1/* 64bit Linux-specific atomic operations for ARM EABI.
2   Copyright (C) 2008-2015 Free Software Foundation, Inc.
3   Based on linux-atomic.c
4
5   64 bit additions david.gilbert@linaro.org
6
7This file is part of GCC.
8
9GCC is free software; you can redistribute it and/or modify it under
10the terms of the GNU General Public License as published by the Free
11Software Foundation; either version 3, or (at your option) any later
12version.
13
14GCC is distributed in the hope that it will be useful, but WITHOUT ANY
15WARRANTY; without even the implied warranty of MERCHANTABILITY or
16FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
17for more details.
18
19Under Section 7 of GPL version 3, you are granted additional
20permissions described in the GCC Runtime Library Exception, version
213.1, as published by the Free Software Foundation.
22
23You should have received a copy of the GNU General Public License and
24a copy of the GCC Runtime Library Exception along with this program;
25see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
26<http://www.gnu.org/licenses/>.  */
27
28/* 64bit helper functions for atomic operations; the compiler will
29   call these when the code is compiled for a CPU without ldrexd/strexd.
30   (If the CPU had those then the compiler inlines the operation).
31
32   These helpers require a kernel helper that's only present on newer
33   kernels; we check for that in an init section and bail out rather
34   unceremoneously.  */
35
36extern int write (int fd, const void *buf, unsigned int count);
37extern void abort (void);
38
39/* Kernel helper for compare-and-exchange.  */
40typedef int (__kernel_cmpxchg64_t) (const long long* oldval,
41					const long long* newval,
42					long long *ptr);
43#define __kernel_cmpxchg64 (*(__kernel_cmpxchg64_t *) 0xffff0f60)
44
45/* Kernel helper page version number.  */
46#define __kernel_helper_version (*(unsigned int *)0xffff0ffc)
47
48/* Check that the kernel has a new enough version at load.  */
49static void __check_for_sync8_kernelhelper (void)
50{
51  if (__kernel_helper_version < 5)
52    {
53      const char err[] = "A newer kernel is required to run this binary. "
54				"(__kernel_cmpxchg64 helper)\n";
55      /* At this point we need a way to crash with some information
56	 for the user - I'm not sure I can rely on much else being
57	 available at this point, so do the same as generic-morestack.c
58	 write () and abort ().  */
59      write (2 /* stderr.  */, err, sizeof (err));
60      abort ();
61    }
62};
63
64static void (*__sync8_kernelhelper_inithook[]) (void)
65		__attribute__ ((used, section (".init_array"))) = {
66  &__check_for_sync8_kernelhelper
67};
68
69#define HIDDEN __attribute__ ((visibility ("hidden")))
70
71#define FETCH_AND_OP_WORD64(OP, PFX_OP, INF_OP)			\
72  long long HIDDEN						\
73  __sync_fetch_and_##OP##_8 (long long *ptr, long long val)	\
74  {								\
75    int failure;						\
76    long long tmp,tmp2;						\
77								\
78    do {							\
79      tmp = *ptr;						\
80      tmp2 = PFX_OP (tmp INF_OP val);				\
81      failure = __kernel_cmpxchg64 (&tmp, &tmp2, ptr);		\
82    } while (failure != 0);					\
83								\
84    return tmp;							\
85  }
86
87FETCH_AND_OP_WORD64 (add,   , +)
88FETCH_AND_OP_WORD64 (sub,   , -)
89FETCH_AND_OP_WORD64 (or,    , |)
90FETCH_AND_OP_WORD64 (and,   , &)
91FETCH_AND_OP_WORD64 (xor,   , ^)
92FETCH_AND_OP_WORD64 (nand, ~, &)
93
94#define NAME_oldval(OP, WIDTH) __sync_fetch_and_##OP##_##WIDTH
95#define NAME_newval(OP, WIDTH) __sync_##OP##_and_fetch_##WIDTH
96
97/* Implement both __sync_<op>_and_fetch and __sync_fetch_and_<op> for
98   subword-sized quantities.  */
99
100#define OP_AND_FETCH_WORD64(OP, PFX_OP, INF_OP)			\
101  long long HIDDEN						\
102  __sync_##OP##_and_fetch_8 (long long *ptr, long long val)	\
103  {								\
104    int failure;						\
105    long long tmp,tmp2;						\
106								\
107    do {							\
108      tmp = *ptr;						\
109      tmp2 = PFX_OP (tmp INF_OP val);				\
110      failure = __kernel_cmpxchg64 (&tmp, &tmp2, ptr);		\
111    } while (failure != 0);					\
112								\
113    return tmp2;						\
114  }
115
116OP_AND_FETCH_WORD64 (add,   , +)
117OP_AND_FETCH_WORD64 (sub,   , -)
118OP_AND_FETCH_WORD64 (or,    , |)
119OP_AND_FETCH_WORD64 (and,   , &)
120OP_AND_FETCH_WORD64 (xor,   , ^)
121OP_AND_FETCH_WORD64 (nand, ~, &)
122
123long long HIDDEN
124__sync_val_compare_and_swap_8 (long long *ptr, long long oldval,
125				long long newval)
126{
127  int failure;
128  long long actual_oldval;
129
130  while (1)
131    {
132      actual_oldval = *ptr;
133
134      if (__builtin_expect (oldval != actual_oldval, 0))
135	return actual_oldval;
136
137      failure = __kernel_cmpxchg64 (&actual_oldval, &newval, ptr);
138
139      if (__builtin_expect (!failure, 1))
140	return oldval;
141    }
142}
143
144typedef unsigned char bool;
145
146bool HIDDEN
147__sync_bool_compare_and_swap_8 (long long *ptr, long long oldval,
148				 long long newval)
149{
150  int failure = __kernel_cmpxchg64 (&oldval, &newval, ptr);
151  return (failure == 0);
152}
153
154long long HIDDEN
155__sync_lock_test_and_set_8 (long long *ptr, long long val)
156{
157  int failure;
158  long long oldval;
159
160  do {
161    oldval = *ptr;
162    failure = __kernel_cmpxchg64 (&oldval, &val, ptr);
163  } while (failure != 0);
164
165  return oldval;
166}
167