ADD file via upload

init.c

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+/*
+ * Copyright (c) 2013-2019 Huawei Technologies Co., Ltd. All rights reserved.
+ * Copyright (c) 2020-2021 Huawei Device Co., Ltd. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ *    conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list
+ *    of conditions and the following disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * 3. Neither the name of the copyright holder nor the names of its contributors may be used
+ *    to endorse or promote products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
+ * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+#ifdef LOSCFG_QUICK_START
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+
+#define QUICKSTART_IOC_MAGIC    'T'
+#define QUICKSTART_INITSTEP2    _IO(QUICKSTART_IOC_MAGIC, 0)
+#define WAIT_FOR_SAMPLE         300000  // wait 300ms for sample
+#endif
+int main(int argc, char * const *argv)
+{
+    (void)argv; 
+    int ret;  // 声明一个整数变量ret，用于存储函数的返回值
+    pid_t gid;  // 声明一个pid_t类型的变量gid，用于存储进程组ID  
+    const char *shellPath = "/bin/mksh";// 定义一个字符串常量shellPath，存储shell的路径，这里使用的是mksh shell
+ // 以下部分是一个条件编译块，如果定义了LOSCFG_QUICK_START宏，这段代码会被编译进程序  
+#ifdef LOSCFG_QUICK_START
+    const char *samplePath = "/dev/shm/sample_quickstart";// 定义一个字符串常量samplePath，存储sample_quickstart的路径  
+	// 使用fork函数创建子进程，返回值存储在ret变量中  
+    // 如果ret小于0，说明创建子进程失败；如果ret等于0，说明这是子进程；如果ret大于0，说明这是父进程，ret是子进程的ID  
+    ret = fork();
+    if (ret < 0) { // 如果创建子进程失败，输出错误消息  
+        printf("Failed to fork for sample_quickstart\n");
+    } else if (ret == 0) {// 如果是子进程，获取进程组ID并存储在gid变量中，如果获取失败，输出错误消息并退出  
+        (void)execve(samplePath, NULL, NULL);
+        exit(0);
+    }
+
+    usleep(WAIT_FOR_SAMPLE);
+
+    int fd = open("/dev/quickstart", O_RDONLY);
+    if (fd != -1) {
+        ioctl(fd, QUICKSTART_INITSTEP2);
+        close(fd);
+    }
+#endif
+    ret = fork();
+    if (ret < 0) {
+        printf("Failed to fork for shell\n");
+    } else if (ret == 0) {
+        gid = getpgrp();
+        if (gid < 0) {
+            printf("get group id failed, pgrpid %d, errno %d\n", gid, errno);
+            exit(0);
+        }
+        ret = tcsetpgrp(STDIN_FILENO, gid);
+        if (ret != 0) {// 如果是子进程，尝试将STDIN（标准输入）重定向到指定的进程组（通过tcsetpgrp函数实现），如果重定向失败，输出错误消息并退出 
+            printf("tcsetpgrp failed, errno %d\n", errno);
+            exit(0);
+        }
+         // 如果是子进程，使用execve函数执行shellPath指定的shell程序，参数为NULL，环境变量为NULL  
+        (void)execve(shellPath, NULL, NULL);
+        exit(0);
+    }
+
+    while (1) {  // 如果是父进程，进入一个无限循环，不断地调用waitpid函数等待子进程的状态变化（通过WNOHANG标志实现）  
+        ret = waitpid(-1, 0, WNOHANG);            // 如果子进程还在运行，等待1秒后再次检查；如果子进程已经停止运行，继续等待下一次检查（通过waitpid函数实现）  
+        if (ret == 0) {
+            sleep(1);
+        }
+    };
+}