separate source into kernel/ user/ mkfs/

user/cat.c

@@ -0,0 +1,43 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+char buf[512];
+
+void
+cat(int fd)
+{
+  int n;
+
+  while((n = read(fd, buf, sizeof(buf))) > 0) {
+    if (write(1, buf, n) != n) {
+      printf(1, "cat: write error\n");
+      exit();
+    }
+  }
+  if(n < 0){
+    printf(1, "cat: read error\n");
+    exit();
+  }
+}
+
+int
+main(int argc, char *argv[])
+{
+  int fd, i;
+
+  if(argc <= 1){
+    cat(0);
+    exit();
+  }
+
+  for(i = 1; i < argc; i++){
+    if((fd = open(argv[i], 0)) < 0){
+      printf(1, "cat: cannot open %s\n", argv[i]);
+      exit();
+    }
+    cat(fd);
+    close(fd);
+  }
+  exit();
+}

user/echo.c

@@ -0,0 +1,13 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char *argv[])
+{
+  int i;
+
+  for(i = 1; i < argc; i++)
+    printf(1, "%s%s", argv[i], i+1 < argc ? " " : "\n");
+  exit();
+}

user/forktest.c

@@ -0,0 +1,56 @@
+// Test that fork fails gracefully.
+// Tiny executable so that the limit can be filling the proc table.
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+#define N  1000
+
+void
+printf(int fd, const char *s, ...)
+{
+  write(fd, s, strlen(s));
+}
+
+void
+forktest(void)
+{
+  int n, pid;
+
+  printf(1, "fork test\n");
+
+  for(n=0; n<N; n++){
+    pid = fork();
+    if(pid < 0)
+      break;
+    if(pid == 0)
+      exit();
+  }
+
+  if(n == N){
+    printf(1, "fork claimed to work N times!\n", N);
+    exit();
+  }
+
+  for(; n > 0; n--){
+    if(wait() < 0){
+      printf(1, "wait stopped early\n");
+      exit();
+    }
+  }
+
+  if(wait() != -1){
+    printf(1, "wait got too many\n");
+    exit();
+  }
+
+  printf(1, "fork test OK\n");
+}
+
+int
+main(void)
+{
+  forktest();
+  exit();
+}

user/grep.c

@@ -0,0 +1,107 @@
+// Simple grep.  Only supports ^ . * $ operators.
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+char buf[1024];
+int match(char*, char*);
+
+void
+grep(char *pattern, int fd)
+{
+  int n, m;
+  char *p, *q;
+
+  m = 0;
+  while((n = read(fd, buf+m, sizeof(buf)-m-1)) > 0){
+    m += n;
+    buf[m] = '\0';
+    p = buf;
+    while((q = strchr(p, '\n')) != 0){
+      *q = 0;
+      if(match(pattern, p)){
+        *q = '\n';
+        write(1, p, q+1 - p);
+      }
+      p = q+1;
+    }
+    if(p == buf)
+      m = 0;
+    if(m > 0){
+      m -= p - buf;
+      memmove(buf, p, m);
+    }
+  }
+}
+
+int
+main(int argc, char *argv[])
+{
+  int fd, i;
+  char *pattern;
+
+  if(argc <= 1){
+    printf(2, "usage: grep pattern [file ...]\n");
+    exit();
+  }
+  pattern = argv[1];
+
+  if(argc <= 2){
+    grep(pattern, 0);
+    exit();
+  }
+
+  for(i = 2; i < argc; i++){
+    if((fd = open(argv[i], 0)) < 0){
+      printf(1, "grep: cannot open %s\n", argv[i]);
+      exit();
+    }
+    grep(pattern, fd);
+    close(fd);
+  }
+  exit();
+}
+
+// Regexp matcher from Kernighan & Pike,
+// The Practice of Programming, Chapter 9.
+
+int matchhere(char*, char*);
+int matchstar(int, char*, char*);
+
+int
+match(char *re, char *text)
+{
+  if(re[0] == '^')
+    return matchhere(re+1, text);
+  do{  // must look at empty string
+    if(matchhere(re, text))
+      return 1;
+  }while(*text++ != '\0');
+  return 0;
+}
+
+// matchhere: search for re at beginning of text
+int matchhere(char *re, char *text)
+{
+  if(re[0] == '\0')
+    return 1;
+  if(re[1] == '*')
+    return matchstar(re[0], re+2, text);
+  if(re[0] == '$' && re[1] == '\0')
+    return *text == '\0';
+  if(*text!='\0' && (re[0]=='.' || re[0]==*text))
+    return matchhere(re+1, text+1);
+  return 0;
+}
+
+// matchstar: search for c*re at beginning of text
+int matchstar(int c, char *re, char *text)
+{
+  do{  // a * matches zero or more instances
+    if(matchhere(re, text))
+      return 1;
+  }while(*text!='\0' && (*text++==c || c=='.'));
+  return 0;
+}
+

