--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/sysfile.c	Fri May 26 23:11:05 2017 +0900
@@ -0,0 +1,507 @@
+//
+// File-system system calls.
+// Mostly argument checking, since we don't trust
+// user code, and calls into file.c and fs.c.
+//
+
+#include "types.h"
+#include "defs.h"
+#include "param.h"
+#include "stat.h"
+#include "mmu.h"
+#include "proc.h"
+#include "fs.h"
+#include "file.h"
+#include "fcntl.h"
+
+// Fetch the nth word-sized system call argument as a file descriptor
+// and return both the descriptor and the corresponding struct file.
+static int argfd(int n, int *pfd, struct file **pf)
+{
+    int fd;
+    struct file *f;
+
+    if(argint(n, &fd) < 0) {
+        return -1;
+    }
+
+    if(fd < 0 || fd >= NOFILE || (f=proc->ofile[fd]) == 0) {
+        return -1;
+    }
+
+    if(pfd) {
+        *pfd = fd;
+    }
+
+    if(pf) {
+        *pf = f;
+    }
+
+    return 0;
+}
+
+// Allocate a file descriptor for the given file.
+// Takes over file reference from caller on success.
+static int fdalloc(struct file *f)
+{
+    int fd;
+
+    for(fd = 0; fd < NOFILE; fd++){
+        if(proc->ofile[fd] == 0){
+            proc->ofile[fd] = f;
+            return fd;
+        }
+    }
+
+    return -1;
+}
+
+int sys_dup(void)
+{
+    struct file *f;
+    int fd;
+
+    if(argfd(0, 0, &f) < 0) {
+        return -1;
+    }
+
+    if((fd=fdalloc(f)) < 0) {
+        return -1;
+    }
+
+    filedup(f);
+
+    return fd;
+}
+
+int sys_read(void)
+{
+    struct file *f;
+    int n;
+    char *p;
+
+    if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
+        return -1;
+    }
+
+    return fileread(f, p, n);
+}
+
+int sys_write(void)
+{
+    struct file *f;
+    int n;
+    char *p;
+
+    if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) {
+        return -1;
+    }
+
+    return filewrite(f, p, n);
+}
+
+int sys_close(void)
+{
+    int fd;
+    struct file *f;
+
+    if(argfd(0, &fd, &f) < 0) {
+        return -1;
+    }
+
+    proc->ofile[fd] = 0;
+    fileclose(f);
+
+    return 0;
+}
+
+int sys_fstat(void)
+{
+    struct file *f;
+    struct stat *st;
+
+    if(argfd(0, 0, &f) < 0 || argptr(1, (void*)&st, sizeof(*st)) < 0) {
+        return -1;
+    }
+
+    return filestat(f, st);
+}
+
+// Create the path new as a link to the same inode as old.
+int sys_link(void)
+{
+    char name[DIRSIZ], *new, *old;
+    struct inode *dp, *ip;
+
+    if(argstr(0, &old) < 0 || argstr(1, &new) < 0) {
+        return -1;
+    }
+
+    if((ip = namei(old)) == 0) {
+        return -1;
+    }
+
+    begin_trans();
+
+    ilock(ip);
+
+    if(ip->type == T_DIR){
+        iunlockput(ip);
+        commit_trans();
+        return -1;
+    }
+
+    ip->nlink++;
+    iupdate(ip);
+    iunlock(ip);
+
+    if((dp = nameiparent(new, name)) == 0) {
+        goto bad;
+    }
+
+    ilock(dp);
+
+    if(dp->dev != ip->dev || dirlink(dp, name, ip->inum) < 0){
+        iunlockput(dp);
+        goto bad;
+    }
+
+    iunlockput(dp);
+    iput(ip);
+
+    commit_trans();
+
+    return 0;
+
+    bad:
+    ilock(ip);
+    ip->nlink--;
+    iupdate(ip);
+    iunlockput(ip);
+    commit_trans();
+    return -1;
+}
+
+// Is the directory dp empty except for "." and ".." ?
+static int isdirempty(struct inode *dp)
+{
+    int off;
+    struct dirent de;
+
+    for(off=2*sizeof(de); off<dp->size; off+=sizeof(de)){
+        if(readi(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
+            panic("isdirempty: readi");
+        }
+
+        if(de.inum != 0) {
+            return 0;
+        }
+    }
+    return 1;
+}
+
+//PAGEBREAK!
+int sys_unlink(void)
+{
+    struct inode *ip, *dp;
+    struct dirent de;
+    char name[DIRSIZ], *path;
+    uint off;
+
+    if(argstr(0, &path) < 0) {
+        return -1;
+    }
+
+    if((dp = nameiparent(path, name)) == 0) {
+        return -1;
+    }
+
+    begin_trans();
+
+    ilock(dp);
+
+    // Cannot unlink "." or "..".
