554 lines
15 KiB
C
554 lines
15 KiB
C
/*
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* This file contains the procedures that look up path names in the directory
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* system and determine the pnode number that goes with a given path name.
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*
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* Created (based on MFS):
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* June 2011 (Evgeniy Ivanov)
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*/
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#include "fs.h"
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#include <sys/cdefs.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <assert.h>
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#include <errno.h>
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#include <puffs.h>
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#include <stdlib.h>
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#include <string.h>
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#include <minix/endpoint.h>
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#include <minix/vfsif.h>
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#include <minix/libminixfs.h>
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#include "puffs.h"
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#include "puffs_priv.h"
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char dot2[3] = ".."; /* permissions for . and .. */
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static char *get_name(char *name, char string[NAME_MAX+1]);
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static int ltraverse(struct puffs_node *pn, char *suffix);
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static int parse_path(pino_t dir_ino, pino_t root_ino, int flags, struct
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puffs_node **res_inop, size_t *offsetp, int *symlinkp);
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/*===========================================================================*
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* fs_lookup *
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*===========================================================================*/
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int fs_lookup(void)
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{
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cp_grant_id_t grant;
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int r, r1, flags, symlinks;
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unsigned int len;
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size_t offset = 0, path_size;
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pino_t dir_ino, root_ino;
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struct puffs_node *pn;
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grant = (cp_grant_id_t) fs_m_in.REQ_GRANT;
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path_size = (size_t) fs_m_in.REQ_PATH_SIZE; /* Size of the buffer */
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len = (int) fs_m_in.REQ_PATH_LEN; /* including terminating nul */
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dir_ino = (pino_t) fs_m_in.REQ_DIR_INO;
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root_ino = (pino_t) fs_m_in.REQ_ROOT_INO;
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flags = (int) fs_m_in.REQ_FLAGS;
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/* Check length. */
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if (len > sizeof(user_path)) return(E2BIG); /* too big for buffer */
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if (len == 0) return(EINVAL); /* too small */
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/* Copy the pathname and set up caller's user and group id */
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r = sys_safecopyfrom(VFS_PROC_NR, grant, /*offset*/ 0,
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(vir_bytes) user_path, (size_t) len);
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if (r != OK) return(r);
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/* Verify this is a null-terminated path. */
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if (user_path[len - 1] != '\0') return(EINVAL);
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memset(&credentials, 0, sizeof(credentials));
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if(!(flags & PATH_GET_UCRED)) { /* Do we have to copy uid/gid credentials? */
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caller_uid = (uid_t) fs_m_in.REQ_UID;
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caller_gid = (gid_t) fs_m_in.REQ_GID;
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} else {
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if((r=fs_lookup_credentials(&credentials,
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&caller_uid, &caller_gid,
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(cp_grant_id_t) fs_m_in.REQ_GRANT2,
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(size_t) fs_m_in.REQ_UCRED_SIZE)) != OK)
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return r;
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}
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/* Lookup pnode */
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pn = NULL;
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r = parse_path(dir_ino, root_ino, flags, &pn, &offset, &symlinks);
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if (symlinks != 0 && (r == ELEAVEMOUNT || r == EENTERMOUNT || r == ESYMLINK)){
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len = strlen(user_path)+1;
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if (len > path_size) return(ENAMETOOLONG);
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r1 = sys_safecopyto(VFS_PROC_NR, grant, (vir_bytes) 0,
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(vir_bytes) user_path, (size_t) len);
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if (r1 != OK) return(r1);
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}
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if (r == ELEAVEMOUNT || r == ESYMLINK) {
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/* Report offset and the error */
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fs_m_out.RES_OFFSET = offset;
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fs_m_out.RES_SYMLOOP = symlinks;
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return(r);
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}
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if (r != OK && r != EENTERMOUNT) {
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return(r);
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}
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if (r == OK) {
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/* Open pnode */
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pn->pn_count++;
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}
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fs_m_out.RES_INODE_NR = pn->pn_va.va_fileid;
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fs_m_out.RES_MODE = pn->pn_va.va_mode;
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fs_m_out.RES_FILE_SIZE = pn->pn_va.va_size;
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fs_m_out.RES_SYMLOOP = symlinks;
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fs_m_out.RES_UID = pn->pn_va.va_uid;
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fs_m_out.RES_GID = pn->pn_va.va_gid;
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/* This is only valid for block and character specials. But it doesn't
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* cause any harm to set RES_DEV always. */
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fs_m_out.RES_DEV = pn->pn_va.va_rdev;
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if (r == EENTERMOUNT) {
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fs_m_out.RES_OFFSET = offset;
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}
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return(r);
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}
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/*===========================================================================*
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* parse_path *
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*===========================================================================*/
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static int parse_path(
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pino_t dir_ino,
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pino_t root_ino,
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int flags,
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struct puffs_node **res_inop,
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size_t *offsetp,
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int *symlinkp
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)
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{
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/* Parse the path in user_path, starting at dir_ino. If the path is the empty
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* string, just return dir_ino. It is upto the caller to treat an empty
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* path in a special way. Otherwise, if the path consists of just one or
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* more slash ('/') characters, the path is replaced with ".". Otherwise,
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* just look up the first (or only) component in path after skipping any
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* leading slashes.
