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784 lines
16 KiB
784 lines
16 KiB
/*
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* linux/fs/namei.c
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*
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* (C) 1991 Linus Torvalds
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*/
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/*
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* Some corrections by tytso.
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*/
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <asm/segment.h>
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#include <string.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <const.h>
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#include <sys/stat.h>
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#define ACC_MODE(x) ("\004\002\006\377"[(x)&O_ACCMODE])
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/*
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* comment out this line if you want names > NAME_LEN chars to be
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* truncated. Else they will be disallowed.
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*/
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/* #define NO_TRUNCATE */
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#define MAY_EXEC 1
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#define MAY_WRITE 2
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#define MAY_READ 4
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/*
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* permission()
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*
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* is used to check for read/write/execute permissions on a file.
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* I don't know if we should look at just the euid or both euid and
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* uid, but that should be easily changed.
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*/
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static int permission(struct m_inode * inode,int mask)
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{
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int mode = inode->i_mode;
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/* special case: not even root can read/write a deleted file */
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if (inode->i_dev && !inode->i_nlinks)
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return 0;
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else if (current->euid==inode->i_uid)
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mode >>= 6;
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else if (current->egid==inode->i_gid)
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mode >>= 3;
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if (((mode & mask & 0007) == mask) || suser())
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return 1;
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return 0;
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}
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/*
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* ok, we cannot use strncmp, as the name is not in our data space.
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* Thus we'll have to use match. No big problem. Match also makes
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* some sanity tests.
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*
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* NOTE! unlike strncmp, match returns 1 for success, 0 for failure.
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*/
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static int match(int len,const char * name,struct dir_entry * de)
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{
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register int same __asm__("ax");
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if (!de || !de->inode || len > NAME_LEN)
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return 0;
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if (len < NAME_LEN && de->name[len])
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return 0;
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__asm__("cld\n\t"
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"fs ; repe ; cmpsb\n\t"
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"setz %%al"
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:"=a" (same)
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:"0" (0),"S" ((long) name),"D" ((long) de->name),"c" (len)
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);
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return same;
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}
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/*
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* find_entry()
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*
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* finds an entry in the specified directory with the wanted name. It
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* returns the cache buffer in which the entry was found, and the entry
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* itself (as a parameter - res_dir). It does NOT read the inode of the
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* entry - you'll have to do that yourself if you want to.
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*
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* This also takes care of the few special cases due to '..'-traversal
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* over a pseudo-root and a mount point.
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*/
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static struct buffer_head * find_entry(struct m_inode ** dir,
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const char * name, int namelen, struct dir_entry ** res_dir)
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{
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int entries;
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int block,i;
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struct buffer_head * bh;
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struct dir_entry * de;
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struct super_block * sb;
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#ifdef NO_TRUNCATE
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if (namelen > NAME_LEN)
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return NULL;
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#else
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if (namelen > NAME_LEN)
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namelen = NAME_LEN;
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#endif
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entries = (*dir)->i_size / (sizeof (struct dir_entry));
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*res_dir = NULL;
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if (!namelen)
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return NULL;
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/* check for '..', as we might have to do some "magic" for it */
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if (namelen==2 && get_fs_byte(name)=='.' && get_fs_byte(name+1)=='.') {
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/* '..' in a pseudo-root results in a faked '.' (just change namelen) */
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if ((*dir) == current->root)
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namelen=1;
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else if ((*dir)->i_num == ROOT_INO) {
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/* '..' over a mount-point results in 'dir' being exchanged for the mounted
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directory-inode. NOTE! We set mounted, so that we can iput the new dir */
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sb=get_super((*dir)->i_dev);
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if (sb->s_imount) {
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iput(*dir);
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(*dir)=sb->s_imount;
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(*dir)->i_count++;
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}
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}
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}
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if (!(block = (*dir)->i_zone[0]))
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return NULL;
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if (!(bh = bread((*dir)->i_dev,block)))
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return NULL;
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i = 0;
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de = (struct dir_entry *) bh->b_data;
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while (i < entries) {
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if ((char *)de >= BLOCK_SIZE+bh->b_data) {
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brelse(bh);
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bh = NULL;
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if (!(block = bmap(*dir,i/DIR_ENTRIES_PER_BLOCK)) ||
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!(bh = bread((*dir)->i_dev,block))) {
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i += DIR_ENTRIES_PER_BLOCK;
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continue;
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}
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de = (struct dir_entry *) bh->b_data;
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}
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if (match(namelen,name,de)) {
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*res_dir = de;
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return bh;
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}
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de++;
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i++;
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}
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brelse(bh);
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return NULL;
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}
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/*
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* add_entry()
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*
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* adds a file entry to the specified directory, using the same
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* semantics as find_entry(). It returns NULL if it failed.
