Date: Thu, 02 Sep 2010 16:08:15 +0300 From: Andriy Gapon <avg@freebsd.org> To: freebsd-current@freebsd.org Subject: Re: problem with amd64 minidump Message-ID: <4C7FA1BF.30206@freebsd.org> In-Reply-To: <4C7F782B.8050507@freebsd.org> References: <4C7F782B.8050507@freebsd.org>
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on 02/09/2010 13:10 Andriy Gapon said the following: > > Not sure if this is some local issue or a problem in FreeBSD code. > I remember minidumps working perfectly well for me, but now I can not get data > from them. > Example: > dmesg -M /var/crash/vmcore.4 > dmesg: _kvm_vatop: direct map address 0xffffff012fffffe0 not in minidump > dmesg: kvm_read: invalid address (0xffffff012fffffe0) Not sure if it can help, but it seems that this virtual address in DMAP corresponds to a physical address in the last page of RAM. Do we use that for anything special? Message buffer? I had a quick look at getmemsize() function in sys/amd64/amd64/machdep.c and it looks like the following code in the function could be doing just that: Maxmem = atop(phys_avail[pa_indx]); /* Trim off space for the message buffer. */ phys_avail[pa_indx] -= round_page(MSGBUF_SIZE); /* Map the message buffer. */ msgbufp = (struct msgbuf *)PHYS_TO_DMAP(phys_avail[pa_indx]); Oh, and yeah: (gdb) p msgbufp $4 = (struct msgbuf *) 0xffffff012fffffe0 But we do dump the message buffer. But somehow its dmap address is not resolved correctly. This should ring a bell for someone knowledgeable of minidump and libkvm code, I believe. > Needless to say kgdb refuses to work with that core too. > > With kgdb on live system I can access that address: > (gdb) x/a 0xffffff012fffffe0 > 0xffffff012fffffe0: 0xffffff012ffe0000 -- Andriy Gapon
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