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