Linux0.96c/fs/namei.c
/*
* linux/fs/namei.c
*
* (C) 1991 Linus Torvalds
*/
/*
* Some corrections by tytso.
*/
#include <errno.h>
#include <const.h>
#include <asm/segment.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
struct inode * _namei(const char * filename, struct inode * base,
int follow_links);
#define ACC_MODE(x) ("\004\002\006\377"[(x)&O_ACCMODE])
/*
* comment out this line if you want names > MINIX_NAME_LEN chars to be
* truncated. Else they will be disallowed.
*/
/* #define NO_TRUNCATE */
/*
* permission()
*
* is used to check for read/write/execute permissions on a file.
* I don't know if we should look at just the euid or both euid and
* uid, but that should be easily changed.
*/
int permission(struct inode * inode,int mask)
{
int mode = inode->i_mode;
/* special case: not even root can read/write a deleted file */
if (inode->i_dev && !inode->i_nlink)
return 0;
else if (current->euid == inode->i_uid)
mode >>= 6;
else if (in_group_p(inode->i_gid))
mode >>= 3;
if (((mode & mask & 0007) == mask) || suser())
return 1;
return 0;
}
/*
* lookup() looks up one part of a pathname, using the fs-dependent
* routines (currently minix_lookup) for it. It also checks for
* fathers (pseudo-roots, mount-points)
*/
int lookup(struct inode * dir,const char * name, int len,
struct inode ** result)
{
struct super_block * sb;
*result = NULL;
if (len==2 && get_fs_byte(name)=='.' && get_fs_byte(name+1)=='.') {
if (dir == current->root)
len = 1;
else if ((sb = dir->i_sb) && (dir == sb->s_mounted)) {
sb = dir->i_sb;
iput(dir);
if (dir = sb->s_covered)
dir->i_count++;
}
}
if (!dir)
return -ENOENT;
if (!permission(dir,MAY_EXEC)) {
iput(dir);
return -EACCES;
}
if (!len) {
*result = dir;
return 0;
}
if (!dir->i_op || !dir->i_op->lookup) {
iput(dir);
return -ENOENT;
}
return dir->i_op->lookup(dir,name,len,result);
}
struct inode * follow_link(struct inode * dir, struct inode * inode)
{
if (!dir || !inode) {
iput(dir);
iput(inode);
return NULL;
}
if (!inode->i_op || !inode->i_op->follow_link) {
iput(dir);
return inode;
}
return inode->i_op->follow_link(dir,inode);
}
/*
* dir_namei()
*
* dir_namei() returns the inode of the directory of the
* specified name, and the name within that directory.
*/
static struct inode * dir_namei(const char * pathname,
int * namelen, const char ** name, struct inode * base)
{
char c;
const char * thisname;
int len,error;
struct inode * inode;
if (!base) {
base = current->pwd;
base->i_count++;
}
if ((c=get_fs_byte(pathname))=='/') {
iput(base);
base = current->root;
pathname++;
base->i_count++;
}
while (1) {
thisname = pathname;
for(len=0;(c=get_fs_byte(pathname++))&&(c!='/');len++)
/* nothing */ ;
if (!c)
break;
base->i_count++;
error = lookup(base,thisname,len,&inode);
if (error) {
iput(base);
return NULL;
}
if (!(base = follow_link(base,inode)))
return NULL;
}
*name = thisname;
*namelen = len;
return base;
}
struct inode * _namei(const char * pathname, struct inode * base,
int follow_links)
{
const char * basename;
int namelen,error;
struct inode * inode;
if (!(base = dir_namei(pathname,&namelen,&basename,base)))
return NULL;
base->i_count++; /* lookup uses up base */
error = lookup(base,basename,namelen,&inode);
if (error) {
iput(base);
return NULL;
}
if (follow_links)
inode = follow_link(base,inode);
else
iput(base);
return inode;
}
struct inode * lnamei(const char * pathname)
{
return _namei(pathname, NULL, 0);
}
/*
* namei()
*
* is used by most simple commands to get the inode of a specified name.
* Open, link etc use their own routines, but this is enough for things
* like 'chmod' etc.
*/
struct inode * namei(const char * pathname)
{
return _namei(pathname,NULL,1);
}
/*
* open_namei()
*
* namei for open - this is in fact almost the whole open-routine.
