Android binder解析及示例

Android binder解析及示例

一、ServerManager

1.ServerManager目录：

2.ServerManager执行流程：

1.打开驱动完成映射

bs = binder_open(driver, 128*1024);

2.成为服务管理者

 if (binder_become_context_manager(bs)) {
     
     //ioctl(bs->fd,BINDER_SET_CONTEXT_MGR,0),0标记为ServerManager
        ALOGE("cannot become context manager (%s)\n", strerror(errno));
        return -1;
    }

3.循环

• 1.读取数据
• 2.解析数据
• 3.回复数据

binder_loop(bs, svcmgr_handler);
/*
	for (;;) {
				1.读取数据
        res = ioctl(bs->fd, BINDER_WRITE_READ, &bwr);
        		2.解析数据
        res = binder_parse(bs, 0, (uintptr_t) readbuf, bwr.read_consumed, func);
        		3.回复数据
        binder_send_reply(bs, &reply, txn.transaction_data.data.ptr.buffer, res);
        }
*/

service_manager.c:

/* Copyright 2008 The Android Open Source Project
 */

#include 
#include 
#include 
#include 
#include 
#include 

#include 

#include 
#include 

#include "binder.h"

#if 0
#define ALOGI(x...) fprintf(stderr, "svcmgr: " x)
#define ALOGE(x...) fprintf(stderr, "svcmgr: " x)
#else
#define LOG_TAG "ServiceManager"
#include 
#endif

const char *str8(const uint16_t *x, size_t x_len)
{
     
    static char buf[128];
    size_t max = 127;
    char *p = buf;

    if (x_len < max) {
     
        max = x_len;
    }

    if (x) {
     
        while ((max > 0) && (*x != '\0')) {
     
            *p++ = *x++;
            max--;
        }
    }
    *p++ = 0;
    return buf;
}

int str16eq(const uint16_t *a, const char *b)
{
     
    while (*a && *b)
        if (*a++ != *b++) return 0;
    if (*a || *b)
        return 0;
    return 1;
}

static int selinux_enabled;
static char *service_manager_context;
static struct selabel_handle* sehandle;

static bool check_mac_perms(pid_t spid, const char *tctx, const char *perm, const char *name)
{
     
    char *sctx = NULL;
    const char *class = "service_manager";
    bool allowed;

    if (getpidcon(spid, &sctx) < 0) {
     
        ALOGE("SELinux: getpidcon(pid=%d) failed to retrieve pid context.\n", spid);
        return false;
    }

    int result = selinux_check_access(sctx, tctx, class, perm, (void *) name);
    allowed = (result == 0);

    freecon(sctx);
    return allowed;
}

static bool check_mac_perms_from_getcon(pid_t spid, const char *perm)
{
     
    if (selinux_enabled <= 0) {
     
        return true;
    }

    return check_mac_perms(spid, service_manager_context, perm, NULL);
}

static bool check_mac_perms_from_lookup(pid_t spid, const char *perm, const char *name)
{
     
    bool allowed;
    char *tctx = NULL;

    if (selinux_enabled <= 0) {
     
        return true;
    }

    if (!sehandle) {
     
        ALOGE("SELinux: Failed to find sehandle. Aborting service_manager.\n");
        abort();
    }

    if (selabel_lookup(sehandle, &tctx, name, 0) != 0) {
     
        ALOGE("SELinux: No match for %s in service_contexts.\n", name);
        return false;
    }

    allowed = check_mac_perms(spid, tctx, perm, name);
    freecon(tctx);
    return allowed;
}

static int svc_can_register(const uint16_t *name, size_t name_len, pid_t spid)
{
     
    const char *perm = "add";
    return check_mac_perms_from_lookup(spid, perm, str8(name, name_len)) ? 1 : 0;
}

static int svc_can_list(pid_t spid)
{
     
    const char *perm = "list";
    return check_mac_perms_from_getcon(spid, perm) ? 1 : 0;
}

static int svc_can_find(const uint16_t *name, size_t name_len, pid_t spid)
{
     
    const char *perm = "find";
    return check_mac_perms_from_lookup(spid, perm, str8(name, name_len)) ? 1 : 0;
}

struct svcinfo
{
     
    struct svcinfo *next;
    uint32_t handle;
    struct binder_death death;
    int allow_isolated;
    size_t len;
    uint16_t name[0];
};

struct svcinfo *svclist = NULL;

struct svcinfo *find_svc(const uint16_t *s16, size_t len)
{
     
    struct svcinfo *si;

    for (si = svclist; si; si = si->next) {
     
        if ((len == si->len) &&
            !memcmp(s16, si->name, len * sizeof(uint16_t))) {
     
            return si;
        }
    }
    return NULL;
}

void svcinfo_death(struct binder_state *bs, void *ptr)
{
     
    struct svcinfo *si = (struct svcinfo* ) ptr;

