| 1 | /* |
| 2 | * compat_arch.c |
| 3 | * |
| 4 | * Userspace RCU library - architecture compatibility checks |
| 5 | * |
| 6 | * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 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 <urcu/arch.h> |
| 24 | |
| 25 | #if defined(URCU_ARCH_I386) |
| 26 | |
| 27 | #include <stdio.h> |
| 28 | #include <pthread.h> |
| 29 | #include <signal.h> |
| 30 | #include <assert.h> |
| 31 | #include <urcu/uatomic.h> |
| 32 | |
| 33 | /* |
| 34 | * Using attribute "weak" for __rcu_cas_avail and |
| 35 | * __urcu_x86_compat_mutex. Those are globally visible by the entire |
| 36 | * program, even though many shared objects may have their own version. |
| 37 | * The first version that gets loaded will be used by the entire |
| 38 | * program (executable and all shared objects). |
| 39 | */ |
| 40 | |
| 41 | /* |
| 42 | * It does not really matter if the constructor is called before using |
| 43 | * the library, as long as the caller checks if __rcu_cas_avail < 0 and calls |
| 44 | * compat_arch_init() explicitely if needed. |
| 45 | */ |
| 46 | int __attribute__((constructor)) __rcu_cas_init(void); |
| 47 | |
| 48 | /* |
| 49 | * -1: unknown |
| 50 | * 1: available |
| 51 | * 0: unavailable |
| 52 | */ |
| 53 | __attribute__((weak)) |
| 54 | int __rcu_cas_avail = -1; |
| 55 | |
| 56 | __attribute__((weak)) |
| 57 | pthread_mutex_t __urcu_x86_compat_mutex = PTHREAD_MUTEX_INITIALIZER; |
| 58 | |
| 59 | /* |
| 60 | * get_eflags/set_eflags/compare_and_swap_is_available imported from glibc |
| 61 | * 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h. |
| 62 | */ |
| 63 | |
| 64 | static int get_eflags (void) |
| 65 | { |
| 66 | int res; |
| 67 | __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : ); |
| 68 | return res; |
| 69 | } |
| 70 | |
| 71 | static void set_eflags (int newflags) |
| 72 | { |
| 73 | __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc"); |
| 74 | } |
| 75 | |
| 76 | static int compare_and_swap_is_available (void) |
| 77 | { |
| 78 | int oldflags = get_eflags (); |
| 79 | int changed; |
| 80 | /* Flip AC bit in EFLAGS. */ |
| 81 | set_eflags (oldflags ^ 0x40000); |
| 82 | /* See if bit changed. */ |
| 83 | changed = (get_eflags () ^ oldflags) & 0x40000; |
| 84 | /* Restore EFLAGS. */ |
| 85 | set_eflags (oldflags); |
| 86 | /* If the AC flag did not change, it's a 386 and it lacks cmpxchg. |
| 87 | Otherwise, it's a 486 or above and it has cmpxchg. */ |
| 88 | return changed != 0; |
| 89 | } |
| 90 | |
| 91 | static void mutex_lock_signal_save(pthread_mutex_t *mutex, sigset_t *oldmask) |
| 92 | { |
| 93 | sigset_t newmask; |
| 94 | int ret; |
| 95 | |
| 96 | /* Disable signals */ |
| 97 | ret = sigfillset(&newmask); |
| 98 | assert(!ret); |
| 99 | ret = pthread_sigmask(SIG_BLOCK, &newmask, oldmask); |
| 100 | assert(!ret); |
| 101 | ret = pthread_mutex_lock(&__urcu_x86_compat_mutex); |
| 102 | assert(!ret); |
| 103 | } |
| 104 | |
| 105 | static void mutex_lock_signal_restore(pthread_mutex_t *mutex, sigset_t *oldmask) |
| 106 | { |
| 107 | int ret; |
| 108 | |
| 109 | ret = pthread_mutex_unlock(&__urcu_x86_compat_mutex); |
| 110 | assert(!ret); |
| 111 | ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL); |
| 112 | assert(!ret); |
| 113 | } |
| 114 | |
| 115 | unsigned long _compat_uatomic_set(void *addr, unsigned long _new, int len) |
| 116 | { |
| 117 | sigset_t mask; |
| 118 | unsigned long result; |
| 119 | |
| 120 | mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask); |
| 121 | switch (len) { |
| 122 | case 1: |
| 123 | *(unsigned char *)addr = (unsigned char)_new; |
| 124 | result = *(unsigned char *)addr; |
| 125 | break; |
| 126 | case 2: |
| 127 | *(unsigned short *)addr = (unsigned short)_new; |
| 128 | result = *(unsigned short *)addr; |
| 129 | break; |
| 130 | case 4: |
| 131 | *(unsigned int *)addr = (unsigned int)_new; |
| 132 | result = *(unsigned int *)addr; |
| 133 | break; |
| 134 | default: |
| 135 | /* |
| 136 | * generate an illegal instruction. Cannot catch this with |
| 137 | * linker tricks when optimizations are disabled. |
| 138 | */ |
| 139 | result = 0; |
| 140 | __asm__ __volatile__("ud2"); |
| 141 | } |
| 142 | mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask); |
| 143 | return result; |
| 144 | } |
| 145 | |
| 146 | unsigned long _compat_uatomic_xchg(void *addr, unsigned long _new, int len) |
| 147 | { |
| 148 | sigset_t mask; |
| 149 | unsigned long retval; |
| 150 | |
| 151 | mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask); |
| 152 | switch (len) { |
| 153 | case 1: |
| 154 | retval = *(unsigned char *)addr; |
| 155 | *(unsigned char *)addr = (unsigned char)_new; |
| 156 | break; |
| 157 | case 2: |
| 158 | retval = *(unsigned short *)addr; |
| 159 | *(unsigned short *)addr = (unsigned short)_new; |
