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redir.c revision 1.43 
      1 /*	$NetBSD: redir.c,v 1.43 2016/05/02 01:46:31 christos Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1991, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Kenneth Almquist.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. Neither the name of the University nor the names of its contributors
     19  *    may be used to endorse or promote products derived from this software
     20  *    without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     32  * SUCH DAMAGE.
     33  */
     34 
     35 #include <sys/cdefs.h>
     36 #ifndef lint
     37 #if 0
     38 static char sccsid[] = "@(#)redir.c	8.2 (Berkeley) 5/4/95";
     39 #else
     40 __RCSID("$NetBSD: redir.c,v 1.43 2016/05/02 01:46:31 christos Exp $");
     41 #endif
     42 #endif /* not lint */
     43 
     44 #include <sys/types.h>
     45 #include <sys/param.h>	/* PIPE_BUF */
     46 #include <signal.h>
     47 #include <string.h>
     48 #include <fcntl.h>
     49 #include <errno.h>
     50 #include <unistd.h>
     51 #include <stdlib.h>
     52 
     53 /*
     54  * Code for dealing with input/output redirection.
     55  */
     56 
     57 #include "main.h"
     58 #include "shell.h"
     59 #include "nodes.h"
     60 #include "jobs.h"
     61 #include "options.h"
     62 #include "expand.h"
     63 #include "redir.h"
     64 #include "output.h"
     65 #include "memalloc.h"
     66 #include "error.h"
     67 
     68 
     69 #define EMPTY -2		/* marks an unused slot in redirtab */
     70 #define	CLOSED -1		/* fd was not open before redir */
     71 #ifndef PIPE_BUF
     72 # define PIPESIZE 4096		/* amount of buffering in a pipe */
     73 #else
     74 # define PIPESIZE PIPE_BUF
     75 #endif
     76 
     77 
     78 MKINIT
     79 struct renamelist {
     80 	struct renamelist *next;
     81 	int orig;
     82 	int into;
     83 };
     84 
     85 MKINIT
     86 struct redirtab {
     87 	struct redirtab *next;
     88 	struct renamelist *renamed;
     89 };
     90 
     91 
     92 MKINIT struct redirtab *redirlist;
     93 
     94 /*
     95  * We keep track of whether or not fd0 has been redirected.  This is for
     96  * background commands, where we want to redirect fd0 to /dev/null only
     97  * if it hasn't already been redirected.
     98  */
     99 STATIC int fd0_redirected = 0;
    100 
    101 /*
    102  * And also where to put internal use fds that should be out of the
    103  * way of user defined fds (normally)
    104  */
    105 STATIC int big_sh_fd = 0;
    106 
    107 STATIC const struct renamelist *is_renamed(const struct renamelist *, int);
    108 STATIC void fd_rename(struct redirtab *, int, int);
    109 STATIC void free_rl(struct redirtab *, int);
    110 STATIC void openredirect(union node *, char[10], int);
    111 STATIC int openhere(const union node *);
    112 STATIC void find_big_fd(void);
    113 
    114 STATIC const struct renamelist *
    115 is_renamed(const struct renamelist *rl, int fd)
    116 {
    117 	while (rl != NULL) {
    118 		if (rl->orig == fd)
    119 			return rl;
    120 		rl = rl->next;
    121 	}
    122 	return NULL;
    123 }
    124 
    125 STATIC void
    126 free_rl(struct redirtab *rt, int reset)
    127 {
    128 	struct renamelist *rl, *rn = rt->renamed;
    129 
    130 	while ((rl = rn) != NULL) {
    131 		rn = rl->next;
    132 		if (rl->orig == 0)
    133 			fd0_redirected--;
    134 		if (reset) {
    135 			if (rl->into < 0)
    136 				close(rl->orig);
    137 			else
    138 				movefd(rl->into, rl->orig);
    139 		}
    140 		ckfree(rl);
    141 	}
    142 	rt->renamed = NULL;
    143 }
    144 
    145 STATIC void
    146 fd_rename(struct redirtab *rt, int from, int to)
    147 {
    148 	struct renamelist *rl = ckmalloc(sizeof(struct renamelist));
    149 
    150 	rl->next = rt->renamed;
    151 	rt->renamed = rl;
    152 
    153 	rl->orig = from;
    154 	rl->into = to;
    155 }
    156 
    157 /*
    158  * Process a list of redirection commands.  If the REDIR_PUSH flag is set,
    159  * old file descriptors are stashed away so that the redirection can be
    160  * undone by calling popredir.  If the REDIR_BACKQ flag is set, then the
    161  * standard output, and the standard error if it becomes a duplicate of
    162  * stdout, is saved in memory.
