linux-kernel - Re: [RFC 00/13] objtool: Function validation tracing

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Message-ID: <7e803ed0-60ac-4d5e-a039-904c3fba8e80@oracle.com>
Date: Wed, 11 Jun 2025 08:00:32 +0200
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: alexandre.chartre@...cle.com, linux-kernel@...r.kernel.org,
        mingo@...nel.org, peterz@...radead.org
Subject: Re: [RFC 00/13] objtool: Function validation tracing


On 6/10/25 23:05, Josh Poimboeuf wrote:
> On Tue, Jun 10, 2025 at 03:00:50PM +0200, Alexandre Chartre wrote:
>> Here is the patch to handle both old and new binutils versions:
>>
>> 8<------------------------------------------------------------------->8
>> diff --git a/tools/objtool/Makefile b/tools/objtool/Makefile
>> index 00350fc7c662..91a2858fea14 100644
>> --- a/tools/objtool/Makefile
>> +++ b/tools/objtool/Makefile
>> @@ -7,6 +7,11 @@ srctree := $(patsubst %/,%,$(dir $(CURDIR)))
>>   srctree := $(patsubst %/,%,$(dir $(srctree)))
>>   endif
>> +FEATURE_USER = .objtool
>> +FEATURE_TESTS = disassembler-init-styled
>> +FEATURE_DISPLAY = disassembler-init-styled
>> +include $(srctree)/tools/build/Makefile.feature
> 
> Thanks, that worked.
> 
> That Makefile.feature thing is nice (except it prints an annoying
> newline on every build after the first one).
> 
> Can we also use that to determine if binutils-devel (or binutils-dev or
> whatever) is installed, and then make the build of disas.c optional?

This would probably require a new feature test, I will look at it.

> Then if somebody tries to use '--trace', it could tell them to install
> the binutils development package and rebuild objtool.  That way we don't
> disrupt everybody's kernel build for a feature they probably won't use.
> 
> That would also mean disas_warned_funcs() would be disabled on missing
> binutils-devel.  But I think that's probably fine.  In fact that will
> now have less reason for existing now that we have this tracing.  Maybe
> we won't need it at all.
> 

We can also fall back to using objdump if binutils-devel is not there.

And thanks for all the other comments, I will address them and resubmit. I am
also adding the "disas" option.

alex.