linux-kernel - Re: [PATCH] Kbuild: Check for CONFIG_READABLE

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Date:	Tue, 07 Oct 2014 15:45:43 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	Borislav Petkov <bp@...en8.de>
CC:	linux-kbuild@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>
Subject: Re: [PATCH] Kbuild: Check for CONFIG_READABLE_ASM when building .s
 targets

On 2014-10-07 14:27, Borislav Petkov wrote:
> On Tue, Oct 07, 2014 at 02:13:56PM +0200, Michal Marek wrote:
>> This violates the principle of least surprise:
>>
>> make $file.s
>> as -o $file.o $file.s
>>
>> should be equivalent to
>>
>> make $file.o
> 
> I know but we need to enable -g for .s targets so that we get the .loc
> annotation (i.e., line numbers) in asm which is very helpful.
> 
> But the least surprise principle is a valid point. Maybe we should warn
> about it too when building .s targets...?
> 
> Or, maybe I should try to find out whether there's another gcc option
> which adds ".loc" annotations alone...

Such option would be best of course. BTW, do you know about make
$file.lst to produce an 'annotated disassembly'?


>> Why not simply check both READABLE_ASM and DEBUG_INFO?  Also, it's more
>> straightforward to print the warning in the top-level Makefile rule than
>> to add a conditional to the generic rule, like this:
> 
> The problem here is that we're building a couple of .s targets
> regardless of what the make command contains, like bounds.s and such.

The toplevel Makefile rule (where your patch adds the asm_target=$@
variable) is only used for manual invocation. bounds.s and the like are
handled by Makefile.build directly.

Michal
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