1 /*
2 * Copyright (C) 2016 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 "core_jni_helpers.h"
18 #include <cutils/ashmem.h>
19 #include <linux/ashmem.h>
20 #include <sys/mman.h>
21
22 namespace android {
23
android_util_MemoryIntArray_create(JNIEnv * env,jobject clazz,jstring name,jint size)24 static jint android_util_MemoryIntArray_create(JNIEnv* env, jobject clazz, jstring name,
25 jint size)
26 {
27 if (name == NULL) {
28 jniThrowException(env, "java/io/IOException", "bad name");
29 return -1;
30 }
31
32 if (size <= 0) {
33 jniThrowException(env, "java/io/IOException", "bad size");
34 return -1;
35 }
36
37 const char* nameStr = env->GetStringUTFChars(name, NULL);
38 const int ashmemSize = sizeof(std::atomic_int) * size;
39 int fd = ashmem_create_region(nameStr, ashmemSize);
40 env->ReleaseStringUTFChars(name, nameStr);
41
42 if (fd < 0) {
43 jniThrowException(env, "java/io/IOException", "ashmem creation failed");
44 return -1;
45 }
46
47 int setProtResult = ashmem_set_prot_region(fd, PROT_READ | PROT_WRITE);
48 if (setProtResult < 0) {
49 jniThrowException(env, "java/io/IOException", "cannot set ashmem prot mode");
50 return -1;
51 }
52
53 return fd;
54 }
55
android_util_MemoryIntArray_open(JNIEnv * env,jobject clazz,jint fd,jboolean owner)56 static jlong android_util_MemoryIntArray_open(JNIEnv* env, jobject clazz, jint fd,
57 jboolean owner)
58 {
59 if (fd < 0) {
60 jniThrowException(env, "java/io/IOException", "bad file descriptor");
61 return -1;
62 }
63
64 int ashmemSize = ashmem_get_size_region(fd);
65 if (ashmemSize <= 0) {
66 jniThrowException(env, "java/io/IOException", "bad ashmem size");
67 return -1;
68 }
69
70 // IMPORTANT: Ashmem allows the caller to change its size until
71 // it is memory mapped for the first time which lazily creates
72 // the underlying VFS file. So the size we get above may not
73 // reflect the size of the underlying shared memory region. Therefore,
74 // we first memory map to set the size in stone an verify if
75 // the underlying ashmem region has the same size as the one we
76 // memory mapped. This is critical as we use the underlying
77 // ashmem size for boundary checks and memory unmapping.
78 int protMode = owner ? (PROT_READ | PROT_WRITE) : PROT_READ;
79 void* ashmemAddr = mmap(NULL, ashmemSize, protMode, MAP_SHARED, fd, 0);
80 if (ashmemAddr == MAP_FAILED) {
81 jniThrowException(env, "java/io/IOException", "cannot mmap ashmem");
82 return -1;
83 }
84
85 // Check if the mapped size is the same as the ashmem region.
86 int mmapedSize = ashmem_get_size_region(fd);
87 if (mmapedSize != ashmemSize) {
88 munmap(reinterpret_cast<void *>(ashmemAddr), ashmemSize);
89 jniThrowException(env, "java/io/IOException", "bad file descriptor");
90 return -1;
91 }
92
93 if (owner) {
94 int size = ashmemSize / sizeof(std::atomic_int);
95 new (ashmemAddr) std::atomic_int[size];
96 }
97
98 if (owner) {
99 int setProtResult = ashmem_set_prot_region(fd, PROT_READ);
100 if (setProtResult < 0) {
101 jniThrowException(env, "java/io/IOException", "cannot set ashmem prot mode");
102 return -1;
103 }
104 }
105
106 return reinterpret_cast<jlong>(ashmemAddr);
107 }
108
android_util_MemoryIntArray_close(JNIEnv * env,jobject clazz,jint fd,jlong ashmemAddr,jboolean owner)109 static void android_util_MemoryIntArray_close(JNIEnv* env, jobject clazz, jint fd,
110 jlong ashmemAddr, jboolean owner)
111 {
112 if (fd < 0) {
113 jniThrowException(env, "java/io/IOException", "bad file descriptor");
114 return;
115 }
116
117 int ashmemSize = ashmem_get_size_region(fd);
118 if (ashmemSize <= 0) {
119 jniThrowException(env, "java/io/IOException", "bad ashmem size");
120 return;
121 }
122
123 int unmapResult = munmap(reinterpret_cast<void *>(ashmemAddr), ashmemSize);
124 if (unmapResult < 0) {
125 jniThrowException(env, "java/io/IOException", "munmap failed");
126 return;
127 }
128
129 // We don't deallocate the atomic ints we created with placement new in the ashmem
130 // region as the kernel we reclaim all pages when the ashmem region is destroyed.
