diff options
Diffstat (limited to 'linux/fs/namei.c')
| -rw-r--r-- | linux/fs/namei.c | 678 |
1 files changed, 678 insertions, 0 deletions
diff --git a/linux/fs/namei.c b/linux/fs/namei.c new file mode 100644 index 0000000..600737b --- /dev/null +++ b/linux/fs/namei.c @@ -0,0 +1,678 @@ +#include <linux/sched.h> +#include <linux/kernel.h> +#include <asm/segment.h> + +#include <string.h> +#include <fcntl.h> +#include <errno.h> +#include <const.h> +#include <sys/stat.h> + +#define ACC_MODE(x) ("\004\002\006\377"[(x)&O_ACCMODE]) + +/* + * comment out this line if you want names > NAME_LEN chars to be + * truncated. Else they will be disallowed. + */ +/* #define NO_TRUNCATE */ + +#define MAY_EXEC 1 +#define MAY_WRITE 2 +#define MAY_READ 4 + +/* + * 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. + */ +static int permission(struct m_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_nlinks) + return 0; + if (!(current->uid && current->euid)) + mode=0777; + else if (current->uid==inode->i_uid || current->euid==inode->i_uid) + mode >>= 6; + else if (current->gid==inode->i_gid || current->egid==inode->i_gid) + mode >>= 3; + return mode & mask & 0007; +} + +/* + * ok, we cannot use strncmp, as the name is not in our data space. + * Thus we'll have to use match. No big problem. Match also makes + * some sanity tests. + * + * NOTE! unlike strncmp, match returns 1 for success, 0 for failure. + */ +static int match(int len,const char * name,struct dir_entry * de) +{ + register int same __asm__("ax"); + + if (!de || !de->inode || len > NAME_LEN) + return 0; + if (len < NAME_LEN && de->name[len]) + return 0; + __asm__("cld\n\t" + "fs ; repe ; cmpsb\n\t" + "setz %%al" + :"=a" (same) + :"0" (0),"S" ((long) name),"D" ((long) de->name),"c" (len) + :"cx","di","si"); + return same; +} + +/* + * find_entry() + * + * finds and entry in the specified directory with the wanted name. It + * returns the cache buffer in which the entry was found, and the entry + * itself (as a parameter - res_dir). It does NOT read the inode of the + * entry - you'll have to do that yourself if you want to. + */ +static struct buffer_head * find_entry(struct m_inode * dir, + const char * name, int namelen, struct dir_entry ** res_dir) +{ + int entries; + int block,i; + struct buffer_head * bh; + struct dir_entry * de; + +#ifdef NO_TRUNCATE + if (namelen > NAME_LEN) + return NULL; +#else + if (namelen > NAME_LEN) + namelen = NAME_LEN; +#endif + entries = dir->i_size / (sizeof (struct dir_entry)); + *res_dir = NULL; + if (!namelen) + return NULL; + if (!(block = dir->i_zone[0])) + return NULL; + if (!(bh = bread(dir->i_dev,block))) + return NULL; + i = 0; + de = (struct dir_entry *) bh->b_data; + while (i < entries) { + if ((char *)de >= BLOCK_SIZE+bh->b_data) { + brelse(bh); + bh = NULL; + if (!(block = bmap(dir,i/DIR_ENTRIES_PER_BLOCK)) || + !(bh = bread(dir->i_dev,block))) { + i += DIR_ENTRIES_PER_BLOCK; + continue; + } + de = (struct dir_entry *) bh->b_data; + } + if (match(namelen,name,de)) { + *res_dir = de; + return bh; + } + de++; + i++; + } + brelse(bh); + return NULL; +} + +/* + * add_entry() + * + * adds a file entry to the specified directory, using the same + * semantics as find_entry(). It returns NULL if it failed. + * + * NOTE!! The inode part of 'de' is left at 0 - which means you + * may not sleep between calling this and putting something into + * the entry, as someone else might have used it while you slept. + */ +static struct buffer_head * add_entry(struct m_inode * dir, + const char * name, int namelen, struct dir_entry ** res_dir) +{ + int block,i; + struct buffer_head * bh; + struct dir_entry * de; + + *res_dir = NULL; +#ifdef NO_TRUNCATE + if (namelen > NAME_LEN) + return NULL; +#else + if (namelen > NAME_LEN) + namelen = NAME_LEN; +#endif + if (!namelen) + return NULL; + if (!(block = dir->i_zone[0])) + return NULL; + if (!(bh = bread(dir->i_dev,block))) + return NULL; + i = 0; + de = (struct dir_entry *) bh->b_data; + while (1) { + if ((char *)de >= BLOCK_SIZE+bh->b_data) { + brelse(bh); + bh = NULL; + block = create_block(dir,i/DIR_ENTRIES_PER_BLOCK); + if (!block) + return NULL; + if (!