uatomic: add uatomic_or
[urcu.git] / compat_arch_x86.c
CommitLineData
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1/*
2 * compat_arch_x86.c
3 *
4 * Userspace RCU library - x86 compatibility checks
5 *
6982d6d7 6 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23#include <stdio.h>
24#include <pthread.h>
25#include <signal.h>
26#include <assert.h>
27#include <urcu/uatomic_arch.h>
28
29/*
30 * It does not really matter if the constructor is called before using
02be5561 31 * the library, as long as the caller checks if __rcu_cas_avail < 0 and calls
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32 * compat_arch_init() explicitely if needed.
33 */
02be5561 34int __attribute__((constructor)) __rcu_cas_init(void);
d45599f4 35
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36/*
37 * -1: unknown
38 * 1: available
39 * 0: unavailable
40 */
02be5561 41int __rcu_cas_avail = -1;
d45599f4 42
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43static pthread_mutex_t compat_mutex = PTHREAD_MUTEX_INITIALIZER;
44
d45599f4 45/*
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46 * get_eflags/set_eflags/compare_and_swap_is_available imported from glibc
47 * 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h.
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48 */
49
bf9de1b7 50static int get_eflags (void)
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51{
52 int res;
53 __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
54 return res;
55}
56
bf9de1b7 57static void set_eflags (int newflags)
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58{
59 __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
60}
61
bf9de1b7 62static int compare_and_swap_is_available (void)
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63{
64 int oldflags = get_eflags ();
65 int changed;
66 /* Flip AC bit in EFLAGS. */
67 set_eflags (oldflags ^ 0x40000);
68 /* See if bit changed. */
69 changed = (get_eflags () ^ oldflags) & 0x40000;
70 /* Restore EFLAGS. */
71 set_eflags (oldflags);
72 /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
73 Otherwise, it's a 486 or above and it has cmpxchg. */
74 return changed != 0;
75}
76
bf9de1b7 77static void mutex_lock_signal_save(pthread_mutex_t *mutex, sigset_t *oldmask)
d45599f4 78{
bf9de1b7 79 sigset_t newmask;
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80 int ret;
81
82 /* Disable signals */
83 ret = sigemptyset(&newmask);
84 assert(!ret);
bf9de1b7 85 ret = pthread_sigmask(SIG_SETMASK, &newmask, oldmask);
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86 assert(!ret);
87 ret = pthread_mutex_lock(&compat_mutex);
88 assert(!ret);
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89}
90
91static void mutex_lock_signal_restore(pthread_mutex_t *mutex, sigset_t *oldmask)
92{
93 int ret;
94
95 ret = pthread_mutex_unlock(&compat_mutex);
96 assert(!ret);
97 ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL);
98 assert(!ret);
99}
100
101unsigned long _compat_uatomic_set(void *addr, unsigned long _new, int len)
102{
103 sigset_t mask;
104 unsigned long result;
105
106 mutex_lock_signal_save(&compat_mutex, &mask);
107 switch (len) {
108 case 1:
109 *(unsigned char *)addr = (unsigned char)_new;
110 result = *(unsigned char *)addr;
111 break;
112 case 2:
113 *(unsigned short *)addr = (unsigned short)_new;
114 result = *(unsigned short *)addr;
115 break;
116 case 4:
117 *(unsigned int *)addr = (unsigned int)_new;
118 result = *(unsigned int *)addr;
119 break;
120 default:
121 /*
122 * generate an illegal instruction. Cannot catch this with
123 * linker tricks when optimizations are disabled.
124 */
125 __asm__ __volatile__("ud2");
126 }
127 mutex_lock_signal_restore(&compat_mutex, &mask);
128 return _new;
129}
d45599f4 130
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131unsigned long _compat_uatomic_xchg(void *addr, unsigned long _new, int len)
132{
133 sigset_t mask;
134 unsigned long retval;
135
136 mutex_lock_signal_save(&compat_mutex, &mask);
137 switch (len) {
138 case 1:
139 retval = *(unsigned char *)addr;
140 *(unsigned char *)addr = (unsigned char)_new;
141 break;
142 case 2:
143 retval = *(unsigned short *)addr;
144 *(unsigned short *)addr = (unsigned short)_new;
145 break;
146 case 4:
147 retval = *(unsigned int *)addr;
148 *(unsigned int *)addr = (unsigned int)_new;
149 break;
150 default:
151 /*
152 * generate an illegal instruction. Cannot catch this with
153 * linker tricks when optimizations are disabled.
