Commit | Line | Data |
---|---|---|
d45599f4 MD |
1 | /* |
2 | * compat_arch_x86.c | |
3 | * | |
4 | * Userspace RCU library - x86 compatibility checks | |
5 | * | |
6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | |
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 |
d45599f4 MD |
32 | * compat_arch_init() explicitely if needed. |
33 | */ | |
02be5561 | 34 | int __attribute__((constructor)) __rcu_cas_init(void); |
d45599f4 | 35 | |
d45599f4 MD |
36 | /* |
37 | * -1: unknown | |
38 | * 1: available | |
39 | * 0: unavailable | |
40 | */ | |
02be5561 | 41 | int __rcu_cas_avail = -1; |
d45599f4 | 42 | |
bf9de1b7 MD |
43 | static pthread_mutex_t compat_mutex = PTHREAD_MUTEX_INITIALIZER; |
44 | ||
d45599f4 | 45 | /* |
bf9de1b7 MD |
46 | * get_eflags/set_eflags/compare_and_swap_is_available imported from glibc |
47 | * 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h. | |
d45599f4 MD |
48 | */ |
49 | ||
bf9de1b7 | 50 | static int get_eflags (void) |
d45599f4 MD |
51 | { |
52 | int res; | |
53 | __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : ); | |
54 | return res; | |
55 | } | |
56 | ||
bf9de1b7 | 57 | static void set_eflags (int newflags) |
d45599f4 MD |
58 | { |
59 | __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc"); | |
60 | } | |
61 | ||
bf9de1b7 | 62 | static int compare_and_swap_is_available (void) |
d45599f4 MD |
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 | 77 | static void mutex_lock_signal_save(pthread_mutex_t *mutex, sigset_t *oldmask) |
d45599f4 | 78 | { |
bf9de1b7 | 79 | sigset_t newmask; |
d45599f4 MD |
80 | int ret; |
81 | ||
82 | /* Disable signals */ | |
83 | ret = sigemptyset(&newmask); | |
84 | assert(!ret); | |
bf9de1b7 | 85 | ret = pthread_sigmask(SIG_SETMASK, &newmask, oldmask); |
d45599f4 MD |
86 | assert(!ret); |
87 | ret = pthread_mutex_lock(&compat_mutex); | |
88 | assert(!ret); | |
bf9de1b7 MD |
89 | } |
90 | ||
91 | static 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 | ||
101 | unsigned 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 | |
bf9de1b7 MD |
131 | unsigned 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 | ||
161 | unsigned 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); | |
d45599f4 MD |
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; |
bf9de1b7 MD |
174 | retval = result; |
175 | break; | |
d45599f4 MD |
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; |
bf9de1b7 MD |
182 | retval = result; |
183 | break; | |
d45599f4 MD |
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; |
bf9de1b7 MD |
190 | retval = result; |
191 | break; | |
d45599f4 | 192 | } |
bf9de1b7 MD |
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 | } |
bf9de1b7 MD |
200 | mutex_lock_signal_restore(&compat_mutex, &mask); |
201 | return retval; | |
202 | } | |
d45599f4 | 203 | |
bf9de1b7 MD |
204 | unsigned long _compat_uatomic_add_return(void *addr, unsigned long v, int len) |
205 | { | |
206 | sigset_t mask; | |
207 | unsigned long result; | |
208 | ||
209 | mutex_lock_signal_save(&compat_mutex, &mask); | |
210 | switch (len) { | |
211 | case 1: | |
212 | *(unsigned char *)addr += (unsigned char)v; | |
213 | result = *(unsigned char *)addr; | |
214 | break; | |
215 | case 2: | |
216 | *(unsigned short *)addr += (unsigned short)v; | |
217 | result = *(unsigned short *)addr; | |
218 | break; | |
219 | case 4: | |
220 | *(unsigned int *)addr += (unsigned int)v; | |
221 | result = *(unsigned int *)addr; | |
222 | break; | |
223 | default: | |
224 | /* | |
225 | * generate an illegal instruction. Cannot catch this with | |
226 | * linker tricks when optimizations are disabled. | |
227 | */ | |
228 | __asm__ __volatile__("ud2"); | |
229 | } | |
230 | mutex_lock_signal_restore(&compat_mutex, &mask); | |
231 | return result; | |
d45599f4 MD |
232 | } |
233 | ||
02be5561 | 234 | int __rcu_cas_init(void) |
d45599f4 | 235 | { |
02be5561 MD |
236 | if (__rcu_cas_avail < 0) |
237 | __rcu_cas_avail = compare_and_swap_is_available(); | |
238 | return __rcu_cas_avail; | |
d45599f4 | 239 | } |