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redir.c revision 1.46 
      1 /*	$NetBSD: redir.c,v 1.46 2016/05/09 20:50:08 kre 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 1.46 2016/05/09 20:50:08 kre 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 		}
    223 		if (fd == 0)
    224 			fd0_redirected++;
    225 		openredirect(n, memory, flags);
    226 	}
    227 	if (memory[1])
    228 		out1 = &memout;
    229 	if (memory[2])
    230 		out2 = &memout;
    231 }
    232 
    233 
    234 STATIC void
    235 openredirect(union node *redir, char memory[10], int flags)
    236 {
    237 	struct stat sb;
    238 	int fd = redir->nfile.fd;
    239 	char *fname;
    240 	int f;
    241 	int eflags, cloexec;
    242 
    243 	/*
    244 	 * We suppress interrupts so that we won't leave open file
    245 	 * descriptors around.  This may not be such a good idea because
    246 	 * an open of a device or a fifo can block indefinitely.
    247 	 */
    248 	INTOFF;
    249 	if (fd < 10)
    250 		memory[fd] = 0;
    251 	switch (redir->nfile.type) {
    252 	case NFROM:
    253 		fname = redir->nfile.expfname;
    254 		if (flags & REDIR_VFORK)
    255 			eflags = O_NONBLOCK;
    256 		else
    257 			eflags = 0;
    258 		if ((f = open(fname, O_RDONLY|eflags)) < 0)
    259 			goto eopen;
    260 		if (eflags)
    261 			(void)fcntl(f, F_SETFL, fcntl(f, F_GETFL, 0) & ~eflags);
    262 		break;
    263 	case NFROMTO:
    264 		fname = redir->nfile.expfname;
    265 		if ((f = open(fname, O_RDWR|O_CREAT|O_TRUNC, 0666)) < 0)
    266 			goto ecreate;
    267 		break;
    268 	case NTO:
    269 		if (Cflag) {
    270 			fname = redir->nfile.expfname;
    271 			if ((f = open(fname, O_WRONLY)) == -1) {
    272 				if ((f = open(fname, O_WRONLY|O_CREAT|O_EXCL,
    273 				    0666)) < 0)
    274 					goto ecreate;
    275 			} else if (fstat(f, &sb) == -1) {
    276 				int serrno = errno;
    277 				close(f);
    278 				errno = serrno;
    279 				goto ecreate;
    280 			} else if (S_ISREG(sb.st_mode)) {
    281 				close(f);
    282 				errno = EEXIST;
    283 				goto ecreate;
    284 			}
    285 			break;
    286 		}
    287 		/* FALLTHROUGH */
    288 	case NCLOBBER:
    289 		fname = redir->nfile.expfname;
    290 		if ((f = open(fname, O_WRONLY|O_CREAT|O_TRUNC, 0666)) < 0)
    291 			goto ecreate;
    292 		break;
    293 	case NAPPEND:
    294 		fname = redir->nfile.expfname;
    295 		if ((f = open(fname, O_WRONLY|O_CREAT|O_APPEND, 0666)) < 0)
    296 			goto ecreate;
    297 		break;
    298 	case NTOFD:
    299 	case NFROMFD:
    300 		if (redir->ndup.dupfd >= 0) {	/* if not ">&-" */
    301 			if (fd < 10 && redir->ndup.dupfd < 10 &&
    302 			    memory[redir->ndup.dupfd])
    303 				memory[fd] = 1;
    304 			else
    305 				copyfd(redir->ndup.dupfd, fd, 1, (flags &
    306 				    (REDIR_PUSH|REDIR_KEEP)) == REDIR_PUSH);
    307 		} else
    308 			close(fd);
    309 		INTON;
    310 		return;
    311 	case NHERE:
    312 	case NXHERE:
    313 		f = openhere(redir);
    314 		break;
    315 	default:
    316 		abort();
    317 	}
    318 
    319 	cloexec = fd > 2 && (flags & REDIR_KEEP) == 0;
    320 	if (f != fd) {
    321 		copyfd(f, fd, 1, cloexec);
    322 		close(f);
    323 	} else if (cloexec)
    324 		(void)fcntl(f, F_SETFD, FD_CLOEXEC);
    325 
    326 	INTON;
    327 	return;
    328 ecreate:
    329 	exerrno = 1;
    330 	error("cannot create %s: %s", fname, errmsg(errno, E_CREAT));
    331 eopen:
    332 	exerrno = 1;
    333 	error("cannot open %s: %s", fname, errmsg(errno, E_OPEN));
    334 }
    335 
    336 
    337 /*
    338  * Handle here documents.  Normally we fork off a process to write the
    339  * data to a pipe.  If the document is short, we can stuff the data in
    340  * the pipe without forking.
