1/* Duplicate a file descriptor to a given number, with flags. Hurd version.
2 Copyright (C) 1991-2024 Free Software Foundation, Inc.
3
4 This file is part of the GNU C Library.
5
6 The GNU C Library is free software; you can redistribute it and/or
7 modify it under the terms of the GNU Lesser General Public
8 License as published by the Free Software Foundation; either
9 version 2.1 of the License, or (at your option) any later version.
10
11 The GNU C Library is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
15
16 You should have received a copy of the GNU Lesser General Public
17 License along with the GNU C Library; see the file COPYING.LIB. If
18 not, see <https://www.gnu.org/licenses/>. */
19
20#include <errno.h>
21#include <fcntl.h>
22#include <unistd.h>
23#include <hurd.h>
24#include <hurd/fd.h>
25
26/* Duplicate FD to FD2, closing the old FD2 and making FD2 be
27 open on the same file as FD is, and setting FD2's flags according to FLAGS.
28 Return FD2 or -1. */
29int
30__dup3 (int fd, int fd2, int flags)
31{
32 struct hurd_fd *d;
33
34 /* Both passing flags different from O_CLOEXEC and FD2 being the same as FD
35 are invalid. */
36 if ((flags & ~O_CLOEXEC
37 || fd2 == fd)
38 /* ... with the exception in case that dup2 behavior is requested: if FD
39 is valid and FD2 is already the same then just return it. */
40 && ! (flags == -1
41 && fd2 == fd))
42 return __hurd_fail (EINVAL);
43
44 /* Extract the ports and flags from FD. */
45 d = _hurd_fd_get (fd);
46 if (d == NULL)
47 return __hurd_fail (EBADF);
48
49 HURD_CRITICAL_BEGIN;
50
51 __spin_lock (&d->port.lock);
52 if (d->port.port == MACH_PORT_NULL)
53 {
54 __spin_unlock (&d->port.lock);
55 fd2 = __hurd_fail (EBADF);
56 }
57 else if (fd2 == fd)
58 __spin_unlock (&d->port.lock);
59 else
60 {
61 struct hurd_userlink ulink, ctty_ulink;
62 int d_flags = d->flags;
63 io_t ctty = _hurd_port_get (&d->ctty, &ctty_ulink);
64 io_t port = _hurd_port_locked_get (&d->port, &ulink); /* Unlocks D. */
65
66 if (fd2 < 0)
67 fd2 = __hurd_fail (EBADF);
68 else
69 {
70 /* Get a hold of the destination descriptor. */
71 struct hurd_fd *d2;
72
73 __mutex_lock (&_hurd_dtable_lock);
74
75 if (fd2 >= _hurd_dtablesize)
76 {
77 /* The table is not large enough to hold the destination
78 descriptor. Enlarge it as necessary to allocate this
79 descriptor. */
80 __mutex_unlock (&_hurd_dtable_lock);
81 d2 = _hurd_alloc_fd (NULL, fd2);
82 if (d2)
83 __spin_unlock (&d2->port.lock);
84 __mutex_lock (&_hurd_dtable_lock);
85 }
86 else
87 {
88 d2 = _hurd_dtable[fd2];
89 if (d2 == NULL)
90 {
91 /* Must allocate a new one. We don't initialize the port
92 cells with this call so that if it fails (out of
93 memory), we will not have already added user
94 references for the ports, which we would then have to
95 deallocate. */
96 d2 = _hurd_dtable[fd2] = _hurd_new_fd (MACH_PORT_NULL,
97 MACH_PORT_NULL);
98 }
99 }
100 __mutex_unlock (&_hurd_dtable_lock);
101
102 if (d2 == NULL)
103 {
104 fd2 = -1;
105 if (errno == EINVAL)
106 __hurd_fail (EBADF); /* POSIX.1-1990 6.2.1.2 ll 54-55. */
107 }
108 else
109 {
110 /* Give the ports each a user ref for the new descriptor. */
111 __mach_port_mod_refs (__mach_task_self (), port,
112 MACH_PORT_RIGHT_SEND, 1);
113 if (ctty != MACH_PORT_NULL)
114 __mach_port_mod_refs (__mach_task_self (), ctty,
115 MACH_PORT_RIGHT_SEND, 1);
116
117 /* Install the ports and flags in the new descriptor slot. */
118 __spin_lock (&d2->port.lock);
119 if (flags & O_CLOEXEC)
120 d2->flags = d_flags | FD_CLOEXEC;
121 else
122 /* dup clears FD_CLOEXEC. */
123 d2->flags = d_flags & ~FD_CLOEXEC;
124 _hurd_port_set (&d2->ctty, ctty);
125 _hurd_port_locked_set (&d2->port, port); /* Unlocks D2. */
126 }
127 }
128
129 _hurd_port_free (&d->port, &ulink, port);
130 if (ctty != MACH_PORT_NULL)
131 _hurd_port_free (&d->ctty, &ctty_ulink, port);
132 }
133
134 HURD_CRITICAL_END;
135
136 return fd2;
137}
138libc_hidden_def (__dup3)
139weak_alias (__dup3, dup3)
140

source code of glibc/sysdeps/mach/hurd/dup3.c