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*
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* NOTE!! The inode part of 'de' is left at 0 - which means you
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* may not sleep between calling this and putting something into
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* the entry, as someone else might have used it while you slept.
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*/
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static struct buffer_head * add_entry(struct m_inode * dir,
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const char * name, int namelen, struct dir_entry ** res_dir)
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{
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int block,i;
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struct buffer_head * bh;
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struct dir_entry * de;
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*res_dir = NULL;
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#ifdef NO_TRUNCATE
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if (namelen > NAME_LEN)
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return NULL;
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#else
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if (namelen > NAME_LEN)
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namelen = NAME_LEN;
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#endif
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if (!namelen)
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return NULL;
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if (!(block = dir->i_zone[0]))
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return NULL;
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if (!(bh = bread(dir->i_dev,block)))
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return NULL;
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i = 0;
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de = (struct dir_entry *) bh->b_data;
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while (1) {
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if ((char *)de >= BLOCK_SIZE+bh->b_data) {
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brelse(bh);
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bh = NULL;
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block = create_block(dir,i/DIR_ENTRIES_PER_BLOCK);
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if (!block)
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return NULL;
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if (!(bh = bread(dir->i_dev,block))) {
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i += DIR_ENTRIES_PER_BLOCK;
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continue;
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}
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de = (struct dir_entry *) bh->b_data;
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}
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if (i*sizeof(struct dir_entry) >= dir->i_size) {
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de->inode=0;
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dir->i_size = (i+1)*sizeof(struct dir_entry);
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dir->i_dirt = 1;
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dir->i_ctime = CURRENT_TIME;
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}
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if (!de->inode) {
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dir->i_mtime = CURRENT_TIME;
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for (i=0; i < NAME_LEN ; i++)
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de->name[i]=(i<namelen)?get_fs_byte(name+i):0;
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bh->b_dirt = 1;
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*res_dir = de;
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return bh;
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}
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de++;
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i++;
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}
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brelse(bh);
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return NULL;
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}
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/*
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* get_dir()
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*
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* Getdir traverses the pathname until it hits the topmost directory.
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* It returns NULL on failure.
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*/
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static struct m_inode * get_dir(const char * pathname)
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{
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char c;
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const char * thisname;
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struct m_inode * inode;
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struct buffer_head * bh;
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int namelen,inr,idev;
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struct dir_entry * de;
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if (!current->root || !current->root->i_count)
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panic("No root inode");
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if (!current->pwd || !current->pwd->i_count)
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panic("No cwd inode");
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if ((c=get_fs_byte(pathname))=='/') {
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inode = current->root;
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pathname++;
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} else if (c)
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inode = current->pwd;
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else
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return NULL; /* empty name is bad */
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inode->i_count++;
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while (1) {
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thisname = pathname;
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if (!S_ISDIR(inode->i_mode) || !permission(inode,MAY_EXEC)) {
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iput(inode);
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return NULL;
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}
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for(namelen=0;(c=get_fs_byte(pathname++))&&(c!='/');namelen++)
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/* nothing */ ;
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if (!c)
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return inode;
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if (!(bh = find_entry(&inode,thisname,namelen,&de))) {
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iput(inode);
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return NULL;
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}
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inr = de->inode;
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idev = inode->i_dev;
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brelse(bh);
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iput(inode);
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if (!(inode = iget(idev,inr)))
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return NULL;
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}
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}
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/*
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* dir_namei()
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*
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* dir_namei() returns the inode of the directory of the
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* specified name, and the name within that directory.
