#include "kernel/param.h"
#include "kernel/types.h"
#include "kernel/stat.h"
#include "user/user.h"
#include "kernel/fs.h"
#include "kernel/fcntl.h"
#include "kernel/syscall.h"
#include "kernel/memlayout.h"
#include "kernel/riscv.h"

//
// Tests xv6 system calls.  usertests without arguments runs them all
// and usertests <name> runs <name> test. The test runner creates for
// each test a process and based on the exit status of the process,
// the test runner reports "OK" or "FAILED".  Some tests result in
// kernel printing usertrap messages, which can be ignored if test
// prints "OK".
//

#define BUFSZ (MAXOPBLOCKS + 2) * BSIZE

char buf[BUFSZ];
char name[3];

// what if you pass ridiculous pointers to system calls
// that read user memory with copyin?
void copyin(char *s)
{
  uint64 addrs[] = {0x80000000LL, 0xffffffffffffffff};

  for (int ai = 0; ai < 2; ai++)
  {
    uint64 addr = addrs[ai];

    int fd = open("copyin1", O_CREATE | O_WRONLY);
    if (fd < 0)
    {
      printf("open(copyin1) failed\n");
      exit(1);
    }
    int n = write(fd, (void *)addr, 8192);
    if (n >= 0)
    {
      printf("write(fd, %p, 8192) returned %d, not -1\n", addr, n);
      exit(1);
    }
    close(fd);
    unlink("copyin1");

    n = write(1, (char *)addr, 8192);
    if (n > 0)
    {
      printf("write(1, %p, 8192) returned %d, not -1 or 0\n", addr, n);
      exit(1);
    }

    int fds[2];
    if (pipe(fds) < 0)
    {
      printf("pipe() failed\n");
      exit(1);
    }
    n = write(fds[1], (char *)addr, 8192);
    if (n > 0)
    {
      printf("write(pipe, %p, 8192) returned %d, not -1 or 0\n", addr, n);
      exit(1);
    }
    close(fds[0]);
    close(fds[1]);
  }
}

// what if you pass ridiculous pointers to system calls
// that write user memory with copyout?
void copyout(char *s)
{
  uint64 addrs[] = {0x80000000LL, 0xffffffffffffffff};

  for (int ai = 0; ai < 2; ai++)
  {
    uint64 addr = addrs[ai];

    int fd = open("README", 0);
    if (fd < 0)
    {
      printf("open(README) failed\n");
      exit(1);
    }
    int n = read(fd, (void *)addr, 8192);
    if (n > 0)
    {
      printf("read(fd, %p, 8192) returned %d, not -1 or 0\n", addr, n);
      exit(1);
    }
    close(fd);

    int fds[2];
    if (pipe(fds) < 0)
    {
      printf("pipe() failed\n");
      exit(1);
    }
    n = write(fds[1], "x", 1);
    if (n != 1)
    {
      printf("pipe write failed\n");
      exit(1);
    }
    n = read(fds[0], (void *)addr, 8192);
    if (n > 0)
    {
      printf("read(pipe, %p, 8192) returned %d, not -1 or 0\n", addr, n);
      exit(1);
    }
    close(fds[0]);
    close(fds[1]);
  }
}

// what if you pass ridiculous string pointers to system calls?
void copyinstr1(char *s)
{
  uint64 addrs[] = {0x80000000LL, 0xffffffffffffffff};

  for (int ai = 0; ai < 2; ai++)
  {
    uint64 addr = addrs[ai];

    int fd = open((char *)addr, O_CREATE | O_WRONLY);
    if (fd >= 0)
    {
      printf("open(%p) returned %d, not -1\n", addr, fd);
      exit(1);
    }
  }
}

// what if a string system call argument is exactly the size
// of the kernel buffer it is copied into, so that the null
// would fall just beyond the end of the kernel buffer?
void copyinstr2(char *s)
{
  char b[MAXPATH + 1];

  for (int i = 0; i < MAXPATH; i++)
    b[i] = 'x';
  b[MAXPATH] = '\0';

  int ret = unlink(b);
  if (ret != -1)
  {
    printf("unlink(%s) returned %d, not -1\n", b, ret);
    exit(1);
  }

  int fd = open(b, O_CREATE | O_WRONLY);
  if (fd != -1)
  {
    printf("open(%s) returned %d, not -1\n", b, fd);
    exit(1);
  }

  ret = link(b, b);
  if (ret != -1)
  {
    printf("link(%s, %s) returned %d, not -1\n", b, b, ret);
    exit(1);
  }

  char *args[] = {"xx", 0};
  ret = exec(b, args);
  if (ret != -1)
  {
    printf("exec(%s) returned %d, not -1\n", b, fd);
    exit(1);
  }

  int pid = fork();
  if (pid < 0)
  {
    printf("fork failed\n");
    exit(1);
  }
  if (pid == 0)
  {
    static char big[PGSIZE + 1];
    for (int i = 0; i < PGSIZE; i++)
      big[i] = 'x';
    big[PGSIZE] = '\0';
    char *args2[] = {big, big, big, 0};
    ret = exec("echo", args2);
    if (ret != -1)
    {
      printf("exec(echo, BIG) returned %d, not -1\n", fd);
      exit(1);
    }
    exit(747); // OK
  }

  int st = 0;
  wait(&st);
  if (st != 747)
  {
    printf("exec(echo, BIG) succeeded, should have failed\n");
    exit(1);
  }
}

// what if a string argument crosses over the end of last user page?
void copyinstr3(char *s)
{
  sbrk(8192);
  uint64 top = (uint64)sbrk(0);
  if ((top % PGSIZE) != 0)
  {
    sbrk(PGSIZE - (top % PGSIZE));
  }
  top = (uint64)sbrk(0);
  if (top % PGSIZE)
  {
    printf("oops\n");
    exit(1);
  }

  char *b = (char *)(top - 1);
  *b = 'x';

  int ret = unlink(b);
  if (ret != -1)
  {
    printf("unlink(%s) returned %d, not -1\n", b, ret);
    exit(1);
  }

  int fd = open(b, O_CREATE | O_WRONLY);
  if (fd != -1)
  {
    printf("open(%s) returned %d, not -1\n", b, fd);
    exit(1);
  }

  ret = link(b, b);
  if (ret != -1)
  {
    printf("link(%s, %s) returned %d, not -1\n", b, b, ret);
    exit(1);
  }

  char *args[] = {"xx", 0};
  ret = exec(b, args);
  if (ret != -1)
  {
    printf("exec(%s) returned %d, not -1\n", b, fd);
    exit(1);
  }
}

// test O_TRUNC.
void truncate1(char *s)
{
  char buf[32];

  unlink("truncfile");
  int fd1 = open("truncfile", O_CREATE | O_WRONLY | O_TRUNC);
  write(fd1, "abcd", 4);
  close(fd1);

  int fd2 = open("truncfile", O_RDONLY);
  int n = read(fd2, buf, sizeof(buf));
  if (n != 4)
  {
    printf("%s: read %d bytes, wanted 4\n", s, n);
    exit(1);
  }

  fd1 = open("truncfile", O_WRONLY | O_TRUNC);

  int fd3 = open("truncfile", O_RDONLY);
  n = read(fd3, buf, sizeof(buf));
  if (n != 0)
  {
    printf("aaa fd3=%d\n", fd3);
    printf("%s: read %d bytes, wanted 0\n", s, n);
    exit(1);
  }

  n = read(fd2, buf, sizeof(buf));
  if (n != 0)
  {
    printf("bbb fd2=%d\n", fd2);
    printf("%s: read %d bytes, wanted 0\n", s, n);
    exit(1);
  }

  write(fd1, "abcdef", 6);

  n = read(fd3, buf, sizeof(buf));
  if (n != 6)
  {
    printf("%s: read %d bytes, wanted 6\n", s, n);
    exit(1);
  }

  n = read(fd2, buf, sizeof(buf));
  if (n != 2)
  {
    printf("%s: read %d bytes, wanted 2\n", s, n);
    exit(1);
  }

  unlink("truncfile");

  close(fd1);
  close(fd2);
  close(fd3);
}

// write to an open FD whose file has just been truncated.
// this causes a write at an offset beyond the end of the file.
// such writes fail on xv6 (unlike POSIX) but at least
// they don't crash.
void truncate2(char *s)
{
  unlink("truncfile");

  int fd1 = open("truncfile", O_CREATE | O_TRUNC | O_WRONLY);
  write(fd1, "abcd", 4);

  int fd2 = open("truncfile", O_TRUNC | O_WRONLY);

  int n = write(fd1, "x", 1);
  if (n != -1)
  {
    printf("%s: write returned %d, expected -1\n", s, n);
    exit(1);
  }

  unlink("truncfile");
  close(fd1);
  close(fd2);
}

void truncate3(char *s)
{
  int pid, xstatus;

