linux-kernel - Re: [PATCH v2 5/9] objtool: Add verbose option for disassembling affected functions

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Message-ID: <20230413150923.45uuaif4y2fclmyq@treble>
Date:   Thu, 13 Apr 2023 08:09:23 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/9] objtool: Add verbose option for disassembling
 affected functions

On Thu, Apr 13, 2023 at 04:03:07PM +0200, Miroslav Benes wrote:
> On Thu, 13 Apr 2023, Peter Zijlstra wrote:
> 
> > On Wed, Apr 12, 2023 at 12:03:20PM -0700, Josh Poimboeuf wrote:
> > > +	objdump_str = "%sobjdump -wdr %s | gawk -M -v _funcs='%s' '"
> > > +			"BEGIN { split(_funcs, funcs); }"
> > > +			"/^$/ { func_match = 0; }"
> > > +			"/<.*>:/ { "
> > > +				"f = gensub(/.*<(.*)>:/, \"\\\\1\", 1);"
> > > +				"for (i in funcs) {"
> > > +					"if (funcs[i] == f) {"
> > > +						"func_match = 1;"
> > > +						"base = strtonum(\"0x\" $1);"
> > > +						"break;"
> > > +					"}"
> > > +				"}"
> > > +			"}"
> > > +			"{"
> > > +				"if (func_match) {"
> > > +					"addr = strtonum(\"0x\" $1);"
> > > +					"printf(\"%%04x \", addr - base);"
> > > +					"print;"
> > > +				"}"
> > > +			"}' 1>&2";
> > 
> > Do we want to have scripts/objdump-func.awk and use that to avoid the
> > duplication and eventual divergence of these awk thingies?
> 
> I vote for that as well. To keep everything in sync can be a nightmare.

Reasons I did it this way for v2:

1) The awk implementation is slightly different (this one doesn't match
   *.cold, etc)

2) Objtool is self-sufficient (doesn't need any other files)

3) Any changes to the objdump-func interface might break objtool

4) It's clearly bug-free and self-contained and I don't expect the code
   to change much in the future

-- 
Josh