关键数据
struct binder_proc {
struct hlist_node proc_node;
struct rb_root threads;
struct rb_root nodes;
struct rb_root refs_by_desc;
struct rb_root refs_by_node;
struct list_head waiting_threads;
int pid;
struct task_struct *tsk;
const struct cred *cred;
struct hlist_node deferred_work_node;
int deferred_work;
int outstanding_txns;
bool is_dead;
bool is_frozen;
bool sync_recv;
bool async_recv;
wait_queue_head_t freeze_wait;
struct list_head todo;
struct binder_stats stats;
struct list_head delivered_death;
int max_threads;
int requested_threads;
int requested_threads_started;
int tmp_ref;
long default_priority;
struct dentry *debugfs_entry;
struct binder_alloc alloc;
struct binder_context *context;
spinlock_t inner_lock;
spinlock_t outer_lock;
struct dentry *binderfs_entry;
bool oneway_spam_detection_enabled;
};
struct binder_buffer {
struct list_head entry; /* free and allocated entries by address */
struct rb_node rb_node; /* free entry by size or allocated entry */
/* by address */
unsigned free:1;
unsigned clear_on_free:1;
unsigned allow_user_free:1;
unsigned async_transaction:1;
unsigned oneway_spam_suspect:1;
unsigned debug_id:27;
struct binder_transaction *transaction;
struct binder_node *target_node;
size_t data_size;
size_t offsets_size;
size_t extra_buffers_size;
void __user *user_data;
int pid;
};
struct binder_alloc {
struct mutex mutex;
struct vm_area_struct *vma;
struct mm_struct *vma_vm_mm;
void __user *buffer;
struct list_head buffers;
struct rb_root free_buffers;
struct rb_root allocated_buffers;
size_t free_async_space;
struct binder_lru_page *pages;
size_t buffer_size;
uint32_t buffer_free;
int pid;
size_t pages_high;
bool oneway_spam_detected;
};
binder_thread代表当前操作binder的线程
struct binder_thread {
struct binder_proc *proc;
struct rb_node rb_node;
struct list_head waiting_thread_node;
int pid;
int looper; /* only modified by this thread */
bool looper_need_return; /* can be written by other thread */
struct binder_transaction *transaction_stack;
struct list_head todo;
bool process_todo;
struct binder_error return_error;
struct binder_error reply_error;
wait_queue_head_t wait;
struct binder_stats stats;
atomic_t tmp_ref;
bool is_dead;
};
ioctl命令
#define BINDER_WRITE_READ _IOWR('b', 1, struct binder_write_read)
#define BINDER_SET_IDLE_TIMEOUT _IOW('b', 3, __s64)
#define BINDER_SET_MAX_THREADS _IOW('b', 5, __u32)
#define BINDER_SET_IDLE_PRIORITY _IOW('b', 6, __s32)
#define BINDER_SET_CONTEXT_MGR _IOW('b', 7, __s32)
#define BINDER_THREAD_EXIT _IOW('b', 8, __s32)
#define BINDER_VERSION _IOWR('b', 9, struct binder_version)
#define BINDER_GET_NODE_DEBUG_INFO _IOWR('b', 11, struct binder_node_debug_info)
#define BINDER_GET_NODE_INFO_FOR_REF _IOWR('b', 12, struct binder_node_info_for_ref)
#define BINDER_SET_CONTEXT_MGR_EXT _IOW('b', 13, struct flat_binder_object)
#define BINDER_FREEZE _IOW('b', 14, struct binder_freeze_info)
#define BINDER_GET_FROZEN_INFO _IOWR('b', 15, struct binder_frozen_status_info)
#define BINDER_ENABLE_ONEWAY_SPAM_DETECTION _IOW('b', 16, __u32)
协议
enum binder_driver_command_protocol {
BC_TRANSACTION = _IOW('c', 0, struct binder_transaction_data),
BC_REPLY = _IOW('c', 1, struct binder_transaction_data),
/*
* binder_transaction_data: the sent command.
*/
BC_ACQUIRE_RESULT = _IOW('c', 2, __s32),
/*
* not currently supported
* int: 0 if the last BR_ATTEMPT_ACQUIRE was not successful.
* Else you have acquired a primary reference on the object.