  close(open("truncfile", O_CREATE | O_TRUNC | O_WRONLY));

  pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }

  if (pid == 0)
  {
    for (int i = 0; i < 100; i++)
    {
      char buf[32];
      int fd = open("truncfile", O_WRONLY);
      if (fd < 0)
      {
        printf("%s: open failed\n", s);
        exit(1);
      }
      int n = write(fd, "1234567890", 10);
      if (n != 10)
      {
        printf("%s: write got %d, expected 10\n", s, n);
        exit(1);
      }
      close(fd);
      fd = open("truncfile", O_RDONLY);
      read(fd, buf, sizeof(buf));
      close(fd);
    }
    exit(0);
  }

  for (int i = 0; i < 150; i++)
  {
    int fd = open("truncfile", O_CREATE | O_WRONLY | O_TRUNC);
    if (fd < 0)
    {
      printf("%s: open failed\n", s);
      exit(1);
    }
    int n = write(fd, "xxx", 3);
    if (n != 3)
    {
      printf("%s: write got %d, expected 3\n", s, n);
      exit(1);
    }
    close(fd);
  }

  wait(&xstatus);
  unlink("truncfile");
  exit(xstatus);
}

// does chdir() call iput(p->cwd) in a transaction?
void iputtest(char *s)
{
  if (mkdir("iputdir") < 0)
  {
    printf("%s: mkdir failed\n", s);
    exit(1);
  }
  if (chdir("iputdir") < 0)
  {
    printf("%s: chdir iputdir failed\n", s);
    exit(1);
  }
  if (unlink("../iputdir") < 0)
  {
    printf("%s: unlink ../iputdir failed\n", s);
    exit(1);
  }
  if (chdir("/") < 0)
  {
    printf("%s: chdir / failed\n", s);
    exit(1);
  }
}

// does exit() call iput(p->cwd) in a transaction?
void exitiputtest(char *s)
{
  int pid, xstatus;

  pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  if (pid == 0)
  {
    if (mkdir("iputdir") < 0)
    {
      printf("%s: mkdir failed\n", s);
      exit(1);
    }
    if (chdir("iputdir") < 0)
    {
      printf("%s: child chdir failed\n", s);
      exit(1);
    }
    if (unlink("../iputdir") < 0)
    {
      printf("%s: unlink ../iputdir failed\n", s);
      exit(1);
    }
    exit(0);
  }
  wait(&xstatus);
  exit(xstatus);
}

// does the error path in open() for attempt to write a
// directory call iput() in a transaction?
// needs a hacked kernel that pauses just after the namei()
// call in sys_open():
//    if((ip = namei(path)) == 0)
//      return -1;
//    {
//      int i;
//      for(i = 0; i < 10000; i++)
//        yield();
//    }
void openiputtest(char *s)
{
  int pid, xstatus;

  if (mkdir("oidir") < 0)
  {
    printf("%s: mkdir oidir failed\n", s);
    exit(1);
  }
  pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  if (pid == 0)
  {
    int fd = open("oidir", O_RDWR);
    if (fd >= 0)
    {
      printf("%s: open directory for write succeeded\n", s);
      exit(1);
    }
    exit(0);
  }
  sleep(1);
  if (unlink("oidir") != 0)
  {
    printf("%s: unlink failed\n", s);
    exit(1);
  }
  wait(&xstatus);
  exit(xstatus);
}

// simple file system tests

void opentest(char *s)
{
  int fd;

  fd = open("echo", 0);
  if (fd < 0)
  {
    printf("%s: open echo failed!\n", s);
    exit(1);
  }
  close(fd);
  fd = open("doesnotexist", 0);
  if (fd >= 0)
  {
    printf("%s: open doesnotexist succeeded!\n", s);
    exit(1);
  }
}

void writetest(char *s)
{
  int fd;
  int i;
  enum
  {
    N = 100,
    SZ = 10
  };

  fd = open("small", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: error: creat small failed!\n", s);
    exit(1);
  }
  for (i = 0; i < N; i++)
  {
    if (write(fd, "aaaaaaaaaa", SZ) != SZ)
    {
      printf("%s: error: write aa %d new file failed\n", i);
      exit(1);
    }
    if (write(fd, "bbbbbbbbbb", SZ) != SZ)
    {
      printf("%s: error: write bb %d new file failed\n", i);
      exit(1);
    }
  }
  close(fd);
  fd = open("small", O_RDONLY);
  if (fd < 0)
  {
    printf("%s: error: open small failed!\n", s);
    exit(1);
  }
  i = read(fd, buf, N * SZ * 2);
  if (i != N * SZ * 2)
  {
    printf("%s: read failed\n", s);
    exit(1);
  }
  close(fd);

  if (unlink("small") < 0)
  {
    printf("%s: unlink small failed\n", s);
    exit(1);
  }
}

void writebig(char *s)
{
  int i, fd, n;

  fd = open("big", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: error: creat big failed!\n", s);
    exit(1);
  }

  for (i = 0; i < MAXFILE; i++)
  {
    ((int *)buf)[0] = i;
    if (write(fd, buf, BSIZE) != BSIZE)
    {
      printf("%s: error: write big file failed\n", i);
      exit(1);
    }
  }

  close(fd);

  fd = open("big", O_RDONLY);
  if (fd < 0)
  {
    printf("%s: error: open big failed!\n", s);
    exit(1);
  }

  n = 0;
  for (;;)
  {
    i = read(fd, buf, BSIZE);
    if (i == 0)
    {
      if (n == MAXFILE - 1)
      {
        printf("%s: read only %d blocks from big", n);
        exit(1);
      }
      break;
    }
    else if (i != BSIZE)
    {
      printf("%s: read failed %d\n", i);
      exit(1);
    }
    if (((int *)buf)[0] != n)
    {
      printf("%s: read content of block %d is %d\n",
             n, ((int *)buf)[0]);
      exit(1);
    }
    n++;
  }
  close(fd);
  if (unlink("big") < 0)
  {
    printf("%s: unlink big failed\n", s);
    exit(1);
  }
}

// many creates, followed by unlink test
void createtest(char *s)
{
  int i, fd;
  enum
  {
    N = 52
  };

  name[0] = 'a';
  name[2] = '\0';
  for (i = 0; i < N; i++)
  {
    name[1] = '0' + i;
    fd = open(name, O_CREATE | O_RDWR);
    close(fd);
  }
  name[0] = 'a';
  name[2] = '\0';
  for (i = 0; i < N; i++)
  {
    name[1] = '0' + i;
    unlink(name);
  }
}

void dirtest(char *s)
{
  printf("mkdir test\n");

  if (mkdir("dir0") < 0)
  {
    printf("%s: mkdir failed\n", s);
    exit(1);
  }

  if (chdir("dir0") < 0)
  {
    printf("%s: chdir dir0 failed\n", s);
    exit(1);
  }

  if (chdir("..") < 0)
  {
    printf("%s: chdir .. failed\n", s);
    exit(1);
  }

  if (unlink("dir0") < 0)
  {
    printf("%s: unlink dir0 failed\n", s);
    exit(1);
  }
  printf("%s: mkdir test ok\n");
}

void exectest(char *s)
{
  int fd, xstatus, pid;
  char *echoargv[] = {"echo", "OK", 0};
  char buf[3];

  unlink("echo-ok");
  pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  if (pid == 0)
  {
    close(1);
    fd = open("echo-ok", O_CREATE | O_WRONLY);
    if (fd < 0)
    {
      printf("%s: create failed\n", s);
      exit(1);
    }
    if (fd != 1)
    {
      printf("%s: wrong fd\n", s);
      exit(1);
    }
    if (exec("echo", echoargv) < 0)
    {
      printf("%s: exec echo failed\n", s);
      exit(1);
    }
    // won't get to here
  }
  if (wait(&xstatus) != pid)
  {
    printf("%s: wait failed!\n", s);
  }
  if (xstatus != 0)
    exit(xstatus);

  fd = open("echo-ok", O_RDONLY);
  if (fd < 0)
  {
    printf("%s: open failed\n", s);
    exit(1);
  }
  if (read(fd, buf, 2) != 2)
  {
    printf("%s: read failed\n", s);
    exit(1);
  }
  unlink("echo-ok");
  if (buf[0] == 'O' && buf[1] == 'K')
    exit(0);
  else
  {
    printf("%s: wrong output\n", s);
    exit(1);
  }
}

