--- /dev/null
+/*
+ * compat_arch_x86.c
+ *
+ * Userspace RCU library - x86 compatibility checks
+ *
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdio.h>
+#include <pthread.h>
+#include <signal.h>
+#include <assert.h>
+#include <urcu/uatomic.h>
+
+/*
+ * Using attribute "weak" for __rcu_cas_avail and
+ * __urcu_x86_compat_mutex. Those are globally visible by the entire
+ * program, even though many shared objects may have their own version.
+ * The first version that gets loaded will be used by the entire
+ * program (executable and all shared objects).
+ */
+
+/*
+ * It does not really matter if the constructor is called before using
+ * the library, as long as the caller checks if __rcu_cas_avail < 0 and calls
+ * compat_arch_init() explicitely if needed.
+ */
+int __attribute__((constructor)) __rcu_cas_init(void);
+
+/*
+ * -1: unknown
+ * 1: available
+ * 0: unavailable
+ */
+__attribute__((weak))
+int __rcu_cas_avail = -1;
+
+__attribute__((weak))
+pthread_mutex_t __urcu_x86_compat_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+/*
+ * get_eflags/set_eflags/compare_and_swap_is_available imported from glibc
+ * 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h.
+ */
+
+static int get_eflags (void)
+{
+ int res;
+ __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
+ return res;
+}
+
+static void set_eflags (int newflags)
+{
+ __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
+}
+
+static int compare_and_swap_is_available (void)
+{
+ int oldflags = get_eflags ();
+ int changed;
+ /* Flip AC bit in EFLAGS. */
+ set_eflags (oldflags ^ 0x40000);
+ /* See if bit changed. */
+ changed = (get_eflags () ^ oldflags) & 0x40000;
+ /* Restore EFLAGS. */
+ set_eflags (oldflags);
+ /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
+ Otherwise, it's a 486 or above and it has cmpxchg. */
+ return changed != 0;
+}
+
+static void mutex_lock_signal_save(pthread_mutex_t *mutex, sigset_t *oldmask)
+{
+ sigset_t newmask;
+ int ret;
+
+ /* Disable signals */
+ ret = sigfillset(&newmask);
+ assert(!ret);
+ ret = pthread_sigmask(SIG_BLOCK, &newmask, oldmask);
+ assert(!ret);
+ ret = pthread_mutex_lock(&__urcu_x86_compat_mutex);
+ assert(!ret);
+}
+
+static void mutex_lock_signal_restore(pthread_mutex_t *mutex, sigset_t *oldmask)
+{
+ int ret;
+
+ ret = pthread_mutex_unlock(&__urcu_x86_compat_mutex);
+ assert(!ret);
+ ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL);
+ assert(!ret);
+}
+
+unsigned long _compat_uatomic_set(void *addr, unsigned long _new, int len)
+{
+ sigset_t mask;
+ unsigned long result;
+
+ mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
+ switch (len) {
+ case 1:
+ *(unsigned char *)addr = (unsigned char)_new;
+ result = *(unsigned char *)addr;
+ break;
+ case 2:
+ *(unsigned short *)addr = (unsigned short)_new;
+ result = *(unsigned short *)addr;
+ break;
+ case 4:
+ *(unsigned int *)addr = (unsigned int)_new;
+ result = *(unsigned int *)addr;
+ break;
+ default:
+ /*
+ * generate an illegal instruction. Cannot catch this with
+ * linker tricks when optimizations are disabled.
+ */
+ result = 0;
+ __asm__ __volatile__("ud2");
+ }
+ mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
+ return result;
+}
+
+unsigned long _compat_uatomic_xchg(void *addr, unsigned long _new, int len)
+{
+ sigset_t mask;
+ unsigned long retval;
+
+ mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
+ switch (len) {
+ case 1:
+ retval = *(unsigned char *)addr;
+ *(unsigned char *)addr = (unsigned char)_new;
+ break;
+ case 2:
+ retval = *(unsigned short *)addr;
+ *(unsigned short *)addr = (unsigned short)_new;
+ break;
+ case 4:
+ retval = *(unsigned int *)addr;
+ *(unsigned int *)addr = (unsigned int)_new;
+ break;
+ default:
+ /*
+ * generate an illegal instruction. Cannot catch this with
+ * linker tricks when optimizations are disabled.
