port/gen/_xftw.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1988 AT&T */
/*    All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*
 *  _xftw - file tree walk the uses expanded stat structure
 *
 *  int _xftw(path, fn, depth)  char *path; int (*fn)(); int depth;
 *
 *  Given a path name, _xftw starts from the file given by that path
 *  name and visits each file and directory in the tree beneath
 *  that file.  If a single file has multiple links within the
 *  structure, it will be visited once for each such link.
 *  For each object visited, fn is called with three arguments.
 *      (*fn) (pathname, statp, ftwflag)
 *  The first contains the path name of the object, the second
 *  contains a pointer to a stat buffer which will usually hold
 *  appropriate information for the object and the third will
 *  contain an integer value giving additional information about
 *
 *      FTW_F   The object is a file for which stat was
 *          successful.  It does not guarantee that the
 *          file can actually be read.
 *
 *      FTW_D   The object is a directory for which stat and
 *          open for read were both successful.
 *
 *      FTW_DNR The object is a directory for which stat
 *          succeeded, but which cannot be read.  Because
 *          the directory cannot be read, fn will not be
 *          called for any descendants of this directory.
 *
 *      FTW_NS  Stat failed on the object because of lack of
 *          appropriate permission.  This indication will
 *          be given for example for each file in a
 *          directory with read but no execute permission.
 *          Because stat failed, it is not possible to
 *          determine whether this object is a file or a
 *          directory.  The stat buffer passed to fn will
 *          contain garbage.  Stat failure for any reason
 *          other than lack of permission will be
 *          considered an error and will cause _xftw to stop
 *          and return -1 to its caller.
 *
 *  If fn returns nonzero, _xftw stops and returns the same value
 *  to its caller.  If _xftw gets into other trouble along the way,
 *  it returns -1 and leaves an indication of the cause in errno.
 *
 *  The third argument to _xftw does not limit the depth to which
 *  _xftw will go.  Rather, it limits the depth to which _xftw will
 *  go before it starts recycling file descriptors.  In general,
 *  it is necessary to use a file descriptor for each level of the
 *  tree, but they can be recycled for deep trees by saving the
 *  position, closing, re-opening, and seeking.  In order to descend
 *  to arbitrary depths, _xftw requires 2 file descriptors to be open
 *  during the call to openat(), therefore if the depth argument
 *  is less than 2 _xftw will not use openat(), and it will fail with
 *  ENAMETOOLONG if it descends to a directory that exceeds PATH_MAX.
 */

/*
 * this interface uses the expanded stat structure and therefore
 * must have EFT enabled.
 */
#ifdef _STYPES
#undef _STYPES
#endif

#include "lint.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/param.h>
#include <dirent.h>
#include <errno.h>
#include <ftw.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>

struct Var {
    int level;
    int odepth;
};

static DIR *nocdopendir(const char *, struct Var *);
static int nocdstat(const char *, struct stat *, struct Var *, int);
static const char *get_unrooted(const char *);
static int fwalk(const char *, int (*)(const char *, const struct stat *, int),
    int, struct Var *);

/*ARGSUSED*/
int
_xftw(int ver, const char *path,
    int (*fn)(const char *, const struct stat *, int), int depth)
{
    struct Var var;
    int rc;

    var.level = 0;
    var.odepth = depth;
    rc = fwalk(path, fn, depth, &var);
    return (rc);
}

/*
 * This is the recursive walker.
 */
static int
fwalk(const char *path, int (*fn)(const char *, const struct stat *, int),
    int depth, struct Var *vp)
{
    size_t  n;
    int rc;
    int save_errno;
    DIR *dirp;
    char *subpath;
    struct stat sb;
    struct dirent *direntp;

    vp->level++;

    /*
     * Try to get file status.
     * If unsuccessful, errno will say why.
     * It's ok to have a symbolic link that points to
     * non-existing file. In this case, pass FTW_NS
     * to a function instead of aborting fwalk() right away.
     */
    if (nocdstat(path, &sb, vp, 0) < 0) {
#ifdef S_IFLNK
        save_errno = errno;
        if ((nocdstat(path, &sb, vp, AT_SYMLINK_NOFOLLOW) != -1) &&
            ((sb.st_mode & S_IFMT) == S_IFLNK)) {
            errno = save_errno;
            return (*fn)(path, &sb, FTW_NS);
        } else  {
            errno = save_errno;
        }
#endif
        return (errno == EACCES? (*fn)(path, &sb, FTW_NS): -1);
    }

    /*
     *  The stat succeeded, so we know the object exists.
     *  If not a directory, call the user function and return.
     */
    if ((sb.st_mode & S_IFMT) != S_IFDIR)
        return ((*fn)(path, &sb, FTW_F));

    /*
     *  The object was a directory.
     *
     *  Open a file to read the directory
     */
    dirp = nocdopendir(path, vp);

    /*
     *  Call the user function, telling it whether
     *  the directory can be read.  If it can't be read
     *  call the user function or indicate an error,
     *  depending on the reason it couldn't be read.
     */
    if (dirp == NULL)
        return (errno == EACCES? (*fn)(path, &sb, FTW_DNR): -1);

    /* We could read the directory.  Call user function. */
    rc = (*fn)(path, &sb, FTW_D);
    if (rc != 0) {
        (void) closedir(dirp);
        return (rc);
    }

