Christopher Ferris | 33c03d3 | 2015-09-11 15:34:23 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2015 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | #include <err.h> |
| 18 | #include <inttypes.h> |
| 19 | #include <stdatomic.h> |
| 20 | #include <stdio.h> |
| 21 | #include <stdlib.h> |
| 22 | #include <string.h> |
| 23 | #include <sys/mman.h> |
| 24 | #include <unistd.h> |
| 25 | |
| 26 | #include "err.h" |
| 27 | #include "Pointers.h" |
| 28 | |
| 29 | Pointers::Pointers(size_t max_allocs) { |
| 30 | size_t pagesize = getpagesize(); |
| 31 | // Create a mmap that contains a 4:1 ratio of allocations to entries. |
| 32 | // Align to a page. |
| 33 | pointers_size_ = (max_allocs * 4 * sizeof(pointer_data) + pagesize - 1) & ~(pagesize - 1); |
| 34 | max_pointers_ = pointers_size_ / sizeof(pointer_data); |
| 35 | void* memory = mmap(nullptr, pointers_size_, PROT_READ | PROT_WRITE, |
| 36 | MAP_ANON | MAP_PRIVATE, -1, 0); |
| 37 | if (memory == MAP_FAILED) { |
| 38 | err(1, "Unable to allocate data for pointer hash: %zu total_allocs\n", max_allocs); |
| 39 | } |
| 40 | // Make sure that all of the PSS for this is counted right away. |
| 41 | memset(memory, 0, pointers_size_); |
| 42 | pointers_ = reinterpret_cast<pointer_data*>(memory); |
| 43 | } |
| 44 | |
| 45 | Pointers::~Pointers() { |
| 46 | if (pointers_ != nullptr) { |
| 47 | munmap(pointers_, pointers_size_); |
| 48 | pointers_ = nullptr; |
| 49 | } |
| 50 | } |
| 51 | |
| 52 | void Pointers::Add(uintptr_t key_pointer, void* pointer) { |
| 53 | pointer_data* data = FindEmpty(key_pointer); |
| 54 | if (data == nullptr) { |
| 55 | err(1, "No empty entry found for 0x%" PRIxPTR "\n", key_pointer); |
| 56 | } |
| 57 | atomic_store(&data->key_pointer, key_pointer); |
| 58 | data->pointer = pointer; |
| 59 | } |
| 60 | |
| 61 | void* Pointers::Remove(uintptr_t key_pointer) { |
| 62 | if (key_pointer == 0) { |
| 63 | err(1, "Illegal zero value passed to Remove\n"); |
| 64 | } |
| 65 | |
| 66 | pointer_data* data = Find(key_pointer); |
| 67 | if (data == nullptr) { |
| 68 | err(1, "No pointer value found for 0x%" PRIxPTR "\n", key_pointer); |
| 69 | } |
| 70 | |
| 71 | void* pointer = data->pointer; |
| 72 | atomic_store(&data->key_pointer, uintptr_t(0)); |
| 73 | |
| 74 | return pointer; |
| 75 | } |
| 76 | |
| 77 | pointer_data* Pointers::Find(uintptr_t key_pointer) { |
| 78 | size_t index = GetHash(key_pointer); |
| 79 | for (size_t entries = max_pointers_; entries != 0; entries--) { |
| 80 | if (atomic_load(&pointers_[index].key_pointer) == key_pointer) { |
| 81 | return pointers_ + index; |
| 82 | } |
| 83 | if (++index == max_pointers_) { |
| 84 | index = 0; |
| 85 | } |
| 86 | } |
| 87 | return nullptr; |
| 88 | } |
| 89 | |
| 90 | pointer_data* Pointers::FindEmpty(uintptr_t key_pointer) { |
| 91 | size_t index = GetHash(key_pointer); |
| 92 | for (size_t entries = 0; entries < max_pointers_; entries++) { |
| 93 | uintptr_t empty = 0; |
| 94 | if (atomic_compare_exchange_strong(&pointers_[index].key_pointer, &empty, |
| 95 | uintptr_t(1))) { |
| 96 | return pointers_ + index; |
| 97 | } |
| 98 | if (++index == max_pointers_) { |
| 99 | index = 0; |
| 100 | } |
| 101 | } |
| 102 | return nullptr; |
| 103 | } |
| 104 | |
| 105 | size_t Pointers::GetHash(uintptr_t key_pointer) { |
| 106 | return key_pointer % max_pointers_; |
| 107 | } |
| 108 | |
| 109 | void Pointers::FreeAll() { |
| 110 | for (size_t i = 0; i < max_pointers_; i++) { |
| 111 | if (atomic_load(&pointers_[i].key_pointer) != 0) { |
| 112 | free(pointers_[i].pointer); |
| 113 | } |
| 114 | } |
| 115 | } |