user/init.c

@@ -0,0 +1,37 @@
+// init: The initial user-level program
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fcntl.h"
+
+char *argv[] = { "sh", 0 };
+
+int
+main(void)
+{
+  int pid, wpid;
+
+  if(open("console", O_RDWR) < 0){
+    mknod("console", 1, 1);
+    open("console", O_RDWR);
+  }
+  dup(0);  // stdout
+  dup(0);  // stderr
+
+  for(;;){
+    printf(1, "init: starting sh\n");
+    pid = fork();
+    if(pid < 0){
+      printf(1, "init: fork failed\n");
+      exit();
+    }
+    if(pid == 0){
+      exec("sh", argv);
+      printf(1, "init: exec sh failed\n");
+      exit();
+    }
+    while((wpid=wait()) >= 0 && wpid != pid)
+      printf(1, "zombie!\n");
+  }
+}

user/initcode.S

@@ -0,0 +1,28 @@
+# Initial process execs /init.
+# This code runs in user space.
+
+#include "syscall.h"
+
+# exec(init, argv)
+.globl start
+start:
+        la a0, init
+        la a1, argv
+        li a7, SYS_exec
+        ecall
+
+# for(;;) exit();
+exit:
+        li a7, SYS_exit
+        ecall
+        jal exit
+
+# char init[] = "/init\0";
+init:
+  .string "/init\0"
+
+# char *argv[] = { init, 0 };
+.p2align 2
+argv:
+  .long init
+  .long 0

user/kill.c

@@ -0,0 +1,17 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char **argv)
+{
+  int i;
+
+  if(argc < 2){
+    printf(2, "usage: kill pid...\n");
+    exit();
+  }
+  for(i=1; i<argc; i++)
+    kill(atoi(argv[i]));
+  exit();
+}

user/ln.c

@@ -0,0 +1,15 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char *argv[])
+{
+  if(argc != 3){
+    printf(2, "Usage: ln old new\n");
+    exit();
+  }
+  if(link(argv[1], argv[2]) < 0)
+    printf(2, "link %s %s: failed\n", argv[1], argv[2]);
+  exit();
+}

user/ls.c

@@ -0,0 +1,85 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fs.h"
+
+char*
+fmtname(char *path)
+{
+  static char buf[DIRSIZ+1];
+  char *p;
+
+  // Find first character after last slash.
+  for(p=path+strlen(path); p >= path && *p != '/'; p--)
+    ;
+  p++;
+
+  // Return blank-padded name.
+  if(strlen(p) >= DIRSIZ)
+    return p;
+  memmove(buf, p, strlen(p));
+  memset(buf+strlen(p), ' ', DIRSIZ-strlen(p));
+  return buf;
+}
+
+void
+ls(char *path)
+{
+  char buf[512], *p;
+  int fd;
+  struct dirent de;
+  struct stat st;
+
+  if((fd = open(path, 0)) < 0){
+    printf(2, "ls: cannot open %s\n", path);
+    return;
+  }
+
+  if(fstat(fd, &st) < 0){
+    printf(2, "ls: cannot stat %s\n", path);
+    close(fd);
+    return;
+  }
+
+  switch(st.type){
+  case T_FILE:
+    printf(1, "%s %d %d %d\n", fmtname(path), st.type, st.ino, st.size);
+    break;
+
+  case T_DIR:
+    if(strlen(path) + 1 + DIRSIZ + 1 > sizeof buf){
+      printf(1, "ls: 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;
+      memmove(p, de.name, DIRSIZ);
+      p[DIRSIZ] = 0;
+      if(stat(buf, &st) < 0){
+        printf(1, "ls: cannot stat %s\n", buf);
+        continue;
+      }
+      printf(1, "%s %d %d %d\n", fmtname(buf), st.type, st.ino, st.size);
+    }
+    break;
+  }
+  close(fd);
+}
+
+int
+main(int argc, char *argv[])
+{
+  int i;
+
+  if(argc < 2){
+    ls(".");
+    exit();
+  }
+  for(i=1; i<argc; i++)
+    ls(argv[i]);
+  exit();
+}

