1 /* Lightweight user references for ports.
2 Copyright (C) 1993-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #ifndef _HURD_PORT_H
20
21 #define _HURD_PORT_H 1
22 #include <features.h>
23
24 #include <mach.h>
25 #include <hurd/userlink.h>
26 #include <spin-lock.h>
27
28
29 /* Structure describing a cell containing a port. With the lock held, a
30 user extracts PORT, and attaches his own link (in local storage) to the
31 USERS chain. PORT can then safely be used. When PORT is no longer
32 needed, with the lock held, the user removes his link from the chain.
33 If his link is the last, and PORT has changed since he fetched it, the
34 user deallocates the port he used. See <hurd/userlink.h>. */
35
36 struct hurd_port
37 {
38 spin_lock_t lock; /* Locks rest. */
39 struct hurd_userlink *users; /* Chain of users; see below. */
40 mach_port_t port; /* Port. */
41 };
42
43
44 /* Evaluate EXPR with the variable `port' bound to the port in PORTCELL. */
45 /* Also see HURD_PORT_USE_CANCEL. */
46
47 #define HURD_PORT_USE(portcell, expr) \
48 ({ struct hurd_port *const __p = (portcell); \
49 struct hurd_userlink __link; \
50 const mach_port_t port = _hurd_port_get (__p, &__link); \
51 __typeof(expr) __result = (expr); \
52 _hurd_port_free (__p, &__link, port); \
53 __result; })
54
55
56 #ifndef _HURD_PORT_H_EXTERN_INLINE
57 #define _HURD_PORT_H_EXTERN_INLINE __extern_inline
58 #endif
59
60
61 /* Initialize *PORT to INIT. */
62
63 extern void _hurd_port_init (struct hurd_port *port, mach_port_t init);
64
65 #if defined __USE_EXTERN_INLINES && defined _LIBC
66 # if IS_IN (libc)
67 _HURD_PORT_H_EXTERN_INLINE void
_hurd_port_init(struct hurd_port * port,mach_port_t init)68 _hurd_port_init (struct hurd_port *port, mach_port_t init)
69 {
70 __spin_lock_init (&port->lock);
71 port->users = NULL;
72 port->port = init;
73 }
74 # endif
75 #endif
76
77
78 /* Cleanup function for non-local exits. */
79 extern void _hurd_port_cleanup (void *, jmp_buf, int);
80
81 /* Get a reference to *PORT, which is locked.
82 Pass return value and LINK to _hurd_port_free when done. */
83
84 extern mach_port_t
85 _hurd_port_locked_get (struct hurd_port *port,
86 struct hurd_userlink *link);
87
88 #if defined __USE_EXTERN_INLINES && defined _LIBC
89 # if IS_IN (libc)
90 _HURD_PORT_H_EXTERN_INLINE mach_port_t
_hurd_port_locked_get(struct hurd_port * port,struct hurd_userlink * link)91 _hurd_port_locked_get (struct hurd_port *port,
92 struct hurd_userlink *link)
93 {
94 mach_port_t result;
95 result = port->port;
96 if (result != MACH_PORT_NULL)
97 {
98 link->cleanup = &_hurd_port_cleanup;
99 link->cleanup_data = (void *) result;
100 _hurd_userlink_link (&port->users, link);
101 }
102 __spin_unlock (&port->lock);
103 return result;
104 }
105 # endif
106 #endif
107
108 /* Same, but locks PORT first. */
109
110 extern mach_port_t
111 _hurd_port_get (struct hurd_port *port,
112 struct hurd_userlink *link);
113
114 #if defined __USE_EXTERN_INLINES && defined _LIBC
115 # if IS_IN (libc)
116 _HURD_PORT_H_EXTERN_INLINE mach_port_t
_hurd_port_get(struct hurd_port * port,struct hurd_userlink * link)117 _hurd_port_get (struct hurd_port *port,
118 struct hurd_userlink *link)
119 {
120 mach_port_t result;
121 HURD_CRITICAL_BEGIN;
122 __spin_lock (&port->lock);
123 result = _hurd_port_locked_get (port, link);
124 HURD_CRITICAL_END;
125 return result;
126 }
127 # endif
128 #endif
129
130
131 /* Relocate LINK to NEW_LINK.
