linux-kernel - Re: [PATCH v2 0/3] x86: kprobes: Show correct blaclkist in debugfs

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Date:   Mon, 17 Dec 2018 16:47:13 +0100
From:   Andrea Righi <righi.andrea@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        "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>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] x86: kprobes: Show correct blaclkist in debugfs

On Mon, Dec 17, 2018 at 05:20:25PM +0900, Masami Hiramatsu wrote:
> This is v2 series for showing correct kprobe blacklist in
> debugfs.
> 
> v1 is here:
> 
>  https://lkml.org/lkml/2018/12/7/517
> 
> I splitted the RFC v1 patch into x86 and generic parts,
> also added a patch to remove unneeded arch-specific
> blacklist check function (because those have been added
> to the generic blacklist.)
> 
> If this style is good, I will make another series for the
> archs which have own arch_within_kprobe_blacklist(), and
> eventually replace that with arch_populate_kprobe_blacklist()
> so that user can get the correct kprobe blacklist in debugfs.
> 
> Thank you,

Looks good to me. Thanks!

Tested-by: Andrea Righi <righi.andrea@...il.com>

Side question: there are certain symbols in arch/x86/xen that should be
blacklisted explicitly, because they're non-attachable.

More exactly, all functions defined in arch/x86/xen/spinlock.c,
arch/x86/xen/time.c and arch/x86/xen/irq.c.

The reason is that these files are compiled without -pg to allow the
usage of ftrace within a Xen domain apparently (from
arch/x86/xen/Makefile):

 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
 CFLAGS_REMOVE_spinlock.o = -pg
 CFLAGS_REMOVE_time.o = -pg
 CFLAGS_REMOVE_irq.o = -pg
 endif

Do you see a nice and clean way to blacklist all these functions
(something like arch_populate_kprobe_blacklist()), or should we just
flag all of them explicitly with NOKPROBE_SYMBOL()?

Thanks,
-Andrea