minix/servers/vfs/path.c

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/* 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.
*
* Jul 2006 (Balazs Gerofi)
*/
#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
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FORWARD _PROTOTYPE( int lookup_rel, (struct vnode *start_node,
int flags, int use_realuid, node_details_t *node) );
/*===========================================================================*
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* lookup_rel_vp *
*===========================================================================*/
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PUBLIC int lookup_rel_vp(start_node, flags, use_realuid, vpp)
struct vnode *start_node;
int flags;
int use_realuid;
struct vnode **vpp;
{
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/* Resolve a pathname (in user_fullpath) starting at start_node to a vnode. */
int r, lookup_res;
struct vnode *new_vp, *vp;
struct vmnt *vmp;
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struct node_details res;
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/* See if free vnode is available */
if ((new_vp = get_free_vnode(__FILE__, __LINE__)) == NIL_VNODE) {
printf("vfs:lookup_rel_vp: no free vnode available\n");
*vpp= NULL;
return EINVAL;
}
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lookup_res = lookup_rel(start_node, flags, use_realuid, &res);
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if (lookup_res != OK)
{
#if 0
printf("vfs:lookup_rel_vp: lookup_rel failed with %d\n", lookup_res);
#endif
return lookup_res;
}
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/* Check whether vnode is already in use or not */
if ((vp = find_vnode(res.fs_e, res.inode_nr)) != NIL_VNODE) {
vp->v_ref_count++;
vp->v_fs_count++; /* We got a reference from the FS */
*vpp= vp;
return OK;
}
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/* 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:lookup_rel_vp: 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;
*vpp= new_vp;
return OK;
}
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/*===========================================================================*
* lookup_vp *
*===========================================================================*/
PUBLIC int lookup_vp(flags, use_realuid, vpp)
int flags;
int use_realuid;
struct vnode **vpp;
{
/* Resolve a pathname (in user_fullpath) starting to a vnode. Call
* lookup_rel_vp to do the actual work.
*/
struct vnode *vp;
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vp= (user_fullpath[0] == '/' ? fp->fp_rd : fp->fp_wd);
return lookup_rel_vp(vp, flags, use_realuid, vpp);
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}
/*===========================================================================*
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* lookup_lastdir_rel *
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*===========================================================================*/
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PUBLIC int lookup_lastdir_rel(start_node, use_realuid, vpp)
struct vnode *start_node;
int use_realuid;
struct vnode **vpp;
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{
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/* This function is for calls that insert or delete entries from a
* directory. The path name (implicitly taken from user_fullpath)
* is split into to parts: the name of the directory and the
* directory entry. The name of the directory is resolved to a
* vnode. The directory entry is copied back to user_fullpath.
* The lookup starts at start_node.
*/
int r;
size_t len;
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char *cp;
char dir_entry[PATH_MAX+1];
len= strlen(user_fullpath);
if (len == 0)
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{
/* Empty path, always fail */
return ENOENT;
}
#if !DO_POSIX_PATHNAME_RES
/* Remove trailing slashes */
while (len > 1 && user_fullpath[len-1] == '/')
{
len--;
user_fullpath[len]= '\0';
}
#endif
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cp= strrchr(user_fullpath, '/');
if (cp == NULL)
{
/* Just one entry in the current working directory */
dup_vnode(start_node);
*vpp= start_node;
return OK;
}
else if (cp[1] == '\0')
{
/* Path ends in a slash. The directory entry is '.' */
strcpy(dir_entry, ".");
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}
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--;
}
/* Request lookup */
r = lookup_rel_vp(start_node, 0 /*no flags*/, use_realuid, vpp);
if (r != OK)
return r;
/* Copy the directory entry back to user_fullpath */
strcpy(user_fullpath, dir_entry);
return OK;
}
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/*===========================================================================*
* lookup_lastdir *
*===========================================================================*/
PUBLIC int lookup_lastdir(use_realuid, vpp)
int use_realuid;
struct vnode **vpp;
{
/* This function is for calls that insert or delete entries from a
* directory. The path name (implicitly taken from user_fullpath)
* is split into to parts: the name of the directory and the
* directory entry. The name of the directory is resolved to a
* vnode. The directory entry is copied back to user_fullpath.
* Just call lookup_lastdir_rel with the appropriate starting vnode.
*/
struct vnode *vp;
vp= (user_fullpath[0] == '/' ? fp->fp_rd : fp->fp_wd);
return lookup_lastdir_rel(vp, use_realuid, vpp);
}
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/*===========================================================================*
* lookup_rel *
*===========================================================================*/
PRIVATE int lookup_rel(start_node, flags, use_realuid, node)
struct vnode *start_node;
int flags;
int use_realuid;
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;
ino_t dir_ino, root_ino;
uid_t uid;
gid_t gid;
struct vnode *dir_vp;
struct vmnt *vmp;
struct lookup_res res;
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/* Empty (start) path? */
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if (user_fullpath[0] == '\0') {
node->inode_nr = 0;
printf("vfs:lookup_rel: returning ENOENT\n");
return ENOENT;
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}
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fs_e = start_node->v_fs_e;
path_off = 0;
dir_ino = start_node->v_inode_nr;
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/* 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)
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root_ino = fp->fp_rd->v_inode_nr;
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else
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root_ino = 0;
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/* Set user and group ids according to the system call */
uid = (use_realuid ? fp->fp_realuid : fp->fp_effuid);
gid = (use_realuid ? fp->fp_realgid : fp->fp_effgid);
symloop= 0; /* Number of symlinks seen so far */
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/* Issue the request */
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r = req_lookup(fs_e, path_off, dir_ino, root_ino, uid, gid, flags, &res);
if (r != OK && r != EENTERMOUNT && r != ELEAVEMOUNT && r != ESYMLINK)
{
#if 0
printf("vfs:lookup_rel: req_lookup_s failed with %d\n", r);
#endif
return r;
}
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/* While the response is related to mount control set the
* new requests respectively */
while (r == EENTERMOUNT || r == ELEAVEMOUNT || r == ESYMLINK) {
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/* Save the place in the (possibly updated) path where we have to
* continue witht henext lookup request.
*/
path_off= res.char_processed;
/* Update the current value of the symloop counter */
symloop += res.symloop;
if (symloop > SYMLOOP_MAX)
{
printf("vfs:lookup_rel: returning ELOOP\n");
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_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) {
printf(
"vfs:lookup_rel: res.inode_nr = %d, res.fs_e = %d\n",
res.inode_nr, res.fs_e);
panic(__FILE__,
"vfs:lookup_s: mounted partition couldn't be found",
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_s: couldn't find vmnt during the climbup",
NO_NUM);
}
/* 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 (fp->fp_rd->v_dev == fp->fp_wd->v_dev)
root_ino = fp->fp_rd->v_inode_nr;
else
root_ino = 0;
/* Issue the request */
r = req_lookup(fs_e, path_off, dir_ino, root_ino, uid, gid, flags,
&res);
if (r != OK && r != EENTERMOUNT && r != ELEAVEMOUNT && r != ESYMLINK)
{
#if 0
printf("vfs:lookup_rel: req_lookup_s failed with %d\n", r);
#endif
return r;
}
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}
/* 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;
}