*/
BC_FREE_BUFFER = _IOW('c', 3, binder_uintptr_t),
/*
* void *: ptr to transaction data received on a read
*/
BC_INCREFS = _IOW('c', 4, __u32),
BC_ACQUIRE = _IOW('c', 5, __u32),
BC_RELEASE = _IOW('c', 6, __u32),
BC_DECREFS = _IOW('c', 7, __u32),
/*
* int: descriptor
*/
BC_INCREFS_DONE = _IOW('c', 8, struct binder_ptr_cookie),
BC_ACQUIRE_DONE = _IOW('c', 9, struct binder_ptr_cookie),
/*
* void *: ptr to binder
* void *: cookie for binder
*/
BC_ATTEMPT_ACQUIRE = _IOW('c', 10, struct binder_pri_desc),
/*
* not currently supported
* int: priority
* int: descriptor
*/
BC_REGISTER_LOOPER = _IO('c', 11),
/*
* No parameters.
* Register a spawned looper thread with the device.
*/
BC_ENTER_LOOPER = _IO('c', 12),
BC_EXIT_LOOPER = _IO('c', 13),
/*
* No parameters.
* These two commands are sent as an application-level thread
* enters and exits the binder loop, respectively. They are
* used so the binder can have an accurate count of the number
* of looping threads it has available.
*/
BC_REQUEST_DEATH_NOTIFICATION = _IOW('c', 14,
struct binder_handle_cookie),
/*
* int: handle
* void *: cookie
*/
BC_CLEAR_DEATH_NOTIFICATION = _IOW('c', 15,
struct binder_handle_cookie),
/*
* int: handle
* void *: cookie
*/
BC_DEAD_BINDER_DONE = _IOW('c', 16, binder_uintptr_t),
/*
* void *: cookie
*/
BC_TRANSACTION_SG = _IOW('c', 17, struct binder_transaction_data_sg),
BC_REPLY_SG = _IOW('c', 18, struct binder_transaction_data_sg),
/*
* binder_transaction_data_sg: the sent command.
*/
};
binder驱动初始化
如果没使用binderfs,则直接注册binder设备，init_binderfs为空实现。binder_devices_param android8.0以后为 "binder,hwbinder,vndbinder"。
static int __init binder_init(void)
{
int ret;
char *device_name, *device_tmp;
struct binder_device *device;
struct hlist_node *tmp;
char *device_names = NULL;
if (!IS_ENABLED(CONFIG_ANDROID_BINDERFS) &&
strcmp(binder_devices_param, "") != 0) {
/*
* Copy the module_parameter string, because we don't want to
* tokenize it in-place.
*/
device_names = kstrdup(binder_devices_param, GFP_KERNEL);
if (!device_names) {
ret = -ENOMEM;
goto err_alloc_device_names_failed;
}
device_tmp = device_names;
while ((device_name = strsep(&device_tmp, ","))) {
ret = init_binder_device(device_name);
if (ret)
goto err_init_binder_device_failed;
}
}
ret = init_binderfs();
if (ret)
goto err_init_binder_device_failed;
return ret;
err_init_binder_device_failed:
hlist_for_each_entry_safe(device, tmp, &binder_devices, hlist) {
misc_deregister(&device->miscdev);
hlist_del(&device->hlist);
kfree(device);
}
kfree(device_names);
return ret;
}
如果设置了binderfs,则不会立即注册binder设备，而是注册binder文件系统
static struct file_system_type binder_fs_type = {
.name = "binder",
.init_fs_context = binderfs_init_fs_context,
.parameters = binderfs_fs_parameters,
.kill_sb = kill_litter_super,
.fs_flags = FS_USERNS_MOUNT,
};
int __init init_binderfs(void)
{
int ret;
const char *name;
size_t len;
/* Allocate new major number for binderfs. */
ret = alloc_chrdev_region(&binderfs_dev, 0, BINDERFS_MAX_MINOR,
"binder");
if (ret)
return ret;
ret = register_filesystem(&binder_fs_type);
if (ret) {
unregister_chrdev_region(binderfs_dev, BINDERFS_MAX_MINOR);
return ret;
}
return ret;
}
注册的设备会加入binder_devices链表，注意binderfs自定义添加的设备不会加入到链表中。
static int __init init_binder_device(const char *name)
{
int ret;
struct binder_device *binder_device;
binder_device = kzalloc(sizeof(*binder_device), GFP_KERNEL);
if (!binder_device)
return -ENOMEM;
binder_device->miscdev.fops = &binder_fops;
binder_device->miscdev.minor = MISC_DYNAMIC_MINOR;
binder_device->miscdev.name = name;
refcount_set(&binder_device->ref, 1);
binder_device->context.binder_context_mgr_uid = INVALID_UID;
binder_device->context.name = name;
mutex_init(&binder_device->context.context_mgr_node_lock);
