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Date: Wed, 30 Mar 2016 15:52:46 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>, linux-kernel@vger.kernel.org,
        Andi Kleen <ak@linux.intel.com>, Stephane Eranian <eranian@google.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Denys Vlasenko <dvlasenk@redhat.com>, Zi Shen Lim <zlim.lnx@gmail.com>
Subject: Re: [PATCH 10/11] perf tools: Add probing for udev86 library
Message-ID: <20160330135246.GA29990@gmail.com>
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* Arnaldo Carvalho de Melo <acme@redhat.com> wrote:

> Em Wed, Mar 30, 2016 at 12:43:27PM +0200, Ingo Molnar escreveu:
> > > From: Andi Kleen <ak@linux.intel.com>
> 
> > > Add autoprobing for the udev86 disassembler library.
>  
> > So the typo in the title is confusing, what is 'udev86'?
>  
> > Also, this library does not seem to be available on stock Ubuntu. We should not be 
> > adding library dependencies that cannot be resolved on major distros:
> 
> Ok, I'll remove, I thought it would be ok because I fired up:
> 
>   # dnf install udis86-devel
> 
> On fedora and it installed straight away, but after I started trying to
> update my docker images I couldn't find it on debian
> experimental/unstable:

> Nor even in OpenSuSE:

> Or even Mageia:

Yeah, so udis86 also seems to be a pretty old, relatively stale library with no 
support for new instructions AFAICS.

So I'd rather encourage librarizing one of the x86 instruction decoders in 
arch/x86/, and adding pretty-printing functionality to it. The code can already 
see instruction boundaries, which is the hardest part.

That would also be better supported on non-x86 architectures in the long run:

 triton:~/tip> find arch/ -name insn.c | xargs ls -l
 -rw-rw-r-- 1 mingo mingo 30244 Mar 29 11:24 arch/arm64/kernel/insn.c
 -rw-rw-r-- 1 mingo mingo  1347 Dec  8 06:27 arch/arm/kernel/insn.c
 -rw-rw-r-- 1 mingo mingo 15123 Mar 30 12:31 arch/x86/lib/insn.c

Such an in-kernel-repo library could also be used by live kernel debuggers such as 
kgdb/kdb, oops/crash-time disassembly printout, etc.

... so how about that direction instead?

Thank,

	Ingo