我怎样才能得到一个内核模块内部的文件描述符的文件名？ [英] How can I get a filename from a file descriptor inside a kernel module?

问题描述

我需要从一个给定的文件描述符获取文件的名字，我写了一个小的Linux内核模块中。我想在给出获取文件名从文件描述符使用C 的解决方案，但由于某些原因，它打印出垃圾值（使用的readlink 在的/ proc /自/ FD / NNN 作为在溶液中提到的）。我该怎么办呢？

I need to get the name of a file from a given file descriptor, inside a small linux kernel module that I wrote. I tried the solution given at Getting Filename from file descriptor in C, but for some reason, it prints out garbage values (on using readlink on /proc/self/fd/NNN as mentioned in the solution). How can I do it?

推荐答案

不要叫 SYS_readlink - 使用同样的方法PROCFS 一样。开始在的code proc_pid_readlink（）和 proc_fd_link（）在 FS / PROC / base.c 。

Don't call SYS_readlink - use the same method that procfs does when one of those links is read. Start with the code in proc_pid_readlink() and proc_fd_link() in fs/proc/base.c.

从广义上讲，给予 INT FD 和结构files_struct *您感兴趣的任务文件（你所采取的引用），你想要做的：

Broadly, given an int fd and a struct files_struct *files from the task you're interested in (which you have taken a reference to), you want to do:

char *tmp;
char *pathname;
struct file *file;
struct path *path;

spin_lock(&files->file_lock);
file = fcheck_files(files, fd);
if (!file) {
    spin_unlock(&files->file_lock);
    return -ENOENT;
}

path = &file->f_path;
path_get(path);
spin_unlock(&files->file_lock);

tmp = (char *)__get_free_page(GFP_TEMPORARY);

if (!tmp) {
    path_put(path);
    return -ENOMEM;
}

pathname = d_path(path, tmp, PAGE_SIZE);
path_put(&path);

if (IS_ERR(pathname)) {
    free_page((unsigned long)tmp);
    return PTR_ERR(pathname);
}

/* do something here with pathname */

free_page((unsigned long)tmp);

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