linux-kernel - Re: [PATCH v2 13/25] scripts: Create objdump-func helper script

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Date:   Tue, 19 Apr 2022 09:09:00 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH v2 13/25] scripts: Create objdump-func helper script

On Tue, Apr 19, 2022 at 01:15:55PM +0200, Peter Zijlstra wrote:
> On Mon, Apr 18, 2022 at 09:50:32AM -0700, Josh Poimboeuf wrote:
> > Add a simple script which disassembles a single function from an object
> > file.  Comes in handy for objtool warnings and kernel stack traces.
> > 
> > Originally-by: Peter Zijlstra <peterz@...radead.org>
> > Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
> > ---
> >  scripts/objdump-func | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> >  create mode 100755 scripts/objdump-func
> > 
> > diff --git a/scripts/objdump-func b/scripts/objdump-func
> > new file mode 100755
> > index 000000000000..140646c456fc
> > --- /dev/null
> > +++ b/scripts/objdump-func
> > @@ -0,0 +1,18 @@
> > +#!/bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +#
> > +# Disassemble a single function.
> > +#
> > +# usage: objdump-func <file> <func>
> > +
> > +set -o errexit
> > +set -o nounset
> > +
> > +OBJDUMP="${CROSS_COMPILE:-}objdump"
> > +
> > +command -v awk >/dev/null 2>&1 || die "awk isn't installed"
> > +
> > +OBJ=$1; shift
> > +FUNC=$1; shift
> > +
> > +${OBJDUMP} -wdr $@ $OBJ | awk "/^\$/ { P=0; } /$FUNC[^>]*>:\$/ { P=1; O=strtonum(\"0x\" \$1); } { if (P) { o=strtonum(\"0x\" \$1); printf(\"%04x \", o-O); print \$0; } }"
> > -- 
> > 2.34.1
> > 
> 
> This might rely on awk being gawk, I'm never very careful about those
> things.

True, running with --posix I get

  awk: cmd. line:1: (FILENAME=- FNR=17142) fatal: function `strtonum' not defined

The non-gawk users always ruin the party.

-- 
Josh