framework 学习笔记8. binder_ioctl 和服
2020-12-10 本文已影响0人
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- 几个用到binder_ioctl()的地方：(framework\native\cmd\servicemanager\binder.c)
（1）ServiceManager进程中：判断binder驱动是否一致：
if ((ioctl(bs->fd, BINDER_VERSION, &vers) == -1) ||
(vers.protocol_version != BINDER_CURRENT_PROTOCOL_VERSION)) {
fprintf(stderr, "binder: driver version differs from user space\n");
goto fail_open;
}
（2）ServiceManager进程中：ServiceManager进程成为管理者：
static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
int ret;
//binder_open()中创建的proc
struct binder_proc *proc = filp->private_data;
struct binder_thread *thread;
unsigned int size = _IOC_SIZE(cmd);
void __user *ubuf = (void __user *)arg;
//查询获取 binder_thread 见注释1
thread = binder_get_thread(proc);
if (thread == NULL) {
ret = -ENOMEM;
goto err;
}
switch (cmd) {
case BINDER_SET_CONTEXT_MGR:
ret = binder_ioctl_set_ctx_mgr(filp); // 见注释2
if (ret)
goto err;
break;
case BINDER_VERSION: {
struct binder_version __user *ver = ubuf;
// 把版本号 拷贝 给 sm进程中的&vers；
if (put_user(BINDER_CURRENT_PROTOCOL_VERSION,
&ver->protocol_version)) {
ret = -EINVAL;
goto err;
}
break;
}
return ret;
}
注释1：
static struct binder_thread *binder_get_thread(struct binder_proc *proc)
{
struct binder_thread *thread = NULL;
struct rb_node *parent = NULL;
struct rb_node **p = &proc->threads.rb_node;
while (*p) {
parent = *p;
//通过proc结构体中rb_node找到binder_threads
thread = rb_entry(parent, struct binder_thread, rb_node);
if (current->pid < thread->pid)
p = &(*p)->rb_left;
else if (current->pid > thread->pid)
p = &(*p)->rb_right;
else
break;
}
if (*p == NULL) {
// 第一次pid创建对象
thread = kzalloc(sizeof(*thread), GFP_KERNEL);
if (thread == NULL)
return NULL;
binder_stats_created(BINDER_STAT_THREAD);
thread->proc = proc;
// current线程
thread->pid = current->pid;
//初始化等待队列和工作队列
init_waitqueue_head(&thread->wait);
INIT_LIST_HEAD(&thread->todo);
//插入到当前进程线程列表的红黑树；
rb_link_node(&thread->rb_node, parent, p);
//调整红黑树的颜色；
rb_insert_color(&thread->rb_node, &proc->threads);
thread->looper |= BINDER_LOOPER_STATE_NEED_RETURN;
}
return thread;
}
注释2：
static int binder_ioctl_set_ctx_mgr(struct file *filp)
{
int ret = 0;
struct binder_proc *proc = filp->private_data;
kuid_t curr_euid = current_euid();
// 判断静态的 binder_context_mgr_node 是否设置过，只能设置过一次(只能有一个应用成为管理者)
if (binder_context_mgr_node != NULL) {
pr_err("BINDER_SET_CONTEXT_MGR already set\n");
ret = -EBUSY;
goto out;
}
// ...省略部分代码
//创建一个binder_node
binder_context_mgr_node = binder_new_node(proc, 0, 0);
if (binder_context_mgr_node == NULL) {
ret = -ENOMEM;
goto out;
}
binder_context_mgr_node->local_weak_refs++;
binder_context_mgr_node->local_strong_refs++;
binder_context_mgr_node->has_strong_ref = 1;
binder_context_mgr_node->has_weak_ref = 1;
out:
return ret;
}
- ServiceManager是如何进入等待的：
（2.1）ServiceManager进程中：设置binder线程进入循环等待(还未进入循环等待的状态)，binder_loop(bs, svcmgr_handler)中的
readbuf[0] = BC_ENTER_LOOPER;
binder_write(bs, readbuf, sizeof(uint32_t));
主要在以上两行代码中实现；
（2.2）ServiceManager进程中：进入循环不断读写 binder 的内容，即for(; ;)循环中的内容
void binder_loop(struct binder_state *bs, binder_handler func)
{
int res;
struct binder_write_read bwr;
uint32_t readbuf[32];
bwr.write_size = 0;
bwr.write_consumed = 0;
bwr.write_buffer = 0;
readbuf[0] = BC_ENTER_LOOPER;
