设置ctl.start 属性启动init.rc 中service以及权限问题

通过property_set("ctl.start", service_xx);

来启动init.rc中的service是一个很方便方法来调用某个可执行程序或某个脚本程序

service service_xx  /system/bin/xx

    disabled

    oneshot

 

但在非AID_ROOT、AID_SYSTEM 用户的进程中调用ctl.start ctl.stop会碰到权限问题:

system/core/init/property_service.c

 

[cpp]
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/* 
 * White list of UID that are allowed to start/stop services. 
 * Currently there are no user apps that require. 
 */  
struct {  
    const char *service;  
    unsigned int uid;  
    unsigned int gid;  
} control_perms[] = {  
    { "dumpstate",AID_SHELL, AID_LOG },  
     {NULL, 0, 0 }  
};  
  
/* 
 * Checks permissions for starting/stoping system services. 
 * AID_SYSTEM and AID_ROOT are always allowed. 
 * 
 * Returns 1 if uid allowed, 0 otherwise. 
 */  
static int check_control_perms(const char *name, int uid, int gid) {  
    int i;  
    if (uid == AID_SYSTEM || uid == AID_ROOT)  
        return 1;  
  
    /* Search the ACL */  
    for (i = 0; control_perms[i].service; i++) {  
        if (strcmp(control_perms[i].service, name) == 0) {  
            if ((uid && control_perms[i].uid == uid) ||  
                (gid && control_perms[i].gid == gid)) {  
                return 1;  
            }  
        }  
    }  
    return 0;  
}  

/*
* White list of UID that are allowed to start/stop services.
* Currently there are no user apps that require.
*/
struct {
const char *service;
unsigned int uid;
unsigned int gid;
} control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },
{NULL, 0, 0 }
};

/*
* Checks permissions for starting/stoping system services.
* AID_SYSTEM and AID_ROOT are always allowed.
*
* Returns 1 if uid allowed, 0 otherwise.
*/
static int check_control_perms(const char *name, int uid, int gid) {
int i;
if (uid == AID_SYSTEM || uid == AID_ROOT)
return 1;

/* Search the ACL */
for (i = 0; control_perms[i].service; i++) {
if (strcmp(control_perms[i].service, name) == 0) {
if ((uid && control_perms[i].uid == uid) ||
(gid && control_perms[i].gid == gid)) {
return 1;
}
}
}
return 0;
}

 

只有uid == AID_SYSTEM || uid == AID_ROOT

或符合 control_perms[] = {

    { "dumpstate",AID_SHELL, AID_LOG },

     {NULL, 0, 0 }

}; 的uid进程才有权限star/stop services

 

因此，如果我们碰到了权限问题，根据log提示，在/system/core/include/private/android_filesystem_config.h

中查到进程定义，添加到control_perms[]列表

 

比如，uid ==AID_WIFI的某个程序需要权限启动service_xx

control_perms[] = {

    { "dumpstate",AID_SHELL, AID_LOG },

+  { "service_xx ",AID_WIFI, AID_WIFI},

     {NULL, 0, 0 }

};