Linux内核:获得符号链接背后的真实路径 [英] Linux Kernel: Get real path behind a symlink

问题描述

我正在处理一些Linux内核，并且我有一个伪造的路径/dev/blah/，它指向/dev/block/real_device

I'm working on some linux kernel stuff and I have a fake path called /dev/blah/whatever that points to /dev/block/real_device

问题是lookup_bdev将无法遵循符号链接，因此我想通过获取真实路径(/dev/block/real_device)预先按摩路径，因此我可以将其传递给lookup_bdev，以使其成功返回错误.

The issue is that lookup_bdev will fail to follow the symlink so I'd like to massage the path upfront by getting the real path (/dev/block/real_device) so I can hand that off to lookup_bdev so it returns successfully instead of an error.

或者在给定初始路径的情况下，可以正确检索block_device信息的任何其他内核调用.

Or any other kernel call that would correctly retrieve the block_device information given the initial path.

谢谢

推荐答案

为此使用VFS层(尤其是dcache/nameidata).

Use VFS layer for this (dcache/nameidata in particular).

#include <linux/namei.h>
#include <linux/dcache.h>

...

struct path path;
char buf[256];
char* ptr;
int err = kern_path("/dev/disk/by-id/dm-name-lkdevel-root", 
                    LOOKUP_FOLLOW, &path);

if(!err) {
    ptr = d_path(&path, buf, 256);        

    if(!IS_ERR(ptr)) {
        /* ptr contains real path */
    }
}

这已在香草Linux 3.12上进行了测试

This was tested on vanilla Linux 3.12

请注意，对于特殊的文件系统，d_path()可能会返回奇怪的结果，并将(deleted)后缀附加到已删除的文件中.

Note that d_path() may return weird results for special filesystems and append (deleted) suffix to deleted files.

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