binder_write(bs, readbuf, sizeof(uint32_t)); //见注释3
for (;;) {
bwr.read_size = sizeof(readbuf);
bwr.read_consumed = 0;
bwr.read_buffer = (uintptr_t) readbuf;
res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr); //见注释4
if (res < 0) {
ALOGE("binder_loop: ioctl failed (%s)\n", strerror(errno));
break;
}
res = binder_parse(bs, 0, (uintptr_t) readbuf, bwr.read_consumed, func);
if (res == 0) {
ALOGE("binder_loop: unexpected reply?!\n");
break;
}
if (res < 0) {
ALOGE("binder_loop: io error %d %s\n", res, strerror(errno));
break;
}
}
}
注释3：在int binder_write(struct binder_state *bs, void *data, size_t len)方法中，我们可以看出调用的还是
binder_ioctl(bs->fd, BINDER_WRITE_READ, &bwr)这个方法；
int binder_write(struct binder_state *bs, void *data, size_t len){
struct binder_write_read bwr;
int res;
bwr.write_size = len;
bwr.write_consumed = 0;
bwr.write_buffer = (uintptr_t) data;
bwr.read_size = 0;
bwr.read_consumed = 0;
bwr.read_buffer = 0;
res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
if (res < 0) {
fprintf(stderr,"binder_write: ioctl failed (%s)\n",
strerror(errno));
}
return res;
}
/*** binder_ioctl(bs->fd, BINDER_WRITE_READ, &bwr) 的实现：==> 也就是调用binder_ioctl_write_read()方法；
case BINDER_WRITE_READ:
ret = binder_ioctl_write_read(filp, cmd, arg, thread); // 见注释4
if (ret)
goto err;
break;
***/
注释4：
static int binder_ioctl_write_read(struct file *filp,
unsigned int cmd, unsigned long arg,
struct binder_thread *thread)
{
int ret = 0;
struct binder_proc *proc = filp->private_data;
unsigned int size = _IOC_SIZE(cmd);
void __user *ubuf = (void __user *)arg;
struct binder_write_read bwr;
// 把数据 ubuf (其实就是binder_write_read ) 复制到 bwr；
if (copy_from_user(&bwr, ubuf, sizeof(bwr))) {
ret = -EFAULT;
goto out;
}
binder_debug(BINDER_DEBUG_READ_WRITE,
"%d:%d write %lld at %016llx, read %lld at %016llx\n",
proc->pid, thread->pid,
(u64)bwr.write_size, (u64)bwr.write_buffer,
(u64)bwr.read_size, (u64)bwr.read_buffer);
if (bwr.write_size > 0) {
// 本次调用未 进入 此分支
}
if (bwr.read_size > 0) {
// 在此方法中进行读操作，见注释5
ret = binder_thread_read(proc, thread, bwr.read_buffer,
bwr.read_size,
&bwr.read_consumed,
filp->f_flags & O_NONBLOCK);
trace_binder_read_done(ret);
if (!list_empty(&proc->todo))
wake_up_interruptible(&proc->wait);
if (ret < 0) {
if (copy_to_user(ubuf, &bwr, sizeof(bwr))) //如果失败了，把bwr中的数据拷回去，还原；
ret = -EFAULT;
goto out;
}
}
if (copy_to_user(ubuf, &bwr, sizeof(bwr))) {
ret = -EFAULT;
goto out;
}
out:
return ret;
}
注释5：
static int binder_thread_read(struct binder_proc *proc,
struct binder_thread *thread,
binder_uintptr_t binder_buffer, size_t size,
binder_size_t *consumed, int non_block)
{
void __user *buffer = (void __user *)(uintptr_t)binder_buffer;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;
int ret = 0;
int wait_for_proc_work;
retry:
// for循环中第一次进入 为true;
wait_for_proc_work = thread->transaction_stack == NULL &&
list_empty(&thread->todo);
// ...
// 改变状态
thread->looper |= BINDER_LOOPER_STATE_WAITING;
if (wait_for_proc_work)
proc->ready_threads++;
binder_unlock(__func__);
trace_binder_wait_for_work(wait_for_proc_work,
!!thread->transaction_stack,
!list_empty(&thread->todo));
if (wait_for_proc_work) {
//BINDER_LOOPER_STATE_ENTERED为1，thread->looper为1，不进该分支
if (!(thread->looper & (BINDER_LOOPER_STATE_REGISTERED |BINDER_LOOPER_STATE_ENTERED))) {
//...
