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minix/servers/mfs/path.c

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/* This file contains the procedures that look up path names in the directory
* system and determine the inode number that goes with a given path name.
*
* The entry points into this file are
* eat_path: the 'main' routine of the path-to-inode conversion mechanism
* last_dir: find the final directory on a given path
* advance: parse one component of a path name
* search_dir: search a directory for a string and return its inode number
*
*/
#include "fs.h"
#include <string.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <sys/stat.h>
#include "buf.h"
#include "inode.h"
#include "super.h"
#include <minix/vfsif.h>
PUBLIC char dot1[2] = "."; /* used for search_dir to bypass the access */
PUBLIC char dot2[3] = ".."; /* permissions for . and .. */
FORWARD _PROTOTYPE( char *get_name, (char *old_name, char string [NAME_MAX]) );
FORWARD _PROTOTYPE( int ltraverse, (struct inode *rip, char *path,
char *suffix) );
/*===========================================================================*
* lookup *
*===========================================================================*/
PUBLIC int lookup()
{
char string[NAME_MAX];
struct inode *rip;
int s_error;
string[0] = '\0';
/* Copy the pathname and set up caller's user and group id */
err_code = sys_datacopy(FS_PROC_NR, (vir_bytes) fs_m_in.REQ_PATH, SELF,
(vir_bytes) user_path, (phys_bytes) fs_m_in.REQ_PATH_LEN);
if (err_code != OK) return err_code;
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
/* Lookup inode */
rip = parse_path(user_path, string, fs_m_in.REQ_FLAGS);
/* Copy back the last name if it is required */
if ((fs_m_in.REQ_FLAGS & LAST_DIR || fs_m_in.REQ_FLAGS & LAST_DIR_EATSYM)
&& err_code != ENAMETOOLONG) {
s_error = sys_datacopy(SELF_E, (vir_bytes) string, FS_PROC_NR,
(vir_bytes) fs_m_in.REQ_USER_ADDR, (phys_bytes)
MIN(strlen(string)+1, NAME_MAX));
if (s_error != OK) return s_error;
}
/* Error or mount point encountered */
if (rip == NIL_INODE)
return err_code;
fs_m_out.RES_INODE_NR = rip->i_num;
fs_m_out.RES_MODE = rip->i_mode;
fs_m_out.RES_FILE_SIZE = rip->i_size;
/* If 'path' is a block special file, return dev number. */
if ( (rip->i_mode & I_TYPE) == I_BLOCK_SPECIAL) {
fs_m_out.RES_DEV = (dev_t) rip->i_zone[0];
}
/* Drop inode (path parse increased the counter) */
put_inode(rip);
return OK;
}
/*===========================================================================*
* parse_path *
*===========================================================================*/
PUBLIC struct inode *parse_path(path, string, action)
char *path; /* the path name to be parsed */
char string[NAME_MAX]; /* the final component is returned here */
int action; /* action on last part of path */
{
/* This is the actual code for last_dir and eat_path. Return the inode of
* the last directory and the name of object within that directory, or the
* inode of the last object (an empty name will be returned). Names are
* returned in string. If string is null the name is discarded. The action
* code determines how "last" is defined. If an error occurs, NIL_INODE
* will be returned with an error code in err_code.
*/
struct inode *rip, *dir_ip;
struct inode *ver_rip;
char *new_name;
char lstring[NAME_MAX];
/* Find starting inode inode according to the request message */
if ((rip = find_inode(fs_dev, fs_m_in.REQ_INODE_NR)) == NIL_INODE) {
printf("FS: couldn't find starting inode req_nr: %d %s\n", req_nr,
user_path);
err_code = ENOENT;
return NIL_INODE;
}
/* Find chroot inode according to the request message */
if (fs_m_in.REQ_CHROOT_NR != 0) {
if ((chroot_dir = find_inode(fs_dev, fs_m_in.REQ_CHROOT_NR))
== NIL_INODE) {
printf("FS: couldn't find chroot inode\n");
err_code = ENOENT;
return NIL_INODE;
}
}
else chroot_dir = NIL_INODE;
/* Set user and group ID */
caller_uid = fs_m_in.REQ_UID;
caller_gid = fs_m_in.REQ_GID;
/* No characters were processed yet */
path_processed = 0;
/* Current number of symlinks encountered */
symloop = fs_m_in.REQ_SYMLOOP;
/* If dir has been removed return ENOENT. */
/* Note: empty (start) path is checked in the VFS process */
if (rip->i_nlinks == 0/* || *path == '\0'*/) {
err_code = ENOENT;
return(NIL_INODE);
}
/* There is only one way how the starting directory of the lookup
* can be a mount point which is not a root directory,
* namely: climbing up on a mount (ELEAVEMOUNT).
