1、在 32 位系统上， Linux 内核将 4G 空间分为 1G 内核空间（3~4G）和 3G（0~3G）用户空间，通过内存管理，每个进程都可以使用 3G 的用户空间
2、基于linux主机调试开发板时，目标板需要gdbserver。将生成的二进制文件作为网络路径挂载在目标板上进行在线调试；
基于windows主机调试开发板时，目标板需要ssh,tftp功能，需要将编译的二进制文件下载到开发板进行在线调试；
3、通过windows主机调试i.mx283开发板时无法通过SSH传输文件，经查开发板未开SSH，参照
https://blog.csdn.net/sements/article/details/84106094
进行编译后，执行sshd，返回“Segmentation fault”，怀疑板载内存不够，内存越界，待研究
4、使用64位Ubuntu时在安装完ARM交叉编译器并设置环境变量后
“运行arm-linux-gcc命令，提示No such file or directory”
原因是需要安装32位兼容包
sudo apt-get install lib32z1
5、电脑能ping通板子，板子ping不通电脑----关闭防火墙。
6、安装vmware tools:https://blog.csdn.net/qq_52310755/article/details/111216213
7、aarch64-none.... 报错，找不到库，aarch64-none-elf-gcc test.c --specs=rdimon.specs
8、hello 模块，dmesg指令查看内核信息
1 #include <linux/init.h> 2 #include <linux/module.h> 3 MODULE_LICENSE("Dual BSD/GPL"); 4 static int hello_init(void) 5 { 6 printk(KERN_ALERT " Hello World enter\n"); 7 return 0; 8 } 9 static void hello_exit(void) 10 { 11 printk(KERN_ALERT " Hello World exit\n "); 12 } 13 module_init(hello_init); 14 module_exit(hello_exit); 15 16 MODULE_AUTHOR("Song Baohua"); 17 MODULE_DESCRIPTION("A simple Hello World Module"); 18 MODULE_ALIAS("a simplest module");
globalmem虚拟字符设备驱动模块--from华清远见
--内核5.4编译加载成功，5.13，5.14编译成功加载报错
1 #include <linux/module.h> 2 #include <linux/types.h> 3 #include <linux/fs.h> 4 #include <linux/errno.h> 5 #include <linux/mm.h> 6 #include <linux/sched.h> 7 #include <linux/init.h> 8 #include <linux/cdev.h> 9 #include <linux/slab.h> 10 #include <asm/io.h> 11 //#include <asm/system.h> 12 #include <asm/switch_to.h> 13 #include <asm/uaccess.h> 14 15 #define GLOBALMEM_SIZE 0x100/*全局内存最大4KB*/ 16 #define MEM_CLEAR 0x1 /*清零全局内存*/ 17 #define GLOBALMEM_MAJOR 256 /*预设的设备主设备号*/ 18 19 static int globalmem_major = GLOBALMEM_MAJOR; 20 /*globalmem设备结构体*/ 21 struct globalmem_dev 22 { 23 struct cdev cdev;/*cdev结构体*/ 24 unsigned char mem[GLOBALMEM_SIZE];/*全局内存*/ 25 }; 26 27 struct globalmem_dev *globalmem_devp;/*设备结构体指针*/ 28 /*文件打开函数*/ 29 int globalmem_open(struct inode *inode, struct file *filp) 30 { 31 /*将设备结构体指针赋值给文件私有数据指针*/ 32 filp->private_data = globalmem_devp; 33 return 0; 34 } 35 /*文件释放函数*/ 36 int globalmem_release(struct inode *inode, struct file *filp) 37 { 38 return 0; 39 } 40 41 /*iocrl 设备控制函数*/ 42 static long globalmem_ioctl( struct file *filp, unsigned int cmd, unsigned long arg) 43 { 44 struct globalmem_dev *dev = filp->private_data;/*获取设备结构体指针*/ 45 46 switch (cmd) 47 { 48 case MEM_CLEAR: 49 memset(dev->mem,0,GLOBALMEM_SIZE); 50 printk(KERN_INFO "globalmem is set to zero\n"); 51 break; 52 default: 53 return -EINVAL; 54 } 55 return 0; 56 } 57 /*读函数*/ 58 static ssize_t globalmem_read(struct file *filp,char __user *buf,size_t size,loff_t *ppos) 59 { 60 unsigned long p = *ppos; 61 unsigned int count = size; 62 int ret = 0; 63 struct globalmem_dev *dev = filp->private_data;/*获得设备结构体指针*/ 64 /*分析和获取有效的写长度*/ 65 if(p >= GLOBALMEM_SIZE) 66 return count ? -ENXIO : 0; 67 if(count > GLOBALMEM_SIZE - p) 68 count = GLOBALMEM_SIZE - p; 69 /*内核空间->用户空间*/ 70 if(copy_to_user(buf, (void*)(dev->mem + p), count)) 71 { 72 ret = -EFAULT; 73 } 74 else 75 { 76 *ppos += count; 77 ret = count; 78 79 printk(KERN_INFO"read %d bytes(s) froom %d \n",count,p); 80 } 81 return ret; 82 } 83 /*写函数*/ 84 static ssize_t globalmem_write(struct file *filp, const char __user *buf,size_t size, loff_t *ppos) 85 { 86 unsigned long p = *ppos; 87 unsigned int count = size; 88 int ret = 0; 89 struct globalmem_dev *dev=filp->private_data;/*获得设备结构体指针*/ 90 /*分析和获取有效的写长度*/ 91 if(p >= GLOBALMEM_SIZE) 92 return count ? -ENXIO : 0; 93 if(count > GLOBALMEM_SIZE - p) 94 count = GLOBALMEM_SIZE - p; 95 /*用户空间->内核空间*/ 96 if(copy_from_user(dev->mem + p, buf, count)) 97 ret = -EFAULT; 98 else 99 { 100 *ppos+= count; 101 ret = count; 102 103 printk(KERN_INFO"written $d bytes(s) from %d\n", count, p); 104 } 105 return ret; 106 } 107 /*seek 文件定位函数*/ 108 static loff_t globalmem_llseek(struct file *filp, loff_t offset, int orig) 109 { 110 loff_t ret = 0; 111 switch (orig) 112 { 113 case 0:/*相对文件开始位置偏移*/ 114 if(offset < 0) 115 { 116 ret = -EINVAL; 117 break; 118 } 119 if((unsigned int) offset > GLOBALMEM_SIZE) 120 { 121 ret = -EINVAL; 122 break; 123 } 124 filp->f_pos = (unsigned int)offset; 125 ret = filp->f_pos; 126 break; 127 case 1:/*相对文件当前位置偏移*/ 128 if ((filp->f_pos + offset) > GLOBALMEM_SIZE) 129 { 130 ret = - EINVAL; 131 break; 132 } 133 if ((filp->f_pos + offset) < 0) 134 { 135 ret = - EINVAL; 136 break; 137 } 138 filp->f_pos += offset; 139 ret = filp->f_pos; 140 break; 141 default: 142 ret = -EINVAL; 143 break; 144 } 145 return ret; 146 } 147 /*文件操作结构体*/ 148 static const struct file_operations globalmem_fops = 149 { 150 .owner = THIS_MODULE, 151 .llseek = globalmem_llseek, 152 .read = globalmem_read, 153 .write = globalmem_write, 154 .unlocked_ioctl = globalmem_ioctl, 155 .open = globalmem_open, 156 .release = globalmem_release, 157 }; 158 /*初始化并注册 cdev*/ 159 static void globalmem_setup_cdev(struct globalmem_dev *dev, int index) 160 { 161 int err, devno = MKDEV(globalmem_major, index); 162 163 cdev_init(&dev->cdev, &globalmem_fops); 164 dev->cdev.owner = THIS_MODULE; 165 dev->cdev.ops = &globalmem_fops; 166 err = cdev_add(&dev->cdev, devno, 1); 167 if (err) 168 printk(KERN_NOTICE "Error %d adding LED%d", err, index); 169 } 170 171 /*设备驱动模块加载函数*/ 172 int globalmem_init(void) 173 { 174 int result; 175 dev_t devno = MKDEV(globalmem_major, 0); 176 177 /* 申请设备号*/ 178 if (globalmem_major) 179 result = register_chrdev_region(devno, 1, "globalmem"); 180 else /* 动态申请设备号 */ 181 { 182 result = alloc_chrdev_region(&devno, 0, 1, "globalmem"); 183 globalmem_major = MAJOR(devno); 184 } 185 if (result < 0) 186 return result; 187 188 /* 动态申请设备结构体的内存*/ 189 globalmem_devp = kmalloc(sizeof(struct globalmem_dev), GFP_KERNEL); 190 if (!globalmem_devp) /*申请失败*/ 191 { 192 result = - ENOMEM; 193 goto fail_malloc; 194 } 195 memset(globalmem_devp, 0, sizeof(struct globalmem_dev)); 196 197 globalmem_setup_cdev(globalmem_devp, 0); 198 return 0; 199 200 fail_malloc: unregister_chrdev_region(devno, 1); 201 return result; 202 } 203 204 /*模块卸载函数*/ 205 void globalmem_exit(void) 206 { 207 cdev_del(&globalmem_devp->cdev); /*注销 cdev*/ 208 kfree(globalmem_devp); /*释放设备结构体内存*/ 209 unregister_chrdev_region(MKDEV(globalmem_major, 0), 1); /*释放设备号*/ 210 } 211 212 MODULE_AUTHOR("Cao chaojie"); 213 MODULE_LICENSE("Dual BSD/GPL"); 214 215 module_param(globalmem_major, int, S_IRUGO); 216 217 module_init(globalmem_init); 218 module_exit(globalmem_exit);
makefile
obj-m :=hello.o DIR := /lib/modules/$(shell uname -r)/build all: make -C $(DIR) M=$(shell pwd) modules clean: make -C $(DIR) M=$(shell pwd) clean
9、通过“mknod /dev/globalmem c 254 0”命令创建“/dev/globalmem”设备节点，并通过“echo 'hello world' > /dev/globalmem”命令和“cat /dev/globalmem”命令分别验证设备的写和读.