Date: Thu, 29 Jun 2017 19:35:02 -0700 From: Mark Millard <markmi@dsl-only.net> To: "Michael W. Lucas" <mwlucas@michaelwlucas.com> Cc: hackers@freebsd.org Subject: Re: extract panic message & debugging from vmcore.0 ? Message-ID: <DC97F55F-7672-4429-9E3F-665CDA98D3F0@dsl-only.net> In-Reply-To: <20170630021205.GA43579@mail.michaelwlucas.com> References: <20170630021205.GA43579@mail.michaelwlucas.com>
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On 2017-Jun-29, at 7:12 PM, Michael W. Lucas <mwlucas@michaelwlucas.com> = wrote: > Short question: how do I get debug information for a PR from a vmcore? >=20 > Long question: we have conflicting docs. Which should I follow? >=20 > Good news: I needed a panic for the new "Absolute FreeBSD" anyway, > this one will do. >=20 > Details: >=20 > I got an actual kernel panic by running "gpart resize" on: >=20 > FreeBSD storm 12.0-CURRENT FreeBSD 12.0-CURRENT #1 r318747: Tue May 23 = 16:27:01 EDT 2017 root@storm:/usr/obj/usr/src/sys/GENERIC amd64 >=20 > I dumped it at the panic prompt, savecore ran at boot. According to > the Handbook, the next step is to run "kgdb kernel.debug vmcore.0" to > recover the panic message. But no kgdb is installed. Look for /usr/libexec/kgdb . But for some, most, or all TARGET_ARCH's the FreeBSD folks now recommend using kgdb from ports. (Which you built and installed.) /usr/libexec/kgdb is more for means-of-last-resort use when one can not get to the point of having the port kgdb around. > After some searching, I installed devel/gdb. >=20 > # kgdb kernel.debug /var/crash/vmcore.0 > GNU gdb (GDB) 7.12.1 [GDB v7.12.1 for FreeBSD] > Copyright (C) 2017 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later = <http://gnu.org/licenses/gpl.html>; > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show = copying" > and "show warranty" for details. > This GDB was configured as "x86_64-portbld-freebsd12.0". > Type "show configuration" for configuration details. > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > Find the GDB manual and other documentation resources online at: > <http://www.gnu.org/software/gdb/documentation/>. > For help, type "help". > Type "apropos word" to search for commands related to "word"... > Reading symbols from kernel.debug...done. > ABI doesn't support a vmcore target >=20 > Well, that's not good. I did more searching and found > /usr/src/tools/debugscripts/README. >=20 > # cd /usr/obj/usr/src/sys/GENERIC > # make gdbinit > # gdb kernel.debug Did you miss a /var/crash/vmcore.0 above? > GNU gdb (GDB) 7.12.1 [GDB v7.12.1 for FreeBSD] > Copyright (C) 2017 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later = <http://gnu.org/licenses/gpl.html>; > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show = copying" > and "show warranty" for details. > This GDB was configured as "x86_64-portbld-freebsd12.0". > Type "show configuration" for configuration details. > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > Find the GDB manual and other documentation resources online at: > <http://www.gnu.org/software/gdb/documentation/>. > For help, type "help". > Type "apropos word" to search for commands related to "word"... > Reading symbols from kernel.debug...done. > .gdbinit:16: Error in sourced command file: > No symbol "remotebaud" in current context. Unsure about the above. Separately. . . I'm no expert but you might need to pick between the default minidump vs. a full memory dump depending on purposes and what information is to be extracted: debug.minidump: 1 vs. debug.minidump: 0 in the sysctl debug.minidump output. I doubt that they are fully equivalent. Of course a full memory dump implies needing space ready to hold that full copy. =3D=3D=3D Mark Millard markmi at dsl-only.net
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