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Date:   Mon, 24 Jan 2011 14:57:13 +0100
From:   Ralf Baechle <ralf@linux-mips.org>
To:     Wu Zhangjin <wuzhangjin@gmail.com>
Cc:     Steven Rostedt <srostedt@redhat.com>, linux-mips@linux-mips.org
Subject: Re: [PATCH 2/5] tracing, MIPS: Substitute in_kernel_space() for
 in_module()
Message-ID: <20110124135713.GA31240@linux-mips.org>
References: <cover.1295464855.git.wuzhangjin@gmail.com>
 <bce694a8e18c01fa0d2cc667561870b56a7d672f.1295464855.git.wuzhangjin@gmail.com>
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On Thu, Jan 20, 2011 at 03:28:29AM +0800, Wu Zhangjin wrote:

> @@ -91,10 +91,16 @@ int ftrace_make_nop(struct module *mod,
>  	unsigned long ip = rec->ip;
>  
>  	/*
> -	 * We have compiled module with -mlong-calls, but compiled the kernel
> -	 * without it, we need to cope with them respectively.
> +	 * If ip is in kernel space, no long call, otherwise, long call is
> +	 * needed.
>  	 */

Or even better, just check if the destination is in the same 28-bit segment
of address space.  Something like:

	if ((src ^ dst) >> 28)  {
		/* out of range of simple R_MIPS_26 relocation */
	}

That way you no longer rely on a particular address layout - and there are
plans to change the address space layout eventually!

  Ralf