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*/
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static struct m_inode * dir_namei(const char * pathname,
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int * namelen, const char ** name)
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{
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char c;
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const char * basename;
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struct m_inode * dir;
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if (!(dir = get_dir(pathname)))
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return NULL;
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basename = pathname;
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while (c=get_fs_byte(pathname++))
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if (c=='/')
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basename=pathname;
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*namelen = pathname-basename-1;
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*name = basename;
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return dir;
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}
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/*
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* namei()
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*
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* is used by most simple commands to get the inode of a specified name.
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* Open, link etc use their own routines, but this is enough for things
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* like 'chmod' etc.
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*/
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struct m_inode * namei(const char * pathname)
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{
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const char * basename;
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int inr,dev,namelen;
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struct m_inode * dir;
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struct buffer_head * bh;
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struct dir_entry * de;
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if (!(dir = dir_namei(pathname,&namelen,&basename)))
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return NULL;
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if (!namelen) /* special case: '/usr/' etc */
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return dir;
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bh = find_entry(&dir,basename,namelen,&de);
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if (!bh) {
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iput(dir);
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return NULL;
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}
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inr = de->inode;
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dev = dir->i_dev;
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brelse(bh);
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iput(dir);
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dir=iget(dev,inr);
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if (dir) {
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dir->i_atime=CURRENT_TIME;
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dir->i_dirt=1;
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}
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return dir;
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}
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/*
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* open_namei()
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*
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* namei for open - this is in fact almost the whole open-routine.
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*/
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int open_namei(const char * pathname, int flag, int mode,
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struct m_inode ** res_inode)
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{
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const char * basename;
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int inr,dev,namelen;
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struct m_inode * dir, *inode;
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struct buffer_head * bh;
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struct dir_entry * de;