// simple fork and pipe read/write

void pipe1(char *s)
{
  int fds[2], pid, xstatus;
  int seq, i, n, cc, total;
  enum
  {
    N = 5,
    SZ = 1033
  };

  if (pipe(fds) != 0)
  {
    printf("%s: pipe() failed\n", s);
    exit(1);
  }
  pid = fork();
  seq = 0;
  if (pid == 0)
  {
    close(fds[0]);
    for (n = 0; n < N; n++)
    {
      for (i = 0; i < SZ; i++)
        buf[i] = seq++;
      if (write(fds[1], buf, SZ) != SZ)
      {
        printf("%s: pipe1 oops 1\n", s);
        exit(1);
      }
    }
    exit(0);
  }
  else if (pid > 0)
  {
    close(fds[1]);
    total = 0;
    cc = 1;
    while ((n = read(fds[0], buf, cc)) > 0)
    {
      for (i = 0; i < n; i++)
      {
        if ((buf[i] & 0xff) != (seq++ & 0xff))
        {
          printf("%s: pipe1 oops 2\n", s);
          return;
        }
      }
      total += n;
      cc = cc * 2;
      if (cc > sizeof(buf))
        cc = sizeof(buf);
    }
    if (total != N * SZ)
    {
      printf("%s: pipe1 oops 3 total %d\n", total);
      exit(1);
    }
    close(fds[0]);
    wait(&xstatus);
    exit(xstatus);
  }
  else
  {
    printf("%s: fork() failed\n", s);
    exit(1);
  }
}

// meant to be run w/ at most two CPUs
void preempt(char *s)
{
  int pid1, pid2, pid3;
  int pfds[2];

  pid1 = fork();
  if (pid1 < 0)
  {
    printf("%s: fork failed");
    exit(1);
  }
  if (pid1 == 0)
    for (;;)
      ;

  pid2 = fork();
  if (pid2 < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  if (pid2 == 0)
    for (;;)
      ;

  pipe(pfds);
  pid3 = fork();
  if (pid3 < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  if (pid3 == 0)
  {
    close(pfds[0]);
    if (write(pfds[1], "x", 1) != 1)
      printf("%s: preempt write error");
    close(pfds[1]);
    for (;;)
      ;
  }

  close(pfds[1]);
  if (read(pfds[0], buf, sizeof(buf)) != 1)
  {
    printf("%s: preempt read error");
    return;
  }
  close(pfds[0]);
  printf("kill... ");
  kill(pid1);
  kill(pid2);
  kill(pid3);
  printf("wait... ");
  wait(0);
  wait(0);
  wait(0);
}

// try to find any races between exit and wait
void exitwait(char *s)
{
  int i, pid;

  for (i = 0; i < 100; i++)
  {
    pid = fork();
    if (pid < 0)
    {
      printf("%s: fork failed\n", s);
      exit(1);
    }
    if (pid)
    {
      int xstate;
      if (wait(&xstate) != pid)
      {
        printf("%s: wait wrong pid\n", s);
        exit(1);
      }
      if (i != xstate)
      {
        printf("%s: wait wrong exit status\n", s);
        exit(1);
      }
    }
    else
    {
      exit(i);
    }
  }
}

// try to find races in the reparenting
// code that handles a parent exiting
// when it still has live children.
void reparent(char *s)
{
  int master_pid = getpid();
  for (int i = 0; i < 200; i++)
  {
    int pid = fork();
    if (pid < 0)
    {
      printf("%s: fork failed\n", s);
      exit(1);
    }
    if (pid)
    {
      if (wait(0) != pid)
      {
        printf("%s: wait wrong pid\n", s);
        exit(1);
      }
    }
    else
    {
      int pid2 = fork();
      if (pid2 < 0)
      {
        kill(master_pid);
        exit(1);
      }
      exit(0);
    }
  }
  exit(0);
}

// what if two children exit() at the same time?
void twochildren(char *s)
{
  for (int i = 0; i < 1000; i++)
  {
    int pid1 = fork();
    if (pid1 < 0)
    {
      printf("%s: fork failed\n", s);
      exit(1);
    }
    if (pid1 == 0)
    {
      exit(0);
    }
    else
    {
      int pid2 = fork();
      if (pid2 < 0)
      {
        printf("%s: fork failed\n", s);
        exit(1);
      }
      if (pid2 == 0)
      {
        exit(0);
      }
      else
      {
        wait(0);
        wait(0);
      }
    }
  }
}

// concurrent forks to try to expose locking bugs.
void forkfork(char *s)
{
  enum
  {
    N = 2
  };

  for (int i = 0; i < N; i++)
  {
    int pid = fork();
    if (pid < 0)
    {
      printf("%s: fork failed", s);
      exit(1);
    }
    if (pid == 0)
    {
      for (int j = 0; j < 200; j++)
      {
        int pid1 = fork();
        if (pid1 < 0)
        {
          exit(1);
        }
        if (pid1 == 0)
        {
          exit(0);
        }
        wait(0);
      }
      exit(0);
    }
  }

  int xstatus;
  for (int i = 0; i < N; i++)
  {
    wait(&xstatus);
    if (xstatus != 0)
    {
      printf("%s: fork in child failed", s);
      exit(1);
    }
  }
}

void forkforkfork(char *s)
{
  unlink("stopforking");

  int pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed", s);
    exit(1);
  }
  if (pid == 0)
  {
    while (1)
    {
      int fd = open("stopforking", 0);
      if (fd >= 0)
      {
        exit(0);
      }
      if (fork() < 0)
      {
        close(open("stopforking", O_CREATE | O_RDWR));
      }
    }

    exit(0);
  }

  sleep(20); // two seconds
  close(open("stopforking", O_CREATE | O_RDWR));
  wait(0);
  sleep(10); // one second
}

// regression test. does reparent() violate the parent-then-child
// locking order when giving away a child to init, so that exit()
// deadlocks against init's wait()? also used to trigger a "panic:
// release" due to exit() releasing a different p->parent->lock than
// it acquired.
void reparent2(char *s)
{
  for (int i = 0; i < 800; i++)
  {
    int pid1 = fork();
    if (pid1 < 0)
    {
      printf("fork failed\n");
      exit(1);
    }
    if (pid1 == 0)
    {
      fork();
      fork();
      exit(0);
    }
    wait(0);
  }

  exit(0);
}

// allocate all mem, free it, and allocate again
void mem(char *s)
{
  void *m1, *m2;
  int pid;

  if ((pid = fork()) == 0)
  {
    m1 = 0;
    while ((m2 = malloc(10001)) != 0)
    {
      *(char **)m2 = m1;
      m1 = m2;
    }
    while (m1)
    {
      m2 = *(char **)m1;
      free(m1);
      m1 = m2;
    }
    m1 = malloc(1024 * 20);
    if (m1 == 0)
    {
      printf("couldn't allocate mem?!!\n", s);
      exit(1);
    }
    free(m1);
    exit(0);
  }
  else
  {
    int xstatus;
    wait(&xstatus);
    if (xstatus == -1)
    {
      // probably page fault, so might be lazy lab,
      // so OK.
      exit(0);
    }
    exit(xstatus);
  }
}

// More file system tests

// two processes write to the same file descriptor
// is the offset shared? does inode locking work?
void sharedfd(char *s)
{
  int fd, pid, i, n, nc, np;
  enum
  {
    N = 1000,
    SZ = 10
  };
  char buf[SZ];

  unlink("sharedfd");
  fd = open("sharedfd", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: cannot open sharedfd for writing", s);
    exit(1);
  }
  pid = fork();
  memset(buf, pid == 0 ? 'c' : 'p', sizeof(buf));
  for (i = 0; i < N; i++)
  {
    if (write(fd, buf, sizeof(buf)) != sizeof(buf))
    {
      printf("%s: write sharedfd failed\n", s);
      exit(1);
    }
  }
  if (pid == 0)
  {
    exit(0);
  }
  else
  {
    int xstatus;
    wait(&xstatus);
    if (xstatus != 0)
      exit(xstatus);
  }

  close(fd);
  fd = open("sharedfd", 0);
  if (fd < 0)
  {
    printf("%s: cannot open sharedfd for reading\n", s);
    exit(1);
  }
  nc = np = 0;
  while ((n = read(fd, buf, sizeof(buf))) > 0)
  {
    for (i = 0; i < sizeof(buf); i++)
    {
      if (buf[i] == 'c')
        nc++;
      if (buf[i] == 'p')
        np++;
    }
  }
  close(fd);
  unlink("sharedfd");
  if (nc == N * SZ && np == N * SZ)
  {
    exit(0);
  }
  else
  {
    printf("%s: nc/np test fails\n", s);
    exit(1);
  }
}