(bh = bread(dir->i_dev,block))) { + i += DIR_ENTRIES_PER_BLOCK; + continue; + } + de = (struct dir_entry *) bh->b_data; + } + if (i*sizeof(struct dir_entry) >= dir->i_size) { + de->inode=0; + dir->i_size = (i+1)*sizeof(struct dir_entry); + dir->i_dirt = 1; + dir->i_ctime = CURRENT_TIME; + } + if (!de->inode) { + dir->i_mtime = CURRENT_TIME; + for (i=0; i < NAME_LEN ; i++) + de->name[i]=(i<namelen)?get_fs_byte(name+i):0; + bh->b_dirt = 1; + *res_dir = de; + return bh; + } + de++; + i++; + } + brelse(bh); + return NULL; +} + +/* + * get_dir() + * + * Getdir traverses the pathname until it hits the topmost directory. + * It returns NULL on failure. + */ +static struct m_inode * get_dir(const char * pathname) +{ + char c; + const char * thisname; + struct m_inode * inode; + struct buffer_head * bh; + int namelen,inr,idev; + struct dir_entry * de; + + if (!current->root || !current->root->i_count) + panic("No root inode"); + if (!current->pwd || !current->pwd->i_count) + panic("No cwd inode"); + if ((c=get_fs_byte(pathname))=='/') { + inode = current->root; + pathname++; + } else if (c) + inode = current->pwd; + else + return NULL; /* empty name is bad */ + inode->i_count++; + while (1) { + thisname = pathname; + if (!S_ISDIR(inode->i_mode) || !permission(inode,MAY_EXEC)) { + iput(inode); + return NULL; + } + for(namelen=0;(c=get_fs_byte(pathname++))&&(c!='/');namelen++) + /* nothing */ ; + if (!c) + return inode; + if (!(bh = find_entry(inode,thisname,namelen,&de))) { + iput(inode); + return NULL; + } + inr = de->inode; + idev = inode->i_dev; + brelse(bh); + iput(inode); + if (!(inode = iget(idev,inr))) + return NULL; + } +} + +/* + * dir_namei() + * + * dir_namei() returns the inode of the directory of the + * specified name, and the name within that directory. + */ +static struct m_inode * dir_namei(const char * pathname, + int * namelen, const char ** name) +{ + char c; + const char * basename; + struct m_inode * dir; + + if (!(dir = get_dir(pathname))) + return NULL; + basename = pathname; + while (c=get_fs_byte(pathname++)) + if (c=='/') + basename=pathname; + *namelen = pathname-basename-1; + *name = basename; + return dir; +} + +/* + * 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 m_inode * namei(const char * pathname) +{ + const char * basename; + int inr,dev,namelen; + struct m_inode * dir; + struct buffer_head * bh; + struct dir_entry * de; + + if (!(dir = dir_namei(pathname,&namelen,&basename))) + return NULL; + if (!namelen) /* special case: '/usr/' etc */ + return dir; + bh = find_entry(dir,basename,namelen,&de); + if (!bh) { + iput(dir); + return NULL; + } + inr = de->inode; + dev = dir->i_dev; + brelse(bh); + iput(dir); + dir=iget(dev,inr); + if (dir) { + dir->i_atime=CURRENT_TIME; + dir->i_dirt=1; + } + return dir; +} + +/* + * 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 m_inode ** res_inode) +{ + const char * basename; + int inr,dev,namelen; + struct m_inode * dir, *inode; + struct buffer_head * bh; + struct dir_entry * de; + + if ((flag & O_TRUNC) && !(flag & O_ACCMODE)) + flag |= O_WRONLY; + mode &= 0777 & ~current->umask; + mode |= I_REGULAR; + if (!(dir = dir_namei(pathname,&namelen,&basename))) + 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; + } + bh = find_entry(dir,basename,namelen,&de); + if (!bh) { + if (!(flag & O_CREAT)) { + iput(dir); + return -ENOENT; + } + if (!permission(dir,MAY_WRITE)) { + iput(dir); + return -EACCES; + } + inode = new_inode(dir->i_dev); + if (!inode) { + iput(dir); + return -ENOSPC; + } + inode->i_mode = mode; + inode->i_dirt = 1; + bh = add_entry(dir,basename,namelen,&de); + if (!bh) { + inode->i_nlinks--; + iput(inode); + iput(dir); + return -ENOSPC; + } + de->inode = inode->i_num; + bh->b_dirt = 1; + brelse(bh); + iput(dir); + *res_inode = inode; + return 0; + } + inr = de->inode; + dev = dir->i_dev; + brelse(bh); + iput(dir); + if (flag & O_EXCL) + return -EEXIST; + if (!(inode=iget(dev,inr))) + return -EACCES; + if ((S_ISDIR(inode->i_mode) && (flag & O_ACCMODE)) || + permission(inode,ACC_MODE(flag))!=ACC_MODE(flag)) { + iput(inode); + return -EPERM; + } + inode->i_atime = CURRENT_TIME; + if (flag & O_TRUNC) + truncate(inode); + *res_inode = inode; + 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 (current->euid && current->uid) + 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 (current->euid && current->uid) + return -EPERM; + if (!(dir = dir_namei(name,&namelen,&basename))) + return -ENOENT; + if (!namelen) { + iput(dir); + return -ENOENT; + } + bh = find_entry(dir,basename,namelen,&de); + if (!bh) { + iput(dir); + return -ENOENT; + } + if (!permission(dir,MAY_WRITE)) { + iput(dir); + brelse(bh); + return -EPERM; + } + if (!(inode = iget(dir->i_dev, de->inode))) { + iput(dir); + 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; + } + inode = iget(dir->i_dev, de->inode); + if (!inode) { + printk("iget failed in delete (%04x:%d)",dir->i_dev,de->inode); + iput(dir); + brelse(bh); + return -ENOENT; + } + if (!S_ISREG(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_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_ISREG(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; +} |