linux-kernel - Re: [PATCH tip/master v4] kprobes: extable: Identify kprobes' insn-slots as kernel text area

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Message-Id: <20170111185745.66af396b4b2bacc02ac343fb@kernel.org>
Date:   Wed, 11 Jan 2017 18:57:45 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH tip/master v4] kprobes: extable: Identify kprobes'
 insn-slots as kernel text area

On Tue, 10 Jan 2017 15:42:07 -0600
Josh Poimboeuf <jpoimboe@...hat.com> wrote:

> On Tue, Jan 10, 2017 at 09:59:23AM +0100, Peter Zijlstra wrote:
> > On Mon, Jan 09, 2017 at 11:36:48AM -0600, Josh Poimboeuf wrote:
> > > BTW, I think we'll have more problems with generated code if/when we
> > > move to an x86 DWARF unwinder, because it won't have any idea how to
> > > unwind past generated code.  Long term I wonder if it would make sense
> > > to create some kind of framework for creating or registering generated
> > > code, so we can solve these types of problems in a single place.
> > 
> > Yes, this seems like a good idea. Maybe we could pull the rbtree thing
> > from modules and make that a more generic interface for code
> > registration.
> 
> Yeah, a generic fast lookup for module+generated code could be useful.
> It would also be nice to associate names with generated functions and
> integrate that with kallsyms.  For DWARF we would also need a way to
> associate CFI metadata with address ranges.

>From the kprobe point of view, kallsyms and DWARF seems a bit overkill.
At least for kprobe insn slots, I think one symbol per page instead of
each entry will be better and CFI also should be generated for each call.

Thank you,

-- 
Masami Hiramatsu <mhiramat@...nel.org>