port/gen/ttyname.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 2007 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

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

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

/*
 * ttyname(f): return "/dev/X" (where X is a relative pathname
 * under /dev/), which is the name of the tty character special
 * file associated with the file descriptor f, or NULL if the
 * pathname cannot be found.
 *
 * Ttyname tries to find the tty file by matching major/minor
 * device, file system ID, and inode numbers of the file
 * descriptor parameter to those of files in the /dev/ directory.
 *
 * It attempts to find a match on major/minor device numbers,
 * file system ID, and inode numbers, but failing to match on
 * all three, settles for just a match on device numbers and
 * file system ID.
 *
 * To achieve higher performance and more flexible functionality,
 * ttyname first looks for the tty file in the directories specified
 * in the configuration file /etc/ttysrch. Entries in /etc/ttysrch
 * may be qualified to specify that a partial match may be acceptable.
 * This further improves performance by allowing an entry which
 * matches major/minor and file system ID, but not inode number
 * without searching the entire /dev tree. If /etc/ttysrch does not
 * exist, ttyname looks in a default list of directories.  If after
 * looking in the most likely places, ttyname still cannot find the
 * tty file, it recursively searches thru the rest of the /dev/
 * directory.
 *
 * In addition to the public interfaces, ttyname() & ttyname_r(), which
 * do the lookup based on an open file descriptor,
 * the private interface _ttyname_dev() does the lookup based on a
 * major/minor device.  It follows the same order of lookup rules and
 * returns similar information, but matches on just the major/minor
 * device numbers.
 */

#pragma weak ttyname = _ttyname
#pragma weak ttyname_r = _ttyname_r

#include "synonyms.h"
#include "mtlib.h"
#include "libc.h"
#include "_libc_gettext.h"
#include <sys/sysmacros.h>
#include <sys/types.h>
#include <dirent.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <thread.h>
#include <synch.h>
#include <errno.h>
#include <limits.h>
#include <sys/mkdev.h>
#include "tsd.h"

typedef struct entry {
	char *name;
	int flags;
} entry_t;

typedef struct special {
	const char *spcl_name;	/* device name */
	dev_t spcl_rdev;	/* matching major/minor devnum */
	dev_t spcl_fsdev;	/* devnum of containing FS */
	ino_t spcl_inum;	/* inum of entry in FS */
} spcl_t;

static int srch_dir(const entry_t path, int match_mask, int depth,
    const entry_t skip_dirs[], struct stat64 *fsb);
static const entry_t *get_pri_dirs(void);
static char *ispts(struct stat64 *fsb, int match_mask);
static char *ispty(struct stat64 *fsb, int match_mask);
static void itoa(int i, char *ptr);
static char *_ttyname_common(struct stat64 *fsp, char *buffer,
    uint_t match_mask);


#define	MAX_DEV_PATH	TTYNAME_MAX
#define	MAX_SRCH_DEPTH	4

#define	MATCH_MM	1
#define	MATCH_FS	2
#define	MATCH_INO	4
#define	MATCH_ALL	7

#define	DEV		"/dev"
#define	TTYSRCH		"/etc/ttysrch"
#define	PTS		"/dev/pts"

static const entry_t dev_dir =
	{ "/dev", MATCH_ALL };

static const entry_t def_srch_dirs[] = {	/* default search list */
	{ "/dev/pts", MATCH_ALL },
	{ "/dev/term", MATCH_ALL },
	{ "/dev/zcons", MATCH_ALL },
	{ NULL, 0 }
};

static char *dir_buf;		/* directory buffer for ttysrch body */
static entry_t *dir_vec;	/* directory vector for ttysrch ptrs */
static size_t dir_size;		/* ttysrch file size */
static timestruc_t dir_mtim;	/* ttysrch file modification time */
static char rbuf[MAX_DEV_PATH]; /* perfect match file name */
static char dev_rbuf[MAX_DEV_PATH]; /* partial match file name */
static int dev_flag;		/* if set, dev + rdev match was found */
static spcl_t special_case[] = {
	"/dev/tty", 0, 0, 0,
	"/dev/console", 0, 0, 0,
	"/dev/conslog", 0, 0, 0,
	"/dev/systty", 0, 0, 0,
	"/dev/wscons", 0, 0, 0
};
#define	NUMSPECIAL	(sizeof (special_case) / sizeof (spcl_t))
static spcl_t ptmspecial = {
	"/dev/ptmx", 0, 0, 0
};
static	dev_t	ptcdev = NODEV;
static	dev_t	ptsldev = NODEV;