// four processes write different files at the same
// time, to test block allocation.
void fourfiles(char *s)
{
  int fd, pid, i, j, n, total, pi;
  char *names[] = {"f0", "f1", "f2", "f3"};
  char *fname;
  enum
  {
    N = 12,
    NCHILD = 4,
    SZ = 500
  };

  for (pi = 0; pi < NCHILD; pi++)
  {
    fname = names[pi];
    unlink(fname);

    pid = fork();
    if (pid < 0)
    {
      printf("fork failed\n", s);
      exit(1);
    }

    if (pid == 0)
    {
      fd = open(fname, O_CREATE | O_RDWR);
      if (fd < 0)
      {
        printf("create failed\n", s);
        exit(1);
      }

      memset(buf, '0' + pi, SZ);
      for (i = 0; i < N; i++)
      {
        if ((n = write(fd, buf, SZ)) != SZ)
        {
          printf("write failed %d\n", n);
          exit(1);
        }
      }
      exit(0);
    }
  }

  int xstatus;
  for (pi = 0; pi < NCHILD; pi++)
  {
    wait(&xstatus);
    if (xstatus != 0)
      exit(xstatus);
  }

  for (i = 0; i < NCHILD; i++)
  {
    fname = names[i];
    fd = open(fname, 0);
    total = 0;
    while ((n = read(fd, buf, sizeof(buf))) > 0)
    {
      for (j = 0; j < n; j++)
      {
        if (buf[j] != '0' + i)
        {
          printf("wrong char\n", s);
          exit(1);
        }
      }
      total += n;
    }
    close(fd);
    if (total != N * SZ)
    {
      printf("wrong length %d\n", total);
      exit(1);
    }
    unlink(fname);
  }
}

// four processes create and delete different files in same directory
void createdelete(char *s)
{
  enum
  {
    N = 20,
    NCHILD = 4
  };
  int pid, i, fd, pi;
  char name[32];

  for (pi = 0; pi < NCHILD; pi++)
  {
    pid = fork();
    if (pid < 0)
    {
      printf("fork failed\n", s);
      exit(1);
    }

    if (pid == 0)
    {
      name[0] = 'p' + pi;
      name[2] = '\0';
      for (i = 0; i < N; i++)
      {
        name[1] = '0' + i;
        fd = open(name, O_CREATE | O_RDWR);
        if (fd < 0)
        {
          printf("%s: create failed\n", s);
          exit(1);
        }
        close(fd);
        if (i > 0 && (i % 2) == 0)
        {
          name[1] = '0' + (i / 2);
          if (unlink(name) < 0)
          {
            printf("%s: unlink failed\n", s);
            exit(1);
          }
        }
      }
      exit(0);
    }
  }

  int xstatus;
  for (pi = 0; pi < NCHILD; pi++)
  {
    wait(&xstatus);
    if (xstatus != 0)
      exit(1);
  }

  name[0] = name[1] = name[2] = 0;
  for (i = 0; i < N; i++)
  {
    for (pi = 0; pi < NCHILD; pi++)
    {
      name[0] = 'p' + pi;
      name[1] = '0' + i;
      fd = open(name, 0);
      if ((i == 0 || i >= N / 2) && fd < 0)
      {
        printf("%s: oops createdelete %s didn't exist\n", s, name);
        exit(1);
      }
      else if ((i >= 1 && i < N / 2) && fd >= 0)
      {
        printf("%s: oops createdelete %s did exist\n", s, name);
        exit(1);
      }
      if (fd >= 0)
        close(fd);
    }
  }

  for (i = 0; i < N; i++)
  {
    for (pi = 0; pi < NCHILD; pi++)
    {
      name[0] = 'p' + i;
      name[1] = '0' + i;
      unlink(name);
    }
  }
}

// can I unlink a file and still read it?
void unlinkread(char *s)
{
  enum
  {
    SZ = 5
  };
  int fd, fd1;

  fd = open("unlinkread", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: create unlinkread failed\n", s);
    exit(1);
  }
  write(fd, "hello", SZ);
  close(fd);

  fd = open("unlinkread", O_RDWR);
  if (fd < 0)
  {
    printf("%s: open unlinkread failed\n", s);
    exit(1);
  }
  if (unlink("unlinkread") != 0)
  {
    printf("%s: unlink unlinkread failed\n", s);
    exit(1);
  }

  fd1 = open("unlinkread", O_CREATE | O_RDWR);
  write(fd1, "yyy", 3);
  close(fd1);

  if (read(fd, buf, sizeof(buf)) != SZ)
  {
    printf("%s: unlinkread read failed", s);
    exit(1);
  }
  if (buf[0] != 'h')
  {
    printf("%s: unlinkread wrong data\n", s);
    exit(1);
  }
  if (write(fd, buf, 10) != 10)
  {
    printf("%s: unlinkread write failed\n", s);
    exit(1);
  }
  close(fd);
  unlink("unlinkread");
}

void linktest(char *s)
{
  enum
  {
    SZ = 5
  };
  int fd;

  unlink("lf1");
  unlink("lf2");

  fd = open("lf1", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: create lf1 failed\n", s);
    exit(1);
  }
  if (write(fd, "hello", SZ) != SZ)
  {
    printf("%s: write lf1 failed\n", s);
    exit(1);
  }
  close(fd);

  if (link("lf1", "lf2") < 0)
  {
    printf("%s: link lf1 lf2 failed\n", s);
    exit(1);
  }
  unlink("lf1");

  if (open("lf1", 0) >= 0)
  {
    printf("%s: unlinked lf1 but it is still there!\n", s);
    exit(1);
  }

  fd = open("lf2", 0);
  if (fd < 0)
  {
    printf("%s: open lf2 failed\n", s);
    exit(1);
  }
  if (read(fd, buf, sizeof(buf)) != SZ)
  {
    printf("%s: read lf2 failed\n", s);
    exit(1);
  }
  close(fd);

  if (link("lf2", "lf2") >= 0)
  {
    printf("%s: link lf2 lf2 succeeded! oops\n", s);
    exit(1);
  }

  unlink("lf2");
  if (link("lf2", "lf1") >= 0)
  {
    printf("%s: link non-existant succeeded! oops\n", s);
    exit(1);
  }

  if (link(".", "lf1") >= 0)
  {
    printf("%s: link . lf1 succeeded! oops\n", s);
    exit(1);
  }
}

// test concurrent create/link/unlink of the same file
void concreate(char *s)
{
  enum
  {
    N = 40
  };
  char file[3];
  int i, pid, n, fd;
  char fa[N];
  struct
  {
    ushort inum;
    char name[DIRSIZ];
  } de;

  file[0] = 'C';
  file[2] = '\0';
  for (i = 0; i < N; i++)
  {
    file[1] = '0' + i;
    unlink(file);
    pid = fork();
    if (pid && (i % 3) == 1)
    {
      link("C0", file);
    }
    else if (pid == 0 && (i % 5) == 1)
    {
      link("C0", file);
    }
    else
    {
      fd = open(file, O_CREATE | O_RDWR);
      if (fd < 0)
      {
        printf("concreate create %s failed\n", file);
        exit(1);
      }
      close(fd);
    }
    if (pid == 0)
    {
      exit(0);
    }
    else
    {
      int xstatus;
      wait(&xstatus);
      if (xstatus != 0)
        exit(1);
    }
  }

  memset(fa, 0, sizeof(fa));
  fd = open(".", 0);
  n = 0;
  while (read(fd, &de, sizeof(de)) > 0)
  {
    if (de.inum == 0)
      continue;
    if (de.name[0] == 'C' && de.name[2] == '\0')
    {
      i = de.name[1] - '0';
      if (i < 0 || i >= sizeof(fa))
      {
        printf("%s: concreate weird file %s\n", s, de.name);
        exit(1);
      }
      if (fa[i])
      {
        printf("%s: concreate duplicate file %s\n", s, de.name);
        exit(1);
      }
      fa[i] = 1;
      n++;
    }
  }
  close(fd);

  if (n != N)
  {
    printf("%s: concreate not enough files in directory listing\n", s);
    exit(1);
  }

  for (i = 0; i < N; i++)
  {
    file[1] = '0' + i;
    pid = fork();
    if (pid < 0)
    {
      printf("%s: fork failed\n", s);
      exit(1);
    }
    if (((i % 3) == 0 && pid == 0) ||
        ((i % 3) == 1 && pid != 0))
    {
      close(open(file, 0));
      close(open(file, 0));
      close(open(file, 0));
      close(open(file, 0));
      close(open(file, 0));
      close(open(file, 0));
    }
    else
    {
      unlink(file);
      unlink(file);
      unlink(file);
      unlink(file);
      unlink(file);
      unlink(file);
    }
    if (pid == 0)
      exit(0);
    else
      wait(0);
  }
}

