Date: Wed, 23 Mar 2011 21:50:57 +0100 (CET) From: Oliver Fromme <olli@lurza.secnetix.de> To: arundel@FreeBSD.ORG (Alexander Best) Cc: bz@FreeBSD.ORG, freebsd-arch@FreeBSD.ORG Subject: Re: kernel memory checks on boot vs. boot time Message-ID: <201103232050.p2NKov4g017463@lurza.secnetix.de> In-Reply-To: <20110323200200.GA85810@freebsd.org>
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Alexander Best wrote: > On Wed Mar 23 11, Oliver Fromme wrote: > > Alexander Best wrote: > > > just as a side note: booting a kernel directly from boot stage 2 is broken on > > > amd64. :( so there's no way around using the boot loader, which will cost extra > > > time (even with autoboot_delay=0). > > > > > > so was the adbility to boot a kernel directly from boot2 abandoned? i heard > > > reports it still works under i386. dunno about the other archs. > > > > The loader checks the type of the kernel binary (i386 vs > > amd64). In case of amd64, it enables "long mode", among > > other things. This is required for amd64, because the > > kernel expects to be started in long mode. boot2 doesn't > > do that, so you can't start an amd64 kernel directly from > > boot2. > > hmm...i can't seem to find the location in loader/main.c. could you pinpoint > me to the exact location? this is something i'd *really* like to try in amd64. The actual code is in sys/boot/i386/libi386/amd64_tramp.S which is called from sys/boot/i386/libi386/elf64_freebsd.c (see the elf64_exec() function), which in turn is called indirectly via a method of a struct file_format from the boot loader. Beware, I don't know if this is the *only* thing preventing boot2 from booting an amd64 kernel. There might be more. I haven't tried booting FreeBSD without the boot loader in a long time. Probably not in this century. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "I made up the term 'object-oriented', and I can tell you I didn't have C++ in mind." -- Alan Kay, OOPSLA '97
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