char *
_ttyname_dev(dev_t rdev, char *buffer, size_t buflen)
{
	struct stat64 fsb;

	fsb.st_rdev = rdev;

	if (buflen < MAX_DEV_PATH) {
		errno = ERANGE;
		return (NULL);
	}

	return (_ttyname_common(&fsb, buffer, MATCH_MM));
}

/*
 * POSIX.1c Draft-6 version of the function ttyname_r.
 * It was implemented by Solaris 2.3.
 */
char *
_ttyname_r(int f, char *buffer, int buflen)
{
	struct stat64 fsb;	/* what we are searching for */
	/*
	 * do we need to search anything at all? (is fildes a char special tty
	 * file?)
	 */
	if (fstat64(f, &fsb) < 0) {
		errno = EBADF;
		return (0);
	}
	if ((isatty(f) == 0) ||
	    ((fsb.st_mode & S_IFMT) != S_IFCHR)) {
		errno = ENOTTY;
		return (0);
	}

	if (buflen < MAX_DEV_PATH) {
		errno = ERANGE;
		return (0);
	}

	return (_ttyname_common(&fsb, buffer, MATCH_ALL));
}

static char *
_ttyname_common(struct stat64 *fsp, char *buffer, uint_t match_mask)
{
	struct stat64 tfsb;
	const entry_t *srch_dirs;	/* priority directories */
	spcl_t *spclp;
	int i;
	int found = 0;
	int dirno = 0;
	int is_pts = 0;
	char *retval = NULL;
	char *pt = NULL;

	/*
	 * We can't use lmutex_lock() here because we call malloc()/free()
	 * and _libc_gettext().  Use the brute-force atfork_lock_enter().
	 */
	atfork_lock_enter();

	/*
	 * match special cases
	 */

	for (spclp = special_case, i = 0; i < NUMSPECIAL; spclp++, i++) {
		if ((spclp->spcl_inum | spclp->spcl_fsdev |
		    spclp->spcl_rdev) == 0) {
			if (stat64(spclp->spcl_name, &tfsb) != 0)
				continue;
			spclp->spcl_rdev = tfsb.st_rdev;
			spclp->spcl_fsdev = tfsb.st_dev;
			spclp->spcl_inum = tfsb.st_ino;
		}
		if (match_mask == MATCH_MM) {
			if (spclp->spcl_rdev == fsp->st_rdev) {
				retval = strcpy(rbuf, spclp->spcl_name);
				goto out;
			}
		} else if (spclp->spcl_fsdev == fsp->st_dev &&
		    spclp->spcl_rdev == fsp->st_rdev &&
		    spclp->spcl_inum == fsp->st_ino) {
			retval = strcpy(rbuf, spclp->spcl_name);
			goto out;
		}
	}
	/*
	 * additional special case: ptm clone device
	 *   ptm devs have no entries in /dev
	 *   if major number matches, just short circuit any further lookup
	 *   NOTE: the minor number of /dev/ptmx is the ptm major number
	 */
	spclp = &ptmspecial;
	if ((spclp->spcl_inum | spclp->spcl_fsdev | spclp->spcl_rdev) == 0) {
		if (stat64(spclp->spcl_name, &tfsb) == 0) {
			spclp->spcl_rdev = tfsb.st_rdev;
			spclp->spcl_fsdev = tfsb.st_dev;
			spclp->spcl_inum = tfsb.st_ino;
		}
	}
	if ((spclp->spcl_rdev != 0) &&
	    (minor(spclp->spcl_rdev) == major(fsp->st_rdev)))
		goto out;

	/*
	 * additional special case: pty dev
	 *  one of the known default pairs of /dev/ptyXX or /dev/ttyXX
	 */
	if ((retval = ispty(fsp, match_mask)) != NULL)
		goto out;

	/*
	 * search the priority directories
	 */


	srch_dirs = get_pri_dirs();
	dev_flag = 0;

	while ((!found) && (srch_dirs[dirno].name != NULL)) {

		/*
		 * if /dev is one of the priority directories, only
		 * search its top level(set depth = MAX_SEARCH_DEPTH)
		 */