    ALOGI("service '%s' died\n", str8(si->name, si->len));
    if (si->handle) {
     
        binder_release(bs, si->handle);
        si->handle = 0;
    }
}

uint16_t svcmgr_id[] = {
     
    'a','n','d','r','o','i','d','.','o','s','.',
    'I','S','e','r','v','i','c','e','M','a','n','a','g','e','r'
};


uint32_t do_find_service(struct binder_state *bs, const uint16_t *s, size_t len, uid_t uid, pid_t spid)
{
     
    struct svcinfo *si = find_svc(s, len);

    if (!si || !si->handle) {
     
        return 0;
    }

    if (!si->allow_isolated) {
     
        // If this service doesn't allow access from isolated processes,
        // then check the uid to see if it is isolated.
        uid_t appid = uid % AID_USER;
        if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END) {
     
            return 0;
        }
    }

    if (!svc_can_find(s, len, spid)) {
     
        return 0;
    }

    return si->handle;
}

int do_add_service(struct binder_state *bs,
                   const uint16_t *s, size_t len,
                   uint32_t handle, uid_t uid, int allow_isolated,
                   pid_t spid)
{
     
    struct svcinfo *si;

    //ALOGI("add_service('%s',%x,%s) uid=%d\n", str8(s, len), handle,
    //        allow_isolated ? "allow_isolated" : "!allow_isolated", uid);

    if (!handle || (len == 0) || (len > 127))
        return -1;

    if (!svc_can_register(s, len, spid)) {
     
        ALOGE("add_service('%s',%x) uid=%d - PERMISSION DENIED\n",
             str8(s, len), handle, uid);
        return -1;
    }

    si = find_svc(s, len);
    if (si) {
     
        if (si->handle) {
     
            ALOGE("add_service('%s',%x) uid=%d - ALREADY REGISTERED, OVERRIDE\n",
                 str8(s, len), handle, uid);
            svcinfo_death(bs, si);
        }
        si->handle = handle;
    } else {
     
        si = malloc(sizeof(*si) + (len + 1) * sizeof(uint16_t));
        if (!si) {
     
            ALOGE("add_service('%s',%x) uid=%d - OUT OF MEMORY\n",
                 str8(s, len), handle, uid);
            return -1;
        }
        si->handle = handle;
        si->len = len;
        memcpy(si->name, s, (len + 1) * sizeof(uint16_t));
        si->name[len] = '\0';
        si->death.func = (void*) svcinfo_death;
        si->death.ptr = si;
        si->allow_isolated = allow_isolated;
        si->next = svclist;
        svclist = si;
    }

    binder_acquire(bs, handle);
    binder_link_to_death(bs, handle, &si->death);
    return 0;
}

int svcmgr_handler(struct binder_state *bs,
                   struct binder_transaction_data *txn,
                   struct binder_io *msg,
                   struct binder_io *reply)
{
     
    struct svcinfo *si;
    uint16_t *s;
    size_t len;
    uint32_t handle;
    uint32_t strict_policy;
    int allow_isolated;

    //ALOGI("target=%p code=%d pid=%d uid=%d\n",
    //      (void*) txn->target.ptr, txn->code, txn->sender_pid, txn->sender_euid);

    if (txn->target.ptr != BINDER_SERVICE_MANAGER)
        return -1;

    if (txn->code == PING_TRANSACTION)
        return 0;

