Date: Mon, 12 Jul 2010 00:38:49 +0300 From: Andriy Gapon <avg@freebsd.org> To: Jeff Roberson <jroberson@jroberson.net> Cc: Peter Wemm <peter@freebsd.org>, freebsd-hackers@freebsd.org, Jeff Roberson <jeff@freebsd.org>, Konstantin Belousov <kib@freebsd.org>, "Bjoern A. Zeeb" <bzeeb-lists@lists.zabbadoz.net> Subject: Re: elf obj load: skip zero-sized sections early Message-ID: <4C3A39E9.1070505@freebsd.org> In-Reply-To: <alpine.BSF.2.00.1007111112490.1414@desktop> References: <4C246CD0.3020606@freebsd.org> <20100702082754.S14969@maildrop.int.zabbadoz.net> <4C320E6E.4040007@freebsd.org> <20100705171155.K14969@maildrop.int.zabbadoz.net> <4C321409.2070500@freebsd.org> <4C343C68.8010302@freebsd.org> <4C36FB32.30901@freebsd.org> <4C39B0E6.3090400@freebsd.org> <4C39B7DE.3030100@freebsd.org> <alpine.BSF.2.00.1007111112490.1414@desktop>
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on 12/07/2010 00:15 Jeff Roberson said the following: > > On Sun, 11 Jul 2010, Andriy Gapon wrote: > >> >> [oops, sorry, this is not a dup - corrected some omissions/mistakes] >> >> on 11/07/2010 14:54 Andriy Gapon said the following: >>> For completeness, here is a patch that simply drops the inline >>> assembly and the >>> comment about it, and GCC-generated assembly and its diff: >>> http://people.freebsd.org/~avg/dpcpu/pcpu.new.patch >>> http://people.freebsd.org/~avg/dpcpu/dpcpu.new.s >>> http://people.freebsd.org/~avg/dpcpu/dpcpu.new.diff >>> >>> As was speculated above, the only thing really changed is section >>> alignment >>> (from 128 to 4). >> >> After making the above analysis I wondered why we require set_pcpu >> section >> alignment at all. After all, it's not used as loaded, data from the >> section >> gets copied into special per-cpu memory areas. So, logically, it's >> those areas >> that need to be aligned, not the section. > > I appreciate your analysis but I don't understand the motivation for > changing working code. Primary reason is that the "working code" produces zero-sized unused/unnecessary pcpu_set sections. See the subject line. As to why I care about those sections - please see the start of this thread. P.S. Short summary: there is no reason to have zero sized sections; some tools either do not expect them or handle them suboptimally. -- Andriy Gapon
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