| /* |
| * 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); |
| } |