    163  */
    164 
    165 void
    166 redirect(union node *redir, int flags)
    167 {
    168 	union node *n;
    169 	struct redirtab *sv = NULL;
    170 	int i;
    171 	int fd;
    172 	char memory[10];	/* file descriptors to write to memory */
    173 
    174 	for (i = 10 ; --i >= 0 ; )
    175 		memory[i] = 0;
    176 	memory[1] = flags & REDIR_BACKQ;
    177 	if (flags & REDIR_PUSH) {
    178 		/* We don't have to worry about REDIR_VFORK here, as
    179 		 * flags & REDIR_PUSH is never true if REDIR_VFORK is set.
    180 		 */
    181 		sv = ckmalloc(sizeof (struct redirtab));
    182 		sv->renamed = NULL;
    183 		sv->next = redirlist;
    184 		redirlist = sv;
    185 	}
    186 	for (n = redir ; n ; n = n->nfile.next) {
    187 		fd = n->nfile.fd;
    188 		if ((n->nfile.type == NTOFD || n->nfile.type == NFROMFD) &&
    189 		    n->ndup.dupfd == fd) {
    190 			/* redirect from/to same file descriptor */
    191 			fcntl(fd, F_SETFD, 0);	/* make sure it stays open */
    192 			continue;
    193 		}
    194 
    195 		if ((flags & REDIR_PUSH) && !is_renamed(sv->renamed, fd)) {
    196 			INTOFF;
    197 			if (big_sh_fd < 10)
    198 				find_big_fd();
    199 			if ((i = fcntl(fd, F_DUPFD, big_sh_fd)) == -1) {
    200 				switch (errno) {
    201 				case EBADF:
    202 					i = CLOSED;
    203 					break;
    204 				case EMFILE:
    205 				case EINVAL:
    206 					find_big_fd();
    207 					i = fcntl(fd, F_DUPFD, big_sh_fd);
    208 					if (i >= 0)
    209 						break;
    210 					/* FALLTHRU */
    211 				default:
    212 					i = errno;
    213 					INTON;    /* XXX not needed here ? */
    214 					error("%d: %s", fd, strerror(i));
    215 					/* NOTREACHED */
    216 				}
    217 			}
    218 			if (i >= 0)
    219 				(void)fcntl(i, F_SETFD, FD_CLOEXEC);
    220 			fd_rename(sv, fd, i);
    221 			INTON;
    222 		} else {
    223 			close(fd);
    224 		}
    225                 if (fd == 0)
    226                         fd0_redirected++;
    227 		openredirect(n, memory, flags);
    228 	}
    229 	if (memory[1])
    230 		out1 = &memout;
    231 	if (memory[2])
    232 		out2 = &memout;
    233 }
    234 
    235 
    236 STATIC void
    237 openredirect(union node *redir, char memory[10], int flags)
    238 {
    239 	struct stat sb;
    240 	int fd = redir->nfile.fd;
    241 	char *fname;
    242 	int f;
    243 	int eflags, cloexec;
    244 
    245 	/*
    246 	 * We suppress interrupts so that we won't leave open file
    247 	 * descriptors around.  This may not be such a good idea because
    248 	 * an open of a device or a fifo can block indefinitely.
