linux-kernel - Re: [PATCH v3 2.6.39-rc1-tip 7/26] 7: x86: analyze instruction and determine fixups.

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Message-ID: <20110421173120.GJ10698@linux.vnet.ibm.com>
Date:	Thu, 21 Apr 2011 23:01:20 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Hellwig <hch@...radead.org>,
	Jonathan Corbet <corbet@....net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	SystemTap <systemtap@...rces.redhat.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v3 2.6.39-rc1-tip 7/26]  7: x86: analyze instruction
 and determine fixups.

* Steven Rostedt <rostedt@...dmis.org> [2011-04-19 09:29:11]:

> On Fri, 2011-04-01 at 20:03 +0530, Srikar Dronamraju wrote:
> 
> > +
> > +static void report_bad_prefix(void)
> > +{
> > +	printk(KERN_ERR "uprobes does not currently support probing "
> > +		"instructions with any of the following prefixes: "
> > +		"cs:, ds:, es:, ss:, lock:\n");
> > +}
> > +
> > +static void report_bad_1byte_opcode(int mode, uprobe_opcode_t op)
> > +{
> > +	printk(KERN_ERR "In %d-bit apps, "
> > +		"uprobes does not currently support probing "
> > +		"instructions whose first byte is 0x%2.2x\n", mode, op);
> > +}
> > +
> > +static void report_bad_2byte_opcode(uprobe_opcode_t op)
> > +{
> > +	printk(KERN_ERR "uprobes does not currently support probing "
> > +		"instructions with the 2-byte opcode 0x0f 0x%2.2x\n", op);
> > +}
> 
> Should these really be KERN_ERR, or is KERN_WARNING a better fit?
> 
> Also, can a non-privileged user cause these printks to spam the console
> and cause a DoS to the system?
> 

Sometimes, the user might try registering a probe at a valid file +
valid offset + valid consumer; but an instruction that we cant probe.
Then trying to figure why its failing would be very hard.

how about pr_warn_ratelimited()?

-- 
Thanks and Regards
Srikar
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