xref: /netbsd-src/sys/compat/linux/common/linux_file.c (revision 1f2744e6e4915c9da2a3f980279398c4cf7d5e6d)
1 /*	$NetBSD: linux_file.c,v 1.2 1995/03/05 23:23:40 fvdl Exp $	*/
2 
3 /*
4  * Copyright (c) 1995 Frank van der Linden
5  * All rights reserved.
6  *
7  * Redistribution and use in source and binary forms, with or without
8  * modification, are permitted provided that the following conditions
9  * are met:
10  * 1. Redistributions of source code must retain the above copyright
11  *    notice, this list of conditions and the following disclaimer.
12  * 2. Redistributions in binary form must reproduce the above copyright
13  *    notice, this list of conditions and the following disclaimer in the
14  *    documentation and/or other materials provided with the distribution.
15  * 3. All advertising materials mentioning features or use of this software
16  *    must display the following acknowledgement:
17  *      This product includes software developed for the NetBSD Project
18  *      by Frank van der Linden
19  * 4. The name of the author may not be used to endorse or promote products
20  *    derived from this software without specific prior written permission
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32  */
33 
34 #include <sys/param.h>
35 #include <sys/systm.h>
36 #include <sys/namei.h>
37 #include <sys/proc.h>
38 #include <sys/file.h>
39 #include <sys/stat.h>
40 #include <sys/filedesc.h>
41 #include <sys/ioctl.h>
42 #include <sys/kernel.h>
43 #include <sys/mount.h>
44 #include <sys/malloc.h>
45 
46 #include <sys/syscallargs.h>
47 
48 #include <compat/linux/linux_types.h>
49 #include <compat/linux/linux_syscallargs.h>
50 #include <compat/linux/linux_fcntl.h>
51 #include <compat/linux/linux_util.h>
52 
53 /*
54  * Some file-related calls are handled here. The usual flag conversion
55  * an structure conversion is done, and alternate emul path searching.
56  */
57 
58 /*
59  * The next two functions convert between the Linux and NetBSD values
60  * of the flags used in open(2) and fcntl(2).
61  */
62 static int
63 linux_to_bsd_ioflags(int lflags)
64 {
65 	int res = 0;
66 
67 	res |= cvtto_bsd_mask(lflags, LINUX_O_WRONLY, O_WRONLY);
68 	res |= cvtto_bsd_mask(lflags, LINUX_O_RDONLY, O_RDONLY);
69 	res |= cvtto_bsd_mask(lflags, LINUX_O_RDWR, O_RDWR);
70 	res |= cvtto_bsd_mask(lflags, LINUX_O_CREAT, O_CREAT);
71 	res |= cvtto_bsd_mask(lflags, LINUX_O_EXCL, O_EXCL);
72 	res |= cvtto_bsd_mask(lflags, LINUX_O_NOCTTY, O_NOCTTY);
73 	res |= cvtto_bsd_mask(lflags, LINUX_O_TRUNC, O_TRUNC);
74 	res |= cvtto_bsd_mask(lflags, LINUX_O_NDELAY, O_NDELAY);
75 	res |= cvtto_bsd_mask(lflags, LINUX_O_SYNC, O_FSYNC);
76 	res |= cvtto_bsd_mask(lflags, LINUX_FASYNC, O_ASYNC);
77 	res |= cvtto_bsd_mask(lflags, LINUX_O_APPEND, O_APPEND);
78 
79 	return res;
80 }
81 
82 static int
83 bsd_to_linux_ioflags(int bflags)
84 {
85 	int res = 0;
86 
87 	res |= cvtto_linux_mask(bflags, O_WRONLY, LINUX_O_WRONLY);
88 	res |= cvtto_linux_mask(bflags, O_RDONLY, LINUX_O_RDONLY);
89 	res |= cvtto_linux_mask(bflags, O_RDWR, LINUX_O_RDWR);
90 	res |= cvtto_linux_mask(bflags, O_CREAT, LINUX_O_CREAT);
91 	res |= cvtto_linux_mask(bflags, O_EXCL, LINUX_O_EXCL);
92 	res |= cvtto_linux_mask(bflags, O_NOCTTY, LINUX_O_NOCTTY);
93 	res |= cvtto_linux_mask(bflags, O_TRUNC, LINUX_O_TRUNC);
94 	res |= cvtto_linux_mask(bflags, O_NDELAY, LINUX_O_NDELAY);
95 	res |= cvtto_linux_mask(bflags, O_FSYNC, LINUX_O_SYNC);
96 	res |= cvtto_linux_mask(bflags, O_ASYNC, LINUX_FASYNC);
97 	res |= cvtto_linux_mask(bflags, O_APPEND, LINUX_O_APPEND);
98 
99 	return res;
100 }
101 
102 /*
103  * creat(2) is an obsolete function, but it's present as a Linux
104  * system call, so let's deal with it.
