linux-kernel - trace: trace_kprobe.c always shows interrupts off

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Date:	Tue, 17 Nov 2015 16:35:35 +0000 (UTC)
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	rostedt <rostedt@...dmis.org>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	"pt, masami" <masami.hiramatsu.pt@...achi.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: trace: trace_kprobe.c always shows interrupts off

Hi,

I notice that trace_kprobe.c does local_save_flags() within
__kprobe_trace_func(), which is called (at least on x86) with
interrupts always disabled. This is then used as interrupt on/off
state within the recorded event, which is misleading.

I also don't understand why arch/x86/kernel/kprobes/ftrace.c
pre handler disables interrupts, considering the following
comment above arch/x86/kernel/kprobes/core.c: kprobe_int3_handler()

 * Interrupts are disabled on entry as trap3 is an interrupt gate and they
 * remain disabled throughout this function.

A struct pt_regs is received by this function, but I don't see
any way to get the state of irq enable/disable from struct pt_regs
across architectures.

Any thoughts on how to fix this ?

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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