linux-kernel - Re: [PATCH 01/10] x86: assembly, ENTRY for fn, GLOBAL for data

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Date:   Mon, 6 Mar 2017 15:09:28 +0100
From:   Jiri Slaby <jslaby@...e.cz>
To:     hpa@...or.com, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     mingo@...hat.com, x86@...nel.org, jpoimboe@...hat.com,
        linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        xen-devel@...ts.xenproject.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linux-pm@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 01/10] x86: assembly, ENTRY for fn, GLOBAL for data

On 03/03/2017, 07:20 PM, hpa@...or.com wrote:
> On March 1, 2017 2:27:54 AM PST, Ingo Molnar <mingo@...nel.org> wrote:
>>
>> * Thomas Gleixner <tglx@...utronix.de> wrote:
>>
>>> On Wed, 1 Mar 2017, Ingo Molnar wrote:
>>>>
>>>> * Jiri Slaby <jslaby@...e.cz> wrote:
>>>>
>>>>> This is a start of series to unify use of ENTRY, ENDPROC, GLOBAL,
>> END,
>>>>> and other macros across x86. When we have all this sorted out,
>> this will
>>>>> help to inject DWARF unwinding info by objtool later.
>>>>>
>>>>> So, let us use the macros this way:
>>>>> * ENTRY -- start of a global function
>>>>> * ENDPROC -- end of a local/global function
>>>>> * GLOBAL -- start of a globally visible data symbol
>>>>> * END -- end of local/global data symbol
>>>>
>>>> So how about using macro names that actually show the purpose,
>> instead of 
>>>> importing all the crappy, historic, essentially randomly chosen
>> debug symbol macro 
>>>> names from the binutils and older kernels?
>>>>
>>>> Something sane, like:
>>>>
>>>> 	SYM__FUNCTION_START
>>>
>>> Sane would be:
>>>
>>>      	SYM_FUNCTION_START
>>>
>>> The double underscore is just not giving any value.
>>
>> So the double underscore (at least in my view) has two advantages:
>>
>> 1) it helps separate the prefix from the postfix.
>>
>> I.e. it's a 'symbols' namespace, and a 'function start', not the
>> 'start' of a 
>> 'symbol function'.
>>
>> 2) It also helps easy greppability.
>>
>> Try this in latest -tip:
>>
>>  git grep e820__
>>
>> To see all the E820 API calls - with no false positives!
>>
>> 'git grep e820_' on the other hand is a lot less reliable...
>>
>> But no strong feelings either way, I just try to sneak in these small
>> namespace 
>> structure tricks when nobody's looking! ;-)
>>
>> Thanks,
>>
>> 	Ingo
> 
> This seems needlessly verbose to me and clutters the code.
> 
> How about:
> 
> PROC..ENDPROC, LOCALPROC..ENDPROC and DATA..ENDDATA.  Clear, unambiguous and balanced.

I tried this, but:
arch/x86/kernel/relocate_kernel_64.S:27:0: warning: "DATA" redefined
 #define DATA(offset)  (KEXEC_CONTROL_CODE_MAX_SIZE+(offset))


I am not saying that I cannot fix it up. I just want to say, that these
names might be too generic, especially "PROC" and "DATA". So should I
really stick to these?

thanks,
-- 
js
suse labs