ret = misc_register(&binder_device->miscdev);
if (ret < 0) {
kfree(binder_device);
return ret;
}
hlist_add_head(&binder_device->hlist, &binder_devices);
return ret;
}
const struct file_operations binder_fops = {
.owner = THIS_MODULE,
.poll = binder_poll,
.unlocked_ioctl = binder_ioctl,
.compat_ioctl = compat_ptr_ioctl,
.mmap = binder_mmap,
.open = binder_open,
.flush = binder_flush,
.release = binder_release,
};
miscdevice.fops关联了该设备的操作函数。
binder_open
(1) 创建binder_proc
(2) 初始化proc innner_lock,outer_lock锁。tsk设置为当前进程主线程。default_priority设置为当前线程的优先级。
(3)binder_proc存放到文件指针filp->private_data中
(4) 每个进程只能有一个binder_proc。毕竟binder是用于跨进程通信的，所以每个进程一个就可以了。
(5)将binder_proc加入入binder_procs链表中
static int binder_open(struct inode *nodp, struct file *filp)
{
struct binder_proc *proc, *itr;
struct binder_device *binder_dev;
struct binderfs_info *info;
struct dentry *binder_binderfs_dir_entry_proc = NULL;
bool existing_pid = false;
binder_debug(BINDER_DEBUG_OPEN_CLOSE, "%s: %d:%d\n", __func__,
current->group_leader->pid, current->pid);
//(1)
proc = kzalloc(sizeof(*proc), GFP_KERNEL);
if (proc == NULL)
return -ENOMEM;
// (2)
spin_lock_init(&proc->inner_lock);
spin_lock_init(&proc->outer_lock);
get_task_struct(current->group_leader);
proc->tsk = current->group_leader;
proc->cred = get_cred(filp->f_cred);
INIT_LIST_HEAD(&proc->todo);
init_waitqueue_head(&proc->freeze_wait);
proc->default_priority = task_nice(current);
/* binderfs stashes devices in i_private */
if (is_binderfs_device(nodp)) {
binder_dev = nodp->i_private;
info = nodp->i_sb->s_fs_info;
binder_binderfs_dir_entry_proc = info->proc_log_dir;
} else {
binder_dev = container_of(filp->private_data,
struct binder_device, miscdev);
}
refcount_inc(&binder_dev->ref);
proc->context = &binder_dev->context;
binder_alloc_init(&proc->alloc);
binder_stats_created(BINDER_STAT_PROC);
proc->pid = current->group_leader->pid;
INIT_LIST_HEAD(&proc->delivered_death);
INIT_LIST_HEAD(&proc->waiting_threads);
//(3)
filp->private_data = proc;
mutex_lock(&binder_procs_lock);
//(4) start
hlist_for_each_entry(itr, &binder_procs, proc_node) {
if (itr->pid == proc->pid) {
existing_pid = true;
break;
}
}
//(4) end
//(5)
hlist_add_head(&proc->proc_node, &binder_procs);
mutex_unlock(&binder_procs_lock);
if (binder_debugfs_dir_entry_proc && !existing_pid) {
char strbuf[11];
snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);
/*
* proc debug entries are shared between contexts.
* Only create for the first PID to avoid debugfs log spamming
* The printing code will anyway print all contexts for a given
* PID so this is not a problem.
*/
proc->debugfs_entry = debugfs_create_file(strbuf, 0444,
binder_debugfs_dir_entry_proc,
(void *)(unsigned long)proc->pid,
&proc_fops);
}
if (binder_binderfs_dir_entry_proc && !existing_pid) {
char strbuf[11];
struct dentry *binderfs_entry;
snprintf(strbuf, sizeof(strbuf), "%u", proc->pid);
/*
* Similar to debugfs, the process specific log file is shared
* between contexts. Only create for the first PID.
* This is ok since same as debugfs, the log file will contain
* information on all contexts of a given PID.
*/
binderfs_entry = binderfs_create_file(binder_binderfs_dir_entry_proc,
strbuf, &proc_fops, (void *)(unsigned long)proc->pid);
if (!IS_ERR(binderfs_entry)) {
proc->binderfs_entry = binderfs_entry;
} else {
int error;
error = PTR_ERR(binderfs_entry);
pr_warn("Unable to create file %s in binderfs (error %d)\n",
strbuf, error);
}
}
return 0;
}
binder_mmap
(1) 要在binder所属的进程组mmap才有效
(2) 禁止对mmap的内存拷贝和写
(3) vma->vm_private_data设置binder_proc，使得可以通过vma取出binder_proc
static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
{
struct binder_proc *proc = filp->private_data;
//(1)
if (proc->tsk != current->group_leader)
return -EINVAL;
......