+    if(namecmp(name, ".") == 0 || namecmp(name, "..") == 0) {
+        goto bad;
+    }
+
+    if((ip = dirlookup(dp, name, &off)) == 0) {
+        goto bad;
+    }
+
+    ilock(ip);
+
+    if(ip->nlink < 1) {
+        panic("unlink: nlink < 1");
+    }
+
+    if(ip->type == T_DIR && !isdirempty(ip)){
+        iunlockput(ip);
+        goto bad;
+    }
+
+    memset(&de, 0, sizeof(de));
+
+    if(writei(dp, (char*)&de, off, sizeof(de)) != sizeof(de)) {
+        panic("unlink: writei");
+    }
+
+    if(ip->type == T_DIR){
+        dp->nlink--;
+        iupdate(dp);
+    }
+
+    iunlockput(dp);
+
+    ip->nlink--;
+    iupdate(ip);
+    iunlockput(ip);
+
+    commit_trans();
+
+    return 0;
+
+    bad:
+    iunlockput(dp);
+    commit_trans();
+    return -1;
+}
+
+static struct inode* create(char *path, short type, short major, short minor)
+{
+    uint off;
+    struct inode *ip, *dp;
+    char name[DIRSIZ];
+
+    if((dp = nameiparent(path, name)) == 0) {
+        return 0;
+    }
+
+    ilock(dp);
+
+    if((ip = dirlookup(dp, name, &off)) != 0){
+        iunlockput(dp);
+        ilock(ip);
+
+        if(type == T_FILE && ip->type == T_FILE) {
+            return ip;
+        }
+
+        iunlockput(ip);
+
+        return 0;
+    }
+
+    if((ip = ialloc(dp->dev, type)) == 0) {
+        panic("create: ialloc");
+    }
+
+    ilock(ip);
+    ip->major = major;
+    ip->minor = minor;
+    ip->nlink = 1;
+    iupdate(ip);
+
+    if(type == T_DIR){  // Create . and .. entries.
+        dp->nlink++;  // for ".."
+        iupdate(dp);
+
+        // No ip->nlink++ for ".": avoid cyclic ref count.
+        if(dirlink(ip, ".", ip->inum) < 0 || dirlink(ip, "..", dp->inum) < 0) {
+            panic("create dots");
+        }
+    }
+
+    if(dirlink(dp, name, ip->inum) < 0) {
+        panic("create: dirlink");
+    }
+
+    iunlockput(dp);
+
+    return ip;
+}
+
+int sys_open(void)
+{
+    char *path;
+    int fd, omode;
+    struct file *f;
+    struct inode *ip;
+
+    if(argstr(0, &path) < 0 || argint(1, &omode) < 0) {
+        return -1;
+    }
+
+    if(omode & O_CREATE){
+        begin_trans();
+        ip = create(path, T_FILE, 0, 0);
+        commit_trans();
+
+        if(ip == 0) {
+            return -1;
+        }
+
+    } else {
+        if((ip = namei(path)) == 0) {
+            return -1;
+        }
+
+        ilock(ip);
+
+        if(ip->type == T_DIR && omode != O_RDONLY){
+            iunlockput(ip);
+            return -1;
+        }
+    }
+
+    if((f = filealloc()) == 0 || (fd = fdalloc(f)) < 0){
+        if(f) {
+            fileclose(f);
+        }
+
+        iunlockput(ip);
+        return -1;
+    }
+
+    iunlock(ip);
+
+    f->type = FD_INODE;
+    f->ip = ip;
+    f->off = 0;
+    f->readable = !(omode & O_WRONLY);
+    f->writable = (omode & O_WRONLY) || (omode & O_RDWR);
+
+    return fd;
+}
+
+int sys_mkdir(void)
+{
+    char *path;
+    struct inode *ip;
+
+    begin_trans();
+
+    if(argstr(0, &path) < 0 || (ip = create(path, T_DIR, 0, 0)) == 0){
+        commit_trans();
+        return -1;
+    }
+
+    iunlockput(ip);
+    commit_trans();
+
+    return 0;
+}
+
+int sys_mknod(void)
+{
+    struct inode *ip;
+    char *path;
+    int len;
+    int major, minor;
+
+    begin_trans();
+
+    if((len=argstr(0, &path)) < 0 ||
+            argint(1, &major) < 0 || argint(2, &minor) < 0 ||
+            (ip = create(path, T_DEV, major, minor)) == 0){
+
+        commit_trans();
+        return -1;
+    }
+
+    iunlockput(ip);
+    commit_trans();
+
+    return 0;
+}
+
+int sys_chdir(void)
+{
+    char *path;
+    struct inode *ip;
+
+    if(argstr(0, &path) < 0 || (ip = namei(path)) == 0) {
+        return -1;
+    }
+
+    ilock(ip);
+
+    if(ip->type != T_DIR){
+        iunlockput(ip);
+        return -1;
+    }
+
+    iunlock(ip);
+
+    iput(proc->cwd);
+    proc->cwd = ip;
+
+    return 0;
+}
+
+int sys_exec(void)
+{
+    char *path, *argv[MAXARG];
+    int i;
+    uint uargv, uarg;
+
+    if(argstr(0, &path) < 0 || argint(1, (int*)&uargv) < 0){
+        return -1;
+    }
+
+    memset(argv, 0, sizeof(argv));
+
+    for(i=0;; i++){
+        if(i >= NELEM(argv)) {
+            return -1;
+        }
+
+        if(fetchint(uargv+4*i, (int*)&uarg) < 0) {
+            return -1;
+        }
+
+        if(uarg == 0){
+            argv[i] = 0;
+            break;
+        }
+
+        if(fetchstr(uarg, &argv[i]) < 0) {
+            return -1;
+        }
+    }
+
+    return exec(path, argv);
+}
+
+int sys_pipe(void)
+{
+    int *fd;
+    struct file *rf, *wf;
+    int fd0, fd1;
+
+    if(argptr(0, (void*)&fd, 2*sizeof(fd[0])) < 0) {
+        return -1;
+    }
+
+    if(pipealloc(&rf, &wf) < 0) {
+        return -1;
+    }
+
+    fd0 = -1;
+
+    if((fd0 = fdalloc(rf)) < 0 || (fd1 = fdalloc(wf)) < 0){
+        if(fd0 >= 0) {
+            proc->ofile[fd0] = 0;
+        }
+
+        fileclose(rf);
+        fileclose(wf);
+
+        return -1;
+    }
+
+    fd[0] = fd0;
+    fd[1] = fd1;
+
+    return 0;
+}