105  *
106  * Just call open(2) with the TRUNC, CREAT and WRONLY flags.
107  */
108 int
109 linux_creat(p, uap, retval)
110 	struct proc *p;
111 	struct linux_creat_args /* {
112 		syscallarg(char *) path;
113 		syscallarg(int) mode;
114 	} */ *uap;
115 	register_t *retval;
116 {
117 	struct open_args oa;
118 	caddr_t sg;
119 
120 	sg = stackgap_init();
121 	CHECK_ALT_CREAT(p, &sg, SCARG(uap, path));
122 
123 	SCARG(&oa, path) = SCARG(uap, path);
124 	SCARG(&oa, flags) = O_CREAT | O_TRUNC | O_WRONLY;
125 	SCARG(&oa, mode) = SCARG(uap, mode);
126 	return open(p, &oa, retval);
127 }
128 
129 /*
130  * open(2). Take care of the different flag values, and let the
131  * NetBSD syscall do the real work. See if this operation
132  * gives the current process a controlling terminal.
133  * (XXX is this necessary?)
134  */
135 int
136 linux_open(p, uap, retval)
137 	struct proc *p;
138 	struct linux_open_args /* {
139 		syscallarg(char *) path;
140 		syscallarg(int) flags;
141 		syscallarg(int) mode;
142 	} */ *uap;
143 	register_t *retval;
144 {
145 	int error, fl;
146 	struct open_args boa;
147 	caddr_t sg;
148 
149 	sg = stackgap_init();
150 
151 	fl = linux_to_bsd_ioflags(SCARG(uap, flags));
152 
153 	if (fl & O_CREAT)
154 		CHECK_ALT_CREAT(p, &sg, SCARG(uap, path));
155 	else
156 		CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
157 
158 	SCARG(&boa, path) = SCARG(uap, path);
159 	SCARG(&boa, flags) = fl;
160 	SCARG(&boa, mode) = SCARG(uap, mode);
161 
162 	if ((error = open(p, &boa, retval)))
163 		return error;
164 
165 	/*
166 	 * this bit from sunos_misc.c (and svr4_fcntl.c).
167 	 * If we are a session leader, and we don't have a controlling
168 	 * terminal yet, and the O_NOCTTY flag is not set, try to make
169 	 * this the controlling terminal.
170 	 */
171         if (!(fl & O_NOCTTY) && SESS_LEADER(p) && !(p->p_flag & P_CONTROLT)) {
172                 struct filedesc *fdp = p->p_fd;
173                 struct file     *fp = fdp->fd_ofiles[*retval];
174 
175                 /* ignore any error, just give it a try */
176                 if (fp->f_type == DTYPE_VNODE)
177                         (fp->f_ops->fo_ioctl) (fp, TIOCSCTTY, (caddr_t) 0, p);
178         }
179 	return 0;
180 }
181 
182 /*
183  * This appears to be part of a Linux attempt to switch to 64 bits file sizes.