		/*
		 * Is /dev/pts then just do a quick check. We don't have
		 * to stat the entire /dev/pts dir.
		 */
		if (strcmp(PTS, srch_dirs[dirno].name) == NULL) {
			if ((pt = ispts(fsp, match_mask)) != NULL) {
				is_pts = 1;
				found = 1;
			}
		} else {
			found = srch_dir(srch_dirs[dirno], match_mask,
			    ((strcmp(srch_dirs[dirno].name, dev_dir.name)
			    == 0) ? MAX_SRCH_DEPTH : 1), 0, fsp);
		}
		dirno++;
	}

	/*
	 * search the /dev/ directory, skipping priority directories
	 */
	if (!found)
		found = srch_dir(dev_dir, match_mask, 0, srch_dirs, fsp);


	/*
	 * return
	 */

	if (found) {
		if (is_pts)
			retval = pt;
		else
			retval = rbuf;
	} else if (dev_flag)
		retval = dev_rbuf;
	else
		retval = NULL;
out:	retval = (retval ? strcpy(buffer, retval) : NULL);
	atfork_lock_exit();
	return (retval);
}

/*
 * POSIX.1c standard version of the function ttyname_r.
 * User gets it via static ttyname_r from the header file.
 */
int
__posix_ttyname_r(int fildes, char *name, size_t namesize)
{
	int nerrno = 0;
	int oerrno = errno;
	int namelen;

	errno = 0;

	if (namesize > INT_MAX)
		namelen = INT_MAX;
	else
		namelen = (int)namesize;

	if (_ttyname_r(fildes, name, namelen) == NULL) {
		if (errno == 0)
			nerrno = EINVAL;
		else
			nerrno = errno;
	}
	errno = oerrno;
	return (nerrno);
}

/*
 * Checks if the name is under /dev/pts directory
 */
static char *
ispts(struct stat64 *fsb, int match_mask)
{
	static  char	buf[MAX_DEV_PATH];
	struct	stat64	stb;

	(void) strcpy(buf, "/dev/pts/");
	itoa(minor(fsb->st_rdev), buf+strlen(buf));

	if (stat64(buf, &stb) != 0)
		return (NULL);

	if (match_mask == MATCH_MM) {
		if (stb.st_rdev == fsb->st_rdev)
			return (buf);
	} else if (stb.st_rdev == fsb->st_rdev && stb.st_dev == fsb->st_dev &&
	    stb.st_ino == fsb->st_ino)
			return (buf);

	return (NULL);
}

/*
 * Checks if the dev is a known pty master or slave device
 */
#define	MAXDEFAULTPTY	48

static char *
ispty(struct stat64 *fsb, int match_mask)
{
	static char	buf[16];	/* big enough for "/dev/XtyXX" */
	struct	stat64	stb;
	minor_t dmin;
	char prefix;

	if (ptsldev == NODEV && stat64("/dev/ttyp0", &stb) == 0)
		ptsldev = stb.st_rdev;

	/*
	 * check for a ptsl dev (/dev/ttyXX)
	 */
	prefix = 't';
	if (major(fsb->st_rdev) != major(ptsldev)) {
		/*
		 * not a ptsl, check for a ptc
		 */
		if (ptcdev == NODEV && stat64("/dev/ptyp0", &stb) == 0)
			ptcdev = stb.st_rdev;

		/*
		 * check for a ptc dev (/dev/ptyXX)
		 */
		prefix = 'p';
		if (major(fsb->st_rdev) != major(ptcdev))
			return (NULL);
	}

	/*
	 * check if minor number is in the known range
	 */
	dmin = minor(fsb->st_rdev);
	if (dmin > MAXDEFAULTPTY)
		return (NULL);

	/*
	 * modify name based on minor number
	 */
	(void) snprintf(buf, sizeof (buf), "/dev/%cty%c%c",
	    prefix, 'p' + dmin / 16, "0123456789abcdef"[dmin % 16]);

	if (stat64(buf, &stb) != 0)
		return (NULL);

	if (match_mask == MATCH_MM) {
		if (stb.st_rdev == fsb->st_rdev)
			return (buf);
	} else if (stb.st_rdev == fsb->st_rdev &&
	    stb.st_dev == fsb->st_dev &&
	    stb.st_ino == fsb->st_ino)
			return (buf);

	return (NULL);
}


/*
 * Converts a number to a string (null terminated).
 */
static void
itoa(int i, char *ptr)
{
	int dig = 0;
	int tempi;

	tempi = i;
	do {
		dig++;
		tempi /= 10;
	} while (tempi);

	ptr += dig;
	*ptr = '\0';
	while (--dig >= 0) {
		*(--ptr) = i % 10 + '0';
		i /= 10;
	}
}

