path: root/sys/arm/arm/stdatomic.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2013 Ed Schouten <ed@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/stdatomic.h>
#include <sys/types.h>

#include <machine/atomic.h>
#include <machine/cpufunc.h>
#include <machine/sysarch.h>

/*
 * Executing statements with interrupts disabled.
 */

#if defined(_KERNEL) && !defined(SMP)
#define	WITHOUT_INTERRUPTS(s) do {					\
	register_t regs;						\
									\
	regs = intr_disable();						\
	do s while (0);							\
	intr_restore(regs);						\
} while (0)
#endif /* _KERNEL && !SMP */

/*
 * Memory barriers.
 *
 * It turns out __sync_synchronize() does not emit any code when used
 * with GCC 4.2. Implement our own version that does work reliably.
 *
 * Although __sync_lock_test_and_set() should only perform an acquire
 * barrier, make it do a full barrier like the other functions. This
 * should make <stdatomic.h>'s atomic_exchange_explicit() work reliably.
 */

#if defined(_KERNEL) && !defined(SMP)
static inline void
do_sync(void)
{

	__asm volatile ("" : : : "memory");
}
#else
static inline void
do_sync(void)
{

	dmb();
}
#endif


#if defined(__SYNC_ATOMICS) || defined(EMIT_SYNC_ATOMICS)

#ifdef __clang__
#pragma redefine_extname __sync_lock_test_and_set_1_c __sync_lock_test_and_set_1
#pragma redefine_extname __sync_lock_test_and_set_2_c __sync_lock_test_and_set_2
#pragma	redefine_extname __sync_lock_test_and_set_4_c __sync_lock_test_and_set_4
#pragma	redefine_extname __sync_val_compare_and_swap_1_c __sync_val_compare_and_swap_1
#pragma	redefine_extname __sync_val_compare_and_swap_2_c __sync_val_compare_and_swap_2
#pragma	redefine_extname __sync_val_compare_and_swap_4_c __sync_val_compare_and_swap_4
#pragma	redefine_extname __sync_fetch_and_add_1_c __sync_fetch_and_add_1
#pragma	redefine_extname __sync_fetch_and_add_2_c __sync_fetch_and_add_2
#pragma	redefine_extname __sync_fetch_and_add_4_c __sync_fetch_and_add_4
#pragma	redefine_extname __sync_fetch_and_and_1_c __sync_fetch_and_and_1
#pragma	redefine_extname __sync_fetch_and_and_2_c __sync_fetch_and_and_2
#pragma	redefine_extname __sync_fetch_and_and_4_c __sync_fetch_and_and_4
#pragma	redefine_extname __sync_fetch_and_or_1_c __sync_fetch_and_or_1
#pragma	redefine_extname __sync_fetch_and_or_2_c __sync_fetch_and_or_2
#pragma	redefine_extname __sync_fetch_and_or_4_c __sync_fetch_and_or_4
#pragma	redefine_extname __sync_fetch_and_xor_1_c __sync_fetch_and_xor_1
#pragma	redefine_extname __sync_fetch_and_xor_2_c __sync_fetch_and_xor_2
#pragma	redefine_extname __sync_fetch_and_xor_4_c __sync_fetch_and_xor_4
#pragma	redefine_extname __sync_fetch_and_sub_1_c __sync_fetch_and_sub_1
#pragma	redefine_extname __sync_fetch_and_sub_2_c __sync_fetch_and_sub_2
#pragma	redefine_extname __sync_fetch_and_sub_4_c __sync_fetch_and_sub_4
#endif

/*
 * Old __sync_* API.
 */


/* Implementations for old GCC versions, lacking support for atomics. */

typedef union {
	uint8_t		v8[4];
	uint32_t	v32;
} reg_t;

/*
 * Given a memory address pointing to an 8-bit or 16-bit integer, return
 * the address of the 32-bit word containing it.
 */

static inline uint32_t *
round_to_word(void *ptr)
{

	return ((uint32_t *)((intptr_t)ptr & ~3));
}

/*
 * Utility functions for loading and storing 8-bit and 16-bit integers
 * in 32-bit words at an offset corresponding with the location of the
 * atomic variable.
 */

static inline void
put_1(reg_t *r, const uint8_t *offset_ptr, uint8_t val)
{
	size_t offset;

	offset = (intptr_t)offset_ptr & 3;
	r->v8[offset] = val;
}

static inline uint8_t
get_1(const reg_t *r, const uint8_t *offset_ptr)
{
	size_t offset;

