linux-kernel - Re: Please don't replace numeric parameter like 0444 with macro

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Date:	Wed, 3 Aug 2016 10:30:16 +0200
From:	Richard Weinberger <richard.weinberger@...il.com>
To:	Konstantin Khlebnikov <koct9i@...il.com>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Russell King - ARM Linux <linux@...linux.org.uk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Baole Ni <baolex.ni@...el.com>, Pavel Machek <pavel@....cz>,
	chuansheng.liu@...el.com,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Please don't replace numeric parameter like 0444 with macro

On Wed, Aug 3, 2016 at 10:07 AM, Konstantin Khlebnikov <koct9i@...il.com> wrote:
> On Wed, Aug 3, 2016 at 3:42 AM, Al Viro <viro@...iv.linux.org.uk> wrote:
>> On Tue, Aug 02, 2016 at 04:58:29PM -0400, Linus Torvalds wrote:
>>> [ So I answered similarly to another patch, but I'll just re-iterate
>>> and change the subject line so that it stands out a bit from the
>>> millions of actual patches ]
>>>
>>> On Tue, Aug 2, 2016 at 1:42 PM, Pavel Machek <pavel@....cz> wrote:
>>> >
>>> > Everyone knows what 0644 is, but noone can read S_IRUSR | S_IWUSR |
>>> > S_IRCRP | S_IROTH (*). Please don't do this.
>>>
>>> Absolutely. It's *much* easier to parse and understand the octal
>>> numbers, while the symbolic macro names are just random line noise and
>>> hard as hell to understand. You really have to think about it.
>>>
>>> So we should rather go the other way: convert existing bad symbolic
>>> permission bit macro use to just use the octal numbers.
>>>
>>> The symbolic names are good for the *other* bits (ie sticky bit, and
>>> the inode mode _type_ numbers etc), but for the permission bits, the
>>> symbolic names are just insane crap. Nobody sane should ever use them.
>>> Not in the kernel, not in user space.
>>
>> Except that you are inviting the mixes like S_IFDIR | 17 /* oops, should've
>> been 017, or do we spell it 0017? */ that way.  I certainly agree that this
>> patch series had been a huge pile of manure, but "let's convert it in other
>> direction" is inviting pretty much the same thing, with lovely potential for
>> typos, etc.
>
> We could add several macro with readable names for really used rwx
> combinations, like:
>
> #define KERN_SECRET_RO 0400
> #define KERN_SECRET_RW 0600
> #define KERN_SECRET_WO 0200
> #define KERN_SECRET_DIR 0500
>
> #define KERN_PUBLIC_RO 0444
> #define KERN_PUBLIC_RW 0644
> #define KERN_PUBLIC_DIR 0555
>
> #define KERN_UNSAFE_RW 0666
> #define KERN_UNSAFE_WO 0222
> #define KERN_UNSAFE_DIR 0777

Or just keep it as-is, everybody can read them.
Why do we have to hide all kind of numbers behind CPP macros?
Is this a thing these days?

-- 
Thanks,
//richard