user/mkdir.c

@@ -0,0 +1,23 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char *argv[])
+{
+  int i;
+
+  if(argc < 2){
+    printf(2, "Usage: mkdir files...\n");
+    exit();
+  }
+
+  for(i = 1; i < argc; i++){
+    if(mkdir(argv[i]) < 0){
+      printf(2, "mkdir: %s failed to create\n", argv[i]);
+      break;
+    }
+  }
+
+  exit();
+}

user/printf.c

@@ -0,0 +1,95 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+#include <stdarg.h>
+
+static char digits[] = "0123456789ABCDEF";
+
+static void
+putc(int fd, char c)
+{
+  write(fd, &c, 1);
+}
+
+static void
+printint(int fd, int xx, int base, int sgn)
+{
+  char buf[16];
+  int i, neg;
+  uint x;
+
+  neg = 0;
+  if(sgn && xx < 0){
+    neg = 1;
+    x = -xx;
+  } else {
+    x = xx;
+  }
+
+  i = 0;
+  do{
+    buf[i++] = digits[x % base];
+  }while((x /= base) != 0);
+  if(neg)
+    buf[i++] = '-';
+
+  while(--i >= 0)
+    putc(fd, buf[i]);
+}
+
+static void
+printptr(int fd, uint64 x) {
+  int i;
+  putc(fd, '0');
+  putc(fd, 'x');
+  for (i = 0; i < (sizeof(uint64) * 2); i++, x <<= 4)
+    putc(fd, digits[x >> (sizeof(uint64) * 8 - 4)]);
+}
+
+// Print to the given fd. Only understands %d, %x, %p, %s.
+void
+printf(int fd, const char *fmt, ...)
+{
+  va_list ap;
+  char *s;
+  int c, i, state;
+
+  va_start(ap, fmt);
+  state = 0;
+  for(i = 0; fmt[i]; i++){
+    c = fmt[i] & 0xff;
+    if(state == 0){
+      if(c == '%'){
+        state = '%';
+      } else {
+        putc(fd, c);
+      }
+    } else if(state == '%'){
+      if(c == 'd'){
+        printint(fd, va_arg(ap, int), 10, 1);
+      } else if(c == 'x') {
+        printint(fd, va_arg(ap, int), 16, 0);
+      } else if(c == 'p') {
+        printptr(fd, va_arg(ap, uint64));
+      } else if(c == 's'){
+        s = va_arg(ap, char*);
+        if(s == 0)
+          s = "(null)";
+        while(*s != 0){
+          putc(fd, *s);
+          s++;
+        }
+      } else if(c == 'c'){
+        putc(fd, va_arg(ap, uint));
+      } else if(c == '%'){
+        putc(fd, c);
+      } else {
+        // Unknown % sequence.  Print it to draw attention.
+        putc(fd, '%');
+        putc(fd, c);
+      }
+      state = 0;
+    }
+  }
+}

user/rm.c

@@ -0,0 +1,23 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(int argc, char *argv[])
+{
+  int i;
+
+  if(argc < 2){
+    printf(2, "Usage: rm files...\n");
+    exit();
+  }
+
+  for(i = 1; i < argc; i++){
+    if(unlink(argv[i]) < 0){
+      printf(2, "rm: %s failed to delete\n", argv[i]);
+      break;
+    }
+  }
+
+  exit();
+}

