Date: Wed, 15 Dec 2004 22:27:33 +0300 From: Igor Shmukler <shmukler@mail.ru> To: Vijay.Singh@nokia.com Cc: hackers@freebsd.org Subject: Re: loading kernel at any physical address Message-ID: <E1Ceeo9-000EFu-00.shmukler-mail-ru@f21.mail.ru> In-Reply-To: <E40595640FD457418D8F9005C2BEC8496456A2@mvebe001.americas.nokia.com>
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I think this might be somewhat off topic, but to support superpages you probably want kernel to be aligned on 4MB boundary. Also, Mach had macros for alignment. I browsed code and it seems there are macros in i386/include/asmacros.h Perhaps I am missing something, but I don't see why would you want to align with NOPS. -----Original Message----- From: <Vijay.Singh@nokia.com> To: <hackers@freebsd.org> Date: Wed, 15 Dec 2004 10:43:45 -0800 Subject: loading kernel at any physical address > Hello all, for a project I am trying to figure out how to boot a FreeBSD kernel loaded at any physical address. Right now the locore.s magic works because the load addres (KERNLOAD) and (KERNBASE) are set such that > > #define R(foo) ((foo)-KERNBASE) > > macro is able to get the addresses before paging is enabled. > > If the loadaddress information is not embedded in defines, then is the following solution expected to work: > > .globl _loadaddress /* should be at 16M aligned ??? */ > .set _loadaddress,KERNBASE > > and then: > > NON_GPROF_ENTRY(btext) > > nop /* nops for 8 byte alignment */ > nop > nop > call 0f > 0: > mov 4(%ebp), %eax > add $-8, %eax /* This is actual physical load addr */ > add $-0x100000, %eax > subl %eax, _loadaddress /* new kernbase w.r.t load addr */ > /* instead of standard 1MB reloc */ > > and then > > #define R(foo) ((foo)- _loadaddress) > > One issue might be loadaddress over 16M, but for this problem we can assume that the processor has been in protected mode, so it has access to that space. > > Any input on this is highly appreciated. > > br > vijay
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