1 /* 64bit Linux-specific atomic operations for ARM EABI.
2 Copyright (C) 2008-2023 Free Software Foundation, Inc.
3 Based on linux-atomic.c
4
5 64 bit additions david.gilbert@linaro.org
6
7 This file is part of GCC.
8
9 GCC is free software; you can redistribute it and/or modify it under
10 the terms of the GNU General Public License as published by the Free
11 Software Foundation; either version 3, or (at your option) any later
12 version.
13
14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 for more details.
18
19 Under Section 7 of GPL version 3, you are granted additional
20 permissions described in the GCC Runtime Library Exception, version
21 3.1, as published by the Free Software Foundation.
22
23 You should have received a copy of the GNU General Public License and
24 a copy of the GCC Runtime Library Exception along with this program;
25 see 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
36 extern int write (int fd, const void *buf, unsigned int count);
37 extern void abort (void);
38
39 /* Kernel helper for compare-and-exchange. */
40 typedef 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. */
49 static 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
64 static 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
87 FETCH_AND_OP_WORD64 (add, , +)
88 FETCH_AND_OP_WORD64 (sub, , -)
89 FETCH_AND_OP_WORD64 (or, , |)
90 FETCH_AND_OP_WORD64 (and, , &)
91 FETCH_AND_OP_WORD64 (xor, , ^)
92 FETCH_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
116 OP_AND_FETCH_WORD64 (add, , +)
117 OP_AND_FETCH_WORD64 (sub, , -)
118 OP_AND_FETCH_WORD64 (or, , |)
119 OP_AND_FETCH_WORD64 (and, , &)
120 OP_AND_FETCH_WORD64 (xor, , ^)
121 OP_AND_FETCH_WORD64 (nand, ~, &)
122
123 long 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
144 typedef unsigned char bool;
145
146 bool 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
154 long 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 }