[userspace-rcu.git] / compat_arch_x86.c

/*
 * 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;
}
Commit	Line	Data
d45599f4 MD	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>
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
	23	#include <stdio.h>
	24	#include <pthread.h>
	25	#include <signal.h>
	26	#include <assert.h>
a2e7bf9c	27	#include <urcu/uatomic.h>
d45599f4	28
976720e4 MD	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
d45599f4 MD	37	/*
d45599f4 MD	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
d45599f4 MD	40	* compat_arch_init() explicitely if needed.
d45599f4 MD	41	*/
02be5561	42	int __attribute__((constructor)) __rcu_cas_init(void);
d45599f4	43
d45599f4 MD	44	/*
	45	* -1: unknown
	46	* 1: available
	47	* 0: unavailable
	48	*/
976720e4	49	__attribute__((weak))
02be5561	50	int __rcu_cas_avail = -1;
d45599f4	51
976720e4 MD	52	__attribute__((weak))
976720e4 MD	53	pthread_mutex_t __urcu_x86_compat_mutex = PTHREAD_MUTEX_INITIALIZER;
bf9de1b7	54
d45599f4	55	/*
bf9de1b7 MD	56	* get_eflags/set_eflags/compare_and_swap_is_available imported from glibc
bf9de1b7 MD	57	* 2.3.5. linuxthreads/sysdeps/i386/pt-machine.h.
d45599f4 MD	58	*/
d45599f4 MD	59
bf9de1b7	60	static int get_eflags (void)
d45599f4 MD	61	{
	62	int res;
	63	__asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
	64	return res;
	65	}
	66
bf9de1b7	67	static void set_eflags (int newflags)
d45599f4 MD	68	{
	69	__asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
	70	}
	71
bf9de1b7	72	static int compare_and_swap_is_available (void)
d45599f4 MD	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	87	static void mutex_lock_signal_save(pthread_mutex_t mutex, sigset_t oldmask)
d45599f4	88	{
bf9de1b7	89	sigset_t newmask;
d45599f4 MD	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);
bf9de1b7 MD	99	}
	100
	101	static 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);
bf9de1b7 MD	106	assert(!ret);
	107	ret = pthread_sigmask(SIG_SETMASK, oldmask, NULL);
	108	assert(!ret);
	109	}
	110
	111	unsigned 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);
bf9de1b7 MD	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;
bf9de1b7 MD	136	__asm__ __volatile__("ud2");
bf9de1b7 MD	137	}
976720e4	138	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
c94627b5	139	return result;
bf9de1b7	140	}
d45599f4	141
bf9de1b7 MD	142	unsigned 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);
bf9de1b7 MD	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 */
bf9de1b7 MD	167	__asm__ __volatile__("ud2");
bf9de1b7 MD	168	}
976720e4	169	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf9de1b7 MD	170	return retval;
	171	}
	172
	173	unsigned 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);
d45599f4 MD	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;
bf9de1b7 MD	186	retval = result;
bf9de1b7 MD	187	break;
d45599f4 MD	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;
bf9de1b7 MD	194	retval = result;
bf9de1b7 MD	195	break;
d45599f4 MD	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;
bf9de1b7 MD	202	retval = result;
bf9de1b7 MD	203	break;
d45599f4	204	}
bf9de1b7 MD	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);
bf9de1b7 MD	214	return retval;
bf9de1b7 MD	215	}
d45599f4	216
985b35b1 PB	217	void _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);
985b35b1 PB	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
bf33aaea PB	235	* linker tricks when optimizations are disabled.
	236	*/
	237	__asm__ __volatile__("ud2");
	238	}
976720e4	239	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf33aaea PB	240	}
	241
	242	void _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);
bf33aaea PB	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
985b35b1 PB	260	* linker tricks when optimizations are disabled.
	261	*/
	262	__asm__ __volatile__("ud2");
	263	}
976720e4	264	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
985b35b1 PB	265	}
985b35b1 PB	266
bf9de1b7 MD	267	unsigned 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);
bf9de1b7 MD	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 */
bf9de1b7 MD	292	__asm__ __volatile__("ud2");
bf9de1b7 MD	293	}
976720e4	294	mutex_lock_signal_restore(&__urcu_x86_compat_mutex, &mask);
bf9de1b7	295	return result;
d45599f4 MD	296	}
d45599f4 MD	297
02be5561	298	int __rcu_cas_init(void)
d45599f4	299	{
02be5561 MD	300	if (__rcu_cas_avail < 0)
	301	__rcu_cas_avail = compare_and_swap_is_available();
	302	return __rcu_cas_avail;
d45599f4	303	}