linux-kernel - Re: [PATCH v2] vsprintf: introduce %dE for error constants

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <61cd079f-d41b-75ec-9a1e-ef80f9d1f8fd@kleine-koenig.org>
Date:   Wed, 28 Aug 2019 18:22:38 +0200
From:   Uwe Kleine-König <uwe@...ine-koenig.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Enrico Weigelt, metux IT consult" <lkml@...ux.net>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vsprintf: introduce %dE for error constants

On 8/28/19 2:59 PM, Sergey Senozhatsky wrote:
> On (08/28/19 14:49), Rasmus Villemoes wrote:
>> On 28/08/2019 14.02, Sergey Senozhatsky wrote:
>>> On (08/28/19 14:54), Jani Nikula wrote:
>>> [..]
>>>>> I personally think that this feature is not worth the code, data,
>>>>> and bikeshedding.
>>>>
>>>> The obvious alternative, I think already mentioned, is to just add
>>>> strerror() or similar as a function. I doubt there'd be much opposition
>>>> to that. Folks could use %s and strerr(ret). And a follow-up could add
>>>> the special format specifier if needed.
>>>
>>> Yeah, I'd say that strerror() would be a better alternative
>>> to vsprintf() specifier. (if we decide to add such functionality).
>>
>> Please no. The .text footprint of the changes at the call sites to do
>> pr_err("...%s...", errcode(err)) instead of the current
>> pr_err("...%d...", err) would very soon dwarf whatever is necessary to
>> implement %pE or %dE.

Yeah, that's what I think, too. I cannot imagine a user of strerror()
who needs the string representation for something different than to feed
it to one of the family members of printk. That's also why I think that
the other already existing format specifier are a good idea.

It might not be the nicest part of the printk code, but this way it is
at least concentrated in one place only.

> New vsprintf() specifiers have some downsides as well. Should %dE
> accidentally (via backport) make it to the -stable kernel, which
> does not support %dE, and we are going to lose the actual error
> code value as well.

That is wrong. When you do

	pr_err("There are no round tuits to give out: %dE\n", -ENOENT);

in a kernel that doesn't support %dE you get:

	There are no round tuits to give out: -2E

That's a bit ugly but I can still work out what the original value was.

Best regards
Uwe



Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)