// another concurrent link/unlink/create test,
// to look for deadlocks.
void linkunlink(char *s)
{
  int pid, i;

  unlink("x");
  pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }

  unsigned int x = (pid ? 1 : 97);
  for (i = 0; i < 100; i++)
  {
    x = x * 1103515245 + 12345;
    if ((x % 3) == 0)
    {
      close(open("x", O_RDWR | O_CREATE));
    }
    else if ((x % 3) == 1)
    {
      link("cat", "x");
    }
    else
    {
      unlink("x");
    }
  }

  if (pid)
    wait(0);
  else
    exit(0);
}

// directory that uses indirect blocks
void bigdir(char *s)
{
  enum
  {
    N = 500
  };
  int i, fd;
  char name[10];

  unlink("bd");

  fd = open("bd", O_CREATE);
  if (fd < 0)
  {
    printf("%s: bigdir create failed\n", s);
    exit(1);
  }
  close(fd);

  for (i = 0; i < N; i++)
  {
    name[0] = 'x';
    name[1] = '0' + (i / 64);
    name[2] = '0' + (i % 64);
    name[3] = '\0';
    if (link("bd", name) != 0)
    {
      printf("%s: bigdir link(bd, %s) failed\n", s, name);
      exit(1);
    }
  }

  unlink("bd");
  for (i = 0; i < N; i++)
  {
    name[0] = 'x';
    name[1] = '0' + (i / 64);
    name[2] = '0' + (i % 64);
    name[3] = '\0';
    if (unlink(name) != 0)
    {
      printf("%s: bigdir unlink failed", s);
      exit(1);
    }
  }
}

void subdir(char *s)
{
  int fd, cc;

  unlink("ff");
  if (mkdir("dd") != 0)
  {
    printf("%s: mkdir dd failed\n", s);
    exit(1);
  }

  fd = open("dd/ff", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: create dd/ff failed\n", s);
    exit(1);
  }
  write(fd, "ff", 2);
  close(fd);

  if (unlink("dd") >= 0)
  {
    printf("%s: unlink dd (non-empty dir) succeeded!\n", s);
    exit(1);
  }

  if (mkdir("/dd/dd") != 0)
  {
    printf("subdir mkdir dd/dd failed\n", s);
    exit(1);
  }

  fd = open("dd/dd/ff", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: create dd/dd/ff failed\n", s);
    exit(1);
  }
  write(fd, "FF", 2);
  close(fd);

  fd = open("dd/dd/../ff", 0);
  if (fd < 0)
  {
    printf("%s: open dd/dd/../ff failed\n", s);
    exit(1);
  }
  cc = read(fd, buf, sizeof(buf));
  if (cc != 2 || buf[0] != 'f')
  {
    printf("%s: dd/dd/../ff wrong content\n", s);
    exit(1);
  }
  close(fd);

  if (link("dd/dd/ff", "dd/dd/ffff") != 0)
  {
    printf("link dd/dd/ff dd/dd/ffff failed\n", s);
    exit(1);
  }

  if (unlink("dd/dd/ff") != 0)
  {
    printf("%s: unlink dd/dd/ff failed\n", s);
    exit(1);
  }
  if (open("dd/dd/ff", O_RDONLY) >= 0)
  {
    printf("%s: open (unlinked) dd/dd/ff succeeded\n", s);
    exit(1);
  }

  if (chdir("dd") != 0)
  {
    printf("%s: chdir dd failed\n", s);
    exit(1);
  }
  if (chdir("dd/../../dd") != 0)
  {
    printf("%s: chdir dd/../../dd failed\n", s);
    exit(1);
  }
  if (chdir("dd/../../../dd") != 0)
  {
    printf("chdir dd/../../dd failed\n", s);
    exit(1);
  }
  if (chdir("./..") != 0)
  {
    printf("%s: chdir ./.. failed\n", s);
    exit(1);
  }

  fd = open("dd/dd/ffff", 0);
  if (fd < 0)
  {
    printf("%s: open dd/dd/ffff failed\n", s);
    exit(1);
  }
  if (read(fd, buf, sizeof(buf)) != 2)
  {
    printf("%s: read dd/dd/ffff wrong len\n", s);
    exit(1);
  }
  close(fd);

  if (open("dd/dd/ff", O_RDONLY) >= 0)
  {
    printf("%s: open (unlinked) dd/dd/ff succeeded!\n", s);
    exit(1);
  }

  if (open("dd/ff/ff", O_CREATE | O_RDWR) >= 0)
  {
    printf("%s: create dd/ff/ff succeeded!\n", s);
    exit(1);
  }
  if (open("dd/xx/ff", O_CREATE | O_RDWR) >= 0)
  {
    printf("%s: create dd/xx/ff succeeded!\n", s);
    exit(1);
  }
  if (open("dd", O_CREATE) >= 0)
  {
    printf("%s: create dd succeeded!\n", s);
    exit(1);
  }
  if (open("dd", O_RDWR) >= 0)
  {
    printf("%s: open dd rdwr succeeded!\n", s);
    exit(1);
  }
  if (open("dd", O_WRONLY) >= 0)
  {
    printf("%s: open dd wronly succeeded!\n", s);
    exit(1);
  }
  if (link("dd/ff/ff", "dd/dd/xx") == 0)
  {
    printf("%s: link dd/ff/ff dd/dd/xx succeeded!\n", s);
    exit(1);
  }
  if (link("dd/xx/ff", "dd/dd/xx") == 0)
  {
    printf("%s: link dd/xx/ff dd/dd/xx succeeded!\n", s);
    exit(1);
  }
  if (link("dd/ff", "dd/dd/ffff") == 0)
  {
    printf("%s: link dd/ff dd/dd/ffff succeeded!\n", s);
    exit(1);
  }
  if (mkdir("dd/ff/ff") == 0)
  {
    printf("%s: mkdir dd/ff/ff succeeded!\n", s);
    exit(1);
  }
  if (mkdir("dd/xx/ff") == 0)
  {
    printf("%s: mkdir dd/xx/ff succeeded!\n", s);
    exit(1);
  }
  if (mkdir("dd/dd/ffff") == 0)
  {
    printf("%s: mkdir dd/dd/ffff succeeded!\n", s);
    exit(1);
  }
  if (unlink("dd/xx/ff") == 0)
  {
    printf("%s: unlink dd/xx/ff succeeded!\n", s);
    exit(1);
  }
  if (unlink("dd/ff/ff") == 0)
  {
    printf("%s: unlink dd/ff/ff succeeded!\n", s);
    exit(1);
  }
  if (chdir("dd/ff") == 0)
  {
    printf("%s: chdir dd/ff succeeded!\n", s);
    exit(1);
  }
  if (chdir("dd/xx") == 0)
  {
    printf("%s: chdir dd/xx succeeded!\n", s);
    exit(1);
  }

  if (unlink("dd/dd/ffff") != 0)
  {
    printf("%s: unlink dd/dd/ff failed\n", s);
    exit(1);
  }
  if (unlink("dd/ff") != 0)
  {
    printf("%s: unlink dd/ff failed\n", s);
    exit(1);
  }
  if (unlink("dd") == 0)
  {
    printf("%s: unlink non-empty dd succeeded!\n", s);
    exit(1);
  }
  if (unlink("dd/dd") < 0)
  {
    printf("%s: unlink dd/dd failed\n", s);
    exit(1);
  }
  if (unlink("dd") < 0)
  {
    printf("%s: unlink dd failed\n", s);
    exit(1);
  }
}

// test writes that are larger than the log.
void bigwrite(char *s)
{
  int fd, sz;

  unlink("bigwrite");
  for (sz = 499; sz < (MAXOPBLOCKS + 2) * BSIZE; sz += 471)
  {
    fd = open("bigwrite", O_CREATE | O_RDWR);
    if (fd < 0)
    {
      printf("%s: cannot create bigwrite\n", s);
      exit(1);
    }
    int i;
    for (i = 0; i < 2; i++)
    {
      int cc = write(fd, buf, sz);
      if (cc != sz)
      {
        printf("%s: write(%d) ret %d\n", s, sz, cc);
        exit(1);
      }
    }
    close(fd);
    unlink("bigwrite");
  }
}

void bigfile(char *s)
{
  enum
  {
    N = 20,
    SZ = 600
  };
  int fd, i, total, cc;

  unlink("bigfile.dat");
  fd = open("bigfile.dat", O_CREATE | O_RDWR);
  if (fd < 0)
  {
    printf("%s: cannot create bigfile", s);
    exit(1);
  }
  for (i = 0; i < N; i++)
  {
    memset(buf, i, SZ);
    if (write(fd, buf, SZ) != SZ)
    {
      printf("%s: write bigfile failed\n", s);
      exit(1);
    }
  }
  close(fd);

  fd = open("bigfile.dat", 0);
  if (fd < 0)
  {
    printf("%s: cannot open bigfile\n", s);
    exit(1);
  }
  total = 0;
  for (i = 0;; i++)
  {
    cc = read(fd, buf, SZ / 2);
    if (cc < 0)
    {
      printf("%s: read bigfile failed\n", s);
      exit(1);
    }
    if (cc == 0)
      break;
    if (cc != SZ / 2)
    {
      printf("%s: short read bigfile\n", s);
      exit(1);
    }
    if (buf[0] != i / 2 || buf[SZ / 2 - 1] != i / 2)
    {
      printf("%s: read bigfile wrong data\n", s);
      exit(1);
    }
    total += cc;
  }
  close(fd);
  if (total != N * SZ)
  {
    printf("%s: read bigfile wrong total\n", s);
    exit(1);
  }
  unlink("bigfile.dat");
}

void fourteen(char *s)
{
  int fd;