user/sh.c

@@ -0,0 +1,493 @@
+// Shell.
+
+#include "kernel/types.h"
+#include "user/user.h"
+#include "kernel/fcntl.h"
+
+// Parsed command representation
+#define EXEC  1
+#define REDIR 2
+#define PIPE  3
+#define LIST  4
+#define BACK  5
+
+#define MAXARGS 10
+
+struct cmd {
+  int type;
+};
+
+struct execcmd {
+  int type;
+  char *argv[MAXARGS];
+  char *eargv[MAXARGS];
+};
+
+struct redircmd {
+  int type;
+  struct cmd *cmd;
+  char *file;
+  char *efile;
+  int mode;
+  int fd;
+};
+
+struct pipecmd {
+  int type;
+  struct cmd *left;
+  struct cmd *right;
+};
+
+struct listcmd {
+  int type;
+  struct cmd *left;
+  struct cmd *right;
+};
+
+struct backcmd {
+  int type;
+  struct cmd *cmd;
+};
+
+int fork1(void);  // Fork but panics on failure.
+void panic(char*);
+struct cmd *parsecmd(char*);
+
+// Execute cmd.  Never returns.
+void
+runcmd(struct cmd *cmd)
+{
+  int p[2];
+  struct backcmd *bcmd;
+  struct execcmd *ecmd;
+  struct listcmd *lcmd;
+  struct pipecmd *pcmd;
+  struct redircmd *rcmd;
+
+  if(cmd == 0)
+    exit();
+
+  switch(cmd->type){
+  default:
+    panic("runcmd");
+
+  case EXEC:
+    ecmd = (struct execcmd*)cmd;
+    if(ecmd->argv[0] == 0)
+      exit();
+    exec(ecmd->argv[0], ecmd->argv);
+    printf(2, "exec %s failed\n", ecmd->argv[0]);
+    break;
+
+  case REDIR:
+    rcmd = (struct redircmd*)cmd;
+    close(rcmd->fd);
+    if(open(rcmd->file, rcmd->mode) < 0){
+      printf(2, "open %s failed\n", rcmd->file);
+      exit();
+    }
+    runcmd(rcmd->cmd);
+    break;
+
+  case LIST:
+    lcmd = (struct listcmd*)cmd;
+    if(fork1() == 0)
+      runcmd(lcmd->left);
+    wait();
+    runcmd(lcmd->right);
+    break;
+
+  case PIPE:
+    pcmd = (struct pipecmd*)cmd;
+    if(pipe(p) < 0)
+      panic("pipe");
+    if(fork1() == 0){
+      close(1);
+      dup(p[1]);
+      close(p[0]);
+      close(p[1]);
+      runcmd(pcmd->left);
+    }
+    if(fork1() == 0){
+      close(0);
+      dup(p[0]);
+      close(p[0]);
+      close(p[1]);
+      runcmd(pcmd->right);
+    }
+    close(p[0]);
+    close(p[1]);
+    wait();
+    wait();
+    break;
+
+  case BACK:
+    bcmd = (struct backcmd*)cmd;
+    if(fork1() == 0)
+      runcmd(bcmd->cmd);
+    break;
+  }
+  exit();
+}
+
+int
+getcmd(char *buf, int nbuf)
+{
+  printf(2, "$ ");
+  memset(buf, 0, nbuf);
+  gets(buf, nbuf);
+  if(buf[0] == 0) // EOF
+    return -1;
+  return 0;
+}
+
+int
+main(void)
+{
+  static char buf[100];
+  int fd;
+
+  // Ensure that three file descriptors are open.
+  while((fd = open("console", O_RDWR)) >= 0){
+    if(fd >= 3){
+      close(fd);
+      break;
+    }
+  }
+
+  // Read and run input commands.
+  while(getcmd(buf, sizeof(buf)) >= 0){
+    if(buf[0] == 'c' && buf[1] == 'd' && buf[2] == ' '){
+      // Chdir must be called by the parent, not the child.
+      buf[strlen(buf)-1] = 0;  // chop \n
+      if(chdir(buf+3) < 0)
+        printf(2, "cannot cd %s\n", buf+3);
+      continue;
+    }
+    if(fork1() == 0)
+      runcmd(parsecmd(buf));
+    wait();
+  }
+  exit();
+}
+
+void
+panic(char *s)
+{
+  printf(2, "%s\n", s);
+  exit();
+}
+
+int
+fork1(void)
+{
+  int pid;
+
+  pid = fork();
+  if(pid == -1)
+    panic("fork");
+  return pid;
+}
+
+//PAGEBREAK!
+// Constructors
+
+struct cmd*
+execcmd(void)
+{
+  struct execcmd *cmd;
+
+  cmd = malloc(sizeof(*cmd));
+  memset(cmd, 0, sizeof(*cmd));
+  cmd->type = EXEC;
+  return (struct cmd*)cmd;
+}
+
+struct cmd*
+redircmd(struct cmd *subcmd, char *file, char *efile, int mode, int fd)
+{
+  struct redircmd *cmd;
+
+  cmd = malloc(sizeof(*cmd));
+  memset(cmd, 0, sizeof(*cmd));
+  cmd->type = REDIR;
+  cmd->cmd = subcmd;
+  cmd->file = file;
+  cmd->efile = efile;
+  cmd->mode = mode;
+  cmd->fd = fd;
+  return (struct cmd*)cmd;
+}
+
+struct cmd*
+pipecmd(struct cmd *left, struct cmd *right)
+{
+  struct pipecmd *cmd;
+
+  cmd = malloc(sizeof(*cmd));
+  memset(cmd, 0, sizeof(*cmd));
+  cmd->type = PIPE;
+  cmd->left = left;
+  cmd->right = right;
+  return (struct cmd*)cmd;
+}
+
+struct cmd*
+listcmd(struct cmd *left, struct cmd *right)
+{
+  struct listcmd *cmd;
+
+  cmd = malloc(sizeof(*cmd));
+  memset(cmd, 0, sizeof(*cmd));
+  cmd->type = LIST;
+  cmd->left = left;
+  cmd->right = right;
+  return (struct cmd*)cmd;
+}
+
+struct cmd*
+backcmd(struct cmd *subcmd)
+{
+  struct backcmd *cmd;
+
+  cmd = malloc(sizeof(*cmd));
+  memset(cmd, 0, sizeof(*cmd));