    // 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);
    s = bio_get_string16(msg, &len);
    if (s == NULL) {
     
        return -1;
    }

    if ((len != (sizeof(svcmgr_id) / 2)) ||
        memcmp(svcmgr_id, s, sizeof(svcmgr_id))) {
     
        fprintf(stderr,"invalid id %s\n", str8(s, len));
        return -1;
    }

    if (sehandle && selinux_status_updated() > 0) {
     
        struct selabel_handle *tmp_sehandle = selinux_android_service_context_handle();
        if (tmp_sehandle) {
     
            selabel_close(sehandle);
            sehandle = tmp_sehandle;
        }
    }

    switch(txn->code) {
     
    case SVC_MGR_GET_SERVICE:
    case SVC_MGR_CHECK_SERVICE:
        s = bio_get_string16(msg, &len);
        if (s == NULL) {
     
            return -1;
        }
        handle = do_find_service(bs, s, len, txn->sender_euid, txn->sender_pid);
        if (!handle)
            break;
        bio_put_ref(reply, handle);
        return 0;

    case SVC_MGR_ADD_SERVICE:
        s = bio_get_string16(msg, &len);
        if (s == NULL) {
     
            return -1;
        }
        handle = bio_get_ref(msg);
        allow_isolated = bio_get_uint32(msg) ? 1 : 0;
        if (do_add_service(bs, s, len, handle, txn->sender_euid,
            allow_isolated, txn->sender_pid))
            return -1;
        break;

    case SVC_MGR_LIST_SERVICES: {
     
        uint32_t n = bio_get_uint32(msg);

        if (!svc_can_list(txn->sender_pid)) {
     
            ALOGE("list_service() uid=%d - PERMISSION DENIED\n",
                    txn->sender_euid);
            return -1;
        }
        si = svclist;
        while ((n-- > 0) && si)
            si = si->next;
        if (si) {
     
            bio_put_string16(reply, si->name);
            return 0;
        }
        return -1;
    }
    default:
        ALOGE("unknown code %d\n", txn->code);
        return -1;
    }

    bio_put_uint32(reply, 0);
    return 0;
}


static int audit_callback(void *data, security_class_t cls, char *buf, size_t len)
{
     
    snprintf(buf, len, "service=%s", !data ? "NULL" : (char *)data);
    return 0;
}

int main(int argc, char **argv)
{
     
    struct binder_state *bs;

    bs = binder_open(128*1024);
    if (!bs) {
     
        ALOGE("failed to open binder driver\n");
        return -1;
    }

    if (binder_become_context_manager(bs)) {
     
        ALOGE("cannot become context manager (%s)\n", strerror(errno));
        return -1;
    }

    selinux_enabled = is_selinux_enabled();
    sehandle = selinux_android_service_context_handle();
    selinux_status_open(true);

    if (selinux_enabled > 0) {
     
        if (sehandle == NULL) {
     
            ALOGE("SELinux: Failed to acquire sehandle. Aborting.\n");
            abort();
        }

        if (getcon(&service_manager_context) != 0) {
     
            ALOGE("SELinux: Failed to acquire service_manager context. Aborting.\n");
            abort();
        }
    }

    union selinux_callback cb;
    cb.func_audit = audit_callback;
    selinux_set_callback(SELINUX_CB_AUDIT, cb);
    cb.func_log = selinux_log_callback;
    selinux_set_callback(SELINUX_CB_LOG, cb);

    binder_loop(bs, svcmgr_handler);

    return 0;
}

二、server

1.打开驱动，完成映射。

2.注册服务。

3.实现循环(读取数据，解析数据，回复)。

/* Copyright 2008 The Android Open Source Project
 */
#define LOG_TAG "binder_c"

#include 
#include 
#include 
#include 
#include 
#include "binder.h"
#include "binder_c.h"
#define SERVER_TEST1 123
#define SERVER_TEST2 456
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 test1(void)
{
     
	ALOGI("this is test1 service.\n");
}

int  test2(char *name)
{
     
	ALOGI("this is test2 service.\n");
	ALOGI("name = %s.\n",name);
	return 123;
}

int server_handler(struct binder_state *bs,
                   struct binder_transaction_data *txn,
                   struct binder_io *msg,
                   struct binder_io *reply)
{
     
	char buf[128];
    uint16_t *s;
    size_t len,i;
	size_t ret;
    uint32_t handle;
    uint32_t strict_policy;
    int allow_isolated;