* In this case the lookup is intrested in the parent dir of the mount
* point, but the last ".." component was processed in the 'previous'
* FS process. Let's do that first.
*/
if (rip->i_mount == I_MOUNT && rip->i_num != ROOT_INODE) {
dir_ip = rip;
rip = advance(&dir_ip, "..");
if (rip == NIL_INODE) return rip;
put_inode(rip); /* advance() increased the counter */
}
dup_inode(rip); /* inode will be returned with put_inode */
/* Looking for the starting directory?
* Note: this happens after EENTERMOUNT or ELEAVEMOUNT
* without more path component */
if (*path == '\0') {
return rip;
}
if (string == (char *) 0) string = lstring;
/* Scan the path component by component. */
while (TRUE) {
/* Extract one component. */
if ( (new_name = get_name(path, string)) == (char*) 0) {
put_inode(rip); /* bad path in user space */
return(NIL_INODE);
}
if (*new_name == '\0' && (action & PATH_PENULTIMATE)) {
if ( (rip->i_mode & I_TYPE) == I_DIRECTORY) {
return(rip); /* normal exit */
} else {
/* last file of path prefix is not a directory */
put_inode(rip);
err_code = ENOTDIR;
return(NIL_INODE);
}
}
/* There is more path. Keep parsing. */
dir_ip = rip;
rip = advance(&dir_ip, string);
/* Mount point encountered? */
if (rip == NIL_INODE && (err_code == EENTERMOUNT ||
err_code == ELEAVEMOUNT)) {
put_inode(dir_ip);
return NIL_INODE;
}
if (rip == NIL_INODE) {
if (*new_name == '\0' && (action & PATH_NONSYMBOLIC) != 0)
return(dir_ip);
else {
put_inode(dir_ip);
return(NIL_INODE);
}
}
/* The call to advance() succeeded. Fetch next component. */
if (S_ISLNK(rip->i_mode)) {
if (*new_name != '\0' || (action & PATH_OPAQUE) == 0) {
if (*new_name != '\0') new_name--;
/* Extract path name from the symlink file */
if (ltraverse(rip, user_path, new_name) != OK) {
put_inode(dir_ip);
err_code = ENOENT;
return NIL_INODE;
}
/* Symloop limit reached? */
if (++symloop > SYMLOOP) {
put_inode(dir_ip);
err_code = ELOOP;
return NIL_INODE;
}
/* Start over counting */
path_processed = 0;
/* Check whether new path is relative or absolute */
if (user_path[0] == '/') {
/* Go back to VFS */
put_inode(dir_ip);
err_code = ESYMLINK;
fs_m_out.RES_OFFSET = path_processed;
fs_m_out.RES_SYMLOOP = symloop;
return NIL_INODE;
}
/* Path is relative */
else {
rip = dir_ip;
path = user_path;
continue;
}
}
}
else if (*new_name != '\0') {
put_inode(dir_ip);
path = new_name;
continue;
}
/* Either last name reached or symbolic link is opaque */
if ((action & PATH_NONSYMBOLIC) != 0) {
put_inode(rip);
return(dir_ip);
} else {
put_inode(dir_ip);
return(rip);
}
}
}
/*===========================================================================*
* ltraverse *
*===========================================================================*/
PRIVATE int ltraverse(rip, path, suffix)
register struct inode *rip; /* symbolic link */
char *path; /* path containing link */
char *suffix; /* suffix following link within path */
{
/* Traverse a symbolic link. Copy the link text from the inode and insert
* the text into the path. Return error code or report success. Base
* directory has to be determined according to the first character of the
* new pathname.
