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SubjectRe: /proc parent &proc_root == NULL?
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Randy.Dunlap wrote:
> John Richard Moser wrote:
>
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>> proc_misc_init() has both these lines in it:
>>
>> entry = create_proc_entry("kmsg", S_IRUSR, &proc_root);
>> proc_root_kcore = create_proc_entry("kcore", S_IRUSR, NULL);
>>
>> Both entries show up in /proc, as /proc/kmsg and /proc/kcore. So I ask,
>> as I can't see after several minutes of examination, what's the
>> difference? Why is NULL used for some and &proc_root used for others?
>>
>> I'm looking at 2.6.10
>
>
> create_proc_entry() passes &parent to proc_create().
> See proc_create():
> ...
> This is an error path:
> if (!(*parent) && xlate_proc_name(name, parent, &fn) != 0)
> goto out;
> but xlate_proc_name() searches for a /proc/.... and returns the
> all-but-final-part-of-name *parent (hope that makes some sense,
> see the comments above the function), so it returns &proc_root.
>
> HTH. If not, fire back.

create_proc_entry("kmsg", S_IRUSR, &proc_root);

So this is asking for proc_root to be filled?

create_proc_entry("kcore", S_IRUSR, NULL);

And this is just saying to shove it in proc's root?


I'm trying to locate a specific proc entry, using this lovely piece of
code I ripped off:

/*
* Find a proc entry
* Duplicated from remove_proc_entry()
*/
struct proc_dir_entry **get_proc_entry(const char *name, struct
proc_dir_entry *parent) {
struct proc_dir_entry **p;
const char *fn = name;
int len;
if (!parent && xlate_proc_name(name, &parent, &fn) != 0)
goto out;
len = strlen(fn);
for (p = &parent->subdir; *p; p=&(*p)->next ) {
if (!proc_match(len, fn, *p))
continue;
return p;
}
out:
return NULL;
}

And I'm trying to figure out if, say, /proc/devices would be found by...

get_proc_entry("devices",NULL);
- -OR-
get_proc_entry("devices",&proc_root);

Oh well. I'll figure it out eventually. :) I've already caused my
kernel to not boot :) figured it out too, it was that very function
above; I replaced a chunk of remove_proc_entry() with a modified version
of that and I'd busted it horribly so it didn't work. Just more things
to remind me that I know not what it is I do.

- --
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Public Domain, unless otherwise explicitly stated.

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