From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
"H. Peter Anvin" <hpa@zytor.com>,
yrl.pp-manager.tt@hitachi.com
Subject: Re: [PATCH 5/6] ftrace/x86: Add separate function to save regs
Date: Thu, 12 Jul 2012 11:08:37 +0900 [thread overview]
Message-ID: <4FFE31A5.2030806@hitachi.com> (raw)
In-Reply-To: <1342024090.14828.45.camel@gandalf.stny.rr.com>
(2012/07/12 1:28), Steven Rostedt wrote:
> On Wed, 2012-07-11 at 12:22 -0400, Steven Rostedt wrote:
>> On Tue, 2012-07-03 at 17:29 +0900, Masami Hiramatsu wrote:
>>
>>
>>>
>>>> + /* Restore flags */
>>>> + pushq EFLAGS(%rsp)
>>>> + popfq
>>>> +
>>>> + MCOUNT_RESTORE_FRAME
>>>
>>> Here, if MCOUNT_RESTORE_FRAME has skip too, I think you don't
>>> need to restore flags before restoring other registers, like
>>> below;
>>>
>>> MCOUNT_RESTORE_FRAME 8
>>> popfq
>>>
>>> And also, this will prevent to modify flags before return by
>>> addq in MCOUNT_RESTORE_FRAME.
>>
>> Ah, because the addq will modify flags :-/
>>
>> Grumble, I guess I should implement this, even though it will make it a
>> little more complex. I thought it was better to restore flags
>> explicitly, but that's not the case.
>>
>
> I know why I did this. Do you want kprobes to be able to modify flags?
> If so, then I need to add, before the restore:
>
> movq EFLAGS(%rsp), %rax
> movq %rax, SS(%rsp)
Yes, kprobes might be used for modifying flags, so, please :)
Thank you,
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
next prev parent reply other threads:[~2012-07-12 2:08 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-02 20:03 [PATCH 0/6] [RFC v3] ftrace/kprobes: Setting up ftrace for kprobes Steven Rostedt
2012-07-02 20:03 ` [PATCH 1/6] ftrace: Pass ftrace_ops as third parameter to function trace callback Steven Rostedt
2012-07-02 20:03 ` [PATCH 2/6] ftrace: Consolidate arch dependent functions with list function Steven Rostedt
2012-07-02 20:03 ` [PATCH 3/6] ftrace: Return pt_regs to function trace callback Steven Rostedt
2012-07-03 5:19 ` Masami Hiramatsu
2012-07-11 15:28 ` Steven Rostedt
2012-08-21 15:00 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-07-02 20:03 ` [PATCH 4/6] ftrace/x86_32: Push ftrace_ops in as 3rd parameter to function tracer Steven Rostedt
2012-07-02 20:03 ` [PATCH 5/6] ftrace/x86: Add separate function to save regs Steven Rostedt
2012-07-03 8:29 ` Masami Hiramatsu
2012-07-11 16:22 ` Steven Rostedt
2012-07-11 16:28 ` Steven Rostedt
2012-07-12 2:08 ` Masami Hiramatsu [this message]
2012-07-03 16:54 ` Alexander van Heukelum
2012-07-05 20:37 ` Steven Rostedt
2012-07-02 20:03 ` [PATCH 6/6] ftrace/x86: Add save_regs for i386 function calls Steven Rostedt
2012-07-03 5:27 ` Masami Hiramatsu
2012-07-03 11:56 ` Steven Rostedt
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