    341  */
    342 
    343 STATIC int
    344 openhere(const union node *redir)
    345 {
    346 	int pip[2];
    347 	int len = 0;
    348 
    349 	if (pipe(pip) < 0)
    350 		error("Pipe call failed");
    351 	if (redir->type == NHERE) {
    352 		len = strlen(redir->nhere.doc->narg.text);
    353 		if (len <= PIPESIZE) {
    354 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    355 			goto out;
    356 		}
    357 	}
    358 	if (forkshell(NULL, NULL, FORK_NOJOB) == 0) {
    359 		close(pip[0]);
    360 		signal(SIGINT, SIG_IGN);
    361 		signal(SIGQUIT, SIG_IGN);
    362 		signal(SIGHUP, SIG_IGN);
    363 #ifdef SIGTSTP
    364 		signal(SIGTSTP, SIG_IGN);
    365 #endif
    366 		signal(SIGPIPE, SIG_DFL);
    367 		if (redir->type == NHERE)
    368 			xwrite(pip[1], redir->nhere.doc->narg.text, len);
    369 		else
    370 			expandhere(redir->nhere.doc, pip[1]);
    371 		_exit(0);
    372 	}
    373 out:
    374 	close(pip[1]);
    375 	return pip[0];
    376 }
    377 
    378 
    379 
    380 /*
    381  * Undo the effects of the last redirection.
    382  */
    383 
    384 void
    385 popredir(void)
    386 {
    387 	struct redirtab *rp = redirlist;
    388 
    389 	INTOFF;
    390 	free_rl(rp, 1);
    391 	redirlist = rp->next;
    392 	ckfree(rp);
    393 	INTON;
    394 }
    395 
    396 /*
    397  * Undo all redirections.  Called on error or interrupt.
    398  */
    399 
    400 #ifdef mkinit
    401 
    402 INCLUDE "redir.h"
    403 
    404 RESET {
    405 	while (redirlist)
    406 		popredir();
    407 }
    408 
    409 SHELLPROC {
    410 	clearredir(0);
    411 }
    412 
    413 #endif
    414 
    415 /* Return true if fd 0 has already been redirected at least once.  */
    416 int
    417 fd0_redirected_p(void)
    418 {
    419 	return fd0_redirected != 0;
    420 }
    421 
    422 /*
    423  * Discard all saved file descriptors.
    424  */
    425 
    426 void
    427 clearredir(int vforked)
    428 {
    429 	struct redirtab *rp;
    430 	struct renamelist *rl;
    431 
    432 	for (rp = redirlist ; rp ; rp = rp->next) {
    433 		if (!vforked)
    434 			free_rl(rp, 0);
    435 		else for (rl = rp->renamed; rl; rl = rl->next)
    436 			if (rl->into >= 0)
    437 				close(rl->into);
    438 	}
    439 }
    440 
    441 
    442 
    443 /*
    444  * Copy a file descriptor to be >= to.  Returns -1
    445  * if the source file descriptor is closed, EMPTY if there are no unused
    446  * file descriptors left.
    447  */
    448 
    449 int
    450 copyfd(int from, int to, int equal, int cloexec)
    451 {
    452 	int newfd;
    453 
    454 	if (cloexec && to > 2) {
    455 	    if (equal)
    456 		    newfd = dup3(from, to, O_CLOEXEC);
    457 	    else
    458 		    newfd = fcntl(from, F_DUPFD_CLOEXEC, to);
    459 	} else {
    460 	    if (equal)
    461 		    newfd = dup2(from, to);
    462 	    else
    463 		    newfd = fcntl(from, F_DUPFD, to);
    464 	}
    465 	if (newfd < 0) {
    466 		if (errno == EMFILE)
    467 			return EMPTY;
    468 		else
    469 			error("%d: %s", from, strerror(errno));
    470 	}
    471 	return newfd;
    472 }
    473 
    474 int
    475 movefd(int from, int to)
    476 {
    477 	if (from == to)
    478 		return to;
    479 
    480 	(void) close(to);
    481 	if (copyfd(from, to, 1, 0) != to)
    482 		error("Unable to make fd %d", to);
    483 	(void) close(from);
    484 
    485 	return to;
    486 }
    487 
    488 STATIC void
    489 find_big_fd(void)
    490 {
    491 	int i, fd;
    492 
    493 	for (i = (1 << 10); i >= 10; i >>= 1) {
    494 		if ((fd = fcntl(0, F_DUPFD, i - 1)) >= 0) {
    495 			close(fd);
    496 			break;
    497 		}
    498 	}
    499 
    500 	fd = (i / 5) * 4;
    501 	if ((i - fd) > 100)
    502 		fd = i - 100;
    503 	else if (fd < 10)
    504 		fd = 10;
    505 
    506 	big_sh_fd = fd;
    507 }
    508 
    509 int
    510 to_upper_fd(int fd)
    511 {
    512 	int i;
    513 
    514 	if (big_sh_fd < 10)
    515 		find_big_fd();
    516 	do {
    517 		i = fcntl(fd, F_DUPFD_CLOEXEC, big_sh_fd);
    518 		if (i >= 0) {
    519 			if (fd != i)
    520 				close(fd);
    521 			return i;
    522 		}
    523 		if (errno != EMFILE)
    524 			break;
    525 		find_big_fd();
    526 	} while (big_sh_fd > 10);
    527 
    528 	/*
    529 	 * If we wamted to move this fd to some random high number
    530 	 * we certainly do not intend to pass it through exec, even
    531 	 * if the reassignment failed.
    532 	 */
    533 	(void)fcntl(fd, F_SETFD, FD_CLOEXEC);
    534 	return fd;
    535 }
    536