linux-kernel - Re: [BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes implementation on arm

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Date:   Sat, 18 Feb 2017 06:43:52 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     "Jon Medhurst (Tixy)" <tixy@...aro.org>
Cc:     Russell King <linux@...linux.org.uk>, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Wang Nan <wangnan0@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "David A . Long" <dave.long@...aro.org>,
        Sandeepa Prabhu <sandeepa.s.prabhu@...il.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [BUGFIX PATCH V2 0/3] kprobes/arm: Improve kprobes
 implementation on arm

On Fri, 17 Feb 2017 11:01:10 +0000
"Jon Medhurst (Tixy)" <tixy@...aro.org> wrote:

> On Wed, 2017-02-15 at 09:27 +0900, Masami Hiramatsu wrote:
> > Hi,
> > 
> > Here is the 2nd version of the patches which improve kprobe
> > on arm implementation (a kind of bugfix). Version 1 is here;
> > 
> > https://lkml.org/lkml/2017/2/13/538
> > 
> > In this version I didn't update the code, just update the
> > patch description according to Tixy's comment and add his Ack.
> > 
> > Thank you,
> > 
> > ---
> > 
> > Masami Hiramatsu (3):
> >       kprobes/arm: Allow to handle reentered kprobe on single-stepping
> >       kprobes/arm: Skip single-stepping in recursing path if possible
> >       kprobes/arm: Fix the return address of multiple kretprobes
> > 
> 
> Thanks for doing these. Am I correct in assuming we don't need to
> consider these fixes urgent or critical? Only the first looks like it
> could be serious, and the x86 fix for that is 3 years old and ARM has
> gone without it all this time. So I'm guessing it's fine to wait for the
> normal development process and deal with it after the about to open
> merge window is completed?

Agreed. I'm not sure how frequently FIQ is used in ARM, but anyway
it happens only when root user intensively uses kprobes on FIQ handlers.

> If so, I propose that I put the patches in a branch for Russell to pull
> later (unless he pipes up with objections or says otherwise). Meantime
> I'll investigate the kprobes test failures I see (which actually looks
> like cache/TLB issues and not test code problems after all).

OK, btw, I couldn't reproduce the kprobes test failure with
CONFIG_DEBUG_RODATA=y on qemu...

> 
> BTW, I added the ARM kernel list to the CC. I spotted you didn't add it
> to you patch postings, which means people interested in ARM (other than
> Russell) wouldn't have seen them.

Ah, I forgot that, Thank you!

> 
> Thanks
> 
> -- 
> Tixy


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