	offset = (intptr_t)offset_ptr & 3;
	return (r->v8[offset]);
}

static inline void
put_2(reg_t *r, const uint16_t *offset_ptr, uint16_t val)
{
	size_t offset;
	union {
		uint16_t in;
		uint8_t out[2];
	} bytes;

	offset = (intptr_t)offset_ptr & 3;
	bytes.in = val;
	r->v8[offset] = bytes.out[0];
	r->v8[offset + 1] = bytes.out[1];
}

static inline uint16_t
get_2(const reg_t *r, const uint16_t *offset_ptr)
{
	size_t offset;
	union {
		uint8_t in[2];
		uint16_t out;
	} bytes;

	offset = (intptr_t)offset_ptr & 3;
	bytes.in[0] = r->v8[offset];
	bytes.in[1] = r->v8[offset + 1];
	return (bytes.out);
}

/*
 * 8-bit and 16-bit routines.
 *
 * These operations are not natively supported by the CPU, so we use
 * some shifting and bitmasking on top of the 32-bit instructions.
 */

#define	EMIT_LOCK_TEST_AND_SET_N(N, uintN_t)				\
uintN_t									\
__sync_lock_test_and_set_##N##_c(uintN_t *mem, uintN_t val)			\
{									\
	uint32_t *mem32;						\
	reg_t val32, negmask, old;					\
	uint32_t temp1, temp2;						\
									\
	mem32 = round_to_word(mem);					\
	val32.v32 = 0x00000000;						\
	put_##N(&val32, mem, val);					\
	negmask.v32 = 0xffffffff;					\
	put_##N(&negmask, mem, 0);					\
									\
	do_sync();							\
	__asm volatile (						\
		"1:"							\
		"\tldrex %0, %6\n"	/* Load old value. */		\
		"\tand   %2, %5, %0\n"	/* Remove the old value. */	\
		"\torr   %2, %2, %4\n"	/* Put in the new value. */	\
		"\tstrex %3, %2, %1\n"	/* Attempt to store. */		\
		"\tcmp   %3, #0\n"	/* Did it succeed? */		\
		"\tbne   1b\n"		/* Spin if failed. */		\
		: "=&r" (old.v32), "=m" (*mem32), "=&r" (temp1),	\
		  "=&r" (temp2)						\
		: "r" (val32.v32), "r" (negmask.v32), "m" (*mem32));	\
	return (get_##N(&old, mem));					\
}

EMIT_LOCK_TEST_AND_SET_N(1, uint8_t)
EMIT_LOCK_TEST_AND_SET_N(2, uint16_t)

#define	EMIT_VAL_COMPARE_AND_SWAP_N(N, uintN_t)				\
uintN_t									\
__sync_val_compare_and_swap_##N##_c(uintN_t *mem, uintN_t expected,		\
    uintN_t desired)							\
{									\
	uint32_t *mem32;						\
	reg_t expected32, desired32, posmask, old;			\
	uint32_t negmask, temp1, temp2;					\
									\
	mem32 = round_to_word(mem);					\
	expected32.v32 = 0x00000000;					\
	put_##N(&expected32, mem, expected);				\
	desired32.v32 = 0x00000000;					\
	put_##N(&desired32, mem, desired);				\
	posmask.v32 = 0x00000000;					\
	put_##N(&posmask, mem, ~0);					\
	negmask = ~posmask.v32;						\
									\
	do_sync();							\
	__asm volatile (						\
		"1:"							\
		"\tldrex %0, %8\n"	/* Load old value. */		\
		"\tand   %2, %6, %0\n"	/* Isolate the old value. */	\
		"\tcmp   %2, %4\n"	/* Compare to expected value. */\
		"\tbne   2f\n"		/* Values are unequal. */	\
		"\tand   %2, %7, %0\n"	/* Remove the old value. */	\
		"\torr   %2, %5\n"	/* Put in the new value. */	\
		"\tstrex %3, %2, %1\n"	/* Attempt to store. */		\
		"\tcmp   %3, #0\n"	/* Did it succeed? */		\
		"\tbne   1b\n"		/* Spin if failed. */		\
		"2:"							\
		: "=&r" (old), "=m" (*mem32), "=&r" (temp1),		\
		  "=&r" (temp2)						\
		: "r" (expected32.v32), "r" (desired32.v32),		\
		  "r" (posmask.v32), "r" (negmask), "m" (*mem32));	\
	return (get_##N(&old, mem));					\
}