/*
 * srch_dir() searches directory path and all directories under it up
 * to depth directories deep for a file described by a stat structure
 * fsb.  It puts the answer into rbuf.  If a match is found on device
 * number only, the file name is put into dev_rbuf and dev_flag is set.
 *
 * srch_dir() returns 1 if a match (on device and inode) is found,
 * or 0 otherwise.
 *
 */

static int
srch_dir(const entry_t path,	/* current path */
	int match_mask,		/* flags mask */
	int depth,		/* current depth (/dev = 0) */
	const entry_t skip_dirs[], /* directories not needing searching */
	struct stat64 *fsb)	/* the file being searched for */
{
	DIR *dirp;
	struct dirent64 *direntp;
	struct stat64 tsb;
	char file_name[MAX_DEV_PATH];
	entry_t file;
	char *last_comp;
	int found = 0;
	int dirno = 0;
	size_t path_len;

	file.name = file_name;
	file.flags = path.flags & match_mask;
	if (file.flags == 0)
		file.flags = match_mask;

	/*
	 * do we need to search this directory? (always search /dev at depth 0)
	 */
	if ((skip_dirs != NULL) && (depth != 0))
		while (skip_dirs[dirno].name != NULL)
			if (strcmp(skip_dirs[dirno++].name, path.name) == 0)
				return (0);

	/*
	 * open directory
	 */
	if ((dirp = opendir(path.name)) == NULL) {
		return (0);
	}

	path_len = strlen(path.name);
	(void) strcpy(file_name, path.name);
	last_comp = file_name + path_len;
	*last_comp++ = '/';

	/*
	 * read thru the directory
	 */
	while ((!found) && ((direntp = readdir64(dirp)) != NULL)) {
		/*
		 * skip "." and ".." entries, if present
		 */
		if (direntp->d_name[0] == '.' &&
		    (strcmp(direntp->d_name, ".") == 0 ||
		    strcmp(direntp->d_name, "..") == 0))
			continue;

		/*
		 * if the file name (path + "/" + d_name + NULL) would be too
		 * long, skip it
		 */
		if ((path_len + strlen(direntp->d_name) + 2) > MAX_DEV_PATH)
			continue;

		(void) strcpy(last_comp, direntp->d_name);
		if (stat64(file_name, &tsb) < 0)
			continue;

		/*
		 * skip "/dev/syscon" because it may be an invalid link after
		 * single user mode.
		 */
		if (strcmp(file_name, "/dev/syscon") == 0)
			continue;

		/*
		 * if a file is a directory and we are not too deep, recurse
		 */
		if ((tsb.st_mode & S_IFMT) == S_IFDIR)
			if (depth < MAX_SRCH_DEPTH)
				found = srch_dir(file, match_mask, depth+1,
				    skip_dirs, fsb);
			else
				continue;

		/*
		 * else if it is not a directory, is it a character special
		 * file?
		 */
		else if ((tsb.st_mode & S_IFMT) == S_IFCHR) {
			int flag = 0;
			if (tsb.st_dev == fsb->st_dev)
				flag |= MATCH_FS;
			if (tsb.st_rdev == fsb->st_rdev)
				flag |= MATCH_MM;
			if (tsb.st_ino == fsb->st_ino)
				flag |= MATCH_INO;

			if ((flag & file.flags) == file.flags) {
				(void) strcpy(rbuf, file.name);
				found = 1;
			} else if ((flag & (MATCH_MM | MATCH_FS)) ==
			    (MATCH_MM | MATCH_FS)) {

				/*
				 * no (inodes do not match), but save the name
				 * for later
				 */
				(void) strcpy(dev_rbuf, file.name);
				dev_flag = 1;
			}
		}
	}
	(void) closedir(dirp);
	return (found);
}


/*
 * get_pri_dirs() - returns a pointer to an array of strings, where each string
 * is a priority directory name.  The end of the array is marked by a NULL
 * pointer.  The priority directories' names are obtained from the file
 * /etc/ttysrch if it exists and is readable, or if not, a default hard-coded
 * list of directories.
 *
 * /etc/ttysrch, if used, is read in as a string of characters into memory and
 * then parsed into strings of priority directory names, omitting comments and
 * blank lines.
 *
 */

#define	START_STATE	1
#define	COMMENT_STATE	2
#define	DIRNAME_STATE	3
#define	FLAG_STATE	4
#define	CHECK_STATE	5

