linux-kernel - Re: [PATCH] kprobes: x86_64: blacklist non-attachable interrupt functions

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Message-Id: <20181217010716.34552c2f21f3dfa5e07ff1b5@kernel.org>
Date:   Mon, 17 Dec 2018 01:07:16 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Andrea Righi <righi.andrea@...il.com>
Cc:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Yonghong Song <yhs@...com>, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kprobes: x86_64: blacklist non-attachable interrupt
 functions

On Sat, 8 Dec 2018 08:09:22 +0100
Andrea Righi <righi.andrea@...il.com> wrote:

> On Sat, Dec 08, 2018 at 12:48:59PM +0900, Masami Hiramatsu wrote:
> > On Fri, 7 Dec 2018 18:58:05 +0100
> > Andrea Righi <righi.andrea@...il.com> wrote:
> > 
> > > On Sat, Dec 08, 2018 at 01:01:20AM +0900, Masami Hiramatsu wrote:
> > > > Hi Andrea and Ingo,
> > > > 
> > > > Here is the patch what I meant. I just ran it on qemu-x86, and seemed working.
> > > > After introducing this patch, I will start adding arch_populate_kprobe_blacklist()
> > > > to some arches.
> > > > 
> > > > Thank you,
> > > > 
> > > > [RFC] kprobes: x86/kprobes: Blacklist symbols in arch-defined prohibited area
> > > > 
> > > > From: Masami Hiramatsu <mhiramat@...nel.org>
> > > > 
> > > > Blacklist symbols in arch-defined probe-prohibited areas.
> > > > With this change, user can see all symbols which are prohibited
> > > > to probe in debugfs.
> > > > 
> > > > All archtectures which have custom prohibit areas should define
> > > > its own arch_populate_kprobe_blacklist() function, but unless that,
> > > > all symbols marked __kprobes are blacklisted.
> > > 
> > > What about iterating all symbols and use arch_within_kprobe_blacklist()
> > > to check if we need to blacklist them or not.
> > 
> > Sorry, I don't want to iterate all ksyms since it may take a long time
> > (especially embedded small devices.)
> > 
> > > 
> > > In this way we don't have to introduce an
> > > arch_populate_kprobe_blacklist() for each architecture.
> > 
> > Hmm, I had a same idea, but there are some arch which prohibit probing
> > extable entries (e.g. arm64.) For correctness of the blacklist, I think
> > it should be listed (not entire the function body).

Aah, my bad memory. I remember that the extable should not be in blacklist,
since it is a kind of "unsupported instruction to be probed" on some arch.
I'll move that in arch_prepare_kprobe() on arm64.

> > I also rather like to remove arch_within_kprobe_blacklist() instead.

Anyway, this is true. If I could make a complete list, I will remove
this function.

Thank you,

> 
> OK. Thanks.
> 
> -Andrea


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