154 */
155 __asm__ __volatile__("ud2");
156 }
157 mutex_lock_signal_restore(&compat_mutex, &mask);
158 return retval;
159}
160
161unsigned long _compat_uatomic_cmpxchg(void *addr, unsigned long old,
162 unsigned long _new, int len)
163{
164 unsigned long retval;
165 sigset_t mask;
166
167 mutex_lock_signal_save(&compat_mutex, &mask);
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168 switch (len) {
169 case 1:
170 {
171 unsigned char result = *(unsigned char *)addr;
bf9de1b7 172 if (result == (unsigned char)old)
d45599f4 173 *(unsigned char *)addr = (unsigned char)_new;
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174 retval = result;
175 break;
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176 }
177 case 2:
178 {
179 unsigned short result = *(unsigned short *)addr;
bf9de1b7 180 if (result == (unsigned short)old)
d45599f4 181 *(unsigned short *)addr = (unsigned short)_new;
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182 retval = result;
183 break;
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184 }
185 case 4:
186 {
187 unsigned int result = *(unsigned int *)addr;
bf9de1b7 188 if (result == (unsigned int)old)
d45599f4 189 *(unsigned int *)addr = (unsigned int)_new;
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190 retval = result;
191 break;
d45599f4 192 }
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193 default:
194 /*
195 * generate an illegal instruction. Cannot catch this with
196 * linker tricks when optimizations are disabled.
197 */
198 __asm__ __volatile__("ud2");
d45599f4 199 }
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200 mutex_lock_signal_restore(&compat_mutex, &mask);
201 return retval;
202}
d45599f4 203
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204void _compat_uatomic_or(void *addr, unsigned long v, int len)
205{
206 sigset_t mask;
207
208 mutex_lock_signal_save(&compat_mutex, &mask);
209 switch (len) {
210 case 1:
211 *(unsigned char *)addr |= (unsigned char)v;
212 break;
213 case 2:
214 *(unsigned short *)addr |= (unsigned short)v;
215 break;
216 case 4:
217 *(unsigned int *)addr |= (unsigned int)v;
218 break;
219 default:
220 /*
221 * generate an illegal instruction. Cannot catch this with
222 * linker tricks when optimizations are disabled.
223 */
224 __asm__ __volatile__("ud2");
225 }
226 mutex_lock_signal_restore(&compat_mutex, &mask);
227}
228
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229unsigned long _compat_uatomic_add_return(void *addr, unsigned long v, int len)
230{
231 sigset_t mask;
232 unsigned long result;
233
234 mutex_lock_signal_save(&compat_mutex, &mask);
235 switch (len) {
236 case 1:
237 *(unsigned char *)addr += (unsigned char)v;
238 result = *(unsigned char *)addr;
239 break;
240 case 2:
241 *(unsigned short *)addr += (unsigned short)v;
242 result = *(unsigned short *)addr;
243 break;
244 case 4:
245 *(unsigned int *)addr += (unsigned int)v;
246 result = *(unsigned int *)addr;
247 break;
248 default:
249 /*
250 * generate an illegal instruction. Cannot catch this with
251 * linker tricks when optimizations are disabled.
252 */
253 __asm__ __volatile__("ud2");
254 }
255 mutex_lock_signal_restore(&compat_mutex, &mask);
256 return result;
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257}
258
02be5561 259int __rcu_cas_init(void)
d45599f4 260{
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261 if (__rcu_cas_avail < 0)
262 __rcu_cas_avail = compare_and_swap_is_available();
263 return __rcu_cas_avail;
d45599f4 264}
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