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*/
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int r, leaving_mount;
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struct puffs_node *pn, *pn_dir;
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char *cp, *next_cp; /* component and next component */
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char component[NAME_MAX+1];
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/* Start parsing path at the first component in user_path */
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cp = user_path;
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/* No symlinks encountered yet */
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*symlinkp = 0;
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/* Find starting pnode according to the request message */
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/* XXX it's deffinitely OK to use nodewalk here */
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if ((pn = puffs_pn_nodewalk(global_pu, 0, &dir_ino)) == NULL) {
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lpuffs_debug("nodewalk failed\n");
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return(ENOENT);
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}
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/* If dir has been removed return ENOENT. */
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if (pn->pn_va.va_nlink == NO_LINK) return(ENOENT);
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/* If the given start pnode is a mountpoint, we must be here because the file
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* system mounted on top returned an ELEAVEMOUNT error. In this case, we must
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* only accept ".." as the first path component.
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*/
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leaving_mount = pn->pn_mountpoint; /* True iff pn is a mountpoint */
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/* Scan the path component by component. */
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while (TRUE) {
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if (cp[0] == '\0') {
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/* We're done; either the path was empty or we've parsed all
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components of the path */
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*res_inop = pn;
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*offsetp += cp - user_path;
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/* Return EENTERMOUNT if we are at a mount point */
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if (pn->pn_mountpoint) return(EENTERMOUNT);
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return(OK);
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}
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while(cp[0] == '/') cp++;
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next_cp = get_name(cp, component);
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if (next_cp == NULL) {
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return(err_code);
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}
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/* Special code for '..'. A process is not allowed to leave a chrooted
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* environment. A lookup of '..' at the root of a mounted filesystem
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* has to return ELEAVEMOUNT. In both cases, the caller needs search
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* permission for the current pnode, as it is used as directory.
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*/
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if (strcmp(component, "..") == 0) {
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/* 'pn' is now accessed as directory */
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if ((r = forbidden(pn, X_BIT)) != OK) {
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return(r);
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}
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if (pn->pn_va.va_fileid == root_ino) {
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cp = next_cp;
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continue; /* Ignore the '..' at a process' root
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and move on to the next component */
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}
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if (pn->pn_va.va_fileid == global_pu->pu_pn_root->pn_va.va_fileid
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&& !is_root_fs) {
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/* Climbing up to parent FS */
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*offsetp += cp - user_path;
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return(ELEAVEMOUNT);
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}
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}
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/* Only check for a mount point if we are not coming from one. */
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if (!leaving_mount && pn->pn_mountpoint) {
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/* Going to enter a child FS */
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*res_inop = pn;
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*offsetp += cp - user_path;
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return(EENTERMOUNT);
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}
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/* There is more path. Keep parsing.
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* If we're leaving a mountpoint, skip directory permission checks.
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*/
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pn_dir = pn;
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if ((pn_dir->pn_va.va_mode & I_TYPE) != I_DIRECTORY) {
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return(ENOTDIR);
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}
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pn = advance(pn_dir, leaving_mount ? dot2 : component, CHK_PERM);
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if (err_code == ELEAVEMOUNT || err_code == EENTERMOUNT)
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err_code = OK;
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if (err_code != OK) {
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return(err_code);
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}
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assert(pn != NULL);
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leaving_mount = 0;
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/* The call to advance() succeeded. Fetch next component. */
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if (S_ISLNK(pn->pn_va.va_mode)) {
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if (next_cp[0] == '\0' && (flags & PATH_RET_SYMLINK)) {
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*res_inop = pn;
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*offsetp += next_cp - user_path;
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return(OK);
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}
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/* Extract path name from the symlink file */
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r = ltraverse(pn, next_cp);
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next_cp = user_path;
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*offsetp = 0;
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/* Symloop limit reached? */
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if (++(*symlinkp) > _POSIX_SYMLOOP_MAX)
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r = ELOOP;
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if (r != OK)
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return(r);
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if (next_cp[0] == '/')
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return(ESYMLINK);
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pn = pn_dir;
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}
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cp = next_cp; /* Process subsequent component in next round */
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}
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}
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/*===========================================================================*
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* ltraverse *
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*===========================================================================*/
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static int ltraverse(
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struct puffs_node *pn, /* symbolic link */
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char *suffix /* current remaining path. Has to point in the
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* user_path buffer
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*/
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)
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{
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/* Traverse a symbolic link. Copy the link text from the pnode and insert
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* the text into the path. Return error code or report success. Base
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* directory has to be determined according to the first character of the
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* new pathname.
