Re: kernel space getcwd()? (using current() to find out cwd)

Brian J. Watson (Brian.J.Watson@compaq.com)
Tue, 17 Apr 2001 15:43:19 -0700


> This is probably a stupid question, and probably directed to the wrong
> list. Apologies in advance, but I'm stumped
>
> I've been working on a kernel module to report on "changed files". It
> works just fine -- I wrap the orignal system calls with my
> [...]

At least in the 2.4 kernels, there's already a __d_path() routine (fs/dcache.c)
that builds the pathname using the mechanism you discussed.

Here's one way you could use it:

char *
kgetcwd()
{
char *path = (char *) __get_free_page(GFP_USER);
struct vfsmnt *pwdmnt;
struct dentry *pwd;

if (!path)
return ERR_PTR(-ENOMEM);

read_lock(&current->fs->lock);
pwdmnt = mntget(current->fs->pwdmnt);
pwd = dget(current->fs->pwd);
read_unlock(&current->fs->lock);

spin_lock(&dcache_lock);
path = __d_path(pwd, pwdmnt, NULL, NULL, path, PAGE_SIZE);
spin_unlock(&dcache_lock);

mntput(pwdmnt);
dput(pwd);

return path;
}

If you only want the pathname back to the process root, use d_path() instead
(and don't grab the dcache_lock).

When you're done with path, free it with free_page() and not kfree().

BTW, I'm not subscribed to the kernel mailing list (I just read it on the web),
so please copy me on any response.

--
Brian Watson
Compaq Computer
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