Cleanup: remove leftover manual pthread detection
[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>
a2e7bf9c 27#include <urcu/uatomic.h>
d45599f4 28
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29/*
30 * Using attribute "weak" for __rcu_cas_avail and
31 * __urcu_x86_compat_mutex. Those are globally visible by the entire
32 * program, even though many shared objects may have their own version.
33 * The first version that gets loaded will be used by the entire
34 * program (executable and all shared objects).
35 */
36
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37/*
38 * It does not really matter if the constructor is called before using
02be5561 39 * the library, as long as the caller checks if __rcu_cas_avail < 0 and calls
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40 * compat_arch_init() explicitely if needed.
41 */
02be5561 42int __attribute__((constructor)) __rcu_cas_init(void);
d45599f4 43
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44/*
45 * -1: unknown
46 * 1: available
47 * 0: unavailable
48 */
976720e4 49__attribute__((weak))
02be5561 50int __rcu_cas_avail = -1;
d45599f4 51
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52__attribute__((weak))
53pthread_mutex_t __urcu_x86_compat_mutex = PTHREAD_MUTEX_INITIALIZER;
bf9de1b7 54
d45599f4 55/*
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56 * get_eflags/set_eflags/compare_and_swap_is_available imported from glibc
57 * 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h.
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58 */
59
bf9de1b7 60static int get_eflags (void)
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61{
62 int res;
63 __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
64 return res;
65}
66
bf9de1b7 67static void set_eflags (int newflags)
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68{
69 __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
70}
71
bf9de1b7 72static int compare_and_swap_is_available (void)
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73{
74 int oldflags = get_eflags ();
75 int changed;
76 /* Flip AC bit in EFLAGS. */
77 set_eflags (oldflags ^ 0x40000);
78 /* See if bit changed. */
79 changed = (get_eflags () ^ oldflags) & 0x40000;
80 /* Restore EFLAGS. */
81 set_eflags (oldflags);
82 /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
83 Otherwise, it's a 486 or above and it has cmpxchg. */
84 return changed != 0;
85}
86
bf9de1b7 87static void mutex_lock_signal_save(pthread_mutex_t *mutex, sigset_t *oldmask)
d45599f4 88{
bf9de1b7 89 sigset_t newmask;
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90 int ret;
91
92 /* Disable signals */
6ed4b2e6 93 ret = sigfillset(&newmask);
d45599f4 94 assert(!ret);
6ed4b2e6 95 ret = pthread_sigmask(SIG_BLOCK, &newmask, oldmask);
d45599f4 96 assert(!ret);
976720e4 97 ret = pthread_mutex_lock(&__urcu_x86_compat_mutex);
d45599f4 98 assert(!ret);
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99}
100
101static void mutex_lock_signal_restore(pthread_mutex_t *mutex, sigset_t *oldmask)
102{
103 int ret;
104
976720e4 105 ret = pthread_mutex_unlock(&__urcu_x86_compat_mutex);
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106 assert(!ret);
107 ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL);
108 assert(!ret);
109}
110
111unsigned long _compat_uatomic_set(void *addr, unsigned long _new, int len)
112{
113 sigset_t mask;
114 unsigned long result;
115
976720e4 116 mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
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117 switch (len) {
118 case 1:
119 *(unsigned char *)addr = (unsigned char)_new;
120 result = *(unsigned char *)addr;
121 break;
122 case 2:
123 *(unsigned short *)addr = (unsigned short)_new;
124 result = *(unsigned short *)addr;
125 break;
126 case 4:
127 *(unsigned int *)addr = (unsigned int)_new;
128 result = *(unsigned int *)addr;
129 break;
130 default:
131 /*
132 * generate an illegal instruction. Cannot catch this with
133 * linker tricks when optimizations are disabled.
134 */
c94627b5 135 result = 0;
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136 __asm__ __volatile__("ud2");
137 }
976720e4 138 mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
c94627b5 139 return result;
bf9de1b7 140}
d45599f4 141
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142unsigned long _compat_uatomic_xchg(void *addr, unsigned long _new, int len)
143{
144 sigset_t mask;
145 unsigned long retval;
146
976720e4 147 mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
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148 switch (len) {
149 case 1:
150 retval = *(unsigned char *)addr;
151 *(unsigned char *)addr = (unsigned char)_new;
152 break;
153 case 2:
154 retval = *(unsigned short *)addr;
155 *(unsigned short *)addr = (unsigned short)_new;
156 break;
157 case 4:
158 retval = *(unsigned int *)addr;
159 *(unsigned int *)addr = (unsigned int)_new;
160 break;
161 default:
162 /*
163 * generate an illegal instruction. Cannot catch this with
164 * linker tricks when optimizations are disabled.