  // DIRSIZ is 14.

  if (mkdir("12345678901234") != 0)
  {
    printf("%s: mkdir 12345678901234 failed\n", s);
    exit(1);
  }
  if (mkdir("12345678901234/123456789012345") != 0)
  {
    printf("%s: mkdir 12345678901234/123456789012345 failed\n", s);
    exit(1);
  }
  fd = open("123456789012345/123456789012345/123456789012345", O_CREATE);
  if (fd < 0)
  {
    printf("%s: create 123456789012345/123456789012345/123456789012345 failed\n", s);
    exit(1);
  }
  close(fd);
  fd = open("12345678901234/12345678901234/12345678901234", 0);
  if (fd < 0)
  {
    printf("%s: open 12345678901234/12345678901234/12345678901234 failed\n", s);
    exit(1);
  }
  close(fd);

  if (mkdir("12345678901234/12345678901234") == 0)
  {
    printf("%s: mkdir 12345678901234/12345678901234 succeeded!\n", s);
    exit(1);
  }
  if (mkdir("123456789012345/12345678901234") == 0)
  {
    printf("%s: mkdir 12345678901234/123456789012345 succeeded!\n", s);
    exit(1);
  }

  // clean up
  unlink("123456789012345/12345678901234");
  unlink("12345678901234/12345678901234");
  unlink("12345678901234/12345678901234/12345678901234");
  unlink("123456789012345/123456789012345/123456789012345");
  unlink("12345678901234/123456789012345");
  unlink("12345678901234");
}

void rmdot(char *s)
{
  if (mkdir("dots") != 0)
  {
    printf("%s: mkdir dots failed\n", s);
    exit(1);
  }
  if (chdir("dots") != 0)
  {
    printf("%s: chdir dots failed\n", s);
    exit(1);
  }
  if (unlink(".") == 0)
  {
    printf("%s: rm . worked!\n", s);
    exit(1);
  }
  if (unlink("..") == 0)
  {
    printf("%s: rm .. worked!\n", s);
    exit(1);
  }
  if (chdir("/") != 0)
  {
    printf("%s: chdir / failed\n", s);
    exit(1);
  }
  if (unlink("dots/.") == 0)
  {
    printf("%s: unlink dots/. worked!\n", s);
    exit(1);
  }
  if (unlink("dots/..") == 0)
  {
    printf("%s: unlink dots/.. worked!\n", s);
    exit(1);
  }
  if (unlink("dots") != 0)
  {
    printf("%s: unlink dots failed!\n", s);
    exit(1);
  }
}

void dirfile(char *s)
{
  int fd;

  fd = open("dirfile", O_CREATE);
  if (fd < 0)
  {
    printf("%s: create dirfile failed\n", s);
    exit(1);
  }
  close(fd);
  if (chdir("dirfile") == 0)
  {
    printf("%s: chdir dirfile succeeded!\n", s);
    exit(1);
  }
  fd = open("dirfile/xx", 0);
  if (fd >= 0)
  {
    printf("%s: create dirfile/xx succeeded!\n", s);
    exit(1);
  }
  fd = open("dirfile/xx", O_CREATE);
  if (fd >= 0)
  {
    printf("%s: create dirfile/xx succeeded!\n", s);
    exit(1);
  }
  if (mkdir("dirfile/xx") == 0)
  {
    printf("%s: mkdir dirfile/xx succeeded!\n", s);
    exit(1);
  }
  if (unlink("dirfile/xx") == 0)
  {
    printf("%s: unlink dirfile/xx succeeded!\n", s);
    exit(1);
  }
  if (link("README", "dirfile/xx") == 0)
  {
    printf("%s: link to dirfile/xx succeeded!\n", s);
    exit(1);
  }
  if (unlink("dirfile") != 0)
  {
    printf("%s: unlink dirfile failed!\n", s);
    exit(1);
  }

  fd = open(".", O_RDWR);
  if (fd >= 0)
  {
    printf("%s: open . for writing succeeded!\n", s);
    exit(1);
  }
  fd = open(".", 0);
  if (write(fd, "x", 1) > 0)
  {
    printf("%s: write . succeeded!\n", s);
    exit(1);
  }
  close(fd);
}

// test that iput() is called at the end of _namei().
// also tests empty file names.
void iref(char *s)
{
  int i, fd;

  for (i = 0; i < NINODE + 1; i++)
  {
    if (mkdir("irefd") != 0)
    {
      printf("%s: mkdir irefd failed\n", s);
      exit(1);
    }
    if (chdir("irefd") != 0)
    {
      printf("%s: chdir irefd failed\n", s);
      exit(1);
    }

    mkdir("");
    link("README", "");
    fd = open("", O_CREATE);
    if (fd >= 0)
      close(fd);
    fd = open("xx", O_CREATE);
    if (fd >= 0)
      close(fd);
    unlink("xx");
  }

  // clean up
  for (i = 0; i < NINODE + 1; i++)
  {
    chdir("..");
    unlink("irefd");
  }

  chdir("/");
}

// test that fork fails gracefully
// the forktest binary also does this, but it runs out of proc entries first.
// inside the bigger usertests binary, we run out of memory first.
void forktest(char *s)
{
  enum
  {
    N = 1000
  };
  int n, pid;

  for (n = 0; n < N; n++)
  {
    pid = fork();
    if (pid < 0)
      break;
    if (pid == 0)
      exit(0);
  }

  if (n == 0)
  {
    printf("%s: no fork at all!\n", s);
    exit(1);
  }

  if (n == N)
  {
    printf("%s: fork claimed to work 1000 times!\n", s);
    exit(1);
  }

  for (; n > 0; n--)
  {
    if (wait(0) < 0)
    {
      printf("%s: wait stopped early\n", s);
      exit(1);
    }
  }

  if (wait(0) != -1)
  {
    printf("%s: wait got too many\n", s);
    exit(1);
  }
}

void sbrkbasic(char *s)
{
  enum
  {
    TOOMUCH = 1024 * 1024 * 1024
  };
  int i, pid, xstatus;
  char *c, *a, *b;

  // does sbrk() return the expected failure value?
  pid = fork();
  if (pid < 0)
  {
    printf("fork failed in sbrkbasic\n");
    exit(1);
  }
  if (pid == 0)
  {
    a = sbrk(TOOMUCH);
    if (a == (char *)0xffffffffffffffffL)
    {
      // it's OK if this fails.
      exit(0);
    }

    for (b = a; b < a + TOOMUCH; b += 4096)
    {
      *b = 99;
    }

    // we should not get here! either sbrk(TOOMUCH)
    // should have failed, or (with lazy allocation)
    // a pagefault should have killed this process.
    exit(1);
  }

  wait(&xstatus);
  if (xstatus == 1)
  {
    printf("%s: too much memory allocated!\n", s);
    exit(1);
  }

  // can one sbrk() less than a page?
  a = sbrk(0);
  for (i = 0; i < 5000; i++)
  {
    b = sbrk(1);
    if (b != a)
    {
      printf("%s: sbrk test failed %d %x %x\n", i, a, b);
      exit(1);
    }
    *b = 1;
    a = b + 1;
  }
  pid = fork();
  if (pid < 0)
  {
    printf("%s: sbrk test fork failed\n", s);
    exit(1);
  }
  c = sbrk(1);
  c = sbrk(1);
  if (c != a + 1)
  {
    printf("%s: sbrk test failed post-fork\n", s);
    exit(1);
  }
  if (pid == 0)
    exit(0);
  wait(&xstatus);
  exit(xstatus);
}

void sbrkmuch(char *s)
{
  enum
  {
    BIG = 100 * 1024 * 1024
  };
  char *c, *oldbrk, *a, *lastaddr, *p;
  uint64 amt;

  oldbrk = sbrk(0);

  // can one grow address space to something big?
  a = sbrk(0);
  amt = BIG - (uint64)a;
  p = sbrk(amt);
  if (p != a)
  {
    printf("%s: sbrk test failed to grow big address space; enough phys mem?\n", s);
    exit(1);
  }

  // touch each page to make sure it exists.
  char *eee = sbrk(0);
  for (char *pp = a; pp < eee; pp += 4096)
    *pp = 1;

  lastaddr = (char *)(BIG - 1);
  *lastaddr = 99;

  // can one de-allocate?
  a = sbrk(0);
  c = sbrk(-PGSIZE);
  if (c == (char *)0xffffffffffffffffL)
  {
    printf("%s: sbrk could not deallocate\n", s);
    exit(1);
  }
  c = sbrk(0);
  if (c != a - PGSIZE)
  {
    printf("%s: sbrk deallocation produced wrong address, a %x c %x\n", a, c);
    exit(1);
  }

