我正在尝试通过内核模块实现sys_open（）调用的系统调用拦截，并为此定义了可作为内核模块插入的其他设备驱动程序MyDevice。 以下是我的内核模块的代码：
#include <linux/version.h> #include <linux/module.h> #include <linux/miscdevice.h> #include <linux/fs.h> #include <linux/highmem.h> #include <asm/unistd.h> MODULE_LICENSE("GPL"); // IOCTL commands #define IOCTL_PATCH_TABLE 0x00000001 #define IOCTL_FIX_TABLE 0x00000004 //Global variables int in_use = 0; //set to 1 in open handler and reset to zero in release handler int is_set = 0; // flag to detect system call interception unsigned long *sys_call_table = (unsigned long*)0xffffffff81801400; //hard coded address of sys_call_table from /boot/System.map //function pointer to original sys_open asmlinkage int (*real_open)(const char* __user, int, int); //Replacement of original call with modified system call asmlinkage int custom_open(const char* __user file_name, int flags, int mode) { printk("interceptor: open(\"%s\", %X, %X)\n", file_name,flags,mode); return real_open(file_name,flags,mode); } /* Make the memory page writable This is little risky as directly arch level protection bit is changed */ int make_rw(unsigned long address) { unsigned int level; pte_t *pte = lookup_address(address, &level); if(pte->pte &~ _PAGE_RW) pte->pte |= _PAGE_RW; return 0; } /* Make the page write protected */ int make_ro(unsigned long address) { unsigned int level; pte_t *pte = lookup_address(address, &level); pte->pte = pte->pte &~ _PAGE_RW; return 0; } /* This function will be invoked each time a user process attempts to open my device. You should keep in mind that the prototype of this function may change along different kernel versions. */ static int my_open(struct inode *inode, struct file *file) { /*Do not allow multiple processes to open this device*/ if(in_use) return -EBUSY; in_use++; printk("MyDevice opened\n"); return 0; } /* This function, in turn, will be called when a process closes our device */ static int my_release(struct inode *inode, struct file *file) { in_use--; printk("MyDevice closed\n"); return 0; } /*This static function handles ioctl calls performed on MyDevice*/ static int my_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { int retval = 0; switch(cmd) { case IOCTL_PATCH_TABLE: make_rw((unsigned long)sys_call_table); real_open = (void*)*(sys_call_table + __NR_open); *(sys_call_table + __NR_open) = (unsigned long)custom_open; make_ro((unsigned long)sys_call_table); is_set=1; break; case IOCTL_FIX_TABLE: make_rw((unsigned long)sys_call_table); *(sys_call_table + __NR_open) = (unsigned long)real_open; make_ro((unsigned long)sys_call_table); is_set=0; break; default: printk("sys_open not executed\n"); break; } return retval; } //populate data struct for file operations static const struct file_operations my_fops = { .owner = THIS_MODULE, .open = &my_open, .release = &my_release, .unlocked_ioctl = (void*)&my_ioctl, .compat_ioctl = (void*)&my_ioctl }; //populate miscdevice data structure static struct miscdevice my_device = { MISC_DYNAMIC_MINOR, "MyDevice", &my_fops }; static int __init init_my_module(void) { int retval; printk(KERN_INFO "Inside kernel space\n"); retval = misc_register(&my_device); return retval; } static void __exit cleanup_my_module(void) { if (is_set) { make_rw((unsigned long)sys_call_table); *(sys_call_table + __NR_open) = (unsigned long)real_open; make_ro((unsigned long)sys_call_table); } misc_deregister(&my_device); printk(KERN_INFO "Exiting kernel space\n"); return; } module_init(init_my_module); module_exit(cleanup_my_module); 我的testing文件的代码如下：
#include <stdio.h> #include <sys/ioctl.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> /* Define ioctl commands */ #define IOCTL_PATCH_TABLE 0x00000001 #define IOCTL_FIX_TABLE 0x00000004 int main(void) { int device = open("/dev/MyDevice", O_RDWR); printf("%d\n",device); ioctl(device, IOCTL_PATCH_TABLE); sleep(2); ioctl(device, IOCTL_FIX_TABLE); close(device); return 0; }
问题是在我的testing文件中打开（“/ dev / MyDevice”，O_RDWR）; 总是回到-1，为什么呢？ 我哪里错了？ 我用ls -l / dev / MyDevice进行了检查，MyDevice已经成功注册了以下详细信息：crw ——- 1 root root 10，56 Dec 9 19:33 / dev / MyDevice
对不起，真是愚蠢的错误，这就是新手做事情时发生的事情。 我只需要授予我的杂项字符设备驱动程序的读写权限。
sudo chmod a+r+w /dev/MyDevice