Android P init进程reboot流程和调试方法

古城微笑少年丶 2023-05-29 15:28 4阅读 0赞

Android中的init进程是安卓系统用户空间启动的第一个进程。

相关源码：  
system\\core\\reboot\\reboot.c  
system\\core\\init\\init.cpp  
system\\core\\init\\reboot.cpp

inti进程源码路径为：  
system/core/init/

**reboot启动路程**  
reboot是一个二进制可执行文件，其源码路径为：  
system\\core\\reboot

该目录只有两个文件，一个编译文件，一个c文件：  
Android.bp  
reboot.c

在system\\core\\reboot目录下编译，生成reboot可执行文件，生成目录在system/bin中

当我们在执行reboot命令时，就是执行的system/bin/reboot

int main(int argc, char* argv[]) { 
        int ret;
        size_t prop_len;
        char property_val[PROPERTY_VALUE_MAX];
        static const char reboot[] = "reboot";
        const char* cmd = reboot;
        char* optarg = "";
    
        opterr = 0;
        do { 
            int c;
    
    
    
            c = getopt(argc, argv, "p");
    
            if (c == -1) { 
                break;
            }
    
            switch (c) { 
            case 'p':
                cmd = "shutdown";
                break;
            case '?':
                fprintf(stderr, "usage: %s [-p] [rebootcommand]\n", argv[0]);
                exit(EXIT_FAILURE);
            }
        } while (1);
    
        if(argc > optind + 1) { 
            fprintf(stderr, "%s: too many arguments\n", argv[0]);
            exit(EXIT_FAILURE);
        }
    
        if (argc > optind)
            optarg = argv[optind];
        if (!optarg || !optarg[0]) optarg = "shell";
    
        prop_len = snprintf(property_val, sizeof(property_val), "%s,%s", cmd, optarg);
        if (prop_len >= sizeof(property_val)) { 
            fprintf(stderr, "%s command too long: %s\n", cmd, optarg);
            exit(EXIT_FAILURE);
        }
    
        ret = property_set(ANDROID_RB_PROPERTY, property_val);
        if (ret < 0) { 
            perror(cmd);
            exit(EXIT_FAILURE);
        }
    
        // Don't return early. Give the reboot command time to take effect
        // to avoid messing up scripts which do "adb shell reboot && adb wait-for-device"
        if (cmd == reboot) { 
            while (1) { 
                pause();
            }
        }
    
        fprintf(stderr, "Done\n");
        return 0;
    }

这里我们主要看ret = property\_set(ANDROID\_RB\_PROPERTY, property\_val);

\#define ANDROID\_RB\_PROPERTY “sys.powerctl”

即设置了属性值sys.powerctl为“reboot,adb”或者“reboot,shell”或者“shutdown,shell”或者“reboot,-p”

“reboot,adb”，表示在adb中输入adb reboot进行重启  
“reboot,shell”，表示在shell中输入reboot进行重启  
“shutdown,shell”，表示在shell中输入reboot -p进行关机  
“reboot,-p”，表示在adb中输入adb reboot -p进行关机

system/core/init/init.cpp

void property_changed(const std::string& name, const std::string& value) { 
        // If the property is sys.powerctl, we bypass the event queue and immediately handle it.
        // This is to ensure that init will always and immediately shutdown/reboot, regardless of
        // if there are other pending events to process or if init is waiting on an exec service or
        // waiting on a property.
        // In non-thermal-shutdown case, 'shutdown' trigger will be fired to let device specific
        // commands to be executed.
        if (name == "sys.powerctl") { 
    		
    		//property_set("vendor.reboot", "reboot");
    		
            // Despite the above comment, we can't call HandlePowerctlMessage() in this function,
            // because it modifies the contents of the action queue, which can cause the action queue
            // to get into a bad state if this function is called from a command being executed by the
            // action queue. Instead we set this flag and ensure that shutdown happens before the next
            // command is run in the main init loop.
            // TODO: once property service is removed from init, this will never happen from a builtin,
            // but rather from a callback from the property service socket, in which case this hack can
            // go away.
            shutdown_command = value;
            do_shutdown = true;
            
            
        }
    
        if (property_triggers_enabled) ActionManager::GetInstance().QueuePropertyChange(name, value);
    
        if (waiting_for_prop) { 
            if (wait_prop_name == name && wait_prop_value == value) { 
                LOG(INFO) << "Wait for property took " << *waiting_for_prop;
                ResetWaitForProp();
            }
        }
    }

property\_changed中监听了系统属性的变化，并且在sys.powerctl属性变化时，将do\_shutdown = true;