//(2)
vma->vm_flags |= VM_DONTCOPY | VM_MIXEDMAP;
vma->vm_flags &= ~VM_MAYWRITE;
vma->vm_ops = &binder_vm_ops;
//(3)
vma->vm_private_data = proc;
return binder_alloc_mmap_handler(&proc->alloc, vma);
}
(1)映射空间最大为4M
(2)alloc->buffer指向vma的起始地址
(3)
(6)将异步事务的空间大小设置为整个空间的一半
int binder_alloc_mmap_handler(struct binder_alloc *alloc,
struct vm_area_struct *vma)
{
int ret;
const char *failure_string;
struct binder_buffer *buffer;
mutex_lock(&binder_alloc_mmap_lock);
if (alloc->buffer_size) {
ret = -EBUSY;
failure_string = "already mapped";
goto err_already_mapped;
}
//(1)
alloc->buffer_size = min_t(unsigned long, vma->vm_end - vma->vm_start,
SZ_4M);
mutex_unlock(&binder_alloc_mmap_lock);
//(2)
alloc->buffer = (void __user *)vma->vm_start;
//(3)
alloc->pages = kcalloc(alloc->buffer_size / PAGE_SIZE,
sizeof(alloc->pages[0]),
GFP_KERNEL);
if (alloc->pages == NULL) {
ret = -ENOMEM;
failure_string = "alloc page array";
goto err_alloc_pages_failed;
}
//(4)
buffer = kzalloc(sizeof(*buffer), GFP_KERNEL);
if (!buffer) {
ret = -ENOMEM;
failure_string = "alloc buffer struct";
goto err_alloc_buf_struct_failed;
}
//(5)
buffer->user_data = alloc->buffer;
list_add(&buffer->entry, &alloc->buffers);
buffer->free = 1;
//(6)
binder_insert_free_buffer(alloc, buffer);
alloc->free_async_space = alloc->buffer_size / 2;
binder_alloc_set_vma(alloc, vma);
mmgrab(alloc->vma_vm_mm);
return 0;
err_alloc_buf_struct_failed:
kfree(alloc->pages);
alloc->pages = NULL;
err_alloc_pages_failed:
alloc->buffer = NULL;
mutex_lock(&binder_alloc_mmap_lock);
alloc->buffer_size = 0;
err_already_mapped:
mutex_unlock(&binder_alloc_mmap_lock);
binder_alloc_debug(BINDER_DEBUG_USER_ERROR,
"%s: %d %lx-%lx %s failed %d\n", __func__,
alloc->pid, vma->vm_start, vma->vm_end,
failure_string, ret);
return ret;
}
binder_ioctl
static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
int ret;
struct binder_proc *proc = filp->private_data;
struct binder_thread *thread;
unsigned int size = _IOC_SIZE(cmd);
void __user *ubuf = (void __user *)arg;
/*pr_info("binder_ioctl: %d:%d %x %lx\n",
proc->pid, current->pid, cmd, arg);*/
binder_selftest_alloc(&proc->alloc);
trace_binder_ioctl(cmd, arg);
ret = wait_event_interruptible(binder_user_error_wait, binder_stop_on_user_error < 2);
if (ret)
goto err_unlocked;
thread = binder_get_thread(proc);
if (thread == NULL) {
ret = -ENOMEM;
goto err;
}
switch (cmd) {
case BINDER_WRITE_READ:
ret = binder_ioctl_write_read(filp, cmd, arg, thread);
if (ret)
goto err;
break;
case BINDER_SET_MAX_THREADS: {
int max_threads;
if (copy_from_user(&max_threads, ubuf,
sizeof(max_threads))) {
ret = -EINVAL;
goto err;
}
binder_inner_proc_lock(proc);
proc->max_threads = max_threads;
binder_inner_proc_unlock(proc);
break;
}
case BINDER_SET_CONTEXT_MGR_EXT: {
struct flat_binder_object fbo;
if (copy_from_user(&fbo, ubuf, sizeof(fbo))) {
ret = -EINVAL;
goto err;
}
ret = binder_ioctl_set_ctx_mgr(filp, &fbo);
if (ret)
goto err;
break;
}
case BINDER_SET_CONTEXT_MGR:
ret = binder_ioctl_set_ctx_mgr(filp, NULL);
if (ret)
goto err;
break;
case BINDER_THREAD_EXIT:
binder_debug(BINDER_DEBUG_THREADS, "%d:%d exit\n",
proc->pid, thread->pid);
binder_thread_release(proc, thread);
thread = NULL;
break;
case BINDER_VERSION: {
struct binder_version __user *ver = ubuf;
if (size != sizeof(struct binder_version)) {
ret = -EINVAL;
goto err;
}