  // can one re-allocate that page?
  a = sbrk(0);
  c = sbrk(PGSIZE);
  if (c != a || sbrk(0) != a + PGSIZE)
  {
    printf("%s: sbrk re-allocation failed, a %x c %x\n", a, c);
    exit(1);
  }
  if (*lastaddr == 99)
  {
    // should be zero
    printf("%s: sbrk de-allocation didn't really deallocate\n", s);
    exit(1);
  }

  a = sbrk(0);
  c = sbrk(-(sbrk(0) - oldbrk));
  if (c != a)
  {
    printf("%s: sbrk downsize failed, a %x c %x\n", a, c);
    exit(1);
  }
}

// can we read the kernel's memory?
void kernmem(char *s)
{
  char *a;
  int pid;

  for (a = (char *)(KERNBASE); a < (char *)(KERNBASE + 2000000); a += 50000)
  {
    pid = fork();
    if (pid < 0)
    {
      printf("%s: fork failed\n", s);
      exit(1);
    }
    if (pid == 0)
    {
      printf("%s: oops could read %x = %x\n", a, *a);
      exit(1);
    }
    int xstatus;
    wait(&xstatus);
    if (xstatus != -1) // did kernel kill child?
      exit(1);
  }
}

// if we run the system out of memory, does it clean up the last
// failed allocation?
void sbrkfail(char *s)
{
  enum
  {
    BIG = 100 * 1024 * 1024
  };
  int i, xstatus;
  int fds[2];
  char scratch;
  char *c, *a;
  int pids[10];
  int pid;

  if (pipe(fds) != 0)
  {
    printf("%s: pipe() failed\n", s);
    exit(1);
  }
  for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++)
  {
    if ((pids[i] = fork()) == 0)
    {
      // allocate a lot of memory
      sbrk(BIG - (uint64)sbrk(0));
      write(fds[1], "x", 1);
      // sit around until killed
      for (;;)
        sleep(1000);
    }
    if (pids[i] != -1)
      read(fds[0], &scratch, 1);
  }

  // if those failed allocations freed up the pages they did allocate,
  // we'll be able to allocate here
  c = sbrk(PGSIZE);
  for (i = 0; i < sizeof(pids) / sizeof(pids[0]); i++)
  {
    if (pids[i] == -1)
      continue;
    kill(pids[i]);
    wait(0);
  }
  if (c == (char *)0xffffffffffffffffL)
  {
    printf("%s: failed sbrk leaked memory\n", s);
    exit(1);
  }

  // test running fork with the above allocated page
  pid = fork();
  if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  if (pid == 0)
  {
    // allocate a lot of memory.
    // this should produce a page fault,
    // and thus not complete.
    a = sbrk(0);
    sbrk(10 * BIG);
    int n = 0;
    for (i = 0; i < 10 * BIG; i += PGSIZE)
    {
      n += *(a + i);
    }
    // print n so the compiler doesn't optimize away
    // the for loop.
    printf("%s: allocate a lot of memory succeeded %d\n", n);
    exit(1);
  }
  wait(&xstatus);
  if (xstatus != -1 && xstatus != 2)
    exit(1);
}

// test reads/writes from/to allocated memory
void sbrkarg(char *s)
{
  char *a;
  int fd, n;

  a = sbrk(PGSIZE);
  fd = open("sbrk", O_CREATE | O_WRONLY);
  unlink("sbrk");
  if (fd < 0)
  {
    printf("%s: open sbrk failed\n", s);
    exit(1);
  }
  if ((n = write(fd, a, PGSIZE)) < 0)
  {
    printf("%s: write sbrk failed\n", s);
    exit(1);
  }
  close(fd);

  // test writes to allocated memory
  a = sbrk(PGSIZE);
  if (pipe((int *)a) != 0)
  {
    printf("%s: pipe() failed\n", s);
    exit(1);
  }
}

void validatetest(char *s)
{
  int hi;
  uint64 p;

  hi = 1100 * 1024;
  for (p = 0; p <= (uint)hi; p += PGSIZE)
  {
    // try to crash the kernel by passing in a bad string pointer
    if (link("nosuchfile", (char *)p) != -1)
    {
      printf("%s: link should not succeed\n", s);
      exit(1);
    }
  }
}

// does unintialized data start out zero?
char uninit[10000];
void bsstest(char *s)
{
  int i;

  for (i = 0; i < sizeof(uninit); i++)
  {
    if (uninit[i] != '\0')
    {
      printf("%s: bss test failed\n", s);
      exit(1);
    }
  }
}

// does exec return an error if the arguments
// are larger than a page? or does it write
// below the stack and wreck the instructions/data?
void bigargtest(char *s)
{
  int pid, fd, xstatus;

  unlink("bigarg-ok");
  pid = fork();
  if (pid == 0)
  {
    static char *args[MAXARG];
    int i;
    for (i = 0; i < MAXARG - 1; i++)
      args[i] = "bigargs test: failed\n                                                                                                                                                                                                       ";
    args[MAXARG - 1] = 0;
    exec("echo", args);
    fd = open("bigarg-ok", O_CREATE);
    close(fd);
    exit(0);
  }
  else if (pid < 0)
  {
    printf("%s: bigargtest: fork failed\n", s);
    exit(1);
  }

  wait(&xstatus);
  if (xstatus != 0)
    exit(xstatus);
  fd = open("bigarg-ok", 0);
  if (fd < 0)
  {
    printf("%s: bigarg test failed!\n", s);
    exit(1);
  }
  close(fd);
}

// what happens when the file system runs out of blocks?
// answer: balloc panics, so this test is not useful.
void fsfull()
{
  int nfiles;
  int fsblocks = 0;

  printf("fsfull test\n");

  for (nfiles = 0;; nfiles++)
  {
    char name[64];
    name[0] = 'f';
    name[1] = '0' + nfiles / 1000;
    name[2] = '0' + (nfiles % 1000) / 100;
    name[3] = '0' + (nfiles % 100) / 10;
    name[4] = '0' + (nfiles % 10);
    name[5] = '\0';
    printf("%s: writing %s\n", name);
    int fd = open(name, O_CREATE | O_RDWR);
    if (fd < 0)
    {
      printf("%s: open %s failed\n", name);
      break;
    }
    int total = 0;
    while (1)
    {
      int cc = write(fd, buf, BSIZE);
      if (cc < BSIZE)
        break;
      total += cc;
      fsblocks++;
    }
    printf("%s: wrote %d bytes\n", total);
    close(fd);
    if (total == 0)
      break;
  }

  while (nfiles >= 0)
  {
    char name[64];
    name[0] = 'f';
    name[1] = '0' + nfiles / 1000;
    name[2] = '0' + (nfiles % 1000) / 100;
    name[3] = '0' + (nfiles % 100) / 10;
    name[4] = '0' + (nfiles % 10);
    name[5] = '\0';
    unlink(name);
    nfiles--;
  }

  printf("fsfull test finished\n");
}

void argptest(char *s)
{
  int fd;
  fd = open("init", O_RDONLY);
  if (fd < 0)
  {
    printf("%s: open failed\n", s);
    exit(1);
  }
  read(fd, sbrk(0) - 1, -1);
  close(fd);
}

unsigned long randstate = 1;
unsigned int
rand()
{
  randstate = randstate * 1664525 + 1013904223;
  return randstate;
}

// check that there's an invalid page beneath
// the user stack, to catch stack overflow.
void stacktest(char *s)
{
  int pid;
  int xstatus;

  pid = fork();
  if (pid == 0)
  {
    char *sp = (char *)r_sp();
    sp -= PGSIZE;
    // the *sp should cause a trap.
    printf("%s: stacktest: read below stack %p\n", *sp);
    exit(1);
  }
  else if (pid < 0)
  {
    printf("%s: fork failed\n", s);
    exit(1);
  }
  wait(&xstatus);
  if (xstatus == -1) // kernel killed child?
    exit(0);
  else
    exit(xstatus);
}

// regression test. copyin(), copyout(), and copyinstr() used to cast
// the virtual page address to uint, which (with certain wild system
// call arguments) resulted in a kernel page faults.
void pgbug(char *s)
{
  char *argv[1];
  argv[0] = 0;
  exec((char *)0xeaeb0b5b00002f5e, argv);

  pipe((int *)0xeaeb0b5b00002f5e);

  exit(0);
}

// regression test. does the kernel panic if a process sbrk()s its
// size to be less than a page, or zero, or reduces the break by an
// amount too small to cause a page to be freed?
void sbrkbugs(char *s)
{
  int pid = fork();
  if (pid < 0)
  {
    printf("fork failed\n");
    exit(1);
  }
  if (pid == 0)
  {
    int sz = (uint64)sbrk(0);
    // free all user memory; there used to be a bug that
    // would not adjust p->sz correctly in this case,
    // causing exit() to panic.
    sbrk(-sz);
    // user page fault here.
    exit(0);
  }
  wait(0);

  pid = fork();
  if (pid < 0)
  {
    printf("fork failed\n");
    exit(1);
  }
  if (pid == 0)
  {
    int sz = (uint64)sbrk(0);
    // set the break to somewhere in the very first
    // page; there used to be a bug that would incorrectly
    // free the first page.
    sbrk(-(sz - 3500));
    exit(0);
  }
  wait(0);

  pid = fork();
  if (pid < 0)
  {
    printf("fork failed\n");
    exit(1);
  }
  if (pid == 0)
  {
    // set the break in the middle of a page.
    sbrk((10 * 4096 + 2048) - (uint64)sbrk(0));