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*/
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int r;
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char sp[PATH_MAX];
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size_t llen = PATH_MAX; /* length of link */
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size_t slen; /* length of suffix */
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PUFFS_MAKECRED(pcr, &global_kcred);
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if (!S_ISLNK(pn->pn_va.va_mode))
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r = EACCES;
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if (global_pu->pu_ops.puffs_node_readlink == NULL)
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return(EINVAL);
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if (global_pu->pu_ops.puffs_node_readlink(global_pu, pn, pcr, sp, &llen) != 0)
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return(EINVAL);
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slen = strlen(suffix);
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/* The path we're parsing looks like this:
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* /already/processed/path/<link> or
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* /already/processed/path/<link>/not/yet/processed/path
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* After expanding the <link>, the path will look like
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* <expandedlink> or
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* <expandedlink>/not/yet/processed
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* In both cases user_path must have enough room to hold <expandedlink>.
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* However, in the latter case we have to move /not/yet/processed to the
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* right place first, before we expand <link>. When strlen(<expandedlink>) is
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* smaller than strlen(/already/processes/path), we move the suffix to the
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* left. Is strlen(<expandedlink>) greater then we move it to the right. Else
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* we do nothing.
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*/
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if (slen > 0) { /* Do we have path after the link? */
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/* For simplicity we require that suffix starts with a slash */
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if (suffix[0] != '/') {
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panic("ltraverse: suffix does not start with a slash");
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}
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/* To be able to expand the <link>, we have to move the 'suffix'
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* to the right place.
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*/
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if (slen + llen + 1 > sizeof(user_path))
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return(ENAMETOOLONG);/* <expandedlink>+suffix+\0 does not fit*/
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if ((unsigned)(suffix - user_path) != llen) {
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/* Move suffix left or right if needed */
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memmove(&user_path[llen], suffix, slen+1);
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}
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} else {
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if (llen + 1 > sizeof(user_path))
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return(ENAMETOOLONG); /* <expandedlink> + \0 does not fit */
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/* Set terminating nul */
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user_path[llen]= '\0';
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}
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/* Everything is set, now copy the expanded link to user_path */
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memmove(user_path, sp, llen);
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return(OK);
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}
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/*===========================================================================*
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* advance *
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*===========================================================================*/
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struct puffs_node *advance(
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struct puffs_node *pn_dir, /* pnode for directory to be searched */
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char string[NAME_MAX + 1], /* component name to look for */
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int chk_perm /* check permissions when string is
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* looked up*/
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)
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{
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/* Given a directory and a component of a path, look up the component in
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* the directory, find the pnode, open it, and return a pointer to its pnode
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* slot.
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* TODO: instead of string, should get pcn.
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*/
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struct puffs_node *pn;
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struct puffs_newinfo pni;
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struct puffs_kcn pkcnp;
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PUFFS_MAKECRED(pcr, &global_kcred);
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struct puffs_cn pcn = {&pkcnp, (struct puffs_cred *) __UNCONST(pcr), {0,0,0}};
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enum vtype node_vtype;
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voff_t size;
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dev_t rdev;
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int error;
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err_code = OK;
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/* If 'string' is empty, return an error. */
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if (string[0] == '\0') {
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err_code = ENOENT;
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return(NULL);
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}
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/* Check for NULL. */
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if (pn_dir == NULL)
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return(NULL);
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if (chk_perm) {
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/* Just search permission is checked */
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if (forbidden(pn_dir, X_BIT)) {
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err_code = EACCES;
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return(NULL);
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}
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}
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if (strcmp(string, ".") == 0) {
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/* Otherwise we will fall into trouble: path for pnode to be looked up
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* will be parent path (same pnode as the one to be looked up) +
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* requested path. E.g. after several lookups we might get advance
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* for "." with parent path "/././././././././.".
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*
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* Another problem is that after lookup pnode will be added
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* to the pu_pnodelst, which already contains pnode instance for this
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* pnode. It will cause lot of troubles.