+  cmd->type = BACK;
+  cmd->cmd = subcmd;
+  return (struct cmd*)cmd;
+}
+//PAGEBREAK!
+// Parsing
+
+char whitespace[] = " \t\r\n\v";
+char symbols[] = "<|>&;()";
+
+int
+gettoken(char **ps, char *es, char **q, char **eq)
+{
+  char *s;
+  int ret;
+
+  s = *ps;
+  while(s < es && strchr(whitespace, *s))
+    s++;
+  if(q)
+    *q = s;
+  ret = *s;
+  switch(*s){
+  case 0:
+    break;
+  case '|':
+  case '(':
+  case ')':
+  case ';':
+  case '&':
+  case '<':
+    s++;
+    break;
+  case '>':
+    s++;
+    if(*s == '>'){
+      ret = '+';
+      s++;
+    }
+    break;
+  default:
+    ret = 'a';
+    while(s < es && !strchr(whitespace, *s) && !strchr(symbols, *s))
+      s++;
+    break;
+  }
+  if(eq)
+    *eq = s;
+
+  while(s < es && strchr(whitespace, *s))
+    s++;
+  *ps = s;
+  return ret;
+}
+
+int
+peek(char **ps, char *es, char *toks)
+{
+  char *s;
+
+  s = *ps;
+  while(s < es && strchr(whitespace, *s))
+    s++;
+  *ps = s;
+  return *s && strchr(toks, *s);
+}
+
+struct cmd *parseline(char**, char*);
+struct cmd *parsepipe(char**, char*);
+struct cmd *parseexec(char**, char*);
+struct cmd *nulterminate(struct cmd*);
+
+struct cmd*
+parsecmd(char *s)
+{
+  char *es;
+  struct cmd *cmd;
+
+  es = s + strlen(s);
+  cmd = parseline(&s, es);
+  peek(&s, es, "");
+  if(s != es){
+    printf(2, "leftovers: %s\n", s);
+    panic("syntax");
+  }
+  nulterminate(cmd);
+  return cmd;
+}
+
+struct cmd*
+parseline(char **ps, char *es)
+{
+  struct cmd *cmd;
+
+  cmd = parsepipe(ps, es);
+  while(peek(ps, es, "&")){
+    gettoken(ps, es, 0, 0);
+    cmd = backcmd(cmd);
+  }
+  if(peek(ps, es, ";")){
+    gettoken(ps, es, 0, 0);
+    cmd = listcmd(cmd, parseline(ps, es));
+  }
+  return cmd;
+}
+
+struct cmd*
+parsepipe(char **ps, char *es)
+{
+  struct cmd *cmd;
+
+  cmd = parseexec(ps, es);
+  if(peek(ps, es, "|")){
+    gettoken(ps, es, 0, 0);
+    cmd = pipecmd(cmd, parsepipe(ps, es));
+  }
+  return cmd;
+}
+
+struct cmd*
+parseredirs(struct cmd *cmd, char **ps, char *es)
+{
+  int tok;
+  char *q, *eq;
+
+  while(peek(ps, es, "<>")){
+    tok = gettoken(ps, es, 0, 0);
+    if(gettoken(ps, es, &q, &eq) != 'a')
+      panic("missing file for redirection");
+    switch(tok){
+    case '<':
+      cmd = redircmd(cmd, q, eq, O_RDONLY, 0);
+      break;
+    case '>':
+      cmd = redircmd(cmd, q, eq, O_WRONLY|O_CREATE, 1);
+      break;
+    case '+':  // >>
+      cmd = redircmd(cmd, q, eq, O_WRONLY|O_CREATE, 1);
+      break;
+    }
+  }
+  return cmd;
+}
+
+struct cmd*
+parseblock(char **ps, char *es)
+{
+  struct cmd *cmd;
+
+  if(!peek(ps, es, "("))
+    panic("parseblock");
+  gettoken(ps, es, 0, 0);
+  cmd = parseline(ps, es);
+  if(!peek(ps, es, ")"))
+    panic("syntax - missing )");
+  gettoken(ps, es, 0, 0);
+  cmd = parseredirs(cmd, ps, es);
+  return cmd;
+}
+
+struct cmd*
+parseexec(char **ps, char *es)
+{
+  char *q, *eq;
+  int tok, argc;
+  struct execcmd *cmd;
+  struct cmd *ret;
+
+  if(peek(ps, es, "("))
+    return parseblock(ps, es);
+
+  ret = execcmd();
+  cmd = (struct execcmd*)ret;
+
+  argc = 0;
+  ret = parseredirs(ret, ps, es);
+  while(!peek(ps, es, "|)&;")){
+    if((tok=gettoken(ps, es, &q, &eq)) == 0)
+      break;
+    if(tok != 'a')
+      panic("syntax");
+    cmd->argv[argc] = q;
+    cmd->eargv[argc] = eq;
+    argc++;
+    if(argc >= MAXARGS)
+      panic("too many args");
+    ret = parseredirs(ret, ps, es);
+  }
+  cmd->argv[argc] = 0;
+  cmd->eargv[argc] = 0;
+  return ret;
+}
+
+// NUL-terminate all the counted strings.
+struct cmd*
+nulterminate(struct cmd *cmd)
+{
+  int i;
+  struct backcmd *bcmd;
+  struct execcmd *ecmd;
+  struct listcmd *lcmd;
+  struct pipecmd *pcmd;
+  struct redircmd *rcmd;
+
+  if(cmd == 0)
+    return 0;
+
+  switch(cmd->type){
+  case EXEC:
+    ecmd = (struct execcmd*)cmd;
+    for(i=0; ecmd->argv[i]; i++)
+      *ecmd->eargv[i] = 0;
+    break;
+
+  case REDIR:
+    rcmd = (struct redircmd*)cmd;
+    nulterminate(rcmd->cmd);
+    *rcmd->efile = 0;
+    break;
+
+  case PIPE:
+    pcmd = (struct pipecmd*)cmd;
+    nulterminate(pcmd->left);
+    nulterminate(pcmd->right);
+    break;
+
+  case LIST:
+    lcmd = (struct listcmd*)cmd;
+    nulterminate(lcmd->left);
+    nulterminate(lcmd->right);
+    break;
+
+  case BACK:
+    bcmd = (struct backcmd*)cmd;
+    nulterminate(bcmd->cmd);
+    break;
+  }
+  return cmd;
+}

