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From: Steven Rostedt <rostedt@goodmis.org>
To: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	yrl.pp-manager.tt@hitachi.com
Subject: Re: [PATCH -tip v2 3/9] ftrace/x86: Support SAVE_REGS feature on i386
Date: Tue, 05 Jun 2012 19:37:50 -0400	[thread overview]
Message-ID: <1338939470.13348.541.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20120605212411.GC11575@redhat.com>

On Tue, 2012-06-05 at 17:24 -0400, Frank Ch. Eigler wrote:
> Hi -
> 
> On Tue, Jun 05, 2012 at 04:37:46PM -0400, Steven Rostedt wrote:
> > [...]
> > I'm not sure we really need to restore all the regs. I'll keep this for
> > now, but for an optimization, we can just restore the ones that mcount
> > mcount needs to.
> > 
> > Or do you expect kprobes to change any of theses?
> 
> That would be the way for a kprobe to modify variables/values that
> happen to be in the registers.  In systemtap, for example:
> 
> # stap -g -e 'probe kernel.function("foo") { $bar = 1 }'
> 

And why would we want to allow this?


Modifying variables with probes is another way to lead to disaster. If
the system did not intend for a variable to be a certain value, why let
someone change it?

What real world example leads to external sources modifying internal
core variables? With the obvious exception of rootkits.

-- Steve



  reply	other threads:[~2012-06-05 23:37 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-05 10:27 [PATCH -tip v2 0/9]ftrace,kprobes: Ftrace-based kprobe optimization Masami Hiramatsu
2012-06-05 10:27 ` [PATCH -tip v2 1/9] ftrace: Add pt_regs acceptable trace callback Masami Hiramatsu
2012-06-05 10:27 ` [PATCH -tip v2 2/9] ftrace/x86-64: support SAVE_REGS feature on x86-64 Masami Hiramatsu
2012-06-05 10:28 ` [PATCH -tip v2 3/9] ftrace/x86: Support SAVE_REGS feature on i386 Masami Hiramatsu
2012-06-05 20:37   ` Steven Rostedt
2012-06-05 21:24     ` Frank Ch. Eigler
2012-06-05 23:37       ` Steven Rostedt [this message]
2012-06-05 23:41         ` Frank Ch. Eigler
2012-06-06 14:37           ` Masami Hiramatsu
2012-06-06 14:46             ` Steven Rostedt
2012-06-05 21:51   ` Andi Kleen
2012-06-06 14:24     ` Masami Hiramatsu
2012-06-05 10:28 ` [PATCH -tip v2 4/9] ftrace: add ftrace_set_filter_ip() for address based filter Masami Hiramatsu
2012-08-21 15:09   ` [tip:perf/core] " tip-bot for Masami Hiramatsu
2012-06-05 10:28 ` [PATCH -tip v2 5/9] kprobes: Inverse taking of module_mutex with kprobe_mutex Masami Hiramatsu
2012-08-21 15:09   ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-06-05 10:28 ` [PATCH -tip v2 6/9] kprobes: cleanup to separate probe-able check Masami Hiramatsu
2012-08-21 15:10   ` [tip:perf/core] " tip-bot for Masami Hiramatsu
2012-06-05 10:28 ` [PATCH -tip v2 7/9] kprobes: Move locks into appropriate functions Masami Hiramatsu
2012-08-21 15:11   ` [tip:perf/core] " tip-bot for Masami Hiramatsu
2012-06-05 10:28 ` [PATCH -tip v2 8/9] kprobes: introduce ftrace based optimization Masami Hiramatsu
2012-08-21 15:13   ` [tip:perf/core] " tip-bot for Masami Hiramatsu
2012-06-05 10:28 ` [PATCH -tip v2 9/9] kprobes/x86: ftrace based optimization for x86 Masami Hiramatsu
2012-08-21 15:14   ` [tip:perf/core] " tip-bot for Masami Hiramatsu
2012-06-05 11:48 ` [PATCH -tip v2 0/9]ftrace,kprobes: Ftrace-based kprobe optimization Steven Rostedt

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