1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
|
/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <stddef.h>
#include <endian.h>
#include "private/bionic_atomic_inline.h"
#include "private/bionic_futex.h"
// This file contains C++ ABI support functions for one time
// constructors as defined in the "Run-time ABI for the ARM Architecture"
// section 4.4.2
//
// ARM C++ ABI and Itanium/x86 C++ ABI has different definition for
// one time construction:
//
// ARM C++ ABI defines the LSB of guard variable should be tested
// by compiler-generated code before calling __cxa_guard_acquire et al.
//
// The Itanium/x86 C++ ABI defines the low-order _byte_ should be
// tested instead.
//
// Meanwhile, guard variable are 32bit aligned for ARM, and 64bit
// aligned for x86.
//
// Reference documentation:
//
// section 3.2.3 of ARM IHI 0041C (for ARM)
// section 3.3.2 of the Itanium C++ ABI specification v1.83 (for x86).
//
// There is no C++ ABI available for other ARCH. But the gcc source
// shows all other ARCH follow the definition of Itanium/x86 C++ ABI.
#if defined(__arm__)
// The ARM C++ ABI mandates that guard variables are 32-bit aligned, 32-bit
// values. The LSB is tested by the compiler-generated code before calling
// __cxa_guard_acquire.
union _guard_t {
int volatile state;
int32_t aligner;
};
const static int ready = 0x1;
const static int pending = 0x2;
const static int waiting = 0x6;
#else
// The Itanium/x86 C++ ABI (used by all other architectures) mandates that
// guard variables are 64-bit aligned, 64-bit values. The LSB is tested by
// the compiler-generated code before calling __cxa_guard_acquire.
union _guard_t {
int volatile state;
int64_t aligner;
};
const static int ready = letoh32(0x1);
const static int pending = letoh32(0x100);
const static int waiting = letoh32(0x10000);
#endif
extern "C" int __cxa_guard_acquire(_guard_t* gv) {
// 0 -> pending, return 1
// pending -> waiting, wait and return 0
// waiting: untouched, wait and return 0
// ready: untouched, return 0
retry:
if (__bionic_cmpxchg(0, pending, &gv->state) == 0) {
ANDROID_MEMBAR_FULL();
return 1;
}
__bionic_cmpxchg(pending, waiting, &gv->state); // Indicate there is a waiter
__futex_wait(&gv->state, waiting, NULL);
if (gv->state != ready) {
// __cxa_guard_abort was called, let every thread try since there is no return code for this condition
goto retry;
}
ANDROID_MEMBAR_FULL();
return 0;
}
extern "C" void __cxa_guard_release(_guard_t* gv) {
// pending -> ready
// waiting -> ready, and wake
ANDROID_MEMBAR_FULL();
if (__bionic_cmpxchg(pending, ready, &gv->state) == 0) {
return;
}
gv->state = ready;
__futex_wake(&gv->state, 0x7fffffff);
}
extern "C" void __cxa_guard_abort(_guard_t* gv) {
ANDROID_MEMBAR_FULL();
gv->state= 0;
__futex_wake(&gv->state, 0x7fffffff);
}
|
