linux-kernel - Re: [PATCH v6 03/30] objtool: Disassemble code with libopcodes instead of running objdump

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Message-ID: <49230c95-290e-4d14-bc4b-b63a1a07fc98@oracle.com>
Date: Wed, 10 Dec 2025 08:06:51 +0100
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: "Maciej W. Rozycki" <macro@...am.me.uk>
Cc: alexandre.chartre@...cle.com, Guenter Roeck <linux@...ck-us.net>,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        jpoimboe@...nel.org, peterz@...radead.org,
        david.laight.linux@...il.com
Subject: Re: [PATCH v6 03/30] objtool: Disassemble code with libopcodes
 instead of running objdump


On 12/9/25 23:25, Maciej W. Rozycki wrote:
> On Tue, 9 Dec 2025, Alexandre Chartre wrote:
> 
>>> Bisect log is attached. I see the problem with gcc 11.4.0, 13.3.0, and
>>> 14.3.0. I tried with both Ubuntu 22.04 and 24.04.
>>
>> This sounds like a configuration issue depending on the binutils version; in
>> particular the setting of DISASM_INIT_STYLED (although that's supposed to be
>> automatically configured by tools/objtool/Makefile).
> 
>   I only came across these patches now.
> 
>   As attractive as it may seem how is this stuff supposed to fly given that
> binutils internal libraries promise no stable API to out-of-tree software.
> The interfaces can change anytime, just as it is with our internals.

Note that bpf (tools/bpf) is also using libbfd and libopcodes.

>   Wouldn't it make sense to improve objdump instead so as to provide the
> features required?

Some disassembly features of objtool can certainly make sense in objdump
(like the support for disassembling alternatives).

But the primary goal was to provide a disassembly tracing option (--trace)
to help troubleshoot objtool validation failures. But this is specific to the
kernel build workflow, so this part would probably not make sense in objdump.

alex.

>   Also is it actually legal to link objtool and libopcodes together, given
> that they are GPLv2 and GPLv3 respectively?
> 
>   FWIW asking as one of the binutils contributors and port maintainers.
> 
>    Maciej