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if ((flag & O_TRUNC) && !(flag & O_ACCMODE))
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flag |= O_WRONLY;
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mode &= 0777 & ~current->umask;
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mode |= I_REGULAR;
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if (!(dir = dir_namei(pathname,&namelen,&basename)))
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return -ENOENT;
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if (!namelen) { /* special case: '/usr/' etc */
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if (!(flag & (O_ACCMODE|O_CREAT|O_TRUNC))) {
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*res_inode=dir;
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return 0;
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}
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iput(dir);
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return -EISDIR;
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}
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bh = find_entry(&dir,basename,namelen,&de);
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if (!bh) {
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if (!(flag & O_CREAT)) {
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iput(dir);
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return -ENOENT;
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}
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if (!permission(dir,MAY_WRITE)) {
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iput(dir);
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return -EACCES;
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}
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inode = new_inode(dir->i_dev);
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if (!inode) {
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iput(dir);
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return -ENOSPC;
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}
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inode->i_uid = current->euid;
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inode->i_mode = mode;
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inode->i_dirt = 1;
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bh = add_entry(dir,basename,namelen,&de);
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if (!bh) {
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inode->i_nlinks--;
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iput(inode);
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iput(dir);
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return -ENOSPC;
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}
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de->inode = inode->i_num;
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bh->b_dirt = 1;
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brelse(bh);
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iput(dir);
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*res_inode = inode;
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return 0;
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}
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inr = de->inode;
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dev = dir->i_dev;
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brelse(bh);
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iput(dir);
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if (flag & O_EXCL)
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return -EEXIST;
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if (!(inode=iget(dev,inr)))
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return -EACCES;
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if ((S_ISDIR(inode->i_mode) && (flag & O_ACCMODE)) ||
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!permission(inode,ACC_MODE(flag))) {
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iput(inode);
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return -EPERM;
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}
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inode->i_atime = CURRENT_TIME;
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if (flag & O_TRUNC)
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truncate(inode);
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*res_inode = inode;
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return 0;
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}
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|
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int sys_mknod(const char * filename, int mode, int dev)
