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Message-ID: <44E5AFD9.1050101@innova-card.com>
Date:	Fri, 18 Aug 2006 14:17:29 +0200
Reply-To: Franck <vagabon.xyz@gmail.com>
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To:	Atsushi Nemoto <anemo@mba.ocn.ne.jp>
CC:	vagabon.xyz@gmail.com, ralf@linux-mips.org,
	linux-mips@linux-mips.org
Subject: Re: [PATCH] Remove mfinfo[64] used by get_wchan()
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From:	Franck Bui-Huu <vagabon.xyz@gmail.com>
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Atsushi Nemoto wrote:
> On Fri, 18 Aug 2006 10:50:01 +0200, Franck Bui-Huu <vagabon.xyz@gmail.com> wrote:
>> Does something like this seem correct ? If an exception occured on a first
>> instruction of a function, show_backtrace() will call get_frame_info()
>> with info->func_size != 0 but very small. In this case it returns 1.
> 
> Why get_frame_info() will be called with info->func_size != 0 ?  The
> offset of a _first_ instruction is 0, so "ofs" of this line in
> unwind_stack() will be 0.
> 
> 	info.func_size = ofs;	/* analyze from start to ofs */
> 

because in unwind_stack(), before the line you showed, we do:

	if (!kallsyms_lookup(pc, &size, &ofs, &modname, namebuf))
		return 0;
	if (ofs == 0)
		return 0;

Maybe we should do instead:

	if (!kallsyms_lookup(pc, &size, &ofs, &modname, namebuf))
		return 0;
	/* return ra if an exception occured at the first instruction */
	if (ofs == 0)
		return ra;

And in any cases, if we pass info->func_size = 0 to get_frame_info(),
then it will consider the function size as unknown.

		Franck