    /*
     *  Read the directory one component at a time.
     *  We must ignore "." and "..", but other than that,
     *  just create a path name and call self to check it out.
     */
    while (direntp = readdir(dirp)) {
        long here;

        if (strcmp(direntp->d_name, ".") == 0 ||
            strcmp(direntp->d_name, "..") == 0)
            continue;

        /* Create a prefix to which we will append component names */
        n = strlen(path);
        subpath = malloc(n + strlen(direntp->d_name) + 2);
        if (subpath == 0) {
            (void) closedir(dirp);
            errno = ENOMEM;
            return (-1);
        }
        (void) strcpy(subpath, path);
        if (subpath[0] != '\0' && subpath[n-1] != '/')
            subpath[n++] = '/';

        /* Append component name to the working path */
        (void) strlcpy(&subpath[n], direntp->d_name, MAXNAMELEN);

        /*
         *  If we are about to exceed our depth,
         *  remember where we are and close a file.
         */
        if (depth <= 1) {
            here = telldir(dirp);
            if (closedir(dirp) < 0) {
                free(subpath);
                return (-1);
            }
        }

        /*
         *  Do a recursive call to process the file.
         *  (watch this, sports fans)
         */
        rc = fwalk(subpath, fn, depth-1, vp);
        if (rc != 0) {
            free(subpath);
            if (depth > 1)
                (void) closedir(dirp);
            return (rc);
        }

        /*
         *  If we closed the file, try to reopen it.
         */
        if (depth <= 1) {
            dirp = nocdopendir(path, vp);
            if (dirp == NULL) {
                free(subpath);
                return (-1);
            }
            seekdir(dirp, here);
        }
        free(subpath);
    }
    (void) closedir(dirp);
    return (0);
}

/*
 * Open a directory with an arbitrarily long path name.  If the original
 * depth arg >= 2, use openat() to make sure that it doesn't fail with
 * ENAMETOOLONG.
 */
static DIR *
nocdopendir(const char *path, struct Var *vp)
{
    int fd, cfd;
    DIR *fdd;
    char *dirp, *token, *ptr;

    fdd = opendir(path);
    if ((vp->odepth > 1) && (fdd == NULL) && (errno == ENAMETOOLONG)) {
        /*
         * Traverse the path using openat() to get the fd for
         * fdopendir().
         */
        if ((dirp = strdup(path)) == NULL) {
            errno = ENAMETOOLONG;
            return (NULL);
        }
        if ((token = strtok_r(dirp, "/", &ptr)) != NULL) {
            if ((fd = openat(AT_FDCWD, dirp, O_RDONLY)) < 0) {
            (void) free(dirp);
            errno = ENAMETOOLONG;
            return (NULL);
            }
            while ((token = strtok_r(NULL, "/", &ptr)) != NULL) {
            if ((cfd = openat(fd, token, O_RDONLY)) < 0) {
                (void) close(fd);
                (void) free(dirp);
                errno = ENAMETOOLONG;
                return (NULL);
            }
            (void) close(fd);
            fd = cfd;
            }
            (void) free(dirp);
            return (fdopendir(fd));
        }
        (void) free(dirp);
        errno = ENAMETOOLONG;
    }
    return (fdd);
}

/*
 * Stat a file with an arbitrarily long path name. If we aren't doing a
 * stat on the arg passed to _xftw() and if the original depth arg >= 2,
 * use openat() to make sure that it doesn't fail with ENAMETOOLONG.
 */
static int
nocdstat(const char *path, struct stat *statp, struct Var *vp, int sym)
{
    int fd, cfd;
    char *dirp, *token, *ptr;
    int rc;
    const char *unrootp;
    int save_err;

    rc = fstatat(AT_FDCWD, path, statp, sym);
    if ((vp->level > 1) && (vp->odepth >= 2) && (rc < 0) &&
        (errno == ENAMETOOLONG)) {
        /* Traverse path using openat() to get fd for fstatat(). */
        if ((dirp = strdup(path)) == NULL) {
            errno = ENAMETOOLONG;
            return (-1);
        }
        if ((token = strtok_r(dirp, "/", &ptr)) != NULL) {
            if ((fd = openat(AT_FDCWD, dirp, O_RDONLY)) < 0) {
            (void) free(dirp);
            errno = ENAMETOOLONG;
            return (-1);
            }
            unrootp = get_unrooted(path);
            while (((token = strtok_r(NULL, "/", &ptr)) != NULL) &&
            (strcmp(token, unrootp) != 0)) {
                if ((cfd = openat(fd, token, O_RDONLY)) < 0) {
                (void) close(fd);
                (void) free(dirp);
                errno = ENAMETOOLONG;
                return (NULL);
                }
                (void) close(fd);
                fd = cfd;
            }
            (void) free(dirp);
            rc = fstatat(fd, unrootp, statp, sym);
            save_err = errno;
            (void) close(fd);
            errno = save_err;
            return (rc);
        }
        (void) free(dirp);
        errno = ENAMETOOLONG;
    }
    return (rc);
}

/*
 * Return pointer basename of path.  This routine doesn't remove
 * trailing slashes, but there won't be any.
 */
static const char *
get_unrooted(const char *path)
{
    const char *ptr;

    if (!path || !*path)
        return (NULL);

    ptr = path + strlen(path);
    /* find last char in path before any trailing slashes */
    while (ptr != path && *--ptr == '/')
        ;

    if (ptr == path)    /* all slashes */
        return (ptr);

    while (ptr != path)
        if (*--ptr == '/')
            return (++ptr);

    return (ptr);
}