Android : 跟我学Binder --- (3) C程序示例
目录：
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Android : 跟我学Binder --- (1) 什么是Binder IPC？为何要使用Binder机制？
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Android : 跟我学Binder --- (2) AIDL分析及手动实现
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Android : 跟我学Binder --- (3) C程序示例
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Android : 跟我学Binder --- (4) 驱动情景分析
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Android : 跟我学Binder --- (5) C++实现
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Android : 跟我学Binder --- (6) JAVA实现
一、Binder框架分析
1、IPC、LPC和RPC的概念：
IPC: （Inter Process Communication ）跨进程通信，泛指进程之间任何形式的通信行为，它不仅包括各种形式的消息传递，还可以指共享资源，以及同步对象；
LPC: （Local Procedure Call ）本地过程调用，用在多任务操作系统中，使得同时运行的任务能互相会话。这些任务共享内存空间使任务同步和互相发送信息；（IPC的封装）
RPC:（Reomote Procedure Call ）远程过程调用，类似于LPC，只是在网上工作。RPC开始是出现在Sun微系统公司和HP公司的运行UNIX操作系统的计算机中；
2、通信架构：
Client/Server <---> service manager 交互流程：
server ---------addservice-------> service manager
client ---------getservice--------> service manager
注：ServiceManager首先向binder驱动注册为服务管理者，handle为0；
3、简析示例代码(非完整流程)：
①android_5.0.2_32\frameworks\native\cmds\servicemanager\service_manager.c //管理server注册的服务（进程）
a. binder_open //打开驱动 b. binder_become_context_manager //告诉驱动注册为service manager c. binder_loop(bs, svcmgr_handler); c.1 res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr); //读数据 c.2 binder_parse // 解析数据 /*处理数据 : svcmgr_handler*/ SVC_MGR_GET_SERVICE/SVC_MGR_CHECK_SERVICE : 获取服务 SVC_MGR_ADD_SERVICE : 注册服务 /*有必要则回复数据*/
.......
②android_5.0.2_32\frameworks\native\cmds\servicemanager\bctest.c //client测试代码
注册服务的过程: a. binder_open //打开驱动 b. svcmgr_publish //构造数据 c. binder_call(bs, &msg, &reply, 0, SVC_MGR_ADD_SERVICE) // 含有服务的名字 // 它会含有servicemanager回复的数据 // 0表示servicemanager // code: 表示要调用servicemanager中的"addservice函数" 获取服务的过程: a. binder_open //打开驱动
b. svcmgr_lookup //构造数据
c. binder_call(bs, &msg, &reply, 0, SVC_MGR_CHECK_SERVICE) // 含有服务的名字 // 它会含有servicemanager回复的数据, 表示提供服务的进程 // 0表示servicemanager // code: 表示要调用servicemanager中的"getservice函数
③android_5.0.2_32\frameworks\native\cmds\servicemanager\binder.c //封装好的C函数
（1）构造参数：放在一个buffer用binder_io来描述；
unsigned iodata[512/4]; //用binder_io来管理这个缓冲区 struct binder_io msg, reply; ... bio_init(&msg, iodata, sizeof(iodata), 4); //初始化binder_io对象 /*可以放入各类型参数，反之通过get方法获取*/ bio_put_uint32(&msg, 0); // strict mode header bio_put_string16_x(&msg, SVC_MGR_NAME); bio_put_string16_x(&msg, name); bio_put_obj(&msg, ptr); ... /*调用binder_call(struct binder_state *bs, struct binder_io *msg/*提供参数*/, struct binder_io *reply/*获得回复*/, uint32_t target/*发送对象*/, uint32_t code/*调用函数*/)*/ if (binder_call(bs, &msg, &reply, target, SVC_MGR_ADD_SERVICE)) return -1;
（2）根据 binder_io、target、code 构造writebuf:
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;
其中binder_write_read 结构体在内核代码中的定义：
struct binder_write_read {
signed long write_size; /* bytes to write */
signed long write_consumed; /* bytes consumed by driver */
unsigned long write_buffer;
signed long read_size; /* bytes to read */
signed long read_consumed; /* bytes consumed by driver */
unsigned long read_buffer;
};
其中binder_transaction_data结构体在内核代码中的定义：
struct binder_transaction_data { /* The first two are only used for bcTRANSACTION and brTRANSACTION, * identifying the target and contents of the transaction. */ union { size_t handle; /* target descriptor of command transaction */ void *ptr; /* target descriptor of return transaction */ } target; void *cookie; /* target object cookie */ unsigned int code; /* transaction command */ /* General information about the transaction. */ unsigned int flags; pid_t sender_pid; uid_t sender_euid; size_t data_size; /* number of bytes of data */ 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 */ const void *buffer; /* offsets from buffer to flat_binder_object structs */ const void *offsets; } ptr; uint8_t buf[8]; } data; };