}
binder_set_nice(proc->default_priority);
if (non_block) { // 非阻塞
if (!binder_has_proc_work(proc, thread))
ret = -EAGAIN;
} else
//关键代码：要不要进入等待，ServiceManager进入等待状态；唤醒：则是todo队列里有东西时唤醒；
ret = wait_event_freezable_exclusive(proc->wait, binder_has_proc_work(proc, thread));
} else {
// ...
}
// ...
return 0;
}
- 服务的添加过程binder_ioctl()：media服务的添加(数据 流向 在笔记5中有详细的介绍) 和 目标进程的唤醒
do {
//调用驱动层的binder_ioctl()方法
if (ioctl(mProcess->mDriverFD, BINDER_WRITE_READ, &bwr) >= 0)
err = NO_ERROR;
else
err = -errno;
} while (err == -EINTR);
==》驱动层binder.c中：binder_ioctl();
==》驱动层binder.c中：binder_ioctl_write_read();
==》驱动层binder.c中：写命令binder_thread_write()；//注释6
==》驱动层binder.c中：binder_transaction(proc, thread, &tr, cmd == BC_REPLY); //注释7
注释6
static int binder_thread_write(struct binder_proc *proc,
struct binder_thread *thread,
binder_uintptr_t binder_buffer, size_t size,
binder_size_t *consumed){
uint32_t cmd;
void __user *buffer = (void __user *)(uintptr_t)binder_buffer;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;
while (ptr < end && thread->return_error == BR_OK) {
if (get_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
switch (cmd) {
//...
//进入此处
case BC_TRANSACTION:
case BC_REPLY: {
struct binder_transaction_data tr;
//把ptr(binder_transaction_data)的数据复制到tr
if (copy_from_user(&tr, ptr, sizeof(tr)))
return -EFAULT;
ptr += sizeof(tr);
binder_transaction(proc, thread, &tr, cmd == BC_REPLY); //见 注释 7
break;
}
//...
}
return 0;
}
注释7：简化代码
static void binder_transaction(struct binder_proc *proc,
struct binder_thread *thread,
struct binder_transaction_data *tr, int reply){
struct binder_transaction *t;
struct binder_work *tcomplete;
binder_size_t *offp, *off_end;
// 目标进程的 binder_proc
struct binder_proc *target_proc;
// 目标进程的 binder_thread
struct binder_thread *target_thread = NULL;
// 目标进程的 binder_node
struct binder_node *target_node = NULL;
// 目标进程的 todo 队列
struct list_head *target_list;
// 目标进程的 等待
wait_queue_head_t *target_wait;
struct binder_transaction *in_reply_to = NULL;
struct binder_transaction_log_entry *e;
e->call_type = reply ? 2 : !!(tr->flags & TF_ONE_WAY);
e->from_proc = proc->pid;
e->from_thread = thread->pid;
// handle 值为 0
e->target_handle = tr->target.handle;
e->data_size = tr->data_size;
e->offsets_size = tr->offsets_size;
if (reply) {
//...
} else {
if (tr->target.handle) {
//...
} else {
// 这里的分支是handle == 0，target_node 赋值，即之前ServiceManager成为管理者时的静态变量；
target_node = binder_context_mgr_node;
}
// 获取到ServiceManager的proc
target_proc = target_node->proc;
}
if (target_thread) {
e->to_thread = target_thread->pid;
target_list = &target_thread->todo;
target_wait = &target_thread->wait;
} else {
target_list = &target_proc->todo;
target_wait = &target_proc->wait;
}
/* TODO: reuse incoming transaction for reply */
// 创建两个结构体
t = kzalloc(sizeof(*t), GFP_KERNEL);
tcomplete = kzalloc(sizeof(*tcomplete), GFP_KERNEL);
// TF_ONE_WAY：表示写过来的数据是不是需要等待回复
// binder驱动记录数据的来源
if (!reply && !(tr->flags & TF_ONE_WAY))
t->from = thread; //执行此句 分支代码
else
t->from = NULL;
// ...
