diff options
Diffstat (limited to 'libcutils/ashmem-dev.c')
| -rw-r--r-- | libcutils/ashmem-dev.c | 184 |
1 files changed, 156 insertions, 28 deletions
diff --git a/libcutils/ashmem-dev.c b/libcutils/ashmem-dev.c index 3089a94..4a07d66 100644 --- a/libcutils/ashmem-dev.c +++ b/libcutils/ashmem-dev.c @@ -19,18 +19,119 @@ * ashmem-enabled kernel. See ashmem-sim.c for the "fake" tmp-based version, * used by the simulator. */ +#define LOG_TAG "ashmem" -#include <unistd.h> +#include <errno.h> +#include <fcntl.h> +#include <pthread.h> #include <string.h> -#include <sys/types.h> -#include <sys/stat.h> #include <sys/ioctl.h> -#include <fcntl.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <unistd.h> #include <linux/ashmem.h> + #include <cutils/ashmem.h> +#include <log/log.h> + +#define ASHMEM_DEVICE "/dev/ashmem" + +/* ashmem identity */ +static dev_t __ashmem_rdev; +/* + * If we trigger a signal handler in the middle of locked activity and the + * signal handler calls ashmem, we could get into a deadlock state. + */ +static pthread_mutex_t __ashmem_lock = PTHREAD_MUTEX_INITIALIZER; + +/* logistics of getting file descriptor for ashmem */ +static int __ashmem_open_locked() +{ + int ret; + struct stat st; + + int fd = TEMP_FAILURE_RETRY(open(ASHMEM_DEVICE, O_RDWR)); + if (fd < 0) { + return fd; + } + + ret = TEMP_FAILURE_RETRY(fstat(fd, &st)); + if (ret < 0) { + int save_errno = errno; + close(fd); + errno = save_errno; + return ret; + } + if (!S_ISCHR(st.st_mode) || !st.st_rdev) { + close(fd); + errno = ENOTTY; + return -1; + } + + __ashmem_rdev = st.st_rdev; + return fd; +} -#define ASHMEM_DEVICE "/dev/ashmem" +static int __ashmem_open() +{ + int fd; + + pthread_mutex_lock(&__ashmem_lock); + fd = __ashmem_open_locked(); + pthread_mutex_unlock(&__ashmem_lock); + + return fd; +} + +/* Make sure file descriptor references ashmem, negative number means false */ +static int __ashmem_is_ashmem(int fd) +{ + dev_t rdev; + struct stat st; + + if (TEMP_FAILURE_RETRY(fstat(fd, &st)) < 0) { + return -1; + } + + rdev = 0; /* Too much complexity to sniff __ashmem_rdev */ + if (S_ISCHR(st.st_mode) && st.st_rdev) { + pthread_mutex_lock(&__ashmem_lock); + rdev = __ashmem_rdev; + if (rdev) { + pthread_mutex_unlock(&__ashmem_lock); + } else { + int fd = __ashmem_open_locked(); + if (fd < 0) { + pthread_mutex_unlock(&__ashmem_lock); + return -1; + } + rdev = __ashmem_rdev; + pthread_mutex_unlock(&__ashmem_lock); + + close(fd); + } + + if (st.st_rdev == rdev) { + return 0; + } + } + + if (rdev) { + LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o %d:%d", + fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev), + S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IRGRP, + major(rdev), minor(rdev)); + } else { + LOG_ALWAYS_FATAL("illegal fd=%d mode=0%o rdev=%d:%d expected 0%o", + fd, st.st_mode, major(st.st_rdev), minor(st.st_rdev), + S_IFCHR | S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IRGRP); + } + /* NOTREACHED */ + + errno = ENOTTY; + return -1; +} /* * ashmem_create_region - creates a new ashmem region and returns the file @@ -41,50 +142,77 @@ */ int ashmem_create_region(const char *name, size_t size) { - int fd, ret; + int ret, save_errno; - fd = open(ASHMEM_DEVICE, O_RDWR); - if (fd < 0) - return fd; + int fd = __ashmem_open(); + if (fd < 0) { + return fd; + } - if (name) { - char buf[ASHMEM_NAME_LEN] = {0}; + if (name) { + char buf[ASHMEM_NAME_LEN] = {0}; - strlcpy(buf, name, sizeof(buf)); - ret = ioctl(fd, ASHMEM_SET_NAME, buf); - if (ret < 0) - goto error; - } + strlcpy(buf, name, sizeof(buf)); + ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_NAME, buf)); + if (ret < 0) { + goto error; + } + } - ret = ioctl(fd, ASHMEM_SET_SIZE, size); - if (ret < 0) - goto error; + ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_SIZE, size)); + if (ret < 0) { + goto error; + } - return fd; + return fd; error: - close(fd); - return ret; + save_errno = errno; + close(fd); + errno = save_errno; + return ret; } int ashmem_set_prot_region(int fd, int prot) { - return ioctl(fd, ASHMEM_SET_PROT_MASK, prot); + int ret = __ashmem_is_ashmem(fd); + if (ret < 0) { + return ret; + } + + return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_PROT_MASK, prot)); } int ashmem_pin_region(int fd, size_t offset, size_t len) { - struct ashmem_pin pin = { offset, len }; - return ioctl(fd, ASHMEM_PIN, &pin); + struct ashmem_pin pin = { offset, len }; + + int ret = __ashmem_is_ashmem(fd); + if (ret < 0) { + return ret; + } + + return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_PIN, &pin)); } int ashmem_unpin_region(int fd, size_t offset, size_t len) { - struct ashmem_pin pin = { offset, len }; - return ioctl(fd, ASHMEM_UNPIN, &pin); + struct ashmem_pin pin = { offset, len }; + + int ret = __ashmem_is_ashmem(fd); + if (ret < 0) { + return ret; + } + + return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_UNPIN, &pin)); } int ashmem_get_size_region(int fd) { - return ioctl(fd, ASHMEM_GET_SIZE, NULL); + int ret = __ashmem_is_ashmem(fd); + if (ret < 0) { + return ret; + } + + return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_GET_SIZE, NULL)); } |