184  */
185 int
186 linux_llseek(p, uap, retval)
187 	struct proc *p;
188 	struct linux_llseek_args /* {
189 		syscallarg(int) fd;
190 		syscallarg(uint32_t) ohigh;
191 		syscallarg(uint32_t) olow;
192 		syscallarg(caddr_t) res;
193 		syscallarg(int) whence;
194 	} */ *uap;
195 	register_t *retval;
196 {
197 	struct lseek_args bla;
198 	int error;
199 	off_t off;
200 
201 	off = SCARG(uap, olow) | (((off_t) SCARG(uap, ohigh)) << 32);
202 
203 	SCARG(&bla, fd) = SCARG(uap, fd);
204 	SCARG(&bla, offset) = off;
205 	SCARG(&bla, whence) = SCARG(uap, whence);
206 
207 	if ((error = lseek(p, &bla, retval)))
208 		return error;
209 
210 	if ((error = copyout(retval, SCARG(uap, res), sizeof (off_t))))
211 		return error;
212 
213 	retval[0] = 0;
214 	return 0;
215 }
216 
217 /*
218  * The next two functions take care of converting the flock
219  * structure back and forth between Linux and NetBSD format.
220  * The only difference in the structures is the order of
221  * the fields, and the 'whence' value.
222  */
223 static void
224 bsd_to_linux_flock(bfp, lfp)
225 	struct flock *bfp;
226 	struct linux_flock *lfp;
227 {
228 	lfp->l_start = bfp->l_start;
229 	lfp->l_len = bfp->l_len;
230 	lfp->l_pid = bfp->l_pid;
231 	lfp->l_type = bfp->l_type;
232 	switch (bfp->l_whence) {
233 	case F_RDLCK:
234 		lfp->l_whence = LINUX_F_RDLCK;
235 		break;
236 	case F_UNLCK:
237 		lfp->l_whence = LINUX_F_UNLCK;
238 		break;
239 	case F_WRLCK:
240 		lfp->l_whence = LINUX_F_WRLCK;
241 		break;
242 	}
243 }
244 
245 static void
246 linux_to_bsd_flock(lfp, bfp)
247 	struct linux_flock *lfp;
248 	struct flock *bfp;
249 {
250 	bfp->l_start = lfp->l_start;
251 	bfp->l_len = lfp->l_len;
252 	bfp->l_pid = lfp->l_pid;
253 	bfp->l_type = lfp->l_type;
254 	switch (lfp->l_whence) {
255 	case LINUX_F_RDLCK:
256 		bfp->l_whence = F_RDLCK;
257 		break;
258 	case LINUX_F_UNLCK:
259 		bfp->l_whence = F_UNLCK;
260 		break;
261 	case LINUX_F_WRLCK:
262 		bfp->l_whence = F_WRLCK;
263 		break;
264 	}
265 }
266 
267 /*
268  * Most actions in the fcntl() call are straightforward; simply
269  * pass control to the NetBSD system call. A few commands need
270  * conversions after the actual system call has done its work,
271  * because the flag values and lock structure are different.
272  */
273 int
274 linux_fcntl(p, uap, retval)
275 	struct proc *p;
276 	struct linux_fcntl_args /* {
277 		syscallarg(int) fd;
278 		syscallarg(int) cmd;
279 		syscallarg(void *) arg;
280 	} */ *uap;
281 	register_t *retval;
282 {
283 	int fd, cmd, error, *tval,val;
284 	caddr_t arg, sg;
285 	struct linux_flock lfl;
286 	struct flock *bfp, bfl;
287 	struct fcntl_args fca;
288 
289 	fd = SCARG(uap, fd);
290 	cmd = SCARG(uap, cmd);
291 	arg = (caddr_t) SCARG(uap, arg);
292 
293 	switch (cmd) {
294 	case LINUX_F_DUPFD:
295 		cmd = F_DUPFD;
296 		break;
297 	case LINUX_F_GETFD:
298 		cmd = F_GETFD;
299 		break;
300 	case LINUX_F_SETFD:
301 		cmd = F_SETFD;
302 		break;
303 	case LINUX_F_GETFL:
304 		SCARG(&fca, fd) = fd;
305 		SCARG(&fca, cmd) = F_GETFL;
306 		SCARG(&fca, arg) = arg;
307 		if ((error = fcntl(p, &fca, retval)))
308 			return error;
309 		retval[0] = bsd_to_linux_ioflags(retval[0]);
310 		return 0;
311 	case LINUX_F_SETFL:
312 		if ((error = copyin(SCARG(uap, arg), &val, sizeof (int))))
313 			return error;
314 		val = linux_to_bsd_ioflags(val);
315 		sg = stackgap_init();
316 		tval = (int *) stackgap_alloc(&sg, sizeof (int));
317 		if ((error = copyout(&val, tval, sizeof (int))))
318 			return error;
319 		SCARG(&fca, fd) = fd;
320 		SCARG(&fca, cmd) = F_SETFL;
321 		SCARG(&fca, arg) = tval;
322 		return fcntl(p, &fca, retval);
323 	case LINUX_F_GETLK:
324 		sg = stackgap_init();
325 		bfp = (struct flock *) stackgap_alloc(&sg, sizeof *bfp);
326 		SCARG(&fca, fd) = fd;
327 		SCARG(&fca, cmd) = F_GETLK;
328 		SCARG(&fca, arg) = bfp;
329 		if ((error = fcntl(p, &fca, retval)))
330 			return error;
331 		if ((error = copyin(bfp, &bfl, sizeof bfl)))
332 			return error;
333 		bsd_to_linux_flock(&bfl, &lfl);
334 		return copyout(&lfl, arg, sizeof lfl);
335 		break;
336 	case LINUX_F_SETLK:
337 	case LINUX_F_SETLKW:
338 		cmd = (cmd == LINUX_F_SETLK ? F_SETLK : F_SETLKW);
339 		if ((error = copyin(arg, &lfl, sizeof lfl)))
340 			return error;
341 		linux_to_bsd_flock(&lfl, &bfl);
342 		sg = stackgap_init();
343 		bfp = (struct flock *) stackgap_alloc(&sg, sizeof *bfp);
344 		if ((error = copyout(&bfl, bfp, sizeof bfl)))
345 			return error;
346 		SCARG(&fca, fd) = fd;
347 		SCARG(&fca, cmd) = cmd;
348 		SCARG(&fca, arg) = bfp;
349 		return fcntl(p, &fca, retval);
350 		break;
351 	case LINUX_F_SETOWN:
352 		cmd = F_SETOWN;
353 		break;
354 	case LINUX_F_GETOWN:
355 		cmd = F_GETOWN;
356 		break;
357 	default:
358 		return EOPNOTSUPP;
359 	}
360 
361 	SCARG(&fca, fd) = fd;
362 	SCARG(&fca, cmd) = cmd;
363 	SCARG(&fca, arg) = arg;
364 	return fcntl(p, uap, retval);
365 }
366 
367 /*
368  * Convert a NetBSD stat structure to a Linux stat structure.
369  * Only the order of the fields and the padding in the structure
370  * is different.
371  */
372 static void
373 bsd_to_linux_stat(bsp, lsp)
374 	struct stat *bsp;
375 	struct linux_stat *lsp;
376 {
377 	lsp->lst_dev     = bsp->st_dev;
378 	lsp->lst_ino     = bsp->st_ino;
379 	lsp->lst_mode    = bsp->st_mode;
380 	lsp->lst_nlink   = bsp->st_nlink;
381 	lsp->lst_uid     = bsp->st_uid;
382 	lsp->lst_gid     = bsp->st_gid;
383 	lsp->lst_rdev    = bsp->st_rdev;
384 	lsp->lst_size    = bsp->st_size;
385 	lsp->lst_blksize = bsp->st_blksize;
386 	lsp->lst_blocks  = bsp->st_blocks;
387 	lsp->lst_atime   = bsp->st_atime;
388 	lsp->lst_mtime   = bsp->st_mtime;
389 	lsp->lst_ctime   = bsp->st_ctime;
390 }
391 
392 /*
393  * The stat functions below are plain sailing. stat and lstat are handled
394  * by one function to avoid code duplication.