165 */
8c43fe72 166 retval = 0; /* silence gcc warnings */
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167 __asm__ __volatile__("ud2");
168 }
976720e4 169 mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
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170 return retval;
171}
172
173unsigned long _compat_uatomic_cmpxchg(void *addr, unsigned long old,
174 unsigned long _new, int len)
175{
176 unsigned long retval;
177 sigset_t mask;
178
976720e4 179 mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
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180 switch (len) {
181 case 1:
182 {
183 unsigned char result = *(unsigned char *)addr;
bf9de1b7 184 if (result == (unsigned char)old)
d45599f4 185 *(unsigned char *)addr = (unsigned char)_new;
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186 retval = result;
187 break;
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188 }
189 case 2:
190 {
191 unsigned short result = *(unsigned short *)addr;
bf9de1b7 192 if (result == (unsigned short)old)
d45599f4 193 *(unsigned short *)addr = (unsigned short)_new;
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194 retval = result;
195 break;
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196 }
197 case 4:
198 {
199 unsigned int result = *(unsigned int *)addr;
bf9de1b7 200 if (result == (unsigned int)old)
d45599f4 201 *(unsigned int *)addr = (unsigned int)_new;
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202 retval = result;
203 break;
d45599f4 204 }
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205 default:
206 /*
207 * generate an illegal instruction. Cannot catch this with
208 * linker tricks when optimizations are disabled.
209 */
8c43fe72 210 retval = 0; /* silence gcc warnings */
bf9de1b7 211 __asm__ __volatile__("ud2");
d45599f4 212 }
976720e4 213 mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
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214 return retval;
215}
d45599f4 216
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217void _compat_uatomic_or(void *addr, unsigned long v, int len)
218{
219 sigset_t mask;
220
976720e4 221 mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
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222 switch (len) {
223 case 1:
224 *(unsigned char *)addr |= (unsigned char)v;
225 break;
226 case 2:
227 *(unsigned short *)addr |= (unsigned short)v;
228 break;
229 case 4:
230 *(unsigned int *)addr |= (unsigned int)v;
231 break;
232 default:
233 /*
234 * generate an illegal instruction. Cannot catch this with
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235 * linker tricks when optimizations are disabled.
236 */
237 __asm__ __volatile__("ud2");
238 }
976720e4 239 mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
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240}
241
242void _compat_uatomic_and(void *addr, unsigned long v, int len)
243{
244 sigset_t mask;
245
976720e4 246 mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
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247 switch (len) {
248 case 1:
249 *(unsigned char *)addr &= (unsigned char)v;
250 break;
251 case 2:
252 *(unsigned short *)addr &= (unsigned short)v;
253 break;
254 case 4:
255 *(unsigned int *)addr &= (unsigned int)v;
256 break;
257 default:
258 /*
259 * generate an illegal instruction. Cannot catch this with
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260 * linker tricks when optimizations are disabled.
261 */
262 __asm__ __volatile__("ud2");
263 }
976720e4 264 mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
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265}
266
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267unsigned long _compat_uatomic_add_return(void *addr, unsigned long v, int len)
268{
269 sigset_t mask;
270 unsigned long result;
271
976720e4 272 mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
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273 switch (len) {
274 case 1:
275 *(unsigned char *)addr += (unsigned char)v;
276 result = *(unsigned char *)addr;
277 break;
278 case 2:
279 *(unsigned short *)addr += (unsigned short)v;
280 result = *(unsigned short *)addr;
281 break;
282 case 4:
283 *(unsigned int *)addr += (unsigned int)v;
284 result = *(unsigned int *)addr;
285 break;
286 default:
287 /*
288 * generate an illegal instruction. Cannot catch this with
289 * linker tricks when optimizations are disabled.
290 */
8c43fe72 291 result = 0; /* silence gcc warnings */
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292 __asm__ __volatile__("ud2");
293 }
976720e4 294 mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 295 return result;
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296}
297
02be5561 298int __rcu_cas_init(void)
d45599f4 299{
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300 if (__rcu_cas_avail < 0)
301 __rcu_cas_avail = compare_and_swap_is_available();
302 return __rcu_cas_avail;
d45599f4 303}
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