if (put_user(BINDER_CURRENT_PROTOCOL_VERSION,
&ver->protocol_version)) {
ret = -EINVAL;
goto err;
}
break;
}
case BINDER_GET_NODE_INFO_FOR_REF: {
struct binder_node_info_for_ref info;
if (copy_from_user(&info, ubuf, sizeof(info))) {
ret = -EFAULT;
goto err;
}
ret = binder_ioctl_get_node_info_for_ref(proc, &info);
if (ret < 0)
goto err;
if (copy_to_user(ubuf, &info, sizeof(info))) {
ret = -EFAULT;
goto err;
}
break;
}
case BINDER_GET_NODE_DEBUG_INFO: {
struct binder_node_debug_info info;
if (copy_from_user(&info, ubuf, sizeof(info))) {
ret = -EFAULT;
goto err;
}
ret = binder_ioctl_get_node_debug_info(proc, &info);
if (ret < 0)
goto err;
if (copy_to_user(ubuf, &info, sizeof(info))) {
ret = -EFAULT;
goto err;
}
break;
}
case BINDER_FREEZE: {
struct binder_freeze_info info;
struct binder_proc **target_procs = NULL, *target_proc;
int target_procs_count = 0, i = 0;
ret = 0;
if (copy_from_user(&info, ubuf, sizeof(info))) {
ret = -EFAULT;
goto err;
}
mutex_lock(&binder_procs_lock);
hlist_for_each_entry(target_proc, &binder_procs, proc_node) {
if (target_proc->pid == info.pid)
target_procs_count++;
}
if (target_procs_count == 0) {
mutex_unlock(&binder_procs_lock);
ret = -EINVAL;
goto err;
}
target_procs = kcalloc(target_procs_count,
sizeof(struct binder_proc *),
GFP_KERNEL);
if (!target_procs) {
mutex_unlock(&binder_procs_lock);
ret = -ENOMEM;
goto err;
}
hlist_for_each_entry(target_proc, &binder_procs, proc_node) {
if (target_proc->pid != info.pid)
continue;
binder_inner_proc_lock(target_proc);
target_proc->tmp_ref++;
binder_inner_proc_unlock(target_proc);
target_procs[i++] = target_proc;
}
mutex_unlock(&binder_procs_lock);
for (i = 0; i < target_procs_count; i++) {
if (ret >= 0)
ret = binder_ioctl_freeze(&info,
target_procs[i]);
binder_proc_dec_tmpref(target_procs[i]);
}
kfree(target_procs);
if (ret < 0)
goto err;
break;
}
case BINDER_GET_FROZEN_INFO: {
struct binder_frozen_status_info info;
if (copy_from_user(&info, ubuf, sizeof(info))) {
ret = -EFAULT;
goto err;
}
ret = binder_ioctl_get_freezer_info(&info);
if (ret < 0)
goto err;
if (copy_to_user(ubuf, &info, sizeof(info))) {
ret = -EFAULT;
goto err;
}
break;
}
case BINDER_ENABLE_ONEWAY_SPAM_DETECTION: {
uint32_t enable;
if (copy_from_user(&enable, ubuf, sizeof(enable))) {
ret = -EFAULT;
goto err;
}
binder_inner_proc_lock(proc);
proc->oneway_spam_detection_enabled = (bool)enable;
binder_inner_proc_unlock(proc);
break;
}
default:
ret = -EINVAL;
goto err;
}
ret = 0;
err:
if (thread)
thread->looper_need_return = false;
wait_event_interruptible(binder_user_error_wait, binder_stop_on_user_error < 2);
if (ret && ret != -EINTR)
pr_info("%d:%d ioctl %x %lx returned %d\n", proc->pid, current->pid, cmd, arg, ret);
err_unlocked:
trace_binder_ioctl_done(ret);
return ret;
}
binder_get_thread获取当前进程中的线程信息，如果没有，则创建一个binder_thread，并初始化
static struct binder_thread *binder_get_thread(struct binder_proc *proc)
{
struct binder_thread *thread;
struct binder_thread *new_thread;
binder_inner_proc_lock(proc);
thread = binder_get_thread_ilocked(proc, NULL);
binder_inner_proc_unlock(proc);
if (!thread) {
new_thread = kzalloc(sizeof(*thread), GFP_KERNEL);
if (new_thread == NULL)
return NULL;
binder_inner_proc_lock(proc);
thread = binder_get_thread_ilocked(proc, new_thread);
binder_inner_proc_unlock(proc);
if (thread != new_thread)
kfree(new_thread);
}
return thread;
}
