linux-kernel - Re: [PATCH 5/5] x86: ftrace: fix the comments for ftrace_modify_code

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Message-ID: <alpine.DEB.2.11.1512051811320.3595@nanos>
Date:	Sat, 5 Dec 2015 18:12:57 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Li Bin <huawei.libin@...wei.com>
cc:	rostedt@...dmis.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	x86@...nel.org
Subject: Re: [PATCH 5/5] x86: ftrace: fix the comments for
 ftrace_modify_code_direct

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?

Thanks,

	tglx
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