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/*
* Copyright (C) 2008 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Implementation of the user-space ashmem API for devices, which have our
* ashmem-enabled kernel. See ashmem-sim.c for the "fake" tmp-based version,
* used by the simulator.
*/
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/ashmem.h>
#include <cutils/ashmem.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;
}
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;
}
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;
}
}
errno = ENOTTY;
return -1;
}
/*
* ashmem_create_region - creates a new ashmem region and returns the file
* descriptor, or <0 on error
*
* `name' is an optional label to give the region (visible in /proc/pid/maps)
* `size' is the size of the region, in page-aligned bytes
*/
int ashmem_create_region(const char *name, size_t size)
{
int ret, save_errno;
int fd = __ashmem_open();
if (fd < 0) {
return fd;
}
if (name) {
char buf[ASHMEM_NAME_LEN] = {0};
strlcpy(buf, name, sizeof(buf));
ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_NAME, buf));
if (ret < 0) {
goto error;
}
}
ret = TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_SET_SIZE, size));
if (ret < 0) {
goto error;
}
return fd;
error:
save_errno = errno;
close(fd);
errno = save_errno;
return ret;
}
int ashmem_set_prot_region(int fd, int 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 };
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 };
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)
{
int ret = __ashmem_is_ashmem(fd);
if (ret < 0) {
return ret;
}
return TEMP_FAILURE_RETRY(ioctl(fd, ASHMEM_GET_SIZE, NULL));
}
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