    // 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 SERVER_TEST1:
		test1();
        return 0;

    case SERVER_TEST2:
        //1.读取字符串
        s = bio_get_string16(msg,&len);
        //2.将字符串传递给test2
		for(i=0; i<len; i++){
     
			buf[i] = s[i];
		}
		buf[i] = '\0';
		
        ret = test2(buf);
		//3回复数据
		bio_put_uint32(reply,ret);
        break;
    default:
        ALOGE("unknown code %d\n", txn->code);
        return -1;
    }

    bio_put_uint32(reply, 0);
    return 0;
}


int main(int argc, char **argv)
{
     
    int fd;
    struct binder_state *bs;
    uint32_t svcmgr = BINDER_SERVICE_MANAGER;
    uint32_t handle;

	//1.打开驱动，完成映射
    bs = binder_open(128*1024);
    if (!bs) {
     
        fprintf(stderr, "failed to open binder driver\n");
        return -1;
    }
	//2.注册服务
					                         //服务名，服务实体
	svcmgr_publish(bs,BINDER_SERVICE_MANAGER,"binder_c","123456");


	//3.实现循环(读取数据，解析数据，回复)
	binder_loop(bs, server_handler);

    return 0;
}

三、client

1.打开驱动，完成映射。

2.查询服务 (handle)。

3.调用服务中的函数。

/* Copyright 2008 The Android Open Source Project
 */
#define LOG_TAG "binder_c"
#include 
#include 
#include 
#include 
#include 
#include "binder.h"
#include "binder_c.h"
#define SERVER_TEST1 123
#define SERVER_TEST2 456
struct binder_state *bs;
uint32_t handle;

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;
}

void test1(void)
{
     
	//构造数据
	 unsigned iodata[512/4];
	 struct binder_io msg, reply;
	
	 bio_init(&msg, iodata, sizeof(iodata), 4);
	 bio_put_uint32(&msg, 0);  //数据头

	//发送数据
	 if (binder_call(bs, &msg, &reply,handle, SERVER_TEST1))
		 return ;

	 binder_done(bs, &msg, &reply);

}

int test2(char * name)
{
     
	//构造数据
	uint32_t ret;
	 unsigned iodata[512/4];
	 struct binder_io msg, reply;
	
	 bio_init(&msg, iodata, sizeof(iodata), 4);
	 bio_put_uint32(&msg, 0);  //数据头
	 bio_put_string16_x(&msg,name);

	//发送数据
	 if (binder_call(bs, &msg, &reply,handle, SERVER_TEST2))
		 return 0;

	//得到返回值，return
	 ret = bio_get_uint32(&reply);

	 binder_done(bs, &msg, &reply);

	 return ret;

}

int main(int argc, char **argv)
{
     
    int fd;
	int ret;
    uint32_t svcmgr = BINDER_SERVICE_MANAGER;
	//1.打开驱动，完成映射
    bs = binder_open(128*1024);
    if (!bs) {
     
        fprintf(stderr, "failed to open binder driver\n");
        return -1;
    }

	//2.查询服务  (handle)
	handle = svcmgr_lookup(bs,BINDER_SERVICE_MANAGER,"binder_c");
	if(handle <= 0){
     
		ALOGI("check service is fail.\n");
		return -1;
	}
	
	//3.调用服务中的函数
	//usage :./client test1
	//usage :./client test2  client
    if(argc == 2){
     
		test1();
	}else if(argc == 3){
     
		ret = test2(argv[2]);
		ALOGI("client test2 : ret = %d",ret);
	}
    return 0;
}

四、Android.mk

LOCAL_PATH:= $(call my-dir)

svc_c_flags =	\
	-Wall -Wextra \

ifneq ($(TARGET_USES_64_BIT_BINDER),true)
ifneq ($(TARGET_IS_64_BIT),true)
svc_c_flags += -DBINDER_IPC_32BIT=1
endif
endif

include $(CLEAR_VARS)
LOCAL_SHARED_LIBRARIES := liblog
LOCAL_SRC_FILES := bctest.c binder.c
LOCAL_CFLAGS += $(svc_c_flags)
LOCAL_MODULE := bctest
LOCAL_MODULE_TAGS := optional
include $(BUILD_EXECUTABLE)

include $(CLEAR_VARS)
LOCAL_SHARED_LIBRARIES := liblog libselinux
LOCAL_SRC_FILES := service_manager.c binder.c
LOCAL_CFLAGS += $(svc_c_flags)
LOCAL_MODULE := servicemanager
include $(BUILD_EXECUTABLE)