[userspace-rcu.git] / src / compat_arch.c

/*
 * compat_arch.c
 *
 * Userspace RCU library - architecture 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 <urcu/arch.h>

#ifdef URCU_ARCH_X86_NO_CAS

#include <stdio.h>
#include <pthread.h>
#include <signal.h>
#include <urcu/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() explicitly 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);
	urcu_posix_assert(!ret);
	ret = pthread_sigmask(SIG_BLOCK, &newmask, oldmask);
	urcu_posix_assert(!ret);
	ret = pthread_mutex_lock(&__urcu_x86_compat_mutex);
	urcu_posix_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);
	urcu_posix_assert(!ret);
	ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL);
	urcu_posix_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;
}
#endif
Commit	Line	Data
d45599f4	1	/*
0b1e236d	2	* compat_arch.c
d45599f4	3	*
0b1e236d	4	* Userspace RCU library - architecture compatibility checks
d45599f4	5	*
6982d6d7	6	* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
d45599f4 MD	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
0b1e236d MJ	23	#include <urcu/arch.h>
0b1e236d MJ	24
101389e4	25	#ifdef URCU_ARCH_X86_NO_CAS
0b1e236d	26
d45599f4 MD	27	#include <stdio.h>
	28	#include <pthread.h>
	29	#include <signal.h>
01477510	30	#include <urcu/assert.h>
a2e7bf9c	31	#include <urcu/uatomic.h>
d45599f4	32
976720e4 MD	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
d45599f4 MD	41	/*
d45599f4 MD	42	* It does not really matter if the constructor is called before using
02be5561	43	* the library, as long as the caller checks if __rcu_cas_avail < 0 and calls
f99c6e92	44	* compat_arch_init() explicitly if needed.
d45599f4	45	*/
02be5561	46	int __attribute__((constructor)) __rcu_cas_init(void);
d45599f4	47
d45599f4 MD	48	/*
	49	* -1: unknown
	50	* 1: available
	51	* 0: unavailable
	52	*/
976720e4	53	__attribute__((weak))
02be5561	54	int __rcu_cas_avail = -1;
d45599f4	55
976720e4 MD	56	__attribute__((weak))
976720e4 MD	57	pthread_mutex_t __urcu_x86_compat_mutex = PTHREAD_MUTEX_INITIALIZER;
bf9de1b7	58
d45599f4	59	/*
bf9de1b7 MD	60	* get_eflags/set_eflags/compare_and_swap_is_available imported from glibc
bf9de1b7 MD	61	* 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h.
d45599f4 MD	62	*/
d45599f4 MD	63
bf9de1b7	64	static int get_eflags (void)
d45599f4 MD	65	{
	66	int res;
	67	__asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
	68	return res;
	69	}
	70
bf9de1b7	71	static void set_eflags (int newflags)
d45599f4 MD	72	{
	73	__asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
	74	}
	75
bf9de1b7	76	static int compare_and_swap_is_available (void)
d45599f4 MD	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
bf9de1b7	91	static void mutex_lock_signal_save(pthread_mutex_t mutex, sigset_t oldmask)
d45599f4	92	{
bf9de1b7	93	sigset_t newmask;
d45599f4 MD	94	int ret;
	95
	96	/* Disable signals */
6ed4b2e6	97	ret = sigfillset(&newmask);
01477510	98	urcu_posix_assert(!ret);
6ed4b2e6	99	ret = pthread_sigmask(SIG_BLOCK, &newmask, oldmask);
01477510	100	urcu_posix_assert(!ret);
976720e4	101	ret = pthread_mutex_lock(&__urcu_x86_compat_mutex);
01477510	102	urcu_posix_assert(!ret);
bf9de1b7 MD	103	}
	104
	105	static void mutex_lock_signal_restore(pthread_mutex_t mutex, sigset_t oldmask)
	106	{
	107	int ret;
	108
976720e4	109	ret = pthread_mutex_unlock(&__urcu_x86_compat_mutex);
01477510	110	urcu_posix_assert(!ret);
bf9de1b7	111	ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL);
01477510	112	urcu_posix_assert(!ret);
bf9de1b7 MD	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
976720e4	120	mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 MD	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	*/