*/
int open_namei(const char * pathname, int flag, int mode,
struct inode ** res_inode)
{
const char * basename;
int namelen,error;
struct inode * dir, *inode;
if ((flag & O_TRUNC) && !(flag & O_ACCMODE))
flag |= O_WRONLY;
mode &= 07777 & ~current->umask;
mode |= I_REGULAR;
if (!(dir = dir_namei(pathname,&namelen,&basename,NULL)))
return -ENOENT;
if (!namelen) { /* special case: '/usr/' etc */
if (!(flag & (O_ACCMODE|O_CREAT|O_TRUNC))) {
*res_inode=dir;
return 0;
}
iput(dir);
return -EISDIR;
}
dir->i_count++; /* lookup eats the dir */
error = lookup(dir,basename,namelen,&inode);
if (error) {
if (!(flag & O_CREAT)) {
iput(dir);
return error;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->create) {
iput(dir);
return -EACCES;
}
return dir->i_op->create(dir,basename,namelen,mode,res_inode);
}
if (flag & O_EXCL) {
iput(dir);
iput(inode);
return -EEXIST;
}
if (!(inode = follow_link(dir,inode)))
return -ELOOP;
if ((S_ISDIR(inode->i_mode) && (flag & O_ACCMODE)) ||
!permission(inode,ACC_MODE(flag))) {
iput(inode);
return -EPERM;
}
inode->i_atime = CURRENT_TIME;
if (flag & O_TRUNC)
if (inode->i_op && inode->i_op->truncate) {
inode->i_size = 0;
inode->i_op->truncate(inode);
}
*res_inode = inode;
return 0;
}
int do_mknod(const char * filename, int mode, int dev)
{
const char * basename;
int namelen;
struct inode * dir;
if (!(dir = dir_namei(filename,&namelen,&basename, NULL)))
return -ENOENT;
if (!namelen) {
iput(dir);
return -ENOENT;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->mknod) {
iput(dir);
return -EPERM;
}
return dir->i_op->mknod(dir,basename,namelen,mode,dev);
}
int sys_mknod(const char * filename, int mode, int dev)
{
if (S_ISFIFO(mode) || suser())
return do_mknod(filename,mode,dev);
return -EPERM;
}
int sys_mkdir(const char * pathname, int mode)
{
const char * basename;
int namelen;
struct inode * dir;
if (!(dir = dir_namei(pathname,&namelen,&basename, NULL)))
return -ENOENT;
if (!namelen) {
iput(dir);
return -ENOENT;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->mkdir) {
iput(dir);
return -EPERM;
}
return dir->i_op->mkdir(dir,basename,namelen,mode);
}
int sys_rmdir(const char * name)
{
const char * basename;
int namelen;
struct inode * dir;
if (!(dir = dir_namei(name,&namelen,&basename, NULL)))
return -ENOENT;
if (!namelen) {
iput(dir);
return -ENOENT;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->rmdir) {
iput(dir);
return -EPERM;
}
return dir->i_op->rmdir(dir,basename,namelen);
}
int sys_unlink(const char * name)
{
const char * basename;
int namelen;
struct inode * dir;
if (!(dir = dir_namei(name,&namelen,&basename, NULL)))
return -ENOENT;
if (!namelen) {
iput(dir);
return -EPERM;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->unlink) {
iput(dir);
return -EPERM;
}
return dir->i_op->unlink(dir,basename,namelen);
}
int sys_symlink(const char * oldname, const char * newname)
{
struct inode * dir;
const char * basename;
int namelen;
dir = dir_namei(newname,&namelen,&basename, NULL);
if (!dir)
return -ENOENT;
if (!namelen) {
iput(dir);
return -ENOENT;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->symlink) {
iput(dir);
return -EPERM;
}
return dir->i_op->symlink(dir,basename,namelen,oldname);
}
int sys_link(const char * oldname, const char * newname)
{
struct inode * oldinode, * dir;
const char * basename;
int namelen;
oldinode = namei(oldname);
if (!oldinode)
return -ENOENT;
dir = dir_namei(newname,&namelen,&basename, NULL);
if (!dir) {
iput(oldinode);
return -EACCES;
}
if (!namelen) {
iput(oldinode);
iput(dir);
return -EPERM;
}
if (dir->i_dev != oldinode->i_dev) {
iput(dir);
iput(oldinode);
return -EXDEV;
}
if (!permission(dir,MAY_WRITE)) {
iput(dir);
iput(oldinode);
return -EACCES;
}
if (!dir->i_op || !dir->i_op->link) {
iput(dir);
iput(oldinode);
return -EPERM;
}
return dir->i_op->link(oldinode, dir, basename, namelen);
}
int sys_rename(const char * oldname, const char * newname)
{
struct inode * old_dir, * new_dir;
const char * old_base, * new_base;
int old_len, new_len;
old_dir = dir_namei(oldname,&old_len,&old_base, NULL);
if (!old_dir)
return -ENOENT;
if (!permission(old_dir,MAY_WRITE)) {
iput(old_dir);
return -EACCES;
}
if (!old_len || (get_fs_byte(old_base) == '.' &&
(old_len == 1 || (get_fs_byte(old_base+1) == '.' &&
old_len == 2)))) {
iput(old_dir);
return -EPERM;
}
new_dir = dir_namei(newname,&new_len,&new_base, NULL);
if (!new_dir) {
iput(old_dir);
return -ENOENT;
}
if (!permission(new_dir,MAY_WRITE)) {
iput(old_dir);
iput(new_dir);
return -EACCES;
}
if (!new_len || (get_fs_byte(new_base) == '.' &&
(new_len == 1 || (get_fs_byte(new_base+1) == '.' &&
new_len == 2)))) {
iput(old_dir);
iput(new_dir);
return -EPERM;
}
if (new_dir->i_dev != old_dir->i_dev) {
iput(old_dir);
iput(new_dir);
return -EXDEV;
}
if (!old_dir->i_op || !old_dir->i_op->rename) {
iput(old_dir);
iput(new_dir);
return -EPERM;
}
return old_dir->i_op->rename(old_dir, old_base, old_len,
new_dir, new_base, new_len);
}