1/* $OpenBSD: filedesc.h,v 1.49 2026/03/08 16:41:19 deraadt Exp $ */
2/* $NetBSD: filedesc.h,v 1.14 1996/04/09 20:55:28 cgd Exp $ */
3
4/*
5 * Copyright (c) 1990, 1993
6 * The Regents of the University of California. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 * @(#)filedesc.h 8.1 (Berkeley) 6/2/93
33 */
34
35#include <sys/mutex.h>
36#include <sys/rwlock.h>
37/*
38 * This structure is used for the management of descriptors. It may be
39 * shared by multiple processes.
40 *
41 * A process is initially started out with NDFILE descriptors stored within
42 * this structure, selected to be enough for typical applications based on
43 * the historical limit of 20 open files (and the usage of descriptors by
44 * shells). If these descriptors are exhausted, a larger descriptor table
45 * may be allocated, up to a process' resource limit; the internal arrays
46 * are then unused. The initial expansion is set to NDEXTENT; each time
47 * it runs out, it is doubled until the resource limit is reached. NDEXTENT
48 * should be selected to be the biggest multiple of OFILESIZE (see below)
49 * that will fit in a power-of-two sized piece of memory.
50 */
51#define NDFILE 20
52#define NDEXTENT 50 /* 250 bytes in 256-byte alloc. */
53#define NDENTRIES 32 /* 32 fds per entry */
54#define NDENTRYMASK (NDENTRIES - 1)
55#define NDENTRYSHIFT 5 /* bits per entry */
56#define NDREDUCE(x) (((x) + NDENTRIES - 1) >> NDENTRYSHIFT)
57#define NDHISLOTS(x) (NDREDUCE(NDREDUCE(x)))
58#define NDLOSLOTS(x) (NDHISLOTS(x) << NDENTRYSHIFT)
59
60struct kqueue;
61
62/*
63 * Locking:
64 * a atomic operations
65 * f fd_lock
66 * f/w fd_lock when writing
67 * K kernel lock
68 * m fd_fplock
69 */
70struct filedesc {
71 struct file **fd_ofiles; /* [f/w,m] file structures for
72 * open files */
73 char *fd_ofileflags; /* [f] per-process open file flags */
74 struct vnode *fd_cdir; /* [K] current directory */
75 struct vnode *fd_rdir; /* [K] root directory */
76 int fd_nfiles; /* [f] number of open files allocated */
77 int fd_openfd; /* [f] number of files currently open */
78 u_int *fd_himap; /* [f] each bit points to 32 fds */
79 u_int *fd_lomap; /* [f] bitmap of free fds */
80 int fd_lastfile; /* [f] high-water mark of fd_ofiles */
81 int fd_freefile; /* [f] approx. next free file */
82 mode_t fd_cmask; /* [f/w] mask for file creation */
83 u_int fd_refcnt; /* [K] reference count */
84 struct rwlock fd_lock; /* lock for the file descs */
85 struct mutex fd_fplock; /* lock for reading fd_ofiles without
86 * fd_lock */
87 LIST_HEAD(, kqueue) fd_kqlist; /* [f] kqueues attached to this
88 * filedesc */
89 int fd_flags; /* [a] flags on this filedesc */
90 u_int fd_nuserevents; /* [a] number of kqueue user events */
91};
92
93/*
94 * Basic allocation of descriptors:
95 * one of the above, plus arrays for NDFILE descriptors.
96 */
97struct filedesc0 {
98 struct filedesc fd_fd;
99 /*
100 * These arrays are used when the number of open files is
101 * <= NDFILE, and are then pointed to by the pointers above.
102 */
103 struct file *fd_dfiles[NDFILE];
104 char fd_dfileflags[NDFILE];
105 /*
106 * There arrays are used when the number of open files is
107 * <= 1024, and are then pointed to by the pointers above.
108 */
109 u_int fd_dhimap[NDENTRIES >> NDENTRYSHIFT];
110 u_int fd_dlomap[NDENTRIES];
111};
112
113/*
114 * Per-process open flags.
115 */
116#define UF_EXCLOSE 0x01 /* auto-close on exec */
117#define UF_PLEDGED 0x02 /* opened after pledge(2) */
118#define UF_FORKCLOSE 0x04 /* auto-close on fork */
119#define UF_PLEDGEOPEN 0x08 /* opened with __pledge_open() */
120
121/*
122 * Flags on the file descriptor table.
123 */
124#define FD_ADVLOCK 0x01 /* May hold a POSIX adv. lock. */
125
126/*
127 * Storage required per open file descriptor.
128 */
129#define OFILESIZE (sizeof(struct file *) + sizeof(char))
130
131#ifdef _KERNEL
132/*
133 * Kernel global variables and routines.
134 */
135void filedesc_init(void);
136int dupfdopen(struct proc *, int, int);
137int fdalloc(struct proc *p, int want, int *result);
138void fdexpand(struct proc *);
139struct file *fnew(struct proc *_p);
140int falloc(struct proc *_p, struct file **_rfp, int *_rfd);
141struct filedesc *fdinit(void);
142struct filedesc *fdshare(struct process *);
143struct filedesc *fdcopy(struct process *);
144void fdfree(struct proc *p);
145int fdrelease(struct proc *p, int);
146void fdinsert(struct filedesc *, int, int, struct file *);
147void fdremove(struct filedesc *, int);
148void fdprepforexec(struct proc *);
149struct file *fd_iterfile(struct file *, struct proc *);
150struct file *fd_getfile(struct filedesc *, int);
151struct file *fd_getfile_mode(struct filedesc *, int, int);
152int fd_checkclosed(struct filedesc *, int, struct file *);
153
154int closef(struct file *, struct proc *);
155int getsock(struct proc *, int, struct file **);
156
157#define fdplock(fdp) do { NET_ASSERT_UNLOCKED(); rw_enter_write(&(fdp)->fd_lock); } while (0)
158#define fdpunlock(fdp) rw_exit_write(&(fdp)->fd_lock)
159#define fdpassertlocked(fdp) rw_assert_wrlock(&(fdp)->fd_lock)
160#endif