linux-kernel - Re: [PATCH v6 26/30 (mawk fix)] objtool: Add function to get the name of a CPU feature

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Message-ID: <9a777b58-15ee-4754-9f2f-caf5de23d95c@oracle.com>
Date: Tue, 25 Nov 2025 08:55:24 +0100
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: alexandre.chartre@...cle.com, linux-kernel@...r.kernel.org,
        mingo@...nel.org, jpoimboe@...nel.org, david.laight.linux@...il.com
Subject: Re: [PATCH v6 26/30 (mawk fix)] objtool: Add function to get the name
 of a CPU feature


On 11/24/25 20:35, Peter Zijlstra wrote:
> On Mon, Nov 24, 2025 at 05:48:55PM +0100, Alexandre Chartre wrote:
>> diff --git a/tools/objtool/arch/x86/Build b/tools/objtool/arch/x86/Build
>> index 3dedb2fd8f3a0..b95448ee01ee4 100644
>> --- a/tools/objtool/arch/x86/Build
>> +++ b/tools/objtool/arch/x86/Build
>> @@ -12,3 +12,13 @@ $(OUTPUT)arch/x86/lib/inat-tables.c: $(inat_tables_script) $(inat_tables_maps)
>>   $(OUTPUT)arch/x86/decode.o: $(OUTPUT)arch/x86/lib/inat-tables.c
>>   
>>   CFLAGS_decode.o += -I$(OUTPUT)arch/x86/lib
>> +
>> +cpu_features = ../arch/x86/include/asm/cpufeatures.h
>> +cpu_features_script = ../arch/x86/tools/gen-cpu-feature-names-x86.awk
>> +
>> +$(OUTPUT)arch/x86/lib/cpu-feature-names.c: $(cpu_features_script) $(cpu_features)
>> +	$(Q)$(call echo-cmd,gen)$(AWK) -f $(cpu_features_script) $(cpu_features) > $@
>> +
>> +$(OUTPUT)arch/x86/special.o: $(OUTPUT)arch/x86/lib/cpu-feature-names.c
>> +
>> +CFLAGS_special.o := -I$(OUTPUT)arch/x86/lib
> 
> If you'd been careful, you'd have taken the commit from tip and noticed
> its Build fragment is slightly different :-)
> 
> You're now re-introducing a race in the build where if you build
> special.o before decode.o the lib directory isn't yet created and it
> goes sideways.
> 
> Anyway, let me fold that awk delta into what I have.

Oups, sorry. I've checked tip but not closely enough :(

Thanks for handling it; that's a good lesson about the many different impacts
and dependencies.

alex.