132 To be used when e.g. reallocating a link array. */
133
134 extern void
135 _hurd_port_move (struct hurd_port *port,
136 struct hurd_userlink *new_link,
137 struct hurd_userlink *link);
138
139 #if defined __USE_EXTERN_INLINES && defined _LIBC
140 # if IS_IN (libc)
141 _HURD_PORT_H_EXTERN_INLINE void
_hurd_port_move(struct hurd_port * port,struct hurd_userlink * new_link,struct hurd_userlink * link)142 _hurd_port_move (struct hurd_port *port,
143 struct hurd_userlink *new_link,
144 struct hurd_userlink *link)
145 {
146 HURD_CRITICAL_BEGIN;
147 __spin_lock (&port->lock);
148 _hurd_userlink_move (new_link, link);
149 __spin_unlock (&port->lock);
150 HURD_CRITICAL_END;
151 }
152 # endif
153 #endif
154
155
156 /* Free a reference gotten with `USED_PORT = _hurd_port_get (PORT, LINK);' */
157
158 extern void
159 _hurd_port_free (struct hurd_port *port,
160 struct hurd_userlink *link,
161 mach_port_t used_port);
162
163 #if defined __USE_EXTERN_INLINES && defined _LIBC
164 # if IS_IN (libc)
165 _HURD_PORT_H_EXTERN_INLINE void
_hurd_port_free(struct hurd_port * port,struct hurd_userlink * link,mach_port_t used_port)166 _hurd_port_free (struct hurd_port *port,
167 struct hurd_userlink *link,
168 mach_port_t used_port)
169 {
170 int dealloc;
171 if (used_port == MACH_PORT_NULL)
172 /* When we fetch an empty port cell with _hurd_port_get,
173 it does not link us on the users chain, since there is
174 no shared resource. */
175 return;
176 HURD_CRITICAL_BEGIN;
177 __spin_lock (&port->lock);
178 dealloc = _hurd_userlink_unlink (link);
179 __spin_unlock (&port->lock);
180 HURD_CRITICAL_END;
181 if (dealloc)
182 __mach_port_deallocate (__mach_task_self (), used_port);
183 }
184 # endif
185 #endif
186
187
188 /* Set *PORT's port to NEWPORT. NEWPORT's reference is consumed by PORT->port.
189 PORT->lock is locked. */
190
191 extern void _hurd_port_locked_set (struct hurd_port *port, mach_port_t newport);
192
193 #if defined __USE_EXTERN_INLINES && defined _LIBC
194 # if IS_IN (libc)
195 _HURD_PORT_H_EXTERN_INLINE void
_hurd_port_locked_set(struct hurd_port * port,mach_port_t newport)196 _hurd_port_locked_set (struct hurd_port *port, mach_port_t newport)
197 {
198 mach_port_t old;
199 old = _hurd_userlink_clear (&port->users) ? port->port : MACH_PORT_NULL;
200 port->port = newport;
201 __spin_unlock (&port->lock);
202 if (old != MACH_PORT_NULL)
203 __mach_port_deallocate (__mach_task_self (), old);
204 }
205 # endif
206 #endif
207
208 /* Same, but locks PORT first. */
209
210 extern void _hurd_port_set (struct hurd_port *port, mach_port_t newport);
211
212 #if defined __USE_EXTERN_INLINES && defined _LIBC
213 # if IS_IN (libc)
214 _HURD_PORT_H_EXTERN_INLINE void
_hurd_port_set(struct hurd_port * port,mach_port_t newport)215 _hurd_port_set (struct hurd_port *port, mach_port_t newport)
216 {
217 HURD_CRITICAL_BEGIN;
218 __spin_lock (&port->lock);
219 _hurd_port_locked_set (port, newport);
220 HURD_CRITICAL_END;
221 }
222 # endif
223 #endif
224
225
226 #endif /* hurd/port.h */
227