1. 打开驱动
struct binder_state *bs;
bs = binder_open(128*1024);
2. 注册为管家
binder_become_context_manager(bs)
3. 开启循环接受和解析数据
sehandle = selinux_android_service_context_handle();
binder_loop(bs, svcmgr_handler);
1. 打开驱动
binder_open
2. 注册到servicemanager
binder_call(bs, &msg, &reply, target, SVC_MGR_ADD_SERVICE)
3. 开启循环接受和解析数据
int res;
struct binder_write_read bwr;
struct {
uint32_t cmd;
struct binder_transaction_data txn;
} __attribute__((packed)) writebuf;
unsigned readbuf[32];
writebuf.cmd = BC_TRANSACTION;
writebuf.txn.target.handle = target;
writebuf.txn.code = code;
writebuf.txn.flags = 0;
writebuf.txn.data_size = msg->data - msg->data0;
writebuf.txn.offsets_size = ((char*) msg->offs) - ((char*) msg->offs0);
writebuf.txn.data.ptr.buffer = (uintptr_t)msg->data0;
writebuf.txn.data.ptr.offsets = (uintptr_t)msg->offs0;
bwr.write_size = sizeof(writebuf);
bwr.write_consumed = 0;
bwr.write_buffer = (uintptr_t) &writebuf;
for (;;) {
res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
res = binder_parse(bs, reply, (uintptr_t) readbuf, bwr.read_consumed, 0);
}
1. 打开驱动
binder_open
2. 从servicemanager获取到server handler
binder_call(bs, &msg, &reply, target, SVC_MGR_CHECK_SERVICE)
3. 传递数据
binder_call(g_bs, &msg, &reply, g_hello_handle, HELLO_SVR_CMD_SAYHELLO_TO)
4. 拿到返回数据
ptr = bio_get_ref(&reply);
数据传输
client--->service
client
- client 构造参数 binder_write_read
struct binder_write_read {
binder_size_t write_size; /* bytes to write */
binder_size_t write_consumed; /* bytes consumed by driver */
binder_uintptr_t write_buffer;
binder_size_t read_size; /* bytes to read */
binder_size_t read_consumed; /* bytes consumed by driver */
binder_uintptr_t read_buffer;
};
1.1. binder_write_read内部结构writebuf标识binder驱动执行的cmd(BC_TRANSACTION/BC_ENTER_LOOPER)和相关具体数据binder_transaction_data
struct {
// BC_TRANSACTION/BC_ENTER_LOOPER
uint32_t cmd;
struct binder_transaction_data txn;
} __attribute__((packed)) writebuf;
1.2 writebuf内结构体binder_transaction_data标识目标服务，目标函数以及参数等,code代表具体执行的函数标识，比如add_service,check_service,buffer代表参数
struct binder_transaction_data {
/* The first two are only used for bcTRANSACTION and brTRANSACTION,
* identifying the target and contents of the transaction.
*/
union {
/* target descriptor of command transaction */
__u32 handle;
/* target descriptor of return transaction */
binder_uintptr_t ptr;
} target;
binder_uintptr_t cookie; /* target object cookie */
__u32 code; /* transaction command */
/* General information about the transaction. */
__u32 flags;
pid_t sender_pid;
uid_t sender_euid;
binder_size_t data_size; /* number of bytes of data */
binder_size_t offsets_size; /* number of bytes of offsets */
/* If this transaction is inline, the data immediately
* follows here; otherwise, it ends with a pointer to
* the data buffer.
*/
union {
struct {
/* transaction data */
binder_uintptr_t buffer;
/* offsets from buffer to flat_binder_object structs */
binder_uintptr_t offsets;
} ptr;
__u8 buf[8];
} data;
};
- 通过ioctl发送数据
res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
- 解析返回数据
res = binder_parse(bs, reply, (uintptr_t) readbuf, bwr.read_consumed, 0);
int binder_call(struct binder_state *bs,
struct binder_io *msg, struct binder_io *reply,
uint32_t target, uint32_t code)
{
int res;
struct binder_write_read bwr;
struct {
uint32_t cmd;
struct binder_transaction_data txn;
} __attribute__((packed)) writebuf;
unsigned readbuf[32];
writebuf.cmd = BC_TRANSACTION;
writebuf.txn.target.handle = target;
writebuf.txn.code = code;
writebuf.txn.flags = 0;
writebuf.txn.data_size = msg->data - msg->data0;
writebuf.txn.offsets_size = ((char*) msg->offs) - ((char*) msg->offs0);
writebuf.txn.data.ptr.buffer = (uintptr_t)msg->data0;
writebuf.txn.data.ptr.offsets = (uintptr_t)msg->offs0;
bwr.write_size = sizeof(writebuf);
bwr.write_consumed = 0;
bwr.write_buffer = (uintptr_t) &writebuf;
for (;;) {
bwr.read_size = sizeof(readbuf);
bwr.read_consumed = 0;
bwr.read_buffer = (uintptr_t) readbuf;
res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
if (res < 0) {
fprintf(stderr,"binder: ioctl failed (%s)\n", strerror(errno));
goto fail;
}
res = binder_parse(bs, reply, (uintptr_t) readbuf, bwr.read_consumed, 0);
if (res == 0) return 0;
if (res < 0) goto fail;
}
}
service端
- 注册到servicemanager
- 开启循环接受数据
- 通过ioctl接受到数据解析成
binder_write_read - 通过
binder_write_read的cmd和readbuf执行对应的函数, 会把readbuf转成binder_transaction_data,具体代码查看
service代码
//开启循环
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));
for (;;) {
bwr.read_size = sizeof(readbuf);
bwr.read_consumed = 0;
bwr.read_buffer = (uintptr_t) readbuf;
res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
res = binder_parse(bs, 0, (uintptr_t) readbuf, bwr.read_consumed, func);
//...
}
}
//参数解析
int binder_parse(struct binder_state *bs, struct binder_io *bio,
uintptr_t ptr, size_t size, binder_handler func)
{
int r = 1;
uintptr_t end = ptr + (uintptr_t) size;
while (ptr < end) {
uint32_t cmd = *(uint32_t *) ptr;
ptr += sizeof(uint32_t);
switch(cmd) {
//...
case BR_TRANSACTION: {
struct binder_transaction_data *txn = (struct binder_transaction_data *) ptr;
//...
if (func) {
unsigned rdata[256/4];
struct binder_io msg;
struct binder_io reply;
int res;
bio_init(&reply, rdata, sizeof(rdata), 4);
bio_init_from_txn(&msg, txn);
res = func(bs, txn, &msg, &reply);
binder_send_reply(bs, &reply, txn->data.ptr.buffer, res);
}
ptr += sizeof(*txn);
break;
}
case BR_REPLY: {
struct binder_transaction_data *txn = (struct binder_transaction_data *) ptr;
//...
break;
}
//...
}
return r;
}
示例demo :github
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