minix/servers/vfs/path.c
Thomas Veerman 958b25be50 - Introduce support for sticky bit.
- Revise VFS-FS protocol and update VFS/MFS/ISOFS accordingly.
- Clean up MFS by removing old, dead code (backwards compatibility is broken by
  the new VFS-FS protocol, anyway) and rewrite other parts. Also, make sure all
  functions have proper banners and prototypes.
- VFS should always provide a (syntactically) valid path to the FS; no need for
  the FS to do sanity checks when leaving/entering mount points.
- Fix several bugs in MFS:
  - Several path lookup bugs in MFS.
  - A link can be too big for the path buffer.
  - A mountpoint can become inaccessible when the creation of a new inode
    fails, because the inode already exists and is a mountpoint.
- Introduce support for supplemental groups.
- Add test 46 to test supplemental group functionality (and removed obsolete
  suppl. tests from test 2).
- Clean up VFS (not everything is done yet).
- ISOFS now opens device read-only. This makes the -r flag in the mount command
  unnecessary (but will still report to be mounted read-write).
- Introduce PipeFS. PipeFS is a new FS that handles all anonymous and
  named pipes. However, named pipes still reside on the (M)FS, as they are part
  of the file system on disk. To make this work VFS now has a concept of
  'mapped' inodes, which causes read, write, truncate and stat requests to be
  redirected to the mapped FS, and all other requests to the original FS.
2009-12-20 20:27:14 +00:00

305 lines
8.7 KiB
C

/* lookup() is the main routine that controls the path name lookup. It
* handles mountpoints and symbolic links. The actual lookup requests
* are sent through the req_lookup wrapper function.
*/
#include "fs.h"
#include <string.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include <minix/keymap.h>
#include <minix/const.h>
#include <minix/endpoint.h>
#include <unistd.h>
#include <minix/vfsif.h>
#include "fproc.h"
#include "vmnt.h"
#include "vnode.h"
#include "param.h"
/* Set to following define to 1 if you really want to use the POSIX definition
* (IEEE Std 1003.1, 2004) of pathname resolution. POSIX requires pathnames
* with a traling slash (and that do not entirely consist of slash characters)
* to be treated as if a single dot is appended. This means that for example
* mkdir("dir/", ...) and rmdir("dir/") will fail because the call tries to
* create or remove the directory '.'. Historically, Unix systems just ignore
* trailing slashes.
*/
#define DO_POSIX_PATHNAME_RES 0
FORWARD _PROTOTYPE( int lookup, (struct vnode *dirp, int flags,
node_details_t *node) );
/*===========================================================================*
* advance *
*===========================================================================*/
PUBLIC struct vnode *advance(dirp, flags)
struct vnode *dirp;
int flags;
{
/* Resolve a pathname (in user_fullpath) starting at dirp to a vnode. */
int r;
struct vnode *new_vp, *vp;
struct vmnt *vmp;
struct node_details res;
/* Get a free vnode */
if((new_vp = get_free_vnode()) == NIL_VNODE) return(NIL_VNODE);
/* Lookup vnode belonging to the file. */
if ((r = lookup(dirp, flags, &res)) != OK) {
err_code = r;
return(NIL_VNODE);
}
/* Check whether vnode is already in use or not */
if ((vp = find_vnode(res.fs_e, res.inode_nr)) != NIL_VNODE) {
dup_vnode(vp);
vp->v_fs_count++; /* We got a reference from the FS */
return(vp);
}
/* Fill in the free vnode's fields */
new_vp->v_fs_e = res.fs_e;
new_vp->v_inode_nr = res.inode_nr;
new_vp->v_mode = res.fmode;
new_vp->v_size = res.fsize;
new_vp->v_uid = res.uid;
new_vp->v_gid = res.gid;
new_vp->v_sdev = res.dev;
if( (vmp = find_vmnt(new_vp->v_fs_e)) == NIL_VMNT)
panic(__FILE__, "VFS advance: vmnt not found", NO_NUM);
new_vp->v_vmnt = vmp;
new_vp->v_dev = vmp->m_dev;
new_vp->v_fs_count = 1;
new_vp->v_ref_count = 1;
return(new_vp);
}
/*===========================================================================*
* eat_path *
*===========================================================================*/
PUBLIC struct vnode *eat_path(flags)
int flags;
{
/* Resolve 'user_fullpath' to a vnode. advance does the actual work. */
struct vnode *vp;
vp = (user_fullpath[0] == '/' ? fp->fp_rd : fp->fp_wd);
return advance(vp, flags);
}
/*===========================================================================*
* last_dir *
*===========================================================================*/
PUBLIC struct vnode *last_dir(void)
{
/* Parse a path, 'user_fullpath', as far as the last directory, fetch the vnode
* for the last directory into the vnode table, and return a pointer to the
* vnode. In addition, return the final component of the path in 'string'. If
* the last directory can't be opened, return NIL_VNODE and the reason for
* failure in 'err_code'. We can't parse component by component as that would
* be too expensive. Alternatively, we cut off the last component of the path,
* and parse the path up to the penultimate component.
