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