395  */
396 int
397 linux_fstat(p, uap, retval)
398 	struct proc *p;
399 	struct linux_fstat_args /* {
400 		syscallarg(int) fd;
401 		syscallarg(linux_stat *) sp;
402 	} */ *uap;
403 	register_t *retval;
404 {
405 	struct fstat_args fsa;
406 	struct linux_stat tmplst;
407 	struct stat *st,tmpst;
408 	caddr_t sg;
409 	int error;
410 
411 	sg = stackgap_init();
412 
413 	st = stackgap_alloc(&sg, sizeof (struct stat));
414 
415 	SCARG(&fsa, fd) = SCARG(uap, fd);
416 	SCARG(&fsa, sb) = st;
417 
418 	if ((error = fstat(p, &fsa, retval)))
419 		return error;
420 
421 	if ((error = copyin(st, &tmpst, sizeof tmpst)))
422 		return error;
423 
424 	bsd_to_linux_stat(&tmpst, &tmplst);
425 
426 	if ((error = copyout(&tmplst, SCARG(uap, sp), sizeof tmplst)))
427 		return error;
428 
429 	return 0;
430 }
431 
432 static int
433 linux_stat1(p, uap, retval, dolstat)
434 	struct proc *p;
435 	struct linux_stat_args *uap;
436 	register_t *retval;
437 	int dolstat;
438 {
439 	struct stat_args sa;
440 	struct linux_stat tmplst;
441 	struct stat *st, tmpst;
442 	caddr_t sg;
443 	int error;
444 
445 	sg = stackgap_init();
446 
447 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
448 
449 	st = stackgap_alloc(&sg, sizeof (struct stat));
450 	SCARG(&sa, ub) = st;
451 	SCARG(&sa, path) = SCARG(uap, path);
452 
453 	if ((error = (dolstat ? lstat(p, &sa, retval) : stat(p, &sa, retval))))
454 		return error;
455 
456 	if ((error = copyin(st, &tmpst, sizeof tmpst)))
457 		return error;
458 
459 	bsd_to_linux_stat(&tmpst, &tmplst);
460 
461 	if ((error = copyout(&tmplst, SCARG(uap, sp), sizeof tmplst)))
462 		return error;
463 
464 	return 0;
465 }
466 
467 int
468 linux_stat(p, uap, retval)
469 	struct proc *p;
470 	struct linux_stat_args /* {
471 		syscallarg(char *) path;
472 		syscallarg(struct linux_stat *) sp;
473 	} */ *uap;
474 	register_t *retval;
475 {
476 	return linux_stat1(p, uap, retval, 0);
477 }
478 
479 int
480 linux_lstat(p, uap, retval)
481 	struct proc *p;
482 	struct linux_lstat_args /* {
483 		syscallarg(char *) path;
484 		syscallarg(struct linux_stat *) sp;
485 	} */ *uap;
486 	register_t *retval;
487 {
488 	return linux_stat1(p, uap, retval, 1);
489 }
490 
491 /*
492  * The following syscalls are only here because of the alternate path check.
