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通過property_set("ctl.start", service_xx);
來啟動init.rc中的service是一個很方便方法來調用某個可執(zhí)行程序或某個腳本程序
service service_xx /system/bin/xx
disabled
oneshot
但在非AID_ROOT、AID_SYSTEM 用戶的進程中調用ctl.start ctl.stop會碰到權限問題:
system/core/init/property_service.c
-
-
-
-
- struct {
- const char *service;
- unsigned int uid;
- unsigned int gid;
- } control_perms[] = {
- { "dumpstate",AID_SHELL, AID_LOG },
- {NULL, 0, 0 }
- };
-
-
-
-
-
-
-
- static int check_control_perms(const char *name, int uid, int gid) {
- int i;
- if (uid == AID_SYSTEM || uid == AID_ROOT)
- return 1;
-
-
- 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進程才有權限star/stop services
因此，如果我們碰到了權限問題，根據(jù)log提示，在/system/core/include/private/android_filesystem_config.h
中查到進程定義，添加到control_perms[]列表
比如，uid ==AID_WIFI的某個程序需要權限啟動service_xx
control_perms[] = {
{ "dumpstate",AID_SHELL, AID_LOG },
+ { "service_xx ",AID_WIFI, AID_WIFI},
{NULL, 0, 0 }
};
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