+ */
+ retval = 0; /* silence gcc warnings */
+ __asm__ __volatile__("ud2");
+ }
+ mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
+ return retval;
+}
+
+unsigned long _compat_uatomic_cmpxchg(void *addr, unsigned long old,
+ unsigned long _new, int len)
+{
+ unsigned long retval;
+ sigset_t mask;
+
+ mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
+ switch (len) {
+ case 1:
+ {
+ unsigned char result = *(unsigned char *)addr;
+ if (result == (unsigned char)old)
+ *(unsigned char *)addr = (unsigned char)_new;
+ retval = result;
+ break;
+ }
+ case 2:
+ {
+ unsigned short result = *(unsigned short *)addr;
+ if (result == (unsigned short)old)
+ *(unsigned short *)addr = (unsigned short)_new;
+ retval = result;
+ break;
+ }
+ case 4:
+ {
+ unsigned int result = *(unsigned int *)addr;
+ if (result == (unsigned int)old)
+ *(unsigned int *)addr = (unsigned int)_new;
+ retval = result;
+ break;
+ }
+ default:
+ /*
+ * generate an illegal instruction. Cannot catch this with
+ * linker tricks when optimizations are disabled.
+ */
+ retval = 0; /* silence gcc warnings */
+ __asm__ __volatile__("ud2");
+ }
+ mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
+ return retval;
+}
+
+void _compat_uatomic_or(void *addr, unsigned long v, int len)
+{
+ sigset_t mask;
+
+ mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
+ switch (len) {
+ case 1:
+ *(unsigned char *)addr |= (unsigned char)v;
+ break;
+ case 2:
+ *(unsigned short *)addr |= (unsigned short)v;
+ break;
+ case 4:
+ *(unsigned int *)addr |= (unsigned int)v;
+ break;
+ default:
+ /*
+ * generate an illegal instruction. Cannot catch this with
+ * linker tricks when optimizations are disabled.
+ */
+ __asm__ __volatile__("ud2");
+ }
+ mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
+}
+
+void _compat_uatomic_and(void *addr, unsigned long v, int len)
+{
+ sigset_t mask;
+
+ mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
+ switch (len) {
+ case 1:
+ *(unsigned char *)addr &= (unsigned char)v;
+ break;
+ case 2:
+ *(unsigned short *)addr &= (unsigned short)v;
+ break;
+ case 4:
+ *(unsigned int *)addr &= (unsigned int)v;
+ break;
+ default:
+ /*
+ * generate an illegal instruction. Cannot catch this with
+ * linker tricks when optimizations are disabled.
+ */
+ __asm__ __volatile__("ud2");
+ }
+ mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
+}
+
+unsigned long _compat_uatomic_add_return(void *addr, unsigned long v, int len)
+{
+ sigset_t mask;
+ unsigned long result;
+
+ mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
+ switch (len) {
+ case 1:
+ *(unsigned char *)addr += (unsigned char)v;
+ result = *(unsigned char *)addr;
+ break;
+ case 2:
+ *(unsigned short *)addr += (unsigned short)v;
+ result = *(unsigned short *)addr;
+ break;
+ case 4:
+ *(unsigned int *)addr += (unsigned int)v;
+ result = *(unsigned int *)addr;
+ break;
+ default:
+ /*
+ * generate an illegal instruction. Cannot catch this with
+ * linker tricks when optimizations are disabled.
+ */
+ result = 0; /* silence gcc warnings */
+ __asm__ __volatile__("ud2");
+ }
+ mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
+ return result;
+}
+
+int __rcu_cas_init(void)
+{
+ if (__rcu_cas_avail < 0)
+ __rcu_cas_avail = compare_and_swap_is_available();
+ return __rcu_cas_avail;
+}
projects / userspace-rcu.git / blobdiff