Date: Fri, 13 Dec 2002 17:07:22 -0800 (PST) From: Julian Elischer <julian@elischer.org> To: Peter Wemm <peter@wemm.org> Cc: Dan Nelson <dnelson@allantgroup.com>, Nate Lawson <nate@root.org>, Kevin Oberman <oberman@es.net>, FreeBSD current users <current@FreeBSD.ORG>, re@freebsd.org Subject: Re: 5.0 showstopper Message-ID: <Pine.BSF.4.21.0212131652110.9978-100000@InterJet.elischer.org> In-Reply-To: <20021214004513.733AB2A7EA@canning.wemm.org>
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On Fri, 13 Dec 2002, Peter Wemm wrote:
> Julian Elischer wrote:
> > On Fri, 13 Dec 2002, Julian Elischer wrote:
> > > On Fri, 13 Dec 2002, Dan Nelson wrote:
> > >
> > > > In the last episode (Dec 13), Julian Elischer said:
> > > > > It's always been there. the question is
> > > > > "Who has broken it?"
> > >
> > > I think this is a 5.0 showstopper. Having 5.0 overwrite your
> > > Windows partition would be "poor" PR.
> > > Having a quick look at it, it shouldn't be too hard for PHK
> > > to fix it as he has all the correct parts currently "loaded"
> > > into his head. Especially such things as making GEOM not allow writes
> > > to -ve blocknumbers (as must have happenned for root to have been
> > > overwritten).
> >
> >
> > looking at the code in src/sys/i386/i386/dump_machdep.c,
> >
> > we see:
> > 78 dumplo = di->mediaoffset + di->mediasize - Maxmem *
> > (off_t)PAGE_SIZE;
> > 79 dumplo -= sizeof kdh * 2;
> > 80 i = di->dumper(di->priv, &kdh, 0, dumplo, sizeof kdh);
> > 81 if (i)
> > 82 printf("\nDump failed writing header (%d)\n", i);
> > 83 dumplo += sizeof kdh;
> > 84 i = 0;
> >
> > It looks like the following test should go after line 77
> >
> > if (di->mediasize < ((Maxmem * (off_t)PAGE_SIZE) +
> > (sizeof kdh * 2) + (16*1024)) {
> > /* 16K is an arbitrary buffer
> > * in case the swap part is
> > * the first part
> > */
> > printf("\nDump failed. Partition too small.\n");
> > return;
> > }
>
> We used to force a 64K safety buffer for swapon, and I think we also did
> 64K for dump before the last MI dump code conversion. I'd feel a little
> happier if you used 64K here instead of 16K.
Actually I think we could put this in the MI code....
somewhat like as follows:
src/sys/kern/kern_shutdown.c
228 static void
229 doadump(void)
230 {
231 savectx(&dumppcb);
232 dumping++;
> > if (dumper.mediasize < ((Maxmem * (off_t)PAGE_SIZE) +
> > (sizeof kdh * 2) + (16*1024)) {
> > /* 16K is an arbitrary buffer
> > * in case the swap part is
> > * the first part
> > */
> > printf("\nDump failed. Partition too small.\n");
> > return;
> > }
233 dumpsys(&dumper);
234 }
but I guess that assumes that each architecture doesn't have sparse
dumps or sparse address spaces..
>
>
> Cheers,
> -Peter
> --
> Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com
> "All of this is for nothing if we don't go to the stars" - JMS/B5
>
>
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