    // reduce the break a bit, but not enough to
    // cause a page to be freed. this used to cause
    // a panic.
    sbrk(-10);

    exit(0);
  }
  wait(0);

  exit(0);
}

// regression test. does write() with an invalid buffer pointer cause
// a block to be allocated for a file that is then not freed when the
// file is deleted? if the kernel has this bug, it will panic: balloc:
// out of blocks. assumed_free may need to be raised to be more than
// the number of free blocks. this test takes a long time.
void badwrite(char *s)
{
  int assumed_free = 600;

  unlink("junk");
  for (int i = 0; i < assumed_free; i++)
  {
    int fd = open("junk", O_CREATE | O_WRONLY);
    if (fd < 0)
    {
      printf("open junk failed\n");
      exit(1);
    }
    write(fd, (char *)0xffffffffffL, 1);
    close(fd);
    unlink("junk");
  }

  int fd = open("junk", O_CREATE | O_WRONLY);
  if (fd < 0)
  {
    printf("open junk failed\n");
    exit(1);
  }
  if (write(fd, "x", 1) != 1)
  {
    printf("write failed\n");
    exit(1);
  }
  close(fd);
  unlink("junk");

  exit(0);
}

// regression test. test whether exec() leaks memory if one of the
// arguments is invalid. the test passes if the kernel doesn't panic.
void badarg(char *s)
{
  for (int i = 0; i < 50000; i++)
  {
    char *argv[2];
    argv[0] = (char *)0xffffffff;
    argv[1] = 0;
    exec("echo", argv);
  }

  exit(0);
}

// test the exec() code that cleans up if it runs out
// of memory. it's really a test that such a condition
// doesn't cause a panic.
void execout(char *s)
{
  for (int avail = 0; avail < 15; avail++)
  {
    int pid = fork();
    if (pid < 0)
    {
      printf("fork failed\n");
      exit(1);
    }
    else if (pid == 0)
    {
      // allocate all of memory.
      while (1)
      {
        uint64 a = (uint64)sbrk(4096);
        if (a == 0xffffffffffffffffLL)
          break;
        *(char *)(a + 4096 - 1) = 1;
      }

      // free a few pages, in order to let exec() make some
      // progress.
      for (int i = 0; i < avail; i++)
        sbrk(-4096);

      close(1);
      char *args[] = {"echo", "x", 0};
      exec("echo", args);
      exit(0);
    }
    else
    {
      wait((int *)0);
    }
  }

  exit(0);
}

//
// use sbrk() to count how many free physical memory pages there are.
// touches the pages to force allocation.
// because out of memory with lazy allocation results in the process
// taking a fault and being killed, fork and report back.
//
int countfree()
{
  int fds[2];

  if (pipe(fds) < 0)
  {
    printf("pipe() failed in countfree()\n");
    exit(1);
  }

  int pid = fork();

  if (pid < 0)
  {
    printf("fork failed in countfree()\n");
    exit(1);
  }

  if (pid == 0)
  {
    close(fds[0]);

    while (1)
    {
      uint64 a = (uint64)sbrk(4096);
      if (a == 0xffffffffffffffff)
      {
        break;
      }

      // modify the memory to make sure it's really allocated.
      *(char *)(a + 4096 - 1) = 1;

      // report back one more page.
      if (write(fds[1], "x", 1) != 1)
      {
        printf("write() failed in countfree()\n");
        exit(1);
      }
    }

    exit(0);
  }

  close(fds[1]);

  int n = 0;
  while (1)
  {
    char c;
    int cc = read(fds[0], &c, 1);
    if (cc < 0)
    {
      printf("read() failed in countfree()\n");
      exit(1);
    }
    if (cc == 0)
      break;
    n += 1;
  }

  close(fds[0]);
  wait((int *)0);

  return n;
}

// run each test in its own process. run returns 1 if child's exit()
// indicates success.
int run(void f(char *), char *s)
{
  int pid;
  int xstatus;

  printf("test %s: ", s);
  if ((pid = fork()) < 0)
  {
    printf("runtest: fork error\n");
    exit(1);
  }
  if (pid == 0)
  {
    f(s);
    exit(0);
  }
  else
  {
    wait(&xstatus);
    if (xstatus != 0)
      printf("FAILED\n");
    else
      printf("OK\n");
    return xstatus == 0;
  }
}

int main(int argc, char *argv[])
{
  int continuous = 0;
  char *justone = 0;

  if (argc == 2 && strcmp(argv[1], "-c") == 0)
  {
    continuous = 1;
  }
  else if (argc == 2 && strcmp(argv[1], "-C") == 0)
  {
    continuous = 2;
  }
  else if (argc == 2 && argv[1][0] != '-')
  {
    justone = argv[1];
  }
  else if (argc > 1)
  {
    printf("Usage: usertests [-c] [testname]\n");
    exit(1);
  }

  struct test
  {
    void (*f)(char *);
    char *s;
  } tests[] = {
      {execout, "execout"},
      {copyin, "copyin"},
      {copyout, "copyout"},
      {copyinstr1, "copyinstr1"},
      {copyinstr2, "copyinstr2"},
      {copyinstr3, "copyinstr3"},
      {truncate1, "truncate1"},
      {truncate2, "truncate2"},
      {truncate3, "truncate3"},
      {reparent2, "reparent2"},
      {pgbug, "pgbug"},
      {sbrkbugs, "sbrkbugs"},
      // {badwrite, "badwrite" },
      {badarg, "badarg"},
      {reparent, "reparent"},
      {twochildren, "twochildren"},
      {forkfork, "forkfork"},
      {forkforkfork, "forkforkfork"},
      {argptest, "argptest"},
      {createdelete, "createdelete"},
      {linkunlink, "linkunlink"},
      {linktest, "linktest"},
      {unlinkread, "unlinkread"},
      {concreate, "concreate"},
      {subdir, "subdir"},
      {fourfiles, "fourfiles"},
      {sharedfd, "sharedfd"},
      {exectest, "exectest"},
      {bigargtest, "bigargtest"},
      {bigwrite, "bigwrite"},
      {bsstest, "bsstest"},
      {sbrkbasic, "sbrkbasic"},
      {sbrkmuch, "sbrkmuch"},
      {kernmem, "kernmem"},
      {sbrkfail, "sbrkfail"},
      {sbrkarg, "sbrkarg"},
      {validatetest, "validatetest"},
      {stacktest, "stacktest"},
      {opentest, "opentest"},
      {writetest, "writetest"},
      {writebig, "writebig"},
      {createtest, "createtest"},
      {openiputtest, "openiput"},
      {exitiputtest, "exitiput"},
      {iputtest, "iput"},
      {mem, "mem"},
      {pipe1, "pipe1"},
      {preempt, "preempt"},
      {exitwait, "exitwait"},
      {rmdot, "rmdot"},
      {fourteen, "fourteen"},
      {bigfile, "bigfile"},
      {dirfile, "dirfile"},
      {iref, "iref"},
      {forktest, "forktest"},
      {bigdir, "bigdir"}, // slow
      {0, 0},
  };

  if (continuous)
  {
    printf("continuous usertests starting\n");
    while (1)
    {
      int fail = 0;
      int free0 = countfree();
      for (struct test *t = tests; t->s != 0; t++)
      {
        if (!run(t->f, t->s))
        {
          fail = 1;
          break;
        }
      }
      if (fail)
      {
        printf("SOME TESTS FAILED\n");
        if (continuous != 2)
          exit(1);
      }
      int free1 = countfree();
      if (free1 < free0)
      {
        printf("FAILED -- lost %d free pages\n", free0 - free1);
        if (continuous != 2)
          exit(1);
      }
    }
  }

  printf("usertests starting\n");
  int free0 = countfree();
  int free1 = 0;
  int fail = 0;
  for (struct test *t = tests; t->s != 0; t++)
  {
    if ((justone == 0) || strcmp(t->s, justone) == 0)
    {
      if (!run(t->f, t->s))
        fail = 1;
    }
  }

  if (fail)
  {
    printf("SOME TESTS FAILED\n");
    exit(1);
  }
  else if ((free1 = countfree()) < free0)
  {
    printf("FAILED -- lost some free pages %d (out of %d)\n", free1, free0);
    exit(1);
  }
  else
  {
    printf("ALL TESTS PASSED\n");
    exit(0);
  }
}
