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

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Message-ID: <20220419214125.hnwust76a7qay3dd@treble>
Date:   Tue, 19 Apr 2022 14:41:25 -0700
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH v2] scripts: Create objdump-func helper script

On Tue, Apr 19, 2022 at 10:14:35PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 19, 2022 at 09:50:01PM +0200, Borislav Petkov wrote:
> > On Tue, Apr 19, 2022 at 09:12:23AM -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>
> > > ---
> > > v2:
> > > - require gawk
> > > 
> > >  scripts/objdump-func | 18 ++++++++++++++++++
> > >  1 file changed, 18 insertions(+)
> > >  create mode 100755 scripts/objdump-func
> > 
> > Was that supposed to be user-friendly too?
> > 
> > $ ./scripts/objdump-func -h
> > ./scripts/objdump-func: line 16: $1: unbound variable
> > 
> > :-)

You mean you don't want to read the script to reverse engineer the usage
before running it???

> > It works tho:
> > 
> > $ ./scripts/objdump-func vmlinux rewind_stack_and_make_dead
> > 0000 ffffffff81001c00 <rewind_stack_and_make_dead>:
> > 0000 ffffffff81001c00:  31 ed                   xor    %ebp,%ebp
> > 0000 ffffffff81001c02:  65 48 8b 04 25 d0 ec 01 00      mov    %gs:0x1ecd0,%rax
> > 0000 ffffffff81001c0b:  48 8d a0 58 ff ff ff    lea    -0xa8(%rax),%rsp
> > 0000 ffffffff81001c12:  e8 39 24 07 00          call   ffffffff81074050 <make_task_dead>
> > ^^^^
> > 
> > I guess those zeros at the beginning are supposed to mean something...
> 
> Use the .o file and it'll work:

Should probably get fixed to work on vmlinux too...

-- 
Josh