*/
block_t b; /* block containing link text */
struct buf *bp; /* buffer containing link text */
size_t sl; /* length of link */
size_t tl; /* length of suffix */
char *sp; /* start of link text */
int r = OK;
bp = NIL_BUF;
if ((b = read_map(rip, (off_t) 0)) != NO_BLOCK) {
bp = get_block(rip->i_dev, b, NORMAL);
sl = rip->i_size;
sp = bp->b_data;
/* Insert symbolic text into path name. */
tl = strlen(suffix);
if (sl > 0 && sl + tl <= PATH_MAX-1) {
memmove(path+sl, suffix, tl);
memmove(path, sp, sl);
path[sl+tl] = 0;
/* Copy back to VFS layer THIS SHOULD BE IN parse_path */
r = sys_datacopy(SELF_E, (vir_bytes) path, FS_PROC_NR,
(vir_bytes) vfs_slink_storage, (phys_bytes) sl+tl+1);
/*
dup_inode(bip = path[0] == '/' ? chroot_dir : ldip);
*/
}
}
else {
r = ENOENT;
}
put_block(bp, DIRECTORY_BLOCK);
put_inode(rip);
return r;
}
/*===========================================================================*
* advance *
*===========================================================================*/
PUBLIC struct inode *advance(pdirp, string)
struct inode **pdirp; /* inode for directory to be searched */
char string[NAME_MAX]; /* component name to look for */
{
/* Given a directory and a component of a path, look up the component in
* the directory, find the inode, open it, and return a pointer to its inode
* slot. If it can't be done, return NIL_INODE.
*/
register struct inode *rip, *dirp;
register struct super_block *sp;
int r, inumb;
dev_t mnt_dev;
ino_t numb;
dirp = *pdirp;
/* If 'string' is empty, yield same inode straight away. */
if (string[0] == '\0') { return(get_inode(dirp->i_dev, (int) dirp->i_num)); }
/* Check for NIL_INODE. */
if (dirp == NIL_INODE) { return(NIL_INODE); }
/* If 'string' is not present in the directory, signal error. */
if ( (r = search_dir(dirp, string, &numb, LOOK_UP)) != OK) {
err_code = r;
return(NIL_INODE);
}
/* Don't go beyond the current root directory, unless the string is dot2.
* Note: it has to be checked only if this FS process owns the chroot
* directory of the process */
if (chroot_dir != NIL_INODE) {
if (dirp == chroot_dir && strcmp(string, "..") == 0 && string != dot2)
return(get_inode(dirp->i_dev, (int) dirp->i_num));
}
/* The component has been found in the directory. Get inode. */
if ( (rip = get_inode(dirp->i_dev, (int) numb)) == NIL_INODE) {
return(NIL_INODE);
}
/* The following test is for "mountpoint/.." where mountpoint is a
* mountpoint. ".." will refer to the root of the mounted filesystem,
* but has to become a reference to the parent of the 'mountpoint'
* directory.
*
* This case is recognized by the looked up name pointing to a
* root inode, and the directory in which it is held being a
* root inode, _and_ the name[1] being '.'. (This is a test for '..'
* and excludes '.'.)
*/
if (rip->i_num == ROOT_INODE) {
if (dirp->i_num == ROOT_INODE) {
if (string[1] == '.') {
sp = rip->i_sp;
if (!sp->s_is_root) {
/*printf("FSadvance: ELEAVEMOUNT callnr: %d, cp: %d, restp: %s\n",
call_nr, path_processed, user_path + path_processed);*/
/* Climbing up mountpoint */
err_code = ELEAVEMOUNT;
/* This will be the FS process endoint */
fs_m_out.m_source = rip->i_dev;
fs_m_out.RES_OFFSET = path_processed;
fs_m_out.RES_SYMLOOP = symloop;
put_inode(rip);
/*put_inode(dirp);*/
rip = NIL_INODE;
}
}
}
}
if (rip == NIL_INODE) return(NIL_INODE);
/* See if the inode is mounted on. If so, switch to root directory of the
* mounted file system. The super_block provides the linkage between the
* inode mounted on and the root directory of the mounted file system.
