On Thu, Oct 26, 2006 at 10:28:09AM -0400, John Baldwin wrote: > On Thursday 26 October 2006 10:18, Ruslan Ermilov wrote: > > On Thu, Oct 26, 2006 at 10:52:30PM +1000, Bruce Evans wrote: > > > On Thu, 26 Oct 2006, Ruslan Ermilov wrote: > > > >3) It's currently broken even on i386; backing out > > > > rev. 1.71 of boot2.c by jhb@ fixes this for me. > > > > > > > >: revision 1.71 > > > >: date: 2004/09/18 02:07:00; author: jhb; state: Exp; lines: +3 -3 > > > >: A long, long time ago in a CVS branch far away (specifically, HEAD > > > >prior > > > >: to 4.0 and RELENG_3), the BTX mini-kernel used paging rather than flat > > > >: mode and clients were limited to a virtual address space of 16 > > > >megabytes. > > > >: Because of this limitation, boot2 silently masked all physical > > > >addresses > > > >: in any binaries it loaded so that they were always loaded into the > > > >first > > > >: 16 Meg. Since BTX no longer has this limitation (and hasn't for a long > > > >: time), remove the masking from boot2. This allows boot2 to load > > > >kernels > > > >: larger than about 12 to 14 meg (12 for non-PAE, 14 for PAE). > > > >: > > > >: Submitted by: Sergey Lyubka devnull at uptsoft dot com > > > >: MFC after: 1 month > > > > > > The kernel is linked at 0xc0000000 but loade din low memory, so the high > > > bits must be masked off like they used to be for the kernel to boot at > > > all. > > > This has nothing to do with paging AFAIK. Rev.1.71 makes no sense, since > > > BTX isn't large, and large kernels are more unbootable than before with > > > 1.71. > > > > > The real purpose of this commit was to allow to directly "load kernels > > larger than about 12 to 14 meg (12 for non-PAE, 14 for PAE)". (Old > > version masked high 8 bits, leaving only 2^24=16MB for the kernel.) > > > > I have compiled GENERIC and PAE kernels; objdump(1) reports that GENERIC > > kernel has virtual "start address 0xc0449cb0", and PAE has virtual "start > > address 0xc02458f0". > > Yes, KERNLOAD for PAE is 2MB and for non-PAE is 4MB (to skip PSE page 0). > > > What happens here is that BTX now uses flat memory model, and by not > > masking higher bits at all, BTX attempts to load kernels at above 3G, > > which silently fails, and then jumps to the entry point located in > > "no memory" unless the machine has enough memory. > > > > If the machine has enough physical memory, e.g. 4G, then it works (I > > think that was the case on the machine John tested this change), but > > on my test machine I only have 3G of memory, so it fails. > > Actually, it should never work, as the kernel assumes it is loaded at > KERNLOAD. > > > My interim solution to the problem that would still allow booting > > larger than 16MB kernels is to mask some of the higher bits. > > Currently, I mask 28 bits that gives possible 256MB which is probably > > practical. > > boot2 should do whatever loader does. > But this would be a regression, since loader(8) does the following, in the ELF32 case:
: 0 edoofus:ttyp2:/sys/boot/i386/libi386 >grep -w entry elf32_freebsd.c
: vm_offset_t entry, bootinfop, modulep, kernend;
: entry = ehdr->e_entry & 0xffffff;
: printf("Start @ 0x%lx ...\n", entry);
: __exec((void *)entry, boothowto, bootdev, 0, 0, 0, bootinfop, modulep,
kernend);
Cheers,
--
Ruslan Ermilov
[EMAIL PROTECTED]
FreeBSD committer
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