（3）通过ioctl发送数据：
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); //解析返回的数据 if (res == 0) return 0; if (res < 0) goto fail; }
框架流程总结：
client端： binder_open ---> 获得服务handle ---> 构造参数binder_io ---> 调用binder_call ---> 解析返回的binder_io；
server端：binder_open ---> 注册服务 ---> ioctl读取数据（binder_write_read ）---> 解析数据（binder_transaction_data ） ---> 获得binder_io并根据code调用对应函数 ---> 把返回值发送给client；
二、编写程序
1.参考service_manager.c编写test_server.c添加服务：
/* Copyright 2008 The Android Open Source Project */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <linux/types.h> #include<stdbool.h> #include <string.h> #include <private/android_filesystem_config.h> #include "binder.h" #include "test_server.h" int svcmgr_publish(struct binder_state *bs, uint32_t target, const char *name, void *ptr) { int status; unsigned iodata[512/4]; struct binder_io msg, reply; bio_init(&msg, iodata, sizeof(iodata), 4); bio_put_uint32(&msg, 0); // strict mode header bio_put_string16_x(&msg, SVC_MGR_NAME); bio_put_string16_x(&msg, name); bio_put_obj(&msg, ptr); if (binder_call(bs, &msg, &reply, target, SVC_MGR_ADD_SERVICE)) return -1; status = bio_get_uint32(&reply); binder_done(bs, &msg, &reply); return status; } void sayhello(void) { static int cnt = 0; fprintf(stderr, "say hello : %d\n", ++cnt); } int sayhello_to(char *name) { static int cnt = 0; fprintf(stderr, "say hello to %s : %d\n", name, ++cnt); return cnt; } void saygoodbye(void) { static int cnt = 0; fprintf(stderr, "say goodbye : %d\n", ++cnt); } int saygoodbye_to(char *name) { static int cnt = 0; fprintf(stderr, "say goodbye to %s : %d\n", name, ++cnt); return cnt; } int hello_service_handler(struct binder_state *bs, struct binder_transaction_data *txn, struct binder_io *msg, struct binder_io *reply) { /* 根据txn->code知道要调用哪一个函数 * 如果需要参数, 可以从msg取出 * 如果要返回结果, 可以把结果放入reply */ /* sayhello * sayhello_to */ uint16_t *s; char name[512]; size_t len; uint32_t handle; uint32_t strict_policy; int i; // Equivalent to Parcel::enforceInterface(), reading the RPC // header with the strict mode policy mask and the interface name. // Note that we ignore the strict_policy and don't propagate it // further (since we do no outbound RPCs anyway). strict_policy = bio_get_uint32(msg); // 取出0，后面才是传过来的所需数据 switch(txn->code) { case HELLO_SVR_CMD_SAYHELLO: sayhello(); bio_put_uint32(reply, 0); /* no exception */ return 0; case HELLO_SVR_CMD_SAYHELLO_TO: /* 从msg里取出字符串（16位转8位） */ s = bio_get_string16(msg, &len); //"IHelloService" s = bio_get_string16(msg, &len); // name if (s == NULL) { return -1; } for (i = 0; i < len; i++) name[i] = s[i]; name[i] = '\0'; /* 处理 */ i = sayhello_to(name); /* 把结果放入reply */ bio_put_uint32(reply, 0); /* no exception */ bio_put_uint32(reply, i); break; default: fprintf(stderr, "unknown code %d\n", txn->code); return -1; } return 0; } int goodbye_service_handler(struct binder_state *bs, struct binder_transaction_data *txn, struct binder_io *msg, struct binder_io *reply) { /* 根据txn->code知道要调用哪一个函数 * 如果需要参数, 可以从msg取出 * 如果要返回结果, 可以把结果放入reply */ /* sayhello * sayhello_to */ uint16_t *s; char name[512]; size_t len; uint32_t handle; uint32_t strict_policy; int i; // Equivalent to Parcel::enforceInterface(), reading the RPC // header with the strict mode policy mask and the interface name. // Note that we ignore the strict_policy and don't propagate it // further (since we do no outbound RPCs anyway). strict_policy = bio_get_uint32(msg); switch(txn->code) { case GOODBYE_SVR_CMD_SAYGOODBYE: saygoodbye(); bio_put_uint32(reply, 0); /* no exception */ return 0; case GOODBYE_SVR_CMD_SAYGOODBYE_TO: /* 从msg里取出字符串（16位转8位） */ s = bio_get_string16(msg, &len); //"IGoodbyeService" s = bio_get_string16(msg, &len); // name if (s == NULL) { return -1; } for (i = 0; i < len; i++) name[i] = s[i]; name[i] = '\0'; /* 处理 */ i = saygoodbye_to(name); /* 把结果放入reply */ bio_put_uint32(reply, 0); /* no exception */ bio_put_uint32(reply, i); break; default: fprintf(stderr, "unknown code %d\n", txn->code); return -1; } return 0; } int test_server_handler(struct binder_state *bs, struct binder_transaction_data *txn, struct binder_io *msg, struct binder_io *reply) { int (*handler)(struct binder_state *bs, struct binder_transaction_data *txn, struct binder_io *msg, struct binder_io *reply); handler = (int (*)(struct binder_state *bs, struct binder_transaction_data *txn, struct binder_io *msg, struct binder_io *reply))txn->target.ptr; return handler(bs, txn, msg, reply); } int main(int argc, char **argv) { int fd; struct binder_state *bs; uint32_t svcmgr = BINDER_SERVICE_MANAGER; uint32_t handle; int ret; bs = binder_open(128*1024); if (!bs) { fprintf(stderr, "failed to open binder driver\n"); return -1; } /* add service */ ret = svcmgr_publish(bs, svcmgr, "hello", hello_service_handler); //第三个参数值需要唯一，obj->binder = (uintptr_t)ptr; if (ret) { fprintf(stderr, "failed to publish hello service\n"); return -1; } ret = svcmgr_publish(bs, svcmgr, "goodbye", goodbye_service_handler); if (ret) { fprintf(stderr, "failed to publish goodbye service\n"); } binder_set_maxthreads(bs, 10); /* //binder_loop已封装如下步骤： while (1) { /* read data */ /* parse data, and process */ /* reply */ } */ binder_loop(bs, test_server_handler); //通过函数test_server_handler处理消息 return 0; }
test_server.h :
#ifndef _TEST_SERVER_H #define _TEST_SERVER_H #define HELLO_SVR_CMD_SAYHELLO 1 #define HELLO_SVR_CMD_SAYHELLO_TO 2 #define GOODBYE_SVR_CMD_SAYGOODBYE 1 #define GOODBYE_SVR_CMD_SAYGOODBYE_TO 2 #endif // _TEST_SERVER_H
2.编写test_client.c获得/使用服务：
/* Copyright 2008 The Android Open Source Project */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <linux/types.h> #include<stdbool.h> #include <string.h> #include <private/android_filesystem_config.h> #include "binder.h" #include "test_server.h" uint32_t svcmgr_lookup(struct binder_state *bs, uint32_t target, const char *name) { uint32_t handle; unsigned iodata[512/4]; struct binder_io msg, reply; bio_init(&msg, iodata, sizeof(iodata), 4); bio_put_uint32(&msg, 0); // strict mode header bio_put_string16_x(&msg, SVC_MGR_NAME); bio_put_string16_x(&msg, name); if (binder_call(bs, &msg, &reply, target, SVC_MGR_CHECK_SERVICE)) return 0; handle = bio_get_ref(&reply); if (handle) binder_acquire(bs, handle); binder_done(bs, &msg, &reply); return handle; } struct binder_state *g_bs; uint32_t g_hello_handle; uint32_t g_goodbye_handle; void sayhello(void) { unsigned iodata[512/4]; struct binder_io msg, reply; /* 构造binder_io */ bio_init(&msg, iodata, sizeof(iodata), 4); bio_put_uint32(&msg, 0); // strict mode header ,传入0 bio_put_string16_x(&msg, "IHelloService"); /* 放入参数 */ /* 调用binder_call */ if (binder_call(g_bs, &msg, &reply, g_hello_handle, HELLO_SVR_CMD_SAYHELLO)) return ; /* 从reply中解析出返回值 */ binder_done(g_bs, &msg, &reply); } /* *带参数 */ int sayhello_to(char *name) { unsigned iodata[512/4]; struct binder_io msg, reply; int ret; int exception; /* 构造binder_io */ bio_init(&msg, iodata, sizeof(iodata), 4); bio_put_uint32(&msg, 0); // strict mode header bio_put_string16_x(&msg, "IHelloService"); /* 放入参数 */ bio_put_string16_x(&msg, name); /* 调用binder_call */ if (binder_call(g_bs, &msg, &reply, g_hello_handle, HELLO_SVR_CMD_SAYHELLO_TO)) return 