user/stressfs.c

@@ -0,0 +1,49 @@
+// Demonstrate that moving the "acquire" in iderw after the loop that
+// appends to the idequeue results in a race.
+
+// For this to work, you should also add a spin within iderw's
+// idequeue traversal loop.  Adding the following demonstrated a panic
+// after about 5 runs of stressfs in QEMU on a 2.1GHz CPU:
+//    for (i = 0; i < 40000; i++)
+//      asm volatile("");
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/fs.h"
+#include "kernel/fcntl.h"
+
+int
+main(int argc, char *argv[])
+{
+  int fd, i;
+  char path[] = "stressfs0";
+  char data[512];
+
+  printf(1, "stressfs starting\n");
+  memset(data, 'a', sizeof(data));
+
+  for(i = 0; i < 4; i++)
+    if(fork() > 0)
+      break;
+
+  printf(1, "write %d\n", i);
+
+  path[8] += i;
+  fd = open(path, O_CREATE | O_RDWR);
+  for(i = 0; i < 20; i++)
+//    printf(fd, "%d\n", i);
+    write(fd, data, sizeof(data));
+  close(fd);
+
+  printf(1, "read\n");
+
+  fd = open(path, O_RDONLY);
+  for (i = 0; i < 20; i++)
+    read(fd, data, sizeof(data));
+  close(fd);
+
+  wait();
+
+  exit();
+}

