Date: Fri, 21 Sep 2012 09:56:56 -0700 From: Julian Elischer <julian@freebsd.org> To: Mikolaj Golub <trociny@freebsd.org> Cc: Anuranjan Shukla <anshukla@juniper.net>, FreeBSD Current <current@freebsd.org> Subject: Proposal for change to kernel linker for fixing a VNET and DPCPU problem. Message-ID: <505C9C58.3060006@freebsd.org> In-Reply-To: <20120921092235.GC66984@gmail.com> References: <5F3C03B6-01D0-42DE-BE9E-323DBDC90C8E@neville-neil.com> <CC6EF6B2.1917A%anshukla@juniper.net> <20120921092235.GC66984@gmail.com>
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On 9/21/12 2:22 AM, Mikolaj Golub wrote: > On Fri, Sep 07, 2012 at 01:28:16AM -0700, Anuranjan Shukla wrote: >> Hi George, >> Thanks for taking a look. Some answers/comments below. >> >>>> Building FreeBSD without the network stack (network stack as a module) >>>> ---------------------------------------------------------------------- >>>> >>> This would be interesting for many reasons, and I think it would be a good >>> contribution. Does the work you've done in this area handle the VNET >>> stuff that is in the stack as well? That is, how well does the network >>> stack >>> as a module play with the vnet architecture? >> I'll follow up on this one separately. > FYI, there is at least this issue with virtualized global variables in modules: > > http://lists.freebsd.org/pipermail/freebsd-virtualization/2011-July/000737.html > > On archs that use link_elf.c (i.e. all except amd64, which uses > link_elf_obj.c) virtualized global variables in modules can not be > accessed from another modules, because link_elf on a module load does > relocation only for VNET variables defined in this module. > > As it was pointed by Marko Zec, the same issue is with DPCPU. > > The latest patch I have (both for VNET and DPCPU): > > http://people.freebsd.org/~trociny/link_elf.c.pcpu_vnet.patch > > The fix is to make the linker on a module load recognize "external" > VNET/DPCPU variables defined in the previously loaded modules and > relocate them accordingly. For this set_pcpu_list and set_vnet_list > are used, where the addresses of modules 'set_pcpu' and 'set_vnet' > linker sets are stored in. it makes sense to me, but I really am not a linker person.. I think it woul be good to get Doug Rabson to weigh in on it, and maybe john Baldwin.. moving to -current as it's not a "net" issue really..
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