ext2文件系统源代码之xattr_trusted.c

迷南。 2022-07-28 00:09 101阅读 0赞

我们来看下xattr\_trusted.c这个文件的代码

/*
     * linux/fs/ext2/xattr_trusted.c
     * 信任的扩展属性处理代码
     *
     * Copyright (C) 2003 by Andreas Gruenbacher, <a.gruenbacher@computer.org>
     */
    
    
    #include <linux/module.h>
    #include <linux/string.h>
    #include <linux/capability.h>
    #include <linux/fs.h>
    #include <linux/ext2_fs.h>
    #include "xattr.h"
    /*属性名前缀*/
    #define XATTR_TRUSTED_PREFIX "trusted."
    /*得到带前缀的属性名称，返回名称长度，list存放全名*/
    static size_t
    ext2_xattr_trusted_list(struct inode *inode, char *list, size_t list_size,
    			const char *name, size_t name_len)
    {
    	/*前缀名长度和总长度*/
    	const int prefix_len = sizeof(XATTR_TRUSTED_PREFIX)-1;
    	const size_t total_len = prefix_len + name_len + 1;
    	/*权限*/
    	if (!capable(CAP_SYS_ADMIN))
    		return 0;
    
    
    	if (list && total_len <= list_size) {
    		/*先复制前缀名，再复制后边名字*/
    		memcpy(list, XATTR_TRUSTED_PREFIX, prefix_len);
    		memcpy(list+prefix_len, name, name_len);
    		list[prefix_len + name_len] = '\0';
    	}
    	return total_len;
    }
    /*得到想要的属性*/
    static int
    ext2_xattr_trusted_get(struct inode *inode, const char *name,
    		       void *buffer, size_t size)
    {
    	/*参数检查*/
    	if (strcmp(name, "") == 0)
    		return -EINVAL;
    	/*调用之前讲过的函数来得到属性*/
    	return ext2_xattr_get(inode, EXT2_XATTR_INDEX_TRUSTED, name,
    			      buffer, size);
    }
    
    
    static int
    ext2_xattr_trusted_set(struct inode *inode, const char *name,
    		       const void *value, size_t size, int flags)
    {
    	/*参数检查*/
    	if (strcmp(name, "") == 0)
    		return -EINVAL;
    	/*调用之前讲过的函数来设置属性*/
    	return ext2_xattr_set(inode, EXT2_XATTR_INDEX_TRUSTED, name,
    			      value, size, flags);
    }
    /*trusted属性处理函数结构体*/
    struct xattr_handler ext2_xattr_trusted_handler = {
    	.prefix	= XATTR_TRUSTED_PREFIX,
    	.list	= ext2_xattr_trusted_list,
    	.get	= ext2_xattr_trusted_get,
    	.set	= ext2_xattr_trusted_set,
    };