trace_binder_transaction(reply, t, target_node);
// 按需加载 在目标进程 开辟 管理 映射内存；我们在mmap()时只映射了 一个物理页；现在根据传入的数据开辟多大的内存
t->buffer = binder_alloc_buf(target_proc, tr->data_size,tr->offsets_size, !reply && (t->flags & TF_ONE_WAY));
if (t->buffer == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_alloc_buf_failed;
}
t->buffer->allow_user_free = 0;
t->buffer->debug_id = t->debug_id;
t->buffer->transaction = t;
t->buffer->target_node = target_node;
trace_binder_transaction_alloc_buf(t->buffer);
//...
offp = (binder_size_t *)(t->buffer->data +ALIGN(tr->data_size, sizeof(void *)));
// 把数据拷贝到目标进程；t->buffer->data：新开辟的目标进程的地址 tr->data.ptr.buffer：客户端数据
if (copy_from_user(t->buffer->data, (const void __user *)(uintptr_t)tr->data.ptr.buffer, tr->data_size)) {
binder_user_error("%d:%d got transaction with invalid data ptr\n",proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
goto err_copy_data_failed;
}
if (copy_from_user(offp, (const void __user *)(uintptr_t)
tr->data.ptr.offsets, tr->offsets_size)) {
binder_user_error("%d:%d got transaction with invalid offsets ptr\n",
proc->pid, thread->pid);
return_error = BR_FAILED_REPLY;
goto err_copy_data_failed;
}
//循环处理 客户端传递的 flat_binder_object 数据
off_end = (void *)offp + tr->offsets_size;
for (; offp < off_end; offp++) {
struct flat_binder_object *fp;
fp = (struct flat_binder_object *)(t->buffer->data + *offp);
switch (fp->type) {
case BINDER_TYPE_BINDER:
case BINDER_TYPE_WEAK_BINDER: {
struct binder_ref *ref;
// 对照笔记5中数据流向图可知 fp 是service对象的弱应用，通过客户端binder地址从自己的进程中找binder_node
struct binder_node *node = binder_get_node(proc, fp->binder);
if (node == NULL) {
// 第一次的时候为空，那么就在本进程中创建一个 binder_node
node = binder_new_node(proc, fp->binder, fp->cookie);
if (node == NULL) {
return_error = BR_FAILED_REPLY;
goto err_binder_new_node_failed;
}
node->min_priority = fp->flags & FLAT_BINDER_FLAG_PRIORITY_MASK;
node->accept_fds = !!(fp->flags & FLAT_BINDER_FLAG_ACCEPTS_FDS);
}
if (fp->cookie != node->cookie) {
binder_user_error("%d:%d sending u%016llx node %d, cookie mismatch %016llx != %016llx\n",
proc->pid, thread->pid,
(u64)fp->binder, node->debug_id,
(u64)fp->cookie, (u64)node->cookie);
return_error = BR_FAILED_REPLY;
goto err_binder_get_ref_for_node_failed;
}
ref = binder_get_ref_for_node(target_proc, node);
//替换 tpye ==》BINDER_TYPE_HANDLE
if (fp->type == BINDER_TYPE_BINDER)
fp->type = BINDER_TYPE_HANDLE;
else
fp->type = BINDER_TYPE_WEAK_HANDLE; //此句分支 不执行
//计算赋值handle，从1开始，累加1 ==》binder_get_ref_for_node()方法中
fp->handle = ref->desc;
binder_inc_ref(ref, fp->type == BINDER_TYPE_HANDLE,
&thread->todo);
trace_binder_transaction_node_to_ref(t, node, ref);
} break;
}
if (reply) {
//...
} else if (!(t->flags & TF_ONE_WAY)) {
// 不是TF_ONE_WAY；
BUG_ON(t->buffer->async_transaction != 0);
// 需要回复
t->need_reply = 1;
// 记录了from_parent
t->from_parent = thread->transaction_stack;
// 记录了transaction_stack
thread->transaction_stack = t;
} else {
//...
