Date: Thu, 10 May 2012 08:32:23 -0400 From: Marcel Moolenaar <marcel@xcllnt.net> To: Tim Kientzle <kientzle@freebsd.org> Cc: arm@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: How does loader(8) decide where to load the kernel? Message-ID: <B09F2C7F-7EAD-4194-BAA2-79319554100A@xcllnt.net> In-Reply-To: <8B01DF29-747A-449C-A762-E852F57C6380@freebsd.org> References: <3B2A320B-3ADE-4F48-B94E-4F0886178251@freebsd.org> <201205070957.03842.jhb@freebsd.org> <8B01DF29-747A-449C-A762-E852F57C6380@freebsd.org>
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On May 8, 2012, at 1:32 AM, Tim Kientzle wrote: >>> On i386, amd64, powerpc, and arm, loadimage subtracts >>> the dest value from the address declared in the actual ELF >>> headers so that the kernel always gets loaded into low memory. >>> (there's some intermediate bit-twiddling I'm glossing over, but >>> this is the general idea). >> >> The bit twiddling is supposed to be the equivalent of subtracting >> KERNBASE from the load address. On both i386 and amd64, there is >> a direct mapping of the kernel text such that KERNBASE maps address >> 0, etc. By default on i386 KERNBASE is 0xc0000000. > > Exactly my problem. This all assumes that you're loading > the kernel into low memory. > > On the AM3358, the DRAM starts at 0x8000 0000 > on boot, so I'm trying to find a clean way to convince > the loader's ELF code to put the kernel there. Look at what I did for ia64. All that frobbing should be done in the machine specific implementation of arch_copyin, arch_copyout and arch_readin. It's a kluge to do it in elf_loadimage. FYI, -- Marcel Moolenaar marcel@xcllnt.net
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