linux-kernel - Re: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86

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Date:	Fri, 7 Oct 2011 17:09:17 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Stephane Eranian <eranian@...gle.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	peterz@...radead.org, mingo@...e.hu, acme@...hat.com,
	ming.m.lin@...el.com, robert.richter@....com, ravitillo@....gov
Subject: Re: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86

> if (kernel_ip(addr) || !test_tsk_thread_flag(current, TIF_IA32))

That's not good, a 64bit process can do 32bit syscalls.

The only fully working way is to check the code segment, unfortunately
that requires checking the LDT to be fully correct :-(

In 2.4 we had some code for that if you want to copy, but it disappeared
later.

-Andi
-- 
ak@...ux.intel.com -- Speaking for myself only.
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