user/ulib.c

@@ -0,0 +1,109 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "kernel/fcntl.h"
+#include "user/user.h"
+
+char*
+strcpy(char *s, const char *t)
+{
+  char *os;
+
+  os = s;
+  while((*s++ = *t++) != 0)
+    ;
+  return os;
+}
+
+int
+strcmp(const char *p, const char *q)
+{
+  while(*p && *p == *q)
+    p++, q++;
+  return (uchar)*p - (uchar)*q;
+}
+
+uint
+strlen(const char *s)
+{
+  int n;
+
+  for(n = 0; s[n]; n++)
+    ;
+  return n;
+}
+
+void*
+memset(void *dst, int c, uint n)
+{
+  char *cdst = (char *) dst;
+  int i;
+  for(i = 0; i < n; i++){
+    cdst[i] = c;
+  }
+  return dst;
+}
+
+char*
+strchr(const char *s, char c)
+{
+  for(; *s; s++)
+    if(*s == c)
+      return (char*)s;
+  return 0;
+}
+
+char*
+gets(char *buf, int max)
+{
+  int i, cc;
+  char c;
+
+  for(i=0; i+1 < max; ){
+    cc = read(0, &c, 1);
+    if(cc < 1)
+      break;
+    buf[i++] = c;
+    if(c == '\n' || c == '\r')
+      break;
+  }
+  buf[i] = '\0';
+  return buf;
+}
+
+int
+stat(const char *n, struct stat *st)
+{
+  int fd;
+  int r;
+
+  fd = open(n, O_RDONLY);
+  if(fd < 0)
+    return -1;
+  r = fstat(fd, st);
+  close(fd);
+  return r;
+}
+
+int
+atoi(const char *s)
+{
+  int n;
+
+  n = 0;
+  while('0' <= *s && *s <= '9')
+    n = n*10 + *s++ - '0';
+  return n;
+}
+
+void*
+memmove(void *vdst, const void *vsrc, int n)
+{
+  char *dst;
+  const char *src;
+
+  dst = vdst;
+  src = vsrc;
+  while(n-- > 0)
+    *dst++ = *src++;
+  return vdst;
+}

user/umalloc.c

@@ -0,0 +1,90 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+#include "kernel/param.h"
+
+// Memory allocator by Kernighan and Ritchie,
+// The C programming Language, 2nd ed.  Section 8.7.
+
+typedef long Align;
+
+union header {
+  struct {
+    union header *ptr;
+    uint size;
+  } s;
+  Align x;
+};
+
+typedef union header Header;
+
+static Header base;
+static Header *freep;
+
+void
+free(void *ap)
+{
+  Header *bp, *p;
+
+  bp = (Header*)ap - 1;
+  for(p = freep; !(bp > p && bp < p->s.ptr); p = p->s.ptr)
+    if(p >= p->s.ptr && (bp > p || bp < p->s.ptr))
+      break;
+  if(bp + bp->s.size == p->s.ptr){
+    bp->s.size += p->s.ptr->s.size;
+    bp->s.ptr = p->s.ptr->s.ptr;
+  } else
+    bp->s.ptr = p->s.ptr;
+  if(p + p->s.size == bp){
+    p->s.size += bp->s.size;
+    p->s.ptr = bp->s.ptr;
+  } else
+    p->s.ptr = bp;
+  freep = p;
+}
+
+static Header*
+morecore(uint nu)
+{
+  char *p;
+  Header *hp;
+
+  if(nu < 4096)
+    nu = 4096;
+  p = sbrk(nu * sizeof(Header));
+  if(p == (char*)-1)
+    return 0;
+  hp = (Header*)p;
+  hp->s.size = nu;
+  free((void*)(hp + 1));
+  return freep;
+}
+
+void*
+malloc(uint nbytes)
+{
+  Header *p, *prevp;
+  uint nunits;
+
+  nunits = (nbytes + sizeof(Header) - 1)/sizeof(Header) + 1;
+  if((prevp = freep) == 0){
+    base.s.ptr = freep = prevp = &base;
+    base.s.size = 0;
+  }
+  for(p = prevp->s.ptr; ; prevp = p, p = p->s.ptr){
+    if(p->s.size >= nunits){
+      if(p->s.size == nunits)
+        prevp->s.ptr = p->s.ptr;
+      else {
+        p->s.size -= nunits;
+        p += p->s.size;
+        p->s.size = nunits;
+      }
+      freep = prevp;
+      return (void*)(p + 1);
+    }
+    if(p == freep)
+      if((p = morecore(nunits)) == 0)
+        return 0;
+  }
+}