我们再来看main函数中的执行：

int main(int argc, char** argv) { 
        while (true) { 
            // By default, sleep until something happens.
            int epoll_timeout_ms = -1;
    
            if (do_shutdown && !shutting_down) { 
                do_shutdown = false;
                //modify by sunxiaolin 20191030
                LOG(INFO) << "sunxiaolin,init,sys.powerctl reboot or shutdown sleep(5000)!";
                property_set("vendor.reboot", "reboot");
                if (!(waiting_for_prop || Service::is_exec_service_running())) { 
    				//LOG(INFO) << "sunxiaolin,init,ExecuteOneCommand!";
                	am.ExecuteOneCommand();
            	}
            
                sleep(3);
            
                if (HandlePowerctlMessage(shutdown_command)) { 
                    shutting_down = true;
                }
            }
    
    		//modify by sunxiaolin 20191105
            if (!(waiting_for_prop || Service::is_exec_service_running())) { 
                am.ExecuteOneCommand();
            }
    	}
    }

如果收到sys.powerctl属性的变化，条件do\_shutdown && !shutting\_down得到满足，将执行：  
HandlePowerctlMessage

system\\core\\init\\reboot.cpp

bool HandlePowerctlMessage(const std::string& command) { 
        unsigned int cmd = 0;
        std::vector<std::string> cmd_params = Split(command, ",");
        std::string reboot_target = "";
        bool run_fsck = false;
        bool command_invalid = false;
    
        if (cmd_params.size() > 3) { 
            command_invalid = true;
        } else if (cmd_params[0] == "shutdown") { 
            cmd = ANDROID_RB_POWEROFF;
            if (cmd_params.size() == 2) { 
                if (cmd_params[1] == "userrequested") { 
                    // The shutdown reason is PowerManager.SHUTDOWN_USER_REQUESTED.
                    // Run fsck once the file system is remounted in read-only mode.
                    run_fsck = true;
                } else if (cmd_params[1] == "thermal") { 
                    // Turn off sources of heat immediately.
                    TurnOffBacklight();
                    // run_fsck is false to avoid delay
                    cmd = ANDROID_RB_THERMOFF;
                }
            }
        } else if (cmd_params[0] == "reboot") { 
            cmd = ANDROID_RB_RESTART2;
            if (cmd_params.size() >= 2) { 
                reboot_target = cmd_params[1];
                // When rebooting to the bootloader notify the bootloader writing
                // also the BCB.
                if (reboot_target == "bootloader") { 
                    std::string err;
                    if (!write_reboot_bootloader(&err)) { 
                        LOG(ERROR) << "reboot-bootloader: Error writing "
                                      "bootloader_message: "
                                   << err;
                    }
                } else if (reboot_target == "recovery") { 
                    std::string err;
                    if (!write_reboot_recovery(&err)) { 
                        LOG(ERROR) << "reboot-recovery: Error writing "
                                      "recovery_message: "
                                   << err;
                    }
                }
                // If there is an additional parameter, pass it along
                if ((cmd_params.size() == 3) && cmd_params[2].size()) { 
                    reboot_target += "," + cmd_params[2];
                }
            }
        } else { 
            command_invalid = true;
        }
        if (command_invalid) { 
            LOG(ERROR) << "powerctl: unrecognized command '" << command << "'";
            return false;
        }
    
        LOG(INFO) << "Clear action queue and start shutdown trigger";
        ActionManager::GetInstance().ClearQueue();
        // Queue shutdown trigger first
        ActionManager::GetInstance().QueueEventTrigger("shutdown");
        // Queue built-in shutdown_done
        auto shutdown_handler = [cmd, command, reboot_target, run_fsck](const BuiltinArguments&) { 
            DoReboot(cmd, command, reboot_target, run_fsck);
            return Success();
        };
        ActionManager::GetInstance().QueueBuiltinAction(shutdown_handler, "shutdown_done");
    
        // Skip wait for prop if it is in progress
        ResetWaitForProp();
    
        // Clear EXEC flag if there is one pending
        for (const auto& s : ServiceList::GetInstance()) { 
            s->UnSetExec();
        }
    
        return true;
    }

**编译**  
在system/core/init下面mm，生成symbols/init

**调试**  
直接push到根目录生效  
adb push Z:\\imx8\_p9.0.0\_2.1.0\_auto\_ga\\android9.0.0\\out\\target\\product\\mek\_8q\\symbols\\init /