0; /* 从reply中解析出返回值 */ exception = bio_get_uint32(&reply); if (exception) ret = -1; else ret = bio_get_uint32(&reply); binder_done(g_bs, &msg, &reply); return ret; } void saygoodbye(void) { unsigned iodata[512/4]; struct binder_io msg, reply; /* 构造binder_io */ bio_init(&msg, iodata, sizeof(iodata), 4); bio_put_uint32(&msg, 0); // strict mode header bio_put_string16_x(&msg, "IGoodbyeService"); /* 放入参数 */ /* 调用binder_call */ if (binder_call(g_bs, &msg, &reply, g_goodbye_handle, GOODBYE_SVR_CMD_SAYGOODBYE)) return ; /* 从reply中解析出返回值 */ binder_done(g_bs, &msg, &reply); } int saygoodbye_to(char *name) { unsigned iodata[512/4]; struct binder_io msg, reply; int ret; int exception; /* 构造binder_io */ bio_init(&msg, iodata, sizeof(iodata), 4); bio_put_uint32(&msg, 0); // strict mode header bio_put_string16_x(&msg, "IGoodbyeService"); /* 放入参数 */ bio_put_string16_x(&msg, name); /* 调用binder_call */ if (binder_call(g_bs, &msg, &reply, g_goodbye_handle, GOODBYE_SVR_CMD_SAYGOODBYE_TO)) return 0; /* 从reply中解析出返回值 */ exception = bio_get_uint32(&reply); if (exception) ret = -1; else ret = bio_get_uint32(&reply); binder_done(g_bs, &msg, &reply); return ret; } /* ./test_client hello * ./test_client hello <name> */ int main(int argc, char **argv) { int fd; struct binder_state *bs; uint32_t svcmgr = BINDER_SERVICE_MANAGER; uint32_t handle; int ret; if (argc < 2){ fprintf(stderr, "Usage:\n"); fprintf(stderr, "%s <hello|goodbye>\n", argv[0]); fprintf(stderr, "%s <hello|goodbye> <name>\n", argv[0]); return -1; } bs = binder_open(128*1024); if (!bs) { fprintf(stderr, "failed to open binder driver\n"); return -1; } g_bs = bs; /* get service */ handle = svcmgr_lookup(bs, svcmgr, "goodbye"); if (!handle) { fprintf(stderr, "failed to get goodbye service\n"); return -1; } g_goodbye_handle = handle; fprintf(stderr, "Handle for goodbye service = %d\n", g_goodbye_handle); handle = svcmgr_lookup(bs, svcmgr, "hello"); if (!handle) { fprintf(stderr, "failed to get hello service\n"); return -1; } g_hello_handle = handle; fprintf(stderr, "Handle for hello service = %d\n", g_hello_handle); /* send data to server */ if (!strcmp(argv[1], "hello")) { if (argc == 2) { sayhello(); } else if (argc == 3) { ret = sayhello_to(argv[2]); fprintf(stderr, "get ret of sayhello_to = %d\n", ret); } } else if (!strcmp(argv[1], "goodbye")) { if (argc == 2) { saygoodbye(); } else if (argc == 3) { ret = saygoodbye_to(argv[2]); fprintf(stderr, "get ret of sayhello_to = %d\n", ret); } } binder_release(bs, handle); return 0; }
3.编译脚本：
（1）Makefile
APPS = service_manager test_client test_server all : $(APPS) service_manager : service_manager.o binder.o arm-linux-gcc -o $@ $^ -lpthread test_client : test_client.o binder.o arm-linux-gcc -o $@ $^ -lpthread test_server : test_server.o binder.o arm-linux-gcc -o $@ $^ -lpthread %.o : %.c arm-linux-gcc -DBINDER_IPC_32BIT=1 -I include -c -o $@ $< clean: rm $(APPS) -f; rm -f *.o
（2）Android.mk
LOCAL_PATH:= $(call my-dir) include $(CLEAR_VARS) LOCAL_CFLAGS += -DBINDER_IPC_32BIT=1 LOCAL_SRC_FILES:= service_manager.c binder.c LOCAL_C_INCLUDES += system/core/include/cutils LOCAL_MODULE:= service_manager_my include $(BUILD_EXECUTABLE) include $(CLEAR_VARS) LOCAL_CFLAGS += -DBINDER_IPC_32BIT=1 LOCAL_SRC_FILES:= test_server.c binder.c LOCAL_C_INCLUDES += system/core/include/cutils LOCAL_MODULE:= test_server include $(BUILD_EXECUTABLE) include $(CLEAR_VARS) LOCAL_CFLAGS += -DBINDER_IPC_32BIT=1 LOCAL_SRC_FILES:= test_client.c binder.c LOCAL_C_INCLUDES += system/core/include/cutils LOCAL_MODULE:= test_client include $(BUILD_EXECUTABLE)
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posted on 2018-12-23 18:10 sheldon_blogs 阅读(3090) 评论(0) 编辑 收藏 举报