    249 	 */
    250 	INTOFF;
    251 	if (fd < 10)
    252 		memory[fd] = 0;
    253 	switch (redir->nfile.type) {
    254 	case NFROM:
    255 		fname = redir->nfile.expfname;
    256 		if (flags & REDIR_VFORK)
    257 			eflags = O_NONBLOCK;
    258 		else
    259 			eflags = 0;
    260 		if ((f = open(fname, O_RDONLY|eflags)) < 0)
    261 			goto eopen;
    262 		if (eflags)
    263 			(void)fcntl(f, F_SETFL, fcntl(f, F_GETFL, 0) & ~eflags);
    264 		break;
    265 	case NFROMTO:
    266 		fname = redir->nfile.expfname;
    267 		if ((f = open(fname, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0)
    268 			goto ecreate;
    269 		break;
    270 	case NTO:
    271 		if (Cflag) {
    272 			fname = redir->nfile.expfname;
    273 			if ((f = open(fname, O_WRONLY)) == -1) {
    274 				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL,
    275 				    0666)) < 0)
    276 					goto ecreate;
    277 			} else if (fstat(f, &sb) == -1) {
    278 				int serrno = errno;
    279 				close(f);
    280 				errno = serrno;
    281 				goto ecreate;
    282 			} else if (S_ISREG(sb.st_mode)) {
    283 				close(f);
    284 				errno = EEXIST;
    285 				goto ecreate;
    286 			}
    287 			break;
    288 		}
    289 		/* FALLTHROUGH */
    290 	case NCLOBBER:
    291 		fname = redir->nfile.expfname;
    292 		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
    293 			goto ecreate;
    294 		break;
    295 	case NAPPEND:
    296 		fname = redir->nfile.expfname;
    297 		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
    298 			goto ecreate;
    299 		break;
    300 	case NTOFD:
    301 	case NFROMFD:
    302 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
    303 			if (fd < 10 && redir->ndup.dupfd < 10 &&
    304 			    memory[redir->ndup.dupfd])
    305 				memory[fd] = 1;
    306 			else
    307 				copyfd(redir->ndup.dupfd, fd, 1,
    308 				    (flags & REDIR_PUSH) != 0);
    309 		}
    310 		INTON;
    311 		return;
    312 	case NHERE:
    313 	case NXHERE:
    314 		f = openhere(redir);
    315 		break;
    316 	default:
    317 		abort();
    318 	}
    319 
    320 	cloexec = fd > 2 && (flags & REDIR_KEEP) == 0;
    321 	if (f != fd) {
    322 		copyfd(f, fd, 1, cloexec);
    323 		close(f);
    324 	} else if (cloexec)
    325 		(void)fcntl(f, F_SETFD, FD_CLOEXEC);
    326 
    327 	INTON;
    328 	return;
    329 ecreate:
    330 	exerrno = 1;
    331 	error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
    332 eopen:
    333 	exerrno = 1;
    334 	error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
    335 }
    336 
    337 
    338 /*
    339  * Handle here documents.  Normally we fork off a process to write the
    340  * data to a pipe.  If the document is short, we can stuff the data in
    341  * the pipe without forking.
    342  */
    343 
    344 STATIC int
    345 openhere(const union node *redir)
    346 {
    347 	int pip[2];
    348 	int len = 0;
    349 
    350 	if (pipe(pip) < 0)
    351 		error("Pipe call failed");
    352 	if (redir->type == NHERE) {
    353 		len = strlen(redir->nhere.doc->narg.text);
    354 		if (len <= PIPESIZE) {
    355 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    356 			goto out;
    357 		}
    358 	}
    359 	if (forkshell(NULL, NULL, FORK_NOJOB) == 0) {
    360 		close(pip[0]);
    361 		signal(SIGINT, SIG_IGN);
    362 		signal(SIGQUIT, SIG_IGN);
    363 		signal(SIGHUP, SIG_IGN);
    364 #ifdef SIGTSTP
    365 		signal(SIGTSTP, SIG_IGN);
    366 #endif
    367 		signal(SIGPIPE, SIG_DFL);
    368 		if (redir->type == NHERE)
    369 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    370 		else
    371 			expandhere(redir->nhere.doc, pip[1]);
    372 		_exit(0);
    373 	}
    374 out:
    375 	close(pip[1]);
    376 	return pip[0];
    377 }
    378 
    379 
    380 
    381 /*
    382  * Undo the effects of the last redirection.
