Date: Mon, 5 Feb 2007 04:00:38 -0800 From: Luigi Rizzo <rizzo@icir.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: current@freebsd.org Subject: Re: link_elf.c vs link_elf_obj.c ? Message-ID: <20070205040037.A35752@xorpc.icir.org> In-Reply-To: <20070205115553.GA3304@deviant.kiev.zoral.com.ua>; from kostikbel@gmail.com on Mon, Feb 05, 2007 at 01:55:53PM %2B0200 References: <20070202172756.A2649@xorpc.icir.org> <20070205115553.GA3304@deviant.kiev.zoral.com.ua>
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On Mon, Feb 05, 2007 at 01:55:53PM +0200, Kostik Belousov wrote: > On Fri, Feb 02, 2007 at 05:27:56PM -0800, Luigi Rizzo wrote: > > does anyone know what is the difference between these two files ? > > They seem to do two similar but slightly different things related > > to elf file loading. > > > > But diff shows large pieces of common code, and there is even > > more commonality if you factor out whitespace changes and > > variable renaming. > > ELF specification defines 3 kinds of objects (putting core files aside); > - executables > - shared objects (AKA .so) > - relocatable objects (AKA .o, created by assembler). > Executables and .so are usually created by linker, while relocatables are the > assembler output (although ld -r can glue several .o files into one). > Executables and .so are in some sense finalized, and they contain a tables > that are useful for dynamic linker. Also, they usually carry different kind > of relocations then relocatables. > > Now, in-kernel dynamic linker used for linking newly-loaded kld, shall deal > with either .so-kind of modules (on FreeBSD, all arches except amd64), or > relocatables (amd64). Two linkers you found deal with .so-kind (link_elf.c) > or relocatables (link_elf_obj.c). > > Reasons why amd64 cannot use shared objects for kld mostly caused by > toolchains limitations and CPU architecture (it is impossible to create > working non-PIC .so there). > > Note that Solaris uses relocatables for modules. so, if one had to write a few lines of comment on top of each of these two files to tell what they do and how they differ, what would you write ? cheers luigi
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