#define	COMMENT_CHAR	'#'
#define	EOLN_CHAR	'\n'

static const entry_t *
get_pri_dirs(void)
{
	int fd, state;
	size_t sz;
	ssize_t size;
	struct stat64 sb;
	char *buf, *ebuf;
	entry_t *vec;

	/*
	 * if no /etc/ttysrch, use defaults
	 */
	if ((fd = open(TTYSRCH, 0)) < 0)
		return (def_srch_dirs);

	if (fstat64(fd, &sb) < 0) {
		(void) close(fd);
		return (def_srch_dirs);
	}

	sz = (size_t)sb.st_size;
	if (dir_vec != NULL && sz == dir_size &&
	    sb.st_mtim.tv_sec == dir_mtim.tv_sec &&
	    sb.st_mtim.tv_nsec == dir_mtim.tv_nsec) {
		/*
		 * size & modification time match
		 * no need to reread TTYSRCH
		 * just return old pointer
		 */
		(void) close(fd);
		return (dir_vec);
	}
	buf = realloc(dir_buf, sz + 1);
	if (buf != NULL) {
		dir_buf = buf;
		size = read(fd, dir_buf, sz);
	}
	(void) close(fd);

	if (buf == NULL || size < 0) {
		if (dir_vec != NULL) {
			free(dir_vec);
			dir_vec = NULL;
		}
		return ((entry_t *)def_srch_dirs);
	}
	dir_size = sz;
	dir_mtim = sb.st_mtim;

	/*
	 * ensure newline termination for buffer.  Add an extra
	 * entry to dir_vec for null terminator
	 */
	ebuf = &dir_buf[size];
	*ebuf++ = '\n';
	for (sz = 1, buf = dir_buf; buf < ebuf; ++buf)
		if (*buf == '\n')
			++sz;

	sz *= sizeof (*dir_vec);
	vec = realloc(dir_vec, sz);
	if (vec == NULL) {
		if (dir_vec != NULL) {
			free(dir_vec);
			dir_vec = NULL;
		}
		return (def_srch_dirs);
	}
	dir_vec = vec;
	state = START_STATE;
	for (buf = dir_buf; buf < ebuf; ++buf) {
		switch (state) {

		case START_STATE:
			if (*buf == COMMENT_CHAR) {
				state = COMMENT_STATE;
				break;
			}
			if (!isspace(*buf))	/* skip leading white space */
				state = DIRNAME_STATE;
				vec->name = buf;
				vec->flags = 0;
			break;

		case COMMENT_STATE:
			if (*buf == EOLN_CHAR)
				state = START_STATE;
			break;

		case DIRNAME_STATE:
			if (*buf == EOLN_CHAR) {
				state = CHECK_STATE;
				*buf = '\0';
			} else if (isspace(*buf)) {
				/* skip trailing white space */
				state = FLAG_STATE;
				*buf = '\0';
			}
			break;

		case FLAG_STATE:
			switch (*buf) {
				case 'M':
					vec->flags |= MATCH_MM;
					break;
				case 'F':
					vec->flags |= MATCH_FS;
					break;
				case 'I':
					vec->flags |= MATCH_INO;
					break;
				case EOLN_CHAR:
					state = CHECK_STATE;
					break;
			}
			break;

		case CHECK_STATE:
			if (strncmp(vec->name, DEV, strlen(DEV)) != 0) {
				int tfd = open("/dev/console", O_WRONLY);
				if (tfd >= 0) {
					char buf[256];
					/* LINTED variable format specifier */
					(void) snprintf(buf, sizeof (buf),
					    _libc_gettext(
"ERROR: Entry '%s' in /etc/ttysrch ignored.\n"), vec->name);
					(void) write(tfd, buf, strlen(buf));
					(void) close(tfd);
				}
			} else {
				char *slash;
				slash = vec->name + strlen(vec->name) - 1;
				while (*slash == '/')
					*slash-- = '\0';
				if (vec->flags == 0)
					vec->flags = MATCH_ALL;
				vec++;
			}
			state = START_STATE;
			/*
			 * This state does not consume a character, so
			 * reposition the pointer.
			 */
			buf--;
			break;

		}
	}
	vec->name = NULL;
	return (dir_vec);
}


char *
ttyname(int f)
{
	char *ans = tsdalloc(_T_TTYNAME, MAX_DEV_PATH, NULL);

	if (ans == NULL)
		return (NULL);
	return (_ttyname_r(f, ans, MAX_DEV_PATH));
}