Date: Thu, 18 Jun 2009 13:42:55 +0200 From: Thomas Backman <serenity@exscape.org> To: Andriy Gapon <avg@icyb.net.ua> Cc: Wesley Shields <wxs@FreeBSD.org>, freebsd-current@FreeBSD.org Subject: Re: DTrace panic while probing syscall::open (and possibly many others) Message-ID: <DD13EADF-CE41-465A-8D70-53DCDEFD65A7@exscape.org> In-Reply-To: <4A3A1D27.4010802@icyb.net.ua> References: <949B5884-5303-4EFF-AC7D-293640FFA012@exscape.org> <0C235698-3ED2-4AE9-A7D1-5DC56D8324A4@exscape.org> <200905212129.47892.mel.flynn%2Bfbsd.current@mailing.thruhere.net> <44F486FA-E798-448D-BE31-F7A51EF1F612@exscape.org> <60173AF0-7E54-4BDD-8927-0DADA9DAD1B4@exscape.org> <20090522200306.GE2630@atarininja.org> <20090617225849.GB28509@atarininja.org> <B2F32C8F-810B-4EA5-9E34-39ADD5E5CED4@exscape.org> <4A3A1D27.4010802@icyb.net.ua>
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On Jun 18, 2009, at 12:55 PM, Andriy Gapon wrote: > on 18/06/2009 12:43 Thomas Backman said the following: >> >> at dtrace_isa.c:527 >> #14 0xffffffff816b31fc in dtrace_copyinstr (uaddr=34365163021, >> kaddr=18446743524025463312, size=256, flags=0xffffffff8146e0c0) >> at dtrace_isa.c:558 > > kaddr=18446743524025463312 == FFFFFF8004467210 > I think kernelbase on amd64 is 0xFFFFFFFF80000000. > FFFFFF8004467210 kaddr > is smaller than > FFFFFFFF80000000 kernelbase > > The numbers do look suspiciously similar, so I am not sure if you > are seeing a > race or a real bug somewhere. > -- > Andriy Gapon Hmmm... Looking around a bit for these numbers, I found, in /sys/amd64/include/ vmparam.h: /* * Virtual addresses of things. Derived from the page directory and * page table indexes from pmap.h for precision. * * 0x0000000000000000 - 0x00007fffffffffff user map * 0x0000800000000000 - 0xffff7fffffffffff does not exist (hole) * 0xffff800000000000 - 0xffff804020100fff recursive page table (512GB slot) * 0xffff804020101000 - 0xfffffeffffffffff unused * 0xffffff0000000000 - 0xffffff7fffffffff 512GB direct map mappings * 0xffffff8000000000 - 0xffffffffffffffff 512GB kernel map * * Within the kernel map: * * 0xffffffff80000000 KERNBASE */ So, kaddr is inside the "kernel map", but not KERNBASE. What this means, I have no clue whatsoever. (I'm not a kernel developer and I don't know too much about (virtual) memory either!) Regards, Thomas
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