*/
if (rip != NIL_INODE && rip->i_mount == I_MOUNT) {
/*printf("FSadvance: EENTERMOUNT callnr: %d, cp: %d, vmnti: %d, restp: %s\n",
call_nr, path_processed, rip->i_vmnt_ind, user_path + path_processed);*/
/* Mountpoint encountered, report it */
err_code = EENTERMOUNT;
fs_m_out.RES_INODE_NR = rip->i_num;
fs_m_out.RES_OFFSET = path_processed;
fs_m_out.RES_SYMLOOP = symloop;
put_inode(rip);
rip = NIL_INODE;
}
return(rip); /* return pointer to inode's component */
}
/*===========================================================================*
* get_name *
*===========================================================================*/
PRIVATE char *get_name(old_name, string)
char *old_name; /* path name to parse */
char string[NAME_MAX]; /* component extracted from 'old_name' */
{
/* Given a pointer to a path name in fs space, 'old_name', copy the next
* component to 'string' and pad with zeros. A pointer to that part of
* the name as yet unparsed is returned. Roughly speaking,
* 'get_name' = 'old_name' - 'string'.
*
* This routine follows the standard convention that /usr/ast, /usr//ast,
* //usr///ast and /usr/ast/ are all equivalent.
*/
register int c;
register char *np, *rnp;
np = string; /* 'np' points to current position */
rnp = old_name; /* 'rnp' points to unparsed string */
while ( (c = *rnp) == '/') {
rnp++; /* skip leading slashes */
path_processed++; /* count characters */
}
/* Copy the unparsed path, 'old_name', to the array, 'string'. */
while ( rnp < &old_name[PATH_MAX] && c != '/' && c != '\0') {
if (np < &string[NAME_MAX]) *np++ = c;
c = *++rnp; /* advance to next character */
path_processed++; /* count characters */
}
/* To make /usr/ast/ equivalent to /usr/ast, skip trailing slashes. */
while (c == '/' && rnp < &old_name[PATH_MAX]) {
c = *++rnp;
path_processed++; /* count characters */
}
if (np < &string[NAME_MAX]) *np = '\0'; /* Terminate string */
if (rnp >= &old_name[PATH_MAX]) {
err_code = ENAMETOOLONG;
return((char *) 0);
}
return(rnp);
}
/*===========================================================================*
* search_dir *
*===========================================================================*/
PUBLIC int search_dir(ldir_ptr, string, numb, flag)
register struct inode *ldir_ptr; /* ptr to inode for dir to search */
char string[NAME_MAX]; /* component to search for */
ino_t *numb; /* pointer to inode number */
int flag; /* LOOK_UP, ENTER, DELETE or IS_EMPTY */
{
/* This function searches the directory whose inode is pointed to by 'ldip':
* if (flag == ENTER) enter 'string' in the directory with inode # '*numb';
* if (flag == DELETE) delete 'string' from the directory;
* if (flag == LOOK_UP) search for 'string' and return inode # in 'numb';
* if (flag == IS_EMPTY) return OK if only . and .. in dir else ENOTEMPTY;
*
* if 'string' is dot1 or dot2, no access permissions are checked.
*/
register struct direct *dp = NULL;
register struct buf *bp = NULL;
int i, r, e_hit, t, match;
mode_t bits;
off_t pos;
unsigned new_slots, old_slots;
block_t b;
struct super_block *sp;
int extended = 0;
/* If 'ldir_ptr' is not a pointer to a dir inode, error. */
if ( (ldir_ptr->i_mode & I_TYPE) != I_DIRECTORY) {
return(ENOTDIR);
}
r = OK;
if (flag != IS_EMPTY) {
bits = (flag == LOOK_UP ? X_BIT : W_BIT | X_BIT);
if (string == dot1 || string == dot2) {
if (flag != LOOK_UP) r = read_only(ldir_ptr);
/* only a writable device is required. */
}
else r = forbidden(ldir_ptr, bits); /* check access permissions */
}
if (r != OK) return(r);
/* Step through the directory one block at a time. */
old_slots = (unsigned) (ldir_ptr->i_size/DIR_ENTRY_SIZE);
new_slots = 0;
e_hit = FALSE;
match = 0; /* set when a string match occurs */
for (pos = 0; pos < ldir_ptr->i_size; pos += ldir_ptr->i_sp->s_block_size) {
b = read_map(ldir_ptr, pos); /* get block number */
/* Since directories don't have holes, 'b' cannot be NO_BLOCK. */