EMIT_VAL_COMPARE_AND_SWAP_N(1, uint8_t)
EMIT_VAL_COMPARE_AND_SWAP_N(2, uint16_t)

#define	EMIT_ARITHMETIC_FETCH_AND_OP_N(N, uintN_t, name, op)		\
uintN_t									\
__sync_##name##_##N##_c(uintN_t *mem, uintN_t val)				\
{									\
	uint32_t *mem32;						\
	reg_t val32, posmask, old;					\
	uint32_t negmask, temp1, temp2;					\
									\
	mem32 = round_to_word(mem);					\
	val32.v32 = 0x00000000;						\
	put_##N(&val32, mem, val);					\
	posmask.v32 = 0x00000000;					\
	put_##N(&posmask, mem, ~0);					\
	negmask = ~posmask.v32;						\
									\
	do_sync();							\
	__asm volatile (						\
		"1:"							\
		"\tldrex %0, %7\n"	/* Load old value. */		\
		"\t"op"  %2, %0, %4\n"	/* Calculate new value. */	\
		"\tand   %2, %5\n"	/* Isolate the new value. */	\
		"\tand   %3, %6, %0\n"	/* Remove the old value. */	\
		"\torr   %2, %2, %3\n"	/* Put in the new value. */	\
		"\tstrex %3, %2, %1\n"	/* Attempt to store. */		\
		"\tcmp   %3, #0\n"	/* Did it succeed? */		\
		"\tbne   1b\n"		/* Spin if failed. */		\
		: "=&r" (old.v32), "=m" (*mem32), "=&r" (temp1),	\
		  "=&r" (temp2)						\
		: "r" (val32.v32), "r" (posmask.v32), "r" (negmask),	\
		  "m" (*mem32));					\
	return (get_##N(&old, mem));					\
}

EMIT_ARITHMETIC_FETCH_AND_OP_N(1, uint8_t, fetch_and_add, "add")
EMIT_ARITHMETIC_FETCH_AND_OP_N(1, uint8_t, fetch_and_sub, "sub")
EMIT_ARITHMETIC_FETCH_AND_OP_N(2, uint16_t, fetch_and_add, "add")
EMIT_ARITHMETIC_FETCH_AND_OP_N(2, uint16_t, fetch_and_sub, "sub")

#define	EMIT_BITWISE_FETCH_AND_OP_N(N, uintN_t, name, op, idempotence)	\
uintN_t									\
__sync_##name##_##N##_c(uintN_t *mem, uintN_t val)				\
{									\
	uint32_t *mem32;						\
	reg_t val32, old;						\
	uint32_t temp1, temp2;						\
									\
	mem32 = round_to_word(mem);					\
	val32.v32 = idempotence ? 0xffffffff : 0x00000000;		\
	put_##N(&val32, mem, val);					\
									\
	do_sync();							\
	__asm volatile (						\
		"1:"							\
		"\tldrex %0, %5\n"	/* Load old value. */		\
		"\t"op"  %2, %4, %0\n"	/* Calculate new value. */	\
		"\tstrex %3, %2, %1\n"	/* Attempt to store. */		\
		"\tcmp   %3, #0\n"	/* Did it succeed? */		\
		"\tbne   1b\n"		/* Spin if failed. */		\
		: "=&r" (old.v32), "=m" (*mem32), "=&r" (temp1),	\
		  "=&r" (temp2)						\
		: "r" (val32.v32), "m" (*mem32));			\
	return (get_##N(&old, mem));					\
}

EMIT_BITWISE_FETCH_AND_OP_N(1, uint8_t, fetch_and_and, "and", 1)
EMIT_BITWISE_FETCH_AND_OP_N(1, uint8_t, fetch_and_or, "orr", 0)
EMIT_BITWISE_FETCH_AND_OP_N(1, uint8_t, fetch_and_xor, "eor", 0)
EMIT_BITWISE_FETCH_AND_OP_N(2, uint16_t, fetch_and_and, "and", 1)
EMIT_BITWISE_FETCH_AND_OP_N(2, uint16_t, fetch_and_or, "orr", 0)
EMIT_BITWISE_FETCH_AND_OP_N(2, uint16_t, fetch_and_xor, "eor", 0)