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{
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const char * basename;
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int namelen;
|
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struct m_inode * dir, * inode;
|
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struct buffer_head * bh;
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struct dir_entry * de;
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if (!suser())
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return -EPERM;
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if (!(dir = dir_namei(filename,&namelen,&basename)))
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return -ENOENT;
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if (!namelen) {
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iput(dir);
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return -ENOENT;
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}
|
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if (!permission(dir,MAY_WRITE)) {
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iput(dir);
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return -EPERM;
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}
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bh = find_entry(&dir,basename,namelen,&de);
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if (bh) {
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brelse(bh);
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iput(dir);
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return -EEXIST;
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}
|
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inode = new_inode(dir->i_dev);
|
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if (!inode) {
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iput(dir);
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return -ENOSPC;
|
|
}
|
|
inode->i_mode = mode;
|
|
if (S_ISBLK(mode) || S_ISCHR(mode))
|
|
inode->i_zone[0] = dev;
|
|
inode->i_mtime = inode->i_atime = CURRENT_TIME;
|
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inode->i_dirt = 1;
|
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bh = add_entry(dir,basename,namelen,&de);
|
|
if (!bh) {
|
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iput(dir);
|
|
inode->i_nlinks=0;
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iput(inode);
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return -ENOSPC;
|
|
}
|
|
de->inode = inode->i_num;
|
|
bh->b_dirt = 1;
|
|
iput(dir);
|
|
iput(inode);
|
|
brelse(bh);
|
|
return 0;
|
|
}
|
|
|
|
int sys_mkdir(const char * pathname, int mode)
|
|
{
|
|
const char * basename;
|
|
int namelen;
|
|
struct m_inode * dir, * inode;
|
|
struct buffer_head * bh, *dir_block;
|
|
struct dir_entry * de;
|
|
|
|
if (!suser())
|
|
return -EPERM;
|
|
if (!(dir = dir_namei(pathname,&namelen,&basename)))
|
|
return -ENOENT;
|
|
if (!namelen) {
|
|
iput(dir);
|
|
return -ENOENT;
|
|
}
|
|
if (!permission(dir,MAY_WRITE)) {
|
|
iput(dir);
|
|
return -EPERM;
|
|
}
|
|
bh = find_entry(&dir,basename,namelen,&de);
|
|
if (bh) {
|
|
brelse(bh);
|
|
iput(dir);
|
|
return -EEXIST;
|
|
}
|
|
inode = new_inode(dir->i_dev);
|
|
if (!inode) {
|
|
iput(dir);
|
|
return -ENOSPC;
|
|
}
|
|
inode->i_size = 32;
|
|
inode->i_dirt = 1;
|
|
inode->i_mtime = inode->i_atime = CURRENT_TIME;
|
|
if (!(inode->i_zone[0]=new_block(inode->i_dev))) {
|
|
iput(dir);
|
|
inode->i_nlinks--;
|
|
iput(inode);
|
|
return -ENOSPC;
|
|
}
|
|
inode->i_dirt = 1;
|
|
if (!(dir_block=bread(inode->i_dev,inode->i_zone[0]))) {
|
|
iput(dir);
|
|
free_block(inode->i_dev,inode->i_zone[0]);
|
|
inode->i_nlinks--;
|
|
iput(inode);
|
|
return -ERROR;
|
|
}
|
|
de = (struct dir_entry *) dir_block->b_data;
|
|
de->inode=inode->i_num;
|
|
strcpy(de->name,".");
|
|
de++;
|
|
de->inode = dir->i_num;
|
|
strcpy(de->name,"..");
|
|
inode->i_nlinks = 2;
|
|
dir_block->b_dirt = 1;
|
|
brelse(dir_block);
|
|
inode->i_mode = I_DIRECTORY | (mode & 0777 & ~current->umask);
|
|
inode->i_dirt = 1;
|
|
bh = add_entry(dir,basename,namelen,&de);
|
|
if (!bh) {
|
|
iput(dir);
|
|
free_block(inode->i_dev,inode->i_zone[0]);
|
|
inode->i_nlinks=0;
|
|
iput(inode);
|
|
return -ENOSPC;
|
|
}
|
|
de->inode = inode->i_num;
|
|
bh->b_dirt = 1;
|
|
dir->i_nlinks++;
|
|
dir->i_dirt = 1;
|
|
iput(dir);
|
|
iput(inode);
|
|
brelse(bh);
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* routine to check that the specified directory is empty (for rmdir)
|
|
*/
|
|
static int empty_dir(struct m_inode * inode)
|
|
{
|
|
int nr,block;
|
|
int len;
|
|
struct buffer_head * bh;
|
|
struct dir_entry * de;
|
|
|
|
len = inode->i_size / sizeof (struct dir_entry);