131 if (owner && (ashmem_unpin_region(fd, 0, 0) != ASHMEM_IS_UNPINNED)) {
132 jniThrowException(env, "java/io/IOException", "ashmem unpinning failed");
133 return;
134 }
135
136 close(fd);
137 }
138
android_util_MemoryIntArray_get(JNIEnv * env,jobject clazz,jint fd,jlong address,jint index)139 static jint android_util_MemoryIntArray_get(JNIEnv* env, jobject clazz,
140 jint fd, jlong address, jint index)
141 {
142 if (fd < 0) {
143 jniThrowException(env, "java/io/IOException", "bad file descriptor");
144 return -1;
145 }
146
147 if (ashmem_pin_region(fd, 0, 0) == ASHMEM_WAS_PURGED) {
148 jniThrowException(env, "java/io/IOException", "ashmem region was purged");
149 return -1;
150 }
151
152 std::atomic_int* value = reinterpret_cast<std::atomic_int*>(address) + index;
153 return value->load(std::memory_order_relaxed);
154 }
155
android_util_MemoryIntArray_set(JNIEnv * env,jobject clazz,jint fd,jlong address,jint index,jint newValue)156 static void android_util_MemoryIntArray_set(JNIEnv* env, jobject clazz,
157 jint fd, jlong address, jint index, jint newValue)
158 {
159 if (fd < 0) {
160 jniThrowException(env, "java/io/IOException", "bad file descriptor");
161 return;
162 }
163
164 if (ashmem_pin_region(fd, 0, 0) == ASHMEM_WAS_PURGED) {
165 jniThrowException(env, "java/io/IOException", "ashmem region was purged");
166 return;
167 }
168
169 std::atomic_int* value = reinterpret_cast<std::atomic_int*>(address) + index;
170 value->store(newValue, std::memory_order_relaxed);
171 }
172
android_util_MemoryIntArray_size(JNIEnv * env,jobject clazz,jint fd)173 static jint android_util_MemoryIntArray_size(JNIEnv* env, jobject clazz, jint fd) {
174 if (fd < 0) {
175 jniThrowException(env, "java/io/IOException", "bad file descriptor");
176 return -1;
177 }
178
179 int ashmemSize = ashmem_get_size_region(fd);
180 if (ashmemSize < 0) {
181 // Some other error, throw exception
182 jniThrowIOException(env, errno);
183 return -1;
184 }
185 return ashmemSize / sizeof(std::atomic_int);
186 }
187
188 static const JNINativeMethod methods[] = {
189 {"nativeCreate", "(Ljava/lang/String;I)I", (void*)android_util_MemoryIntArray_create},
190 {"nativeOpen", "(IZ)J", (void*)android_util_MemoryIntArray_open},
191 {"nativeClose", "(IJZ)V", (void*)android_util_MemoryIntArray_close},
192 {"nativeGet", "(IJI)I", (void*)android_util_MemoryIntArray_get},
193 {"nativeSet", "(IJII)V", (void*) android_util_MemoryIntArray_set},
194 {"nativeSize", "(I)I", (void*) android_util_MemoryIntArray_size},
195 };
196
register_android_util_MemoryIntArray(JNIEnv * env)197 int register_android_util_MemoryIntArray(JNIEnv* env)
198 {
199 return RegisterMethodsOrDie(env, "android/util/MemoryIntArray", methods, NELEM(methods));
200 }
201
202 }
203