*/
int r;
size_t len;
char *cp;
char dir_entry[PATH_MAX+1];
struct vnode *vp, *res;
/* Is the path absolute or relative? Initialize 'vp' accordingly. */
vp = (user_fullpath[0] == '/' ? fp->fp_rd : fp->fp_wd);
len = strlen(user_fullpath);
/* If path is empty, return ENOENT. */
if (len == 0) {
err_code = ENOENT;
return(NIL_VNODE);
}
#if !DO_POSIX_PATHNAME_RES
/* Remove trailing slashes */
while (len > 1 && user_fullpath[len-1] == '/') {
len--;
user_fullpath[len]= '\0';
}
#endif
cp = strrchr(user_fullpath, '/');
if (cp == NULL) {
/* Just one entry in the current working directory */
dup_vnode(vp);
return(vp);
} else if (cp[1] == '\0') {
/* Path ends in a slash. The directory entry is '.' */
strcpy(dir_entry, ".");
} else {
/* A path name for the directory and a directory entry */
strcpy(dir_entry, cp+1);
cp[1]= '\0';
}
/* Remove trailing slashes */
while(cp > user_fullpath && cp[0] == '/') {
cp[0]= '\0';
cp--;
}
res = advance(vp, PATH_NOFLAGS);
if (res == NIL_VNODE) return(NIL_VNODE);
/* Copy the directory entry back to user_fullpath */
strcpy(user_fullpath, dir_entry);
return(res);
}
/*===========================================================================*
* lookup *
*===========================================================================*/
PRIVATE int lookup(start_node, flags, node)
struct vnode *start_node;
int flags;
node_details_t *node;
{
/* Resolve a pathname (in user_fullpath) relative to start_node. */
int r, symloop;
endpoint_t fs_e;
size_t path_off, path_left_len;
ino_t dir_ino, root_ino;
uid_t uid;
gid_t gid;
struct vnode *dir_vp;
struct vmnt *vmp;
struct lookup_res res;
/* Empty (start) path? */
if (user_fullpath[0] == '\0') {
node->inode_nr = 0;
return(ENOENT);
}
if(!fp->fp_rd || !fp->fp_wd) {
printf("VFS: lookup_rel %d: no rd/wd\n", fp->fp_endpoint);
return(ENOENT);
}
fs_e = start_node->v_fs_e;
dir_ino = start_node->v_inode_nr;
/* Is the process' root directory on the same partition?,
* if so, set the chroot directory too. */
if (fp->fp_rd->v_dev == fp->fp_wd->v_dev)
root_ino = fp->fp_rd->v_inode_nr;
else
root_ino = 0;
/* Set user and group ids according to the system call */
uid = (call_nr == ACCESS ? fp->fp_realuid : fp->fp_effuid);
gid = (call_nr == ACCESS ? fp->fp_realgid : fp->fp_effgid);
symloop = 0; /* Number of symlinks seen so far */
/* Issue the request */
r = req_lookup(fs_e, dir_ino, root_ino, uid, gid, flags, &res);
if (r != OK && r != EENTERMOUNT && r != ELEAVEMOUNT && r != ESYMLINK)
return(r); /* i.e., an error occured */
/* While the response is related to mount control set the
* new requests respectively */
while(r == EENTERMOUNT || r == ELEAVEMOUNT || r == ESYMLINK) {
/* Update user_fullpath to reflect what's left to be parsed. */
path_off = res.char_processed;
path_left_len = strlen(&user_fullpath[path_off]);
memmove(user_fullpath, &user_fullpath[path_off], path_left_len);
user_fullpath[path_left_len] = '\0'; /* terminate string */
/* Update the current value of the symloop counter */
symloop += res.symloop;
if (symloop > SYMLOOP_MAX)
return(ELOOP);
/* Symlink encountered with absolute path */
if (r == ESYMLINK) {
dir_vp = fp->fp_rd;
} else if (r == EENTERMOUNT) {
/* Entering a new partition */
dir_vp = 0;
/* Start node is now the mounted partition's root node */
for (vmp = &vmnt[0]; vmp != &vmnt[NR_MNTS]; ++vmp) {
if (vmp->m_dev != NO_DEV) {
if (vmp->m_mounted_on->v_inode_nr == res.inode_nr &&
vmp->m_mounted_on->v_fs_e == res.fs_e) {
dir_vp = vmp->m_root_node;
break;
}
}
}
if (!dir_vp) {
panic(__FILE__,
"VFS lookup: can't find mounted partition",
NO_NUM);
}
} else {
/* Climbing up mount */
/* Find the vmnt that represents the partition on
* which we "climb up". */
if ((vmp = find_vmnt(res.fs_e)) == NIL_VMNT) {
panic(__FILE__,
"VFS lookup: can't find parent vmnt",NO_NUM);
}
/* Make sure that the child FS does not feed a bogus path
* to the parent FS. That is, when we climb up the tree, we
* must've encountered ".." in the path, and that is exactly
* what we're going to feed to the parent */
if(strncmp(user_fullpath, "..", 2) != 0) {
printf("VFS: bogus path: %s\n", user_fullpath);
return(ENOENT);
}
/* Start node is the vnode on which the partition is
* mounted */
dir_vp = vmp->m_mounted_on;
}
/* Set the starting directories inode number and FS endpoint */
fs_e = dir_vp->v_fs_e;
dir_ino = dir_vp->v_inode_nr;
/* Is the process' root directory on the same partition?,
* if so, set the chroot directory too. */
if(dir_vp->v_dev == fp->fp_rd->v_dev)
root_ino = fp->fp_rd->v_inode_nr;
else
root_ino = 0;
r = req_lookup(fs_e, dir_ino, root_ino, uid, gid, flags, &res);
if(r != OK && r != EENTERMOUNT && r != ELEAVEMOUNT && r != ESYMLINK)
return(r);
}
/* Fill in response fields */
node->inode_nr = res.inode_nr;
node->fmode = res.fmode;
node->fsize = res.fsize;
node->dev = res.dev;
node->fs_e = res.fs_e;
node->uid = res.uid;
node->gid = res.gid;
return(r);
}