    383  */
    384 
    385 void
    386 popredir(void)
    387 {
    388 	struct redirtab *rp = redirlist;
    389 
    390 	INTOFF;
    391 	free_rl(rp, 1);
    392 	redirlist = rp->next;
    393 	ckfree(rp);
    394 	INTON;
    395 }
    396 
    397 /*
    398  * Undo all redirections.  Called on error or interrupt.
    399  */
    400 
    401 #ifdef mkinit
    402 
    403 INCLUDE "redir.h"
    404 
    405 RESET {
    406 	while (redirlist)
    407 		popredir();
    408 }
    409 
    410 SHELLPROC {
    411 	clearredir(0);
    412 }
    413 
    414 #endif
    415 
    416 /* Return true if fd 0 has already been redirected at least once.  */
    417 int
    418 fd0_redirected_p(void)
    419 {
    420         return fd0_redirected != 0;
    421 }
    422 
    423 /*
    424  * Discard all saved file descriptors.
    425  */
    426 
    427 void
    428 clearredir(int vforked)
    429 {
    430 	struct redirtab *rp;
    431 	struct renamelist *rl;
    432 
    433 	for (rp = redirlist ; rp ; rp = rp->next) {
    434 		if (!vforked)
    435 			free_rl(rp, 0);
    436 		else for (rl = rp->renamed; rl; rl = rl->next)
    437 			if (rl->into >= 0)
    438 				close(rl->into);
    439 	}
    440 }
    441 
    442 
    443 
    444 /*
    445  * Copy a file descriptor to be >= to.  Returns -1
    446  * if the source file descriptor is closed, EMPTY if there are no unused
    447  * file descriptors left.
    448  */
    449 
    450 int
    451 copyfd(int from, int to, int equal, int cloexec)
    452 {
    453 	int newfd;
    454 
    455 	if (cloexec && to > 2) {
    456 	    if (equal)
    457 		    newfd = dup3(from, to, O_CLOEXEC);
    458 	    else
    459 		    newfd = fcntl(from, F_DUPFD_CLOEXEC, to);
    460 	} else {
    461 	    if (equal)
    462 		    newfd = dup2(from, to);
    463 	    else
    464 		    newfd = fcntl(from, F_DUPFD, to);
    465 	}
    466 	if (newfd < 0) {
    467 		if (errno == EMFILE)
    468 			return EMPTY;
    469 		else
    470 			error("%d: %s", from, strerror(errno));
    471 	}
    472 	return newfd;
    473 }
    474 
    475 int
    476 movefd(int from, int to)
    477 {
    478 	if (from == to)
    479 		return to;
    480 
    481 	(void) close(to);
    482 	if (copyfd(from, to, 1, 0) != to)
    483 		error("Unable to make fd %d", to);
    484 	(void) close(from);
    485 
    486 	return to;
    487 }
    488 
    489 STATIC void
    490 find_big_fd(void)
    491 {
    492 	int i, fd;
    493 
    494 	for (i = (1 << 10); i >= 10; i >>= 1) {
    495 		if ((fd = fcntl(0, F_DUPFD, i - 1)) >= 0) {
    496 			close(fd);
    497 			break;
    498 		}
    499 	}
    500 
    501 	fd = (i / 5) * 4;
    502 	if ((i - fd) > 100)
    503 		fd = i - 100;
    504 	else if (fd < 10)
    505 		fd = 10;
    506 
    507 	big_sh_fd = fd;
    508 }
    509 
    510 int
    511 to_upper_fd(int fd)
    512 {
    513 	int i;
    514 
    515 	if (big_sh_fd < 10)
    516 		find_big_fd();
    517 	do {
    518 		i = fcntl(fd, F_DUPFD, big_sh_fd);
    519 		if (i >= 0) {
    520 			if (fd != i)
    521 				close(fd);
    522 			return i;
    523 		}
    524 		if (errno != EMFILE)
    525 			break;
    526 		find_big_fd();
    527 	} while (big_sh_fd > 10);
    528 
    529 	return fd;
    530 }
    531