bp = get_block(ldir_ptr->i_dev, b, NORMAL); /* get a dir block */
if (bp == NO_BLOCK)
panic(__FILE__,"get_block returned NO_BLOCK", NO_NUM);
/* Search a directory block. */
for (dp = &bp->b_dir[0];
dp < &bp->b_dir[NR_DIR_ENTRIES(ldir_ptr->i_sp->s_block_size)];
dp++) {
if (++new_slots > old_slots) { /* not found, but room left */
if (flag == ENTER) e_hit = TRUE;
break;
}
/* Match occurs if string found. */
if (flag != ENTER && dp->d_ino != 0) {
if (flag == IS_EMPTY) {
/* If this test succeeds, dir is not empty. */
if (strcmp(dp->d_name, "." ) != 0 &&
strcmp(dp->d_name, "..") != 0) match = 1;
} else {
if (strncmp(dp->d_name, string, NAME_MAX) == 0){
match = 1;
}
}
}
if (match) {
/* LOOK_UP or DELETE found what it wanted. */
r = OK;
if (flag == IS_EMPTY) r = ENOTEMPTY;
else if (flag == DELETE) {
/* Save d_ino for recovery. */
t = NAME_MAX - sizeof(ino_t);
*((ino_t *) &dp->d_name[t]) = dp->d_ino;
dp->d_ino = 0; /* erase entry */
bp->b_dirt = DIRTY;
ldir_ptr->i_update |= CTIME | MTIME;
ldir_ptr->i_dirt = DIRTY;
} else {
sp = ldir_ptr->i_sp; /* 'flag' is LOOK_UP */
*numb = conv4(sp->s_native, (int) dp->d_ino);
}
put_block(bp, DIRECTORY_BLOCK);
return(r);
}
/* Check for free slot for the benefit of ENTER. */
if (flag == ENTER && dp->d_ino == 0) {
e_hit = TRUE; /* we found a free slot */
break;
}
}
/* The whole block has been searched or ENTER has a free slot. */
if (e_hit) break; /* e_hit set if ENTER can be performed now */
put_block(bp, DIRECTORY_BLOCK); /* otherwise, continue searching dir */
}
/* The whole directory has now been searched. */
if (flag != ENTER) {
return(flag == IS_EMPTY ? OK : ENOENT);
}
/* This call is for ENTER. If no free slot has been found so far, try to
* extend directory.
*/
if (e_hit == FALSE) { /* directory is full and no room left in last block */
new_slots++; /* increase directory size by 1 entry */
if (new_slots == 0) return(EFBIG); /* dir size limited by slot count */
if ( (bp = new_block(ldir_ptr, ldir_ptr->i_size)) == NIL_BUF)
return(err_code);
dp = &bp->b_dir[0];
extended = 1;
}
/* 'bp' now points to a directory block with space. 'dp' points to slot. */
(void) memset(dp->d_name, 0, (size_t) NAME_MAX); /* clear entry */
for (i = 0; string[i] && i < NAME_MAX; i++) dp->d_name[i] = string[i];
sp = ldir_ptr->i_sp;
dp->d_ino = conv4(sp->s_native, (int) *numb);
bp->b_dirt = DIRTY;
put_block(bp, DIRECTORY_BLOCK);
ldir_ptr->i_update |= CTIME | MTIME; /* mark mtime for update later */
ldir_ptr->i_dirt = DIRTY;
if (new_slots > old_slots) {
ldir_ptr->i_size = (off_t) new_slots * DIR_ENTRY_SIZE;
/* Send the change to disk if the directory is extended. */
if (extended) rw_inode(ldir_ptr, WRITING);
}
return(OK);
}
/*===========================================================================*
* eat_path *
*===========================================================================*/
PUBLIC struct inode *eat_path(path)
char *path; /* the path name to be parsed */
{
/* Parse the path 'path' and put its inode in the inode table. If not possible,
* return NIL_INODE as function value and an error code in 'err_code'.
*/
return parse_path(path, (char *) 0, EAT_PATH);
}
/*===========================================================================*
* last_dir *
*===========================================================================*/
PUBLIC struct inode *last_dir(path, string)
char *path; /* the path name to be parsed */
char string[NAME_MAX]; /* the final component is returned here */
{
/* Given a path, 'path', located in the fs address space, parse it as
* far as the last directory, fetch the inode for the last directory into
* the inode table, and return a pointer to the inode. In
* addition, return the final component of the path in 'string'.
* If the last directory can't be opened, return NIL_INODE and
* the reason for failure in 'err_code'.
*/
return parse_path(path, string, LAST_DIR);
}
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