linux-kernel - Re: [PATCH ftrace/for-next v5 0/5] ftrace, kprobes: Introduce IPMODIFY flag for ftrace

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Message-ID: <20141009112157.17a52571@gandalf.local.home>
Date:	Thu, 9 Oct 2014 11:21:57 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Josh Poimboeuf <jpoimboe@...hat.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>
Subject: Re: [PATCH ftrace/for-next v5 0/5] ftrace, kprobes: Introduce
 IPMODIFY flag for ftrace_ops to detect conflicts

On Thu, 09 Oct 2014 13:00:59 +0000
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> Hi,
> 
> Here is the 5th version of the series of patches which introduces
> IPMODIFY flag for ftrace_ops to detect conflicts of ftrace users
> who can modify regs->ip in their handler.
> 
> The previous version is here;
>  https://lkml.org/lkml/2014/7/28/13
> 
> This version is basically an update of previous version to the
> latest ftrace tree, and adding a test code to selftest.
> 
> Currently, only kprobes can change the regs->ip in the handler,
> but recently kpatch is also want to change it. Moreover, since
> the ftrace itself exported to modules, it might be considerable
> senario.
> 
> Here we talked on github.
>  https://github.com/dynup/kpatch/issues/47
> 
> To protect modified regs-ip from each other, this series
> introduces FTRACE_OPS_FL_IPMODIFY flag and ftrace now ensures
> the flag can be set on each function entry location. If there
> is someone who already reserve regs->ip on target function
> entry, ftrace_set_filter_ip or register_ftrace_function will
> return -EBUSY. Users must handle that.
> The ftrace_ops with IPMODIFY flag requires at least one
> entry for filter hash, and its notrace_hash must be empty,
> because the IPMODIFY action is very address sensitve and
> user must consider the ip address.
> 
> The 3rd patch adds a special reservation of IPMODIFY on the
> jprobed address, since it is the only user who will change
> the regs->ip. Other kprobes do not change it anymore. 
> 
> Thank you,
> 

Masami,

Thanks for sending this. I'm going to look at it after Dusseldorf. It's
too late to get it into 3.18, but it looks like a good fit for the work
I have for 3.19.

Just don't let me forget you sent this :-)  Even though I tagged it as
important, I'm sure I'll be tagging a lot of other emails as important
in the next week.

Also, my main test box has finally died. I ordered a new motherboard
(thanks Linus for the suggestion!) and unfortunately it is due to
arrive tomorrow. That's the same day I leave and I don't trust my wife
to install it for me ;-)

This means I can not do my tests that I like to run before adding to
linux-next.

-- Steve
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