1 /* 2 * Copyright (C) 2008 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 <cutils/ashmem.h> 18 19 /* 20 * Implementation of the user-space ashmem API for devices, which have our 21 * ashmem-enabled kernel. See ashmem-sim.c for the "fake" tmp-based version, 22 * used by the simulator. 23 */ 24 #define LOG_TAG "ashmem" 25 26 #include <errno.h> 27 #include <fcntl.h> 28 #include <linux/ashmem.h> 29 #include <pthread.h> 30 #include <string.h> 31 #include <sys/ioctl.h> 32 #include <sys/stat.h> 33 #include <sys/sysmacros.h> 34 #include <sys/types.h> 35 #include <unistd.h> 36 #include <log/log.h> 37 38 #define ASHMEM_DEVICE "/dev/ashmem" 39 40 /* ashmem identity */ 41 static dev_t __ashmem_rdev; 42 /* 43 * If we trigger a signal handler in the middle of locked activity and the 44 * signal handler calls ashmem, we could get into a deadlock state. 45 */ 46 static pthread_mutex_t __ashmem_lock = PTHREAD_MUTEX_INITIALIZER; 47 48 /* logistics of getting file descriptor for ashmem */ 49 static int __ashmem_open_locked() 50 { 51 int ret; 52 struct stat st; 53 54 int fd = TEMP_FAILURE_RETRY(open(ASHMEM_DEVICE, O_RDWR | O_CLOEXEC)); 55 if (fd < 0) { 56 return fd; 57 } 58 59 ret = TEMP_FAILURE_RETRY(fstat(fd, &st)); 60 if (ret < 0) { 61 int save_errno = errno; 62 close(fd); 63 errno = save_errno; 64 return ret; 65 } 66 if (!S_ISCHR(st.st_mode) || !st.st_rdev) { 67 close(fd); 68 errno = ENOTTY; 69 return -1; 70 } 71 72 __ashmem_rdev = st.st_rdev; 73 return fd; 74 } 75 76 static int __ashmem_open() 77 { 78 int fd; 79 80 pthread_mutex_lock(&__ashmem_lock); 81 fd = __ashmem_open_locked(); 82 pthread_mutex_unlock(&__ashmem_lock); 83 84 return fd; 85 } 86 87 /* Make sure file descriptor references ashmem, negative number means false */ 88 static int __ashmem_is_ashmem(int fd, int fatal) 89 { 90 dev_t rdev; 91 struct stat st; 92 93 if (TEMP_FAILURE_RETRY(fstat(fd, &st)) < 0) { 94 return -1; 95 } 96 97 rdev = 0; /* Too much complexity to sniff __ashmem_rdev */ 98 if (S_ISCHR(st.st_mode) && st.st_rdev) { 99 pthread_mutex_lock(&__ashmem_lock); 100 rdev = __ashmem_rdev; 101 if (rdev) { 102 pthread_mutex_unlock(&__ashmem_lock); 103 } else { 104 int fd = __ashmem_open_locked(); 105 if (fd < 0) { 106 pthread_mutex_unlock(&__ashmem_lock); 107 return -1; 108 } 109 rdev = __ashmem_rdev; 110 pthread_mutex_unlock(&__ashmem_lock); 111 112 close(fd); 113 } 114 115 if (st.st_rdev == rdev) { 116 return 0; 117 } 118 } 119 120 if (fatal) { 121 if (rdev) { 122 LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o %d:%d", 123 fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev), 124 S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IRGRP, 125 major(rdev), minor(rdev)); 126 } else { 127 LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o", 128 fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev), 129 S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IRGRP); 130 } 131 /* NOTREACHED */ 132 } 133 134 errno = ENOTTY; 135 return -1; 136 } 137 138 int ashmem_valid(int fd) 139 { 140 return __ashmem_is_ashmem(fd, 0) >= 0; 141 } 142 143 /* 144 * ashmem_create_region - creates a new ashmem region and returns the file 145 * descriptor, or <0 on error 146 * 147 * `name' is an optional label to give the region (visible in /proc/pid/maps) 148 * `size' is the size of the region, in page-aligned bytes 149 */ 150 int ashmem_create_region(const char *name, size_t size) 151 { 152 int ret, save_errno; 153 154 int fd = __ashmem_open(); 155 if (fd < 0) { 156 return fd; 157 } 158 159 if (name) { 160 char buf[ASHMEM_NAME_LEN] = {0}; 161 162 strlcpy(buf, name, sizeof(buf)); 163 ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_NAME, buf)); 164 if (ret < 0) { 165 goto error; 166 } 167 } 168 169 ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_SIZE, size)); 170 if (ret < 0) { 171 goto error; 172 } 173 174 return fd; 175 176 error: 177 save_errno = errno; 178 close(fd); 179 errno = save_errno; 180 return ret; 181 } 182 183 int ashmem_set_prot_region(int fd, int prot) 184 { 185 int ret = __ashmem_is_ashmem(fd, 1); 186 if (ret < 0) { 187 return ret; 188 } 189 190 return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_PROT_MASK, prot)); 191 } 192 193 int ashmem_pin_region(int fd, size_t offset, size_t len) 194 { 195 // TODO: should LP64 reject too-large offset/len? 196 ashmem_pin pin = { static_cast<uint32_t>(offset), static_cast<uint32_t>(len) }; 197 198 int ret = __ashmem_is_ashmem(fd, 1); 199 if (ret < 0) { 200 return ret; 201 } 202 203 return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_PIN, &pin)); 204 } 205 206 int ashmem_unpin_region(int fd, size_t offset, size_t len) 207 { 208 // TODO: should LP64 reject too-large offset/len? 209 ashmem_pin pin = { static_cast<uint32_t>(offset), static_cast<uint32_t>(len) }; 210 211 int ret = __ashmem_is_ashmem(fd, 1); 212 if (ret < 0) { 213 return ret; 214 } 215 216 return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_UNPIN, &pin)); 217 } 218 219 int ashmem_get_size_region(int fd) 220 { 221 int ret = __ashmem_is_ashmem(fd, 1); 222 if (ret < 0) { 223 return ret; 224 } 225 226 return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_GET_SIZE, NULL)); 227 } 228