/*
 * 32-bit routines.
 */

uint32_t
__sync_lock_test_and_set_4_c(uint32_t *mem, uint32_t val)
{
	uint32_t old, temp;

	do_sync();
	__asm volatile (
		"1:"
		"\tldrex %0, %4\n"	/* Load old value. */
		"\tstrex %2, %3, %1\n"	/* Attempt to store. */
		"\tcmp   %2, #0\n"	/* Did it succeed? */
		"\tbne   1b\n"		/* Spin if failed. */
		: "=&r" (old), "=m" (*mem), "=&r" (temp)
		: "r" (val), "m" (*mem));
	return (old);
}

uint32_t
__sync_val_compare_and_swap_4_c(uint32_t *mem, uint32_t expected,
    uint32_t desired)
{
	uint32_t old, temp;

	do_sync();
	__asm volatile (
		"1:"
		"\tldrex %0, %5\n"	/* Load old value. */
		"\tcmp   %0, %3\n"	/* Compare to expected value. */
		"\tbne   2f\n"		/* Values are unequal. */
		"\tstrex %2, %4, %1\n"	/* Attempt to store. */
		"\tcmp   %2, #0\n"	/* Did it succeed? */
		"\tbne   1b\n"		/* Spin if failed. */
		"2:"
		: "=&r" (old), "=m" (*mem), "=&r" (temp)
		: "r" (expected), "r" (desired), "m" (*mem));
	return (old);
}

#define	EMIT_FETCH_AND_OP_4(name, op)					\
uint32_t								\
__sync_##name##_4##_c(uint32_t *mem, uint32_t val)				\
{									\
	uint32_t old, temp1, temp2;					\
									\
	do_sync();							\
	__asm volatile (						\
		"1:"							\
		"\tldrex %0, %5\n"	/* Load old value. */		\
		"\t"op"  %2, %0, %4\n"	/* Calculate new value. */	\
		"\tstrex %3, %2, %1\n"	/* Attempt to store. */		\
		"\tcmp   %3, #0\n"	/* Did it succeed? */		\
		"\tbne   1b\n"		/* Spin if failed. */		\
		: "=&r" (old), "=m" (*mem), "=&r" (temp1),		\
		  "=&r" (temp2)						\
		: "r" (val), "m" (*mem));				\
	return (old);							\
}

EMIT_FETCH_AND_OP_4(fetch_and_add, "add")
EMIT_FETCH_AND_OP_4(fetch_and_and, "and")
EMIT_FETCH_AND_OP_4(fetch_and_or, "orr")
EMIT_FETCH_AND_OP_4(fetch_and_sub, "sub")
EMIT_FETCH_AND_OP_4(fetch_and_xor, "eor")

#ifndef __clang__
__strong_reference(__sync_lock_test_and_set_1_c, __sync_lock_test_and_set_1);
__strong_reference(__sync_lock_test_and_set_2_c, __sync_lock_test_and_set_2);
__strong_reference(__sync_lock_test_and_set_4_c, __sync_lock_test_and_set_4);
__strong_reference(__sync_val_compare_and_swap_1_c, __sync_val_compare_and_swap_1);
__strong_reference(__sync_val_compare_and_swap_2_c, __sync_val_compare_and_swap_2);
__strong_reference(__sync_val_compare_and_swap_4_c, __sync_val_compare_and_swap_4);
__strong_reference(__sync_fetch_and_add_1_c, __sync_fetch_and_add_1);
__strong_reference(__sync_fetch_and_add_2_c, __sync_fetch_and_add_2);
__strong_reference(__sync_fetch_and_add_4_c, __sync_fetch_and_add_4);
__strong_reference(__sync_fetch_and_and_1_c, __sync_fetch_and_and_1);
__strong_reference(__sync_fetch_and_and_2_c, __sync_fetch_and_and_2);
__strong_reference(__sync_fetch_and_and_4_c, __sync_fetch_and_and_4);
__strong_reference(__sync_fetch_and_sub_1_c, __sync_fetch_and_sub_1);
__strong_reference(__sync_fetch_and_sub_2_c, __sync_fetch_and_sub_2);
__strong_reference(__sync_fetch_and_sub_4_c, __sync_fetch_and_sub_4);
__strong_reference(__sync_fetch_and_or_1_c, __sync_fetch_and_or_1);
__strong_reference(__sync_fetch_and_or_2_c, __sync_fetch_and_or_2);
__strong_reference(__sync_fetch_and_or_4_c, __sync_fetch_and_or_4);
__strong_reference(__sync_fetch_and_xor_1_c, __sync_fetch_and_xor_1);
__strong_reference(__sync_fetch_and_xor_2_c, __sync_fetch_and_xor_2);
__strong_reference(__sync_fetch_and_xor_4_c, __sync_fetch_and_xor_4);
#endif

#endif /* __SYNC_ATOMICS */