} else
target_node->has_async_transaction = 1;
}
// 目标进程，往目标进程 todo 队列 中添加了一个t->work.entry
t->work.type = BINDER_WORK_TRANSACTION;
list_add_tail(&t->work.entry, target_list);
//本进程，往本进程 中添加了一个t->work.entry，然后会向客户端进程发送一条BR_TRANSACTION_COMPLETE
tcomplete->type = BINDER_WORK_TRANSACTION_COMPLETE;
list_add_tail(&tcomplete->entry, &thread->todo);
// 唤醒target_wait
if (target_wait)
wake_up_interruptible(target_wait);
return;
}
- 进程唤醒处理数据：
static int binder_thread_read(struct binder_proc *proc,
struct binder_thread *thread,
binder_uintptr_t binder_buffer, size_t size,
binder_size_t *consumed, int non_block)
{
void __user *buffer = (void __user *)(uintptr_t)binder_buffer;
void __user *ptr = buffer + *consumed;
void __user *end = buffer + size;
if (thread->return_error != BR_OK && ptr < end) {
if (thread->return_error2 != BR_OK) {
} else
ret = wait_event_freezable_exclusive(proc->wait, binder_has_proc_work(proc, thread)); //在此处等待
} else {
}
if (ret)
return ret;
while (1) {
uint32_t cmd;
struct binder_transaction_data tr;
struct binder_work *w;
struct binder_transaction *t = NULL;
if (!list_empty(&thread->todo)) { //唤醒了
w = list_first_entry(&thread->todo, struct binder_work, entry);
} else if (!list_empty(&proc->todo) && wait_for_proc_work) {
} else {
/* no data added */
}
if (end - ptr < sizeof(tr) + 4)
break;
switch (w->type) {
case BINDER_WORK_TRANSACTION: // 目标进程，往目标进程 todo 队列 中添加了一个t->work.entry 后
t = container_of(w, struct binder_transaction, work);
break;
if (!t)
continue;
BUG_ON(t->buffer == NULL);
if (t->buffer->target_node) {
struct binder_node *target_node = t->buffer->target_node;
tr.target.ptr = target_node->ptr; // 0
tr.cookie = target_node->cookie; // 0
t->saved_priority = task_nice(current);
if (t->priority < target_node->min_priority &&!(t->flags & TF_ONE_WAY))
binder_set_nice(t->priority);
else if (!(t->flags & TF_ONE_WAY) ||t->saved_priority > target_node->min_priority)
binder_set_nice(target_node->min_priority);
cmd = BR_TRANSACTION;
} else {
tr.target.ptr = 0;
tr.cookie = 0;
cmd = BR_REPLY;
}
tr.code = t->code;
//...
tr.data_size = t->buffer->data_size;
tr.offsets_size = t->buffer->offsets_size;
tr.data.ptr.buffer = (binder_uintptr_t)(
(uintptr_t)t->buffer->data +
proc->user_buffer_offset);
tr.data.ptr.offsets = tr.data.ptr.buffer +
ALIGN(t->buffer->data_size,
sizeof(void *));
// 1. 首先把命令cmd = BR_TRANSACTION 写到ptr ，readbuffer
if (put_user(cmd, (uint32_t __user *)ptr))
return -EFAULT;
ptr += sizeof(uint32_t);
// 2. 把数据拷贝到readbuffer
ptr += sizeof(tr);
trace_binder_transaction_received(t);
binder_stat_br(proc, thread, cmd);
list_del(&t->work.entry);
t->buffer->allow_user_free = 1;
if (cmd == BR_TRANSACTION && !(t->flags & TF_ONE_WAY)) {
t->to_parent = thread->transaction_stack;
t->to_thread = thread;
thread->transaction_stack = t;
} else {
t->buffer->transaction = NULL;
kfree(t);
binder_stats_deleted(BINDER_STAT_TRANSACTION);
}
break;
}
return 0;
}
服务的添加过程.png
小结：
a. binder 驱动是如何找到 ServiceManager进程的？
根据handle = 0；驱动层创建了一个静态变量 binder_context_mgr_node；
b. ServiceManager进程是如何进入等待，又是怎么被唤醒的？
等待：ServiceManager执行binder_loop()中的binder_thread_read()时，会根据todo队列是否为空进行判断；
唤醒：客户端找到target_proc后，把数据拷到目标进程写入处理命令，然后往自己的进程写入一个接收请求的命令(让自己进入等待)，最后唤醒服务进程的wait队列，这个时候服务进程被唤醒并且继续todo队列中的请求；
c. 数据时如何传递的，handle和type时如何被计算和管理的？
binder驱动会判断type是什么，然后往自己的进程挂一个binder_node，往目标进程挂两个binder_node(一个以handle值为key，一个以地址为key)；handle值是根据数据进行累加的；
d. 内存的拷贝一共有几次？
不是1次；服务端把数据拷贝到内核再拷贝回去2次 + 客户端把数据拷贝到内核再拷贝回去2次 + 客户端把数据拷贝到服务端映射的内存中1次 + 服务端映射的内存拷贝到驱动层创建的内存 = 6次；