user/user.h

@@ -0,0 +1,39 @@
+struct stat;
+struct rtcdate;
+
+// system calls
+int fork(void);
+int exit(void) __attribute__((noreturn));
+int wait(void);
+int pipe(int*);
+int write(int, const void*, int);
+int read(int, void*, int);
+int close(int);
+int kill(int);
+int exec(char*, char**);
+int open(const char*, int);
+int mknod(const char*, short, short);
+int unlink(const char*);
+int fstat(int fd, struct stat*);
+int link(const char*, const char*);
+int mkdir(const char*);
+int chdir(const char*);
+int dup(int);
+int getpid(void);
+char* sbrk(int);
+int sleep(int);
+int uptime(void);
+
+// ulib.c
+int stat(const char*, struct stat*);
+char* strcpy(char*, const char*);
+void *memmove(void*, const void*, int);
+char* strchr(const char*, char c);
+int strcmp(const char*, const char*);
+void printf(int, const char*, ...);
+char* gets(char*, int max);
+uint strlen(const char*);
+void* memset(void*, int, uint);
+void* malloc(uint);
+void free(void*);
+int atoi(const char*);

user/usys.pl

@@ -0,0 +1,38 @@
+#!/usr/bin/perl -w
+
+# Generate usys.S, the stubs for syscalls.
+
+print "# generated by usys.pl - do not edit\n";
+
+print "#include \"kernel/syscall.h\"\n";
+
+sub entry {
+    my $name = shift;
+    print ".global $name\n";
+    print "${name}:\n";
+    print " li a7, SYS_${name}\n";
+    print " ecall\n";
+    print " ret\n";
+}
+	
+entry("fork");
+entry("exit");
+entry("wait");
+entry("pipe");
+entry("read");
+entry("write");
+entry("close");
+entry("kill");
+entry("exec");
+entry("open");
+entry("mknod");
+entry("unlink");
+entry("fstat");
+entry("link");
+entry("mkdir");
+entry("chdir");
+entry("dup");
+entry("getpid");
+entry("sbrk");
+entry("sleep");
+entry("uptime");

user/wc.c

@@ -0,0 +1,54 @@
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+char buf[512];
+
+void
+wc(int fd, char *name)
+{
+  int i, n;
+  int l, w, c, inword;
+
+  l = w = c = 0;
+  inword = 0;
+  while((n = read(fd, buf, sizeof(buf))) > 0){
+    for(i=0; i<n; i++){
+      c++;
+      if(buf[i] == '\n')
+        l++;
+      if(strchr(" \r\t\n\v", buf[i]))
+        inword = 0;
+      else if(!inword){
+        w++;
+        inword = 1;
+      }
+    }
+  }
+  if(n < 0){
+    printf(1, "wc: read error\n");
+    exit();
+  }
+  printf(1, "%d %d %d %s\n", l, w, c, name);
+}
+
+int
+main(int argc, char *argv[])
+{
+  int fd, i;
+
+  if(argc <= 1){
+    wc(0, "");
+    exit();
+  }
+
+  for(i = 1; i < argc; i++){
+    if((fd = open(argv[i], 0)) < 0){
+      printf(1, "wc: cannot open %s\n", argv[i]);
+      exit();
+    }
+    wc(fd, argv[i]);
+    close(fd);
+  }
+  exit();
+}

user/zombie.c

@@ -0,0 +1,14 @@
+// Create a zombie process that
+// must be reparented at exit.
+
+#include "kernel/types.h"
+#include "kernel/stat.h"
+#include "user/user.h"
+
+int
+main(void)
+{
+  if(fork() > 0)
+    sleep(5);  // Let child exit before parent.
+  exit();
+}