findfp.c revision 330897 
1/*-
2 * SPDX-License-Identifier: BSD-3-Clause
3 *
4 * Copyright (c) 1990, 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 * Chris Torek.
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#if defined(LIBC_SCCS) && !defined(lint)
36static char sccsid[] = "@(#)findfp.c	8.2 (Berkeley) 1/4/94";
37#endif /* LIBC_SCCS and not lint */
38#include <sys/cdefs.h>
39__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/findfp.c 330897 2018-03-14 03:19:51Z eadler $");
40
41#include <sys/param.h>
42#include <machine/atomic.h>
43#include <unistd.h>
44#include <stdio.h>
45#include <stdlib.h>
46#include <stdint.h>
47#include <string.h>
48
49#include <spinlock.h>
50
51#include "libc_private.h"
52#include "local.h"
53#include "glue.h"
54
55int	__sdidinit;
56
57#define	NDYNAMIC 10		/* add ten more whenever necessary */
58
59#define	std(flags, file) {		\
60	._flags = (flags),		\
61	._file = (file),		\
62	._cookie = __sF + (file),	\
63	._close = __sclose,		\
64	._read = __sread,		\
65	._seek = __sseek,		\
66	._write = __swrite,		\
67	._fl_mutex = PTHREAD_MUTEX_INITIALIZER, \
68}
69				/* the usual - (stdin + stdout + stderr) */
70static FILE usual[FOPEN_MAX - 3];
71static struct glue uglue = { NULL, FOPEN_MAX - 3, usual };
72
73static FILE __sF[3] = {
74	std(__SRD, STDIN_FILENO),
75	std(__SWR, STDOUT_FILENO),
76	std(__SWR|__SNBF, STDERR_FILENO)
77};
78
79FILE *__stdinp = &__sF[0];
80FILE *__stdoutp = &__sF[1];
81FILE *__stderrp = &__sF[2];
82
83struct glue __sglue = { &uglue, 3, __sF };
84static struct glue *lastglue = &uglue;
85
86static struct glue *	moreglue(int);
87
88spinlock_t __stdio_thread_lock = _SPINLOCK_INITIALIZER;
89
90#if NOT_YET
91#define	SET_GLUE_PTR(ptr, val)	atomic_set_rel_ptr(&(ptr), (uintptr_t)(val))
92#else
93#define	SET_GLUE_PTR(ptr, val)	ptr = val
94#endif
95
96static struct glue *
97moreglue(int n)
98{
99	struct glue *g;
100	static FILE empty = { ._fl_mutex = PTHREAD_MUTEX_INITIALIZER };
101	FILE *p;
102	size_t align;
103
104	align = __alignof__(FILE);
105	g = (struct glue *)malloc(sizeof(*g) + align + n * sizeof(FILE));
106	if (g == NULL)
107		return (NULL);
108	p = (FILE *)roundup((uintptr_t)(g + 1), align);
109	g->next = NULL;
110	g->niobs = n;
111	g->iobs = p;
112	while (--n >= 0)
113		*p++ = empty;
114	return (g);
115}
116
117/*
118 * Find a free FILE for fopen et al.
119 */
120FILE *
121__sfp(void)
122{
123	FILE	*fp;
124	int	n;
125	struct glue *g;
126
127	if (!__sdidinit)
128		__sinit();
129	/*
130	 * The list must be locked because a FILE may be updated.
131	 */
132	STDIO_THREAD_LOCK();
133	for (g = &__sglue; g != NULL; g = g->next) {
134		for (fp = g->iobs, n = g->niobs; --n >= 0; fp++)
135			if (fp->_flags == 0)
136				goto found;
137	}
138	STDIO_THREAD_UNLOCK();	/* don't hold lock while malloc()ing. */
139	if ((g = moreglue(NDYNAMIC)) == NULL)
140		return (NULL);
141	STDIO_THREAD_LOCK();	/* reacquire the lock */
142	SET_GLUE_PTR(lastglue->next, g); /* atomically append glue to list */
143	lastglue = g;		/* not atomic; only accessed when locked */
144	fp = g->iobs;
145found:
146	fp->_flags = 1;		/* reserve this slot; caller sets real flags */
147	STDIO_THREAD_UNLOCK();
148	fp->_p = NULL;		/* no current pointer */
149	fp->_w = 0;		/* nothing to read or write */
150	fp->_r = 0;
151	fp->_bf._base = NULL;	/* no buffer */
152	fp->_bf._size = 0;
153	fp->_lbfsize = 0;	/* not line buffered */
154	fp->_file = -1;		/* no file */
155/*	fp->_cookie = <any>; */	/* caller sets cookie, _read/_write etc */
156	fp->_ub._base = NULL;	/* no ungetc buffer */
157	fp->_ub._size = 0;
158	fp->_lb._base = NULL;	/* no line buffer */
159	fp->_lb._size = 0;
160/*	fp->_fl_mutex = NULL; */ /* once set always set (reused) */
161	fp->_orientation = 0;
162	memset(&fp->_mbstate, 0, sizeof(mbstate_t));
163	fp->_flags2 = 0;
164	return (fp);
165}
166
167/*
168 * XXX.  Force immediate allocation of internal memory.  Not used by stdio,
169 * but documented historically for certain applications.  Bad applications.
170 */
171__warn_references(f_prealloc,
172	"warning: this program uses f_prealloc(), which is not recommended.");
173void f_prealloc(void);
174
175void
176f_prealloc(void)
177{
178	struct glue *g;
179	int n;
180
181	n = getdtablesize() - FOPEN_MAX + 20;		/* 20 for slop. */
182	/*
183	 * It should be safe to walk the list without locking it;
184	 * new nodes are only added to the end and none are ever
185	 * removed.
186	 */
187	for (g = &__sglue; (n -= g->niobs) > 0 && g->next; g = g->next)
188		/* void */;
189	if ((n > 0) && ((g = moreglue(n)) != NULL)) {
190		STDIO_THREAD_LOCK();
191		SET_GLUE_PTR(lastglue->next, g);
192		lastglue = g;
193		STDIO_THREAD_UNLOCK();
194	}
195}
196
197/*
198 * exit() calls _cleanup() through *__cleanup, set whenever we
199 * open or buffer a file.  This chicanery is done so that programs
200 * that do not use stdio need not link it all in.
201 *
202 * The name `_cleanup' is, alas, fairly well known outside stdio.
203 */
204void
205_cleanup(void)
206{
207	/* (void) _fwalk(fclose); */
208	(void) _fwalk(__sflush);		/* `cheating' */
209}
210
211/*
212 * __sinit() is called whenever stdio's internal variables must be set up.
213 */
214void
215__sinit(void)
216{
217
218	/* Make sure we clean up on exit. */
219	__cleanup = _cleanup;		/* conservative */
220	__sdidinit = 1;
221}
222