");
-  if (count > 1) {
-    printf("test2 failed: alarm handler called more than once\n");
-    exit(1);
-  }
-  for (int i = 0; i < 1000*500000; i++) {
-    asm volatile("nop"); // avoid compiler optimizing away loop
-  }
-  sigalarm(0, 0);
-  sigreturn();
-}
-
-//
-// dummy alarm handler; after running immediately uninstall
-// itself and finish signal handling
-void
-dummy_handler()
-{
-  sigalarm(0, 0);
-  sigreturn();
-}
-
-//
-// tests that the return from sys_sigreturn() does not
-// modify the a0 register
-void
-test3()
-{
-  uint64 a0;
-
-  sigalarm(1, dummy_handler);
-  printf("test3 start\n");
-
-  asm volatile("lui a5, 0");
-  asm volatile("addi a0, a5, 0xac" : : : "a0");
-  for(int i = 0; i < 500000000; i++)
-    ;
-  asm volatile("mv %0, a0" : "=r" (a0) );
-
-  if(a0 != 0xac)
-    printf("test3 failed: register a0 changed\n");
-  else
-    printf("test3 passed\n");
-}

user/bttest.c

@@ -1,10 +0,0 @@
-#include "kernel/types.h"
-#include "kernel/stat.h"
-#include "user/user.h"
-
-int
-main(int argc, char *argv[])
-{
-  sleep(1);
-  exit(0);
-}

user/call.c

@@ -1,17 +0,0 @@
-#include "kernel/param.h"
-#include "kernel/types.h"
-#include "kernel/stat.h"
-#include "user/user.h"
-
-int g(int x) {
-  return x+3;
-}
-
-int f(int x) {
-  return g(x);
-}
-
-void main(void) {
-  printf("%d %d\n", f(8)+1, 13);
-  exit(0);
-}

user/cat.c

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

user/find.c

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

user/grep.c

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

user/ls.c

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

user/pingpong.c

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

user/primes.c

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

user/sleep.c

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

user/user.h

@@ -22,8 +22,6 @@ int getpid(void);
 char* sbrk(int);
 int sleep(int);
 int uptime(void);
-int sigalarm(int ticks, void (*handler)());
-int sigreturn(void);
 
 // ulib.c
 int stat(const char*, struct stat*);

user/usys.pl

@@ -36,5 +36,3 @@ entry("getpid");
 entry("sbrk");
 entry("sleep");
 entry("uptime");
-entry("sigalarm");
-entry("sigreturn");

user/wc.c

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

user/xargs.c

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

user/xargstest.sh

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