c94627b5	139	result = 0;
bf9de1b7 MD	140	__asm__ __volatile__("ud2");
bf9de1b7 MD	141	}
976720e4	142	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
c94627b5	143	return result;
bf9de1b7	144	}
d45599f4	145
bf9de1b7 MD	146	unsigned long _compat_uatomic_xchg(void *addr, unsigned long _new, int len)
	147	{
	148	sigset_t mask;
	149	unsigned long retval;
	150
976720e4	151	mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 MD	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	*/
8c43fe72	170	retval = 0; /* silence gcc warnings */
bf9de1b7 MD	171	__asm__ __volatile__("ud2");
bf9de1b7 MD	172	}
976720e4	173	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 MD	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
976720e4	183	mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
d45599f4 MD	184	switch (len) {
	185	case 1:
	186	{
	187	unsigned char result = (unsigned char )addr;
bf9de1b7	188	if (result == (unsigned char)old)
d45599f4	189	(unsigned char )addr = (unsigned char)_new;
bf9de1b7 MD	190	retval = result;
bf9de1b7 MD	191	break;
d45599f4 MD	192	}
	193	case 2:
	194	{
	195	unsigned short result = (unsigned short )addr;
bf9de1b7	196	if (result == (unsigned short)old)
d45599f4	197	(unsigned short )addr = (unsigned short)_new;
bf9de1b7 MD	198	retval = result;
bf9de1b7 MD	199	break;
d45599f4 MD	200	}
	201	case 4:
	202	{
	203	unsigned int result = (unsigned int )addr;
bf9de1b7	204	if (result == (unsigned int)old)
d45599f4	205	(unsigned int )addr = (unsigned int)_new;
bf9de1b7 MD	206	retval = result;
bf9de1b7 MD	207	break;
d45599f4	208	}
bf9de1b7 MD	209	default:
	210	/*
	211	* generate an illegal instruction. Cannot catch this with
	212	* linker tricks when optimizations are disabled.
	213	*/
8c43fe72	214	retval = 0; /* silence gcc warnings */
bf9de1b7	215	__asm__ __volatile__("ud2");
d45599f4	216	}
976720e4	217	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 MD	218	return retval;
bf9de1b7 MD	219	}
d45599f4	220
985b35b1 PB	221	void _compat_uatomic_or(void *addr, unsigned long v, int len)
	222	{
	223	sigset_t mask;
	224
976720e4	225	mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
985b35b1 PB	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
bf33aaea PB	239	* linker tricks when optimizations are disabled.
	240	*/
	241	__asm__ __volatile__("ud2");
	242	}
976720e4	243	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf33aaea PB	244	}
	245
	246	void _compat_uatomic_and(void *addr, unsigned long v, int len)
	247	{
	248	sigset_t mask;
	249
976720e4	250	mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
bf33aaea PB	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
985b35b1 PB	264	* linker tricks when optimizations are disabled.
	265	*/
	266	__asm__ __volatile__("ud2");
	267	}
976720e4	268	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
985b35b1 PB	269	}
985b35b1 PB	270
bf9de1b7 MD	271	unsigned long _compat_uatomic_add_return(void *addr, unsigned long v, int len)
	272	{
	273	sigset_t mask;
	274	unsigned long result;
	275
976720e4	276	mutex_lock_signal_save(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 MD	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	*/
8c43fe72	295	result = 0; /* silence gcc warnings */
bf9de1b7 MD	296	__asm__ __volatile__("ud2");
bf9de1b7 MD	297	}
976720e4	298	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf9de1b7	299	return result;
d45599f4 MD	300	}
d45599f4 MD	301
02be5561	302	int __rcu_cas_init(void)
d45599f4	303	{
02be5561 MD	304	if (__rcu_cas_avail < 0)
	305	__rcu_cas_avail = compare_and_swap_is_available();
	306	return __rcu_cas_avail;
d45599f4	307	}
0b1e236d	308	#endif