|
|
if (len<2 || !inode->i_zone[0] ||
|
|
!(bh=bread(inode->i_dev,inode->i_zone[0]))) {
|
|
printk("warning - bad directory on dev %04x\n",inode->i_dev);
|
|
return 0;
|
|
}
|
|
de = (struct dir_entry *) bh->b_data;
|
|
if (de[0].inode != inode->i_num || !de[1].inode ||
|
|
strcmp(".",de[0].name) || strcmp("..",de[1].name)) {
|
|
printk("warning - bad directory on dev %04x\n",inode->i_dev);
|
|
return 0;
|
|
}
|
|
nr = 2;
|
|
de += 2;
|
|
while (nr<len) {
|
|
if ((void *) de >= (void *) (bh->b_data+BLOCK_SIZE)) {
|
|
brelse(bh);
|
|
block=bmap(inode,nr/DIR_ENTRIES_PER_BLOCK);
|
|
if (!block) {
|
|
nr += DIR_ENTRIES_PER_BLOCK;
|
|
continue;
|
|
}
|
|
if (!(bh=bread(inode->i_dev,block)))
|
|
return 0;
|
|
de = (struct dir_entry *) bh->b_data;
|
|
}
|
|
if (de->inode) {
|
|
brelse(bh);
|
|
return 0;
|
|
}
|
|
de++;
|
|
nr++;
|
|
}
|
|
brelse(bh);
|
|
return 1;
|
|
}
|
|
|
|
int sys_rmdir(const char * name)
|
|
{
|
|
const char * basename;
|
|
int namelen;
|
|
struct m_inode * dir, * inode;
|
|
struct buffer_head * bh;
|
|
struct dir_entry * de;
|
|
|
|
if (!suser())
|
|
return -EPERM;
|
|
if (!(dir = dir_namei(name,&namelen,&basename)))
|
|
return -ENOENT;
|
|
if (!namelen) {
|
|
iput(dir);
|
|
return -ENOENT;
|
|
}
|
|
if (!permission(dir,MAY_WRITE)) {
|
|
iput(dir);
|
|
return -EPERM;
|
|
}
|
|
bh = find_entry(&dir,basename,namelen,&de);
|
|
if (!bh) {
|
|
iput(dir);
|
|
return -ENOENT;
|
|
}
|
|
if (!(inode = iget(dir->i_dev, de->inode))) {
|
|
iput(dir);
|
|
brelse(bh);
|
|
return -EPERM;
|
|
}
|
|
if ((dir->i_mode & S_ISVTX) && current->euid &&
|
|
inode->i_uid != current->euid) {
|
|
iput(dir);
|
|
iput(inode);
|
|
brelse(bh);
|
|
return -EPERM;
|
|
}
|
|
if (inode->i_dev != dir->i_dev || inode->i_count>1) {
|
|
iput(dir);
|
|
iput(inode);
|
|
brelse(bh);
|
|
return -EPERM;
|
|
}
|
|
if (inode == dir) { /* we may not delete ".", but "../dir" is ok */
|
|
iput(inode);
|
|
iput(dir);
|
|
brelse(bh);
|
|
return -EPERM;
|
|
}
|
|
if (!S_ISDIR(inode->i_mode)) {
|
|
iput(inode);
|
|
iput(dir);
|
|
brelse(bh);
|
|
return -ENOTDIR;
|
|
}
|
|
if (!empty_dir(inode)) {
|
|
iput(inode);
|
|
iput(dir);
|
|
brelse(bh);
|
|
return -ENOTEMPTY;
|
|
}
|
|
if (inode->i_nlinks != 2)
|
|
printk("empty directory has nlink!=2 (%d)",inode->i_nlinks);
|
|
de->inode = 0;
|
|
bh->b_dirt = 1;
|
|
brelse(bh);
|
|
inode->i_nlinks=0;
|
|
inode->i_dirt=1;
|
|
dir->i_nlinks--;
|
|
dir->i_ctime = dir->i_mtime = CURRENT_TIME;
|
|
dir->i_dirt=1;
|
|
iput(dir);
|
|
iput(inode);
|
|
return 0;
|
|
}
|
|
|
|
int sys_unlink(const char * name)
|
|
{
|
|
const char * basename;
|
|
int namelen;
|
|
struct m_inode * dir, * inode;
|
|
struct buffer_head * bh;
|
|
struct dir_entry * de;
|
|
|
|
if (!(dir = dir_namei(name,&namelen,&basename)))
|
|
return -ENOENT;
|
|
if (!namelen) {
|
|
iput(dir);
|
|
return -ENOENT;
|
|
}
|
|
if (!permission(dir,MAY_WRITE)) {
|
|
iput(dir);
|
|
return -EPERM;
|
|
}
|
|
bh = find_entry(&dir,basename,namelen,&de);
|
|
if (!bh) {
|
|
iput(dir);
|
|
return -ENOENT;
|
|
}
|
|
if (!(inode = iget(dir->i_dev, de->inode))) {
|
|
iput(dir);
|
|
brelse(bh);
|
|
return -ENOENT;
|
|
}
|
|
if ((dir->i_mode & S_ISVTX) && !suser() &&
|
|
current->euid != inode->i_uid &&
|
|
current->euid != dir->i_uid) {
|
|
iput(dir);
|
|
iput(inode);
|
|
brelse(bh);
|
|
return -EPERM;
|
|
}
|
|
if (S_ISDIR(inode->i_mode)) {
|
|
iput(inode);
|
|
iput(dir);
|
|
brelse(bh);
|
|
return -EPERM;
|
|
}
|
|
if (!inode->i_nlinks) {
|
|
printk("Deleting nonexistent file (%04x:%d), %d\n",
|
|
inode->i_dev,inode->i_num,inode->i_nlinks);
|
|
inode->i_nlinks=1;
|
|
}
|
|
de->inode = 0;
|
|
bh->b_dirt = 1;
|
|
brelse(bh);
|
|
inode->i_nlinks--;
|
|
inode->i_dirt = 1;
|
|
inode->i_ctime = CURRENT_TIME;
|
|
iput(inode);
|
|
iput(dir);
|
|
return 0;
|
|
}
|
|
|
|
int sys_symlink()
|
|
{
|
|
return -ENOSYS;
|
|
}
|
|
|
|
int sys_link(const char * oldname, const char * newname)
|
|
{
|
|
struct dir_entry * de;
|
|
struct m_inode * oldinode, * dir;
|
|
struct buffer_head * bh;
|
|
const char * basename;
|
|
int namelen;
|
|
|
|
oldinode=namei(oldname);
|
|
if (!oldinode)
|
|
return -ENOENT;
|
|
if (S_ISDIR(oldinode->i_mode)) {
|
|
iput(oldinode);
|
|
return -EPERM;
|
|
}
|
|
dir = dir_namei(newname,&namelen,&basename);
|
|
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;
|
|
}
|
|
bh = find_entry(&dir,basename,namelen,&de);
|
|
if (bh) {
|
|
brelse(bh);
|
|
iput(dir);
|
|
iput(oldinode);
|
|
return -EEXIST;
|
|
}
|
|
bh = add_entry(dir,basename,namelen,&de);
|
|
if (!bh) {
|
|
iput(dir);
|
|
iput(oldinode);
|
|
return -ENOSPC;
|
|
}
|
|
de->inode = oldinode->i_num;
|
|
bh->b_dirt = 1;
|
|
brelse(bh);
|
|
iput(dir);
|
|
oldinode->i_nlinks++;
|
|
oldinode->i_ctime = CURRENT_TIME;
|
|
oldinode->i_dirt = 1;
|
|
iput(oldinode);
|
|
return 0;
|
|
}
|