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*/
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return pn_dir;
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}
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pni.pni_cookie = (void** )&pn;
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pni.pni_vtype = &node_vtype;
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pni.pni_size = &size;
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pni.pni_rdev = &rdev;
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pcn.pcn_namelen = strlen(string);
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assert(pcn.pcn_namelen <= MAXPATHLEN);
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strcpy(pcn.pcn_name, string);
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if (buildpath) {
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if (puffs_path_pcnbuild(global_pu, &pcn, pn_dir) != 0) {
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lpuffs_debug("pathbuild error\n");
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err_code = ENOENT;
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return(NULL);
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}
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}
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/* lookup *must* be present */
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error = global_pu->pu_ops.puffs_node_lookup(global_pu, pn_dir,
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&pni, &pcn);
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if (buildpath) {
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if (error) {
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global_pu->pu_pathfree(global_pu, &pcn.pcn_po_full);
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err_code = ENOENT;
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return(NULL);
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} else {
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struct puffs_node *_pn;
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/*
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* did we get a new node or a
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* recycled node?
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*/
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_pn = PU_CMAP(global_pu, pn);
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if (_pn->pn_po.po_path == NULL)
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_pn->pn_po = pcn.pcn_po_full;
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else
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global_pu->pu_pathfree(global_pu, &pcn.pcn_po_full);
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}
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}
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if (error) {
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err_code = error < 0 ? error : -error;
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return(NULL);
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} else {
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/* In MFS/ext2 it's set by search_dir, puffs_node_lookup error codes are unclear,
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* so we use error variable there
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*/
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err_code = OK;
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}
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assert(pn != NULL);
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/* The following test is for "mountpoint/.." where mountpoint is a
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* mountpoint. ".." will refer to the root of the mounted filesystem,
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* but has to become a reference to the parent of the 'mountpoint'
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* directory.
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*
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* This case is recognized by the looked up name pointing to a
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* root pnode, and the directory in which it is held being a
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* root pnode, _and_ the name[1] being '.'. (This is a test for '..'
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* and excludes '.'.)
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*/
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if (pn->pn_va.va_fileid == global_pu->pu_pn_root->pn_va.va_fileid) {
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if (pn_dir->pn_va.va_fileid == global_pu->pu_pn_root->pn_va.va_fileid) {
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if (string[1] == '.') {
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if (!is_root_fs) {
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/* Climbing up mountpoint */
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err_code = ELEAVEMOUNT;
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}
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}
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}
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}
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/* See if the pnode is mounted on. If so, switch to root directory of the
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* mounted file system. The super_block provides the linkage between the
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* pnode mounted on and the root directory of the mounted file system.
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*/
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if (pn->pn_mountpoint) {
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/* Mountpoint encountered, report it */
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err_code = EENTERMOUNT;
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}
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return(pn);
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}
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/*===========================================================================*
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* get_name *
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*===========================================================================*/
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static char *get_name(
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|
char *path_name, /* path name to parse */
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|
char string[NAME_MAX+1] /* component extracted from 'old_name' */
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|
)
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|
{
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|
/* Given a pointer to a path name in fs space, 'path_name', copy the first
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|
* component to 'string' (truncated if necessary, always nul terminated).
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|
* A pointer to the string after the first component of the name as yet
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|
* unparsed is returned. Roughly speaking,
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|
* 'get_name' = 'path_name' - 'string'.
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|
*
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|
* This routine follows the standard convention that /usr/ast, /usr//ast,
|
|
* //usr///ast and /usr/ast/ are all equivalent.
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|
*
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|
* If len of component is greater, than allowed, then return 0.
|
|
*/
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|
size_t len;
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|
char *cp, *ep;
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|
|
|
cp = path_name;
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|
|
|
/* Skip leading slashes */
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|
while (cp[0] == '/') cp++;
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|
|
|
/* Find the end of the first component */
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|
ep = cp;
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|
while (ep[0] != '\0' && ep[0] != '/')
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|
ep++;
|
|
|
|
len = (size_t) (ep - cp);
|
|
|
|
/* XXX we don't check name_max of fileserver (probably we can't) */
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|
if (len > NAME_MAX) {
|
|
err_code = ENAMETOOLONG;
|
|
return(NULL);
|
|
}
|
|
|
|
/* Special case of the string at cp is empty */
|
|
if (len == 0)
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|
strcpy(string, "."); /* Return "." */
|
|
else {
|
|
memcpy(string, cp, len);
|
|
string[len]= '\0';
|
|
}
|
|
|
|
return(ep);
|
|
}
|