| 160 | break; |
| 161 | case 4: |
| 162 | retval = *(unsigned int *)addr; |
| 163 | *(unsigned int *)addr = (unsigned int)_new; |
| 164 | break; |
| 165 | default: |
| 166 | /* |
| 167 | * generate an illegal instruction. Cannot catch this with |
| 168 | * linker tricks when optimizations are disabled. |
| 169 | */ |
| 170 | retval = 0; /* silence gcc warnings */ |
| 171 | __asm__ __volatile__("ud2"); |
| 172 | } |
| 173 | mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask); |
| 174 | return retval; |
| 175 | } |
| 176 | |
| 177 | unsigned long _compat_uatomic_cmpxchg(void *addr, unsigned long old, |
| 178 | unsigned long _new, int len) |
| 179 | { |
| 180 | unsigned long retval; |
| 181 | sigset_t mask; |
| 182 | |
| 183 | mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask); |
| 184 | switch (len) { |
| 185 | case 1: |
| 186 | { |
| 187 | unsigned char result = *(unsigned char *)addr; |
| 188 | if (result == (unsigned char)old) |
| 189 | *(unsigned char *)addr = (unsigned char)_new; |
| 190 | retval = result; |
| 191 | break; |
| 192 | } |
| 193 | case 2: |
| 194 | { |
| 195 | unsigned short result = *(unsigned short *)addr; |
| 196 | if (result == (unsigned short)old) |
| 197 | *(unsigned short *)addr = (unsigned short)_new; |
| 198 | retval = result; |
| 199 | break; |
| 200 | } |
| 201 | case 4: |
| 202 | { |
| 203 | unsigned int result = *(unsigned int *)addr; |
| 204 | if (result == (unsigned int)old) |
| 205 | *(unsigned int *)addr = (unsigned int)_new; |
| 206 | retval = result; |
| 207 | break; |
| 208 | } |
| 209 | default: |
| 210 | /* |
| 211 | * generate an illegal instruction. Cannot catch this with |
| 212 | * linker tricks when optimizations are disabled. |
| 213 | */ |
| 214 | retval = 0; /* silence gcc warnings */ |
| 215 | __asm__ __volatile__("ud2"); |
| 216 | } |
| 217 | mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask); |
| 218 | return retval; |
| 219 | } |
| 220 | |
| 221 | void _compat_uatomic_or(void *addr, unsigned long v, int len) |
| 222 | { |
| 223 | sigset_t mask; |
| 224 | |
| 225 | mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask); |
| 226 | switch (len) { |
| 227 | case 1: |
| 228 | *(unsigned char *)addr |= (unsigned char)v; |
| 229 | break; |
| 230 | case 2: |
| 231 | *(unsigned short *)addr |= (unsigned short)v; |
| 232 | break; |
| 233 | case 4: |
| 234 | *(unsigned int *)addr |= (unsigned int)v; |
| 235 | break; |
| 236 | default: |
| 237 | /* |
| 238 | * generate an illegal instruction. Cannot catch this with |
| 239 | * linker tricks when optimizations are disabled. |
| 240 | */ |
| 241 | __asm__ __volatile__("ud2"); |
| 242 | } |
| 243 | mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask); |
| 244 | } |
| 245 | |
| 246 | void _compat_uatomic_and(void *addr, unsigned long v, int len) |
| 247 | { |
| 248 | sigset_t mask; |
| 249 | |
| 250 | mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask); |
| 251 | switch (len) { |
| 252 | case 1: |
| 253 | *(unsigned char *)addr &= (unsigned char)v; |
| 254 | break; |
| 255 | case 2: |
| 256 | *(unsigned short *)addr &= (unsigned short)v; |
| 257 | break; |
| 258 | case 4: |
| 259 | *(unsigned int *)addr &= (unsigned int)v; |
| 260 | break; |
| 261 | default: |
| 262 | /* |
| 263 | * generate an illegal instruction. Cannot catch this with |
| 264 | * linker tricks when optimizations are disabled. |
| 265 | */ |
| 266 | __asm__ __volatile__("ud2"); |
| 267 | } |
| 268 | mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask); |
| 269 | } |
| 270 | |
| 271 | unsigned long _compat_uatomic_add_return(void *addr, unsigned long v, int len) |
| 272 | { |
| 273 | sigset_t mask; |
| 274 | unsigned long result; |
| 275 | |
| 276 | mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask); |
| 277 | switch (len) { |
| 278 | case 1: |
| 279 | *(unsigned char *)addr += (unsigned char)v; |
| 280 | result = *(unsigned char *)addr; |
| 281 | break; |
| 282 | case 2: |
| 283 | *(unsigned short *)addr += (unsigned short)v; |
| 284 | result = *(unsigned short *)addr; |
| 285 | break; |
| 286 | case 4: |
| 287 | *(unsigned int *)addr += (unsigned int)v; |
| 288 | result = *(unsigned int *)addr; |
| 289 | break; |
| 290 | default: |
| 291 | /* |
| 292 | * generate an illegal instruction. Cannot catch this with |
| 293 | * linker tricks when optimizations are disabled. |
| 294 | */ |
| 295 | result = 0; /* silence gcc warnings */ |
| 296 | __asm__ __volatile__("ud2"); |
| 297 | } |
| 298 | mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask); |
| 299 | return result; |
| 300 | } |
| 301 | |
| 302 | int __rcu_cas_init(void) |
| 303 | { |
| 304 | if (__rcu_cas_avail < 0) |
| 305 | __rcu_cas_avail = compare_and_swap_is_available(); |
| 306 | return __rcu_cas_avail; |
| 307 | } |
| 308 | #endif |