Subject: Re: [PATCH 5/5] x86: ftrace: fix the comments for
 ftrace_modify_code_direct
To: Steven Rostedt <rostedt@goodmis.org>, Thomas Gleixner <tglx@linutronix.de>
References: <1449214067-12177-1-git-send-email-huawei.libin@huawei.com>
 <1449214067-12177-6-git-send-email-huawei.libin@huawei.com>
 <alpine.DEB.2.11.1512051811320.3595@nanos>
 <20151205175233.5a0f75cf@gandalf.local.home>
CC: <mingo@redhat.com>, <linux-kernel@vger.kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>, <x86@kernel.org>
From: Li Bin <huawei.libin@huawei.com>
Message-ID: <56639667.3010508@huawei.com>
Date: Sun, 6 Dec 2015 09:59:03 +0800
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on 2015/12/6 6:52, Steven Rostedt wrote:
> On Sat, 5 Dec 2015 18:12:57 +0100 (CET)
> Thomas Gleixner <tglx@linutronix.de> wrote:
>
>> On Fri, 4 Dec 2015, Li Bin wrote:
>>> --- a/arch/x86/kernel/ftrace.c
>>> +++ b/arch/x86/kernel/ftrace.c
>>> @@ -106,13 +106,12 @@ ftrace_modify_code_direct(unsigned long ip, unsigned const char *old_code,
>>>  	unsigned char replaced[MCOUNT_INSN_SIZE];
>>>  
>>>  	/*
>>> -	 * Note: Due to modules and __init, code can
>>> -	 *  disappear and change, we need to protect against faulting
>>> -	 *  as well as code changing. We do this by using the
>>> -	 *  probe_kernel_* functions.
>>> -	 *
>>> -	 * No real locking needed, this code is run through
>>> -	 * kstop_machine, or before SMP starts.
>>> +	 * Note:
>>> +	 * We are paranoid about modifying text, as if a bug were to happen, it
>>> +	 * could cause us to read or write to someplace that could cause harm.
>>> +	 * Carefully read and modify the code with aarch64_insn_*() which uses  
>> aarch64_insn_() is related to x86 in which way?
>>
>>
> The original comment is incorrect and we discussed this with the
> arm64 code, and said the other archs need the comment updated as
> well. But it seems that Li Bin just cut and pasted the arm64 patch for
> the other archs, or at least with x86 (haven't looked at the others
> yet). This needs to be fixed.

Sorry for my mistake, I will modify it.

Thanks,
Li Bin

> -- Steve
>
> .
>


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