493  */
494 int
495 linux_access(p, uap, retval)
496 	struct proc *p;
497 	struct linux_access_args /* {
498 		syscallarg(char *) path;
499 		syscallarg(int) flags;
500 	} */ *uap;
501 	register_t *retval;
502 {
503 	caddr_t sg = stackgap_init();
504 
505 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
506 
507 	return access(p, uap, retval);
508 }
509 
510 int
511 linux_unlink(p, uap, retval)
512 	struct proc *p;
513 	struct linux_unlink_args /* {
514 		syscallarg(char *) path;
515 	} */ *uap;
516 	register_t *retval;
517 
518 {
519 	caddr_t sg = stackgap_init();
520 
521 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
522 
523 	return unlink(p, uap, retval);
524 }
525 
526 int linux_chdir(p, uap, retval)
527 	struct proc *p;
528 	struct linux_chdir_args /* {
529 		syscallarg(char *) path;
530 	} */ *uap;
531 	register_t *retval;
532 {
533 	caddr_t sg = stackgap_init();
534 
535 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
536 
537 	return chdir(p, uap, retval);
538 }
539 
540 int
541 linux_mknod(p, uap, retval)
542 	struct proc *p;
543 	struct linux_mknod_args /* {
544 		syscallarg(char *) path;
545 		syscallarg(int) mode;
546 		syscallarg(int) dev;
547 	} */ *uap;
548 	register_t *retval;
549 {
550 	caddr_t sg = stackgap_init();
551 
552 	CHECK_ALT_CREAT(p, &sg, SCARG(uap, path));
553 
554 	return mknod(p, uap, retval);
555 }
556 
557 int
558 linux_chmod(p, uap, retval)
559 	struct proc *p;
560 	struct linux_chmod_args /* {
561 		syscallarg(char *) path;
562 		syscallarg(int) mode;
563 	} */ *uap;
564 	register_t *retval;
565 {
566 	caddr_t sg = stackgap_init();
567 
568 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
569 
570 	return chmod(p, uap, retval);
571 }
572 
573 int
574 linux_chown(p, uap, retval)
575 	struct proc *p;
576 	struct linux_chown_args /* {
577 		syscallarg(char *) path;
578 		syscallarg(int) uid;
579 		syscallarg(int) gid;
580 	} */ *uap;
581 	register_t *retval;
582 {
583 	caddr_t sg = stackgap_init();
584 
585 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
586 
587 	return chmod(p, uap, retval);
588 }
589 
590 int
591 linux_rename(p, uap, retval)
592 	struct proc *p;
593 	struct linux_rename_args /* {
594 		syscallarg(char *) from;
595 		syscallarg(char *) to;
596 	} */ *uap;
597 	register_t *retval;
598 {
599 	caddr_t sg = stackgap_init();
600 
601 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, from));
602 	CHECK_ALT_CREAT(p, &sg, SCARG(uap, to));
603 
604 	return rename(p, uap, retval);
605 }
606 
607 int
608 linux_mkdir(p, uap, retval)
609 	struct proc *p;
610 	struct linux_mkdir_args /* {
611 		syscallarg(char *) path;
612 	} */ *uap;
613 	register_t *retval;
614 {
615 	caddr_t sg = stackgap_init();
616 
617 	CHECK_ALT_CREAT(p, &sg, SCARG(uap, path));
618 	return mkdir(p, uap, retval);
619 }
620 
621 int
622 linux_rmdir(p, uap, retval)
623 	struct proc *p;
624 	struct linux_rmdir_args /* {
625 		syscallarg(char *) path;
626 	} */ *uap;
627 	register_t *retval;
628 {
629 	caddr_t sg = stackgap_init();
630 
631 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
632 	return rmdir(p, uap, retval);
633 }
634 
635 int
636 linux_symlink(p, uap, retval)
637 	struct proc *p;
638 	struct linux_symlink_args /* {
639 		syscallarg(char *) path;
640 		syscallarg(char *) to;
641 	} */ *uap;
642 	register_t *retval;
643 {
644 	caddr_t sg = stackgap_init();
645 
646 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
647 	CHECK_ALT_CREAT(p, &sg, SCARG(uap, to));
648 
649 	return symlink(p, uap, retval);
650 }
651 
652 int
653 linux_readlink(p, uap, retval)
654 	struct proc *p;
655 	struct linux_readlink_args /* {
656 		syscallarg(char *) name;
657 		syscallarg(char *) buf;
658 		syscallarg(int) count;
659 	} */ *uap;
660 {
661 	caddr_t sg = stackgap_init();
662 
663 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, name));
664 	return readlink(p, uap, retval);
665 }
666 
667 int
668 linux_truncate(p, uap, retval)
669 	struct proc *p;
670 	struct linux_truncate_args /* {
671 		syscallarg(char *) path;
672 		syscallarg(long) length;
673 	} */ *uap;
674 {
675 	caddr_t sg = stackgap_init();
676 
677 	CHECK_ALT_EXIST(p, &sg, SCARG(uap, path));
678 	return compat_43_truncate(p, uap, retval);
679 }
680