Re: kernel core debugging

Reply: Mark Millard : "Re: kernel core debugging"
In reply to: Mark Millard : "Re: kernel core debugging"
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From: <tuexen_at_freebsd.org>
Date: Wed, 06 Nov 2024 18:07:06 UTC
> On 6. Nov 2024, at 17:51, Mark Millard <marklmi@yahoo.com> wrote:
> 
> 
> 
> On Nov 6, 2024, at 09:28, tuexen@freebsd.org <tuexen@FreeBSD.org> wrote:
> 
>>> On 6. Nov 2024, at 15:12, Mark Millard <marklmi@yahoo.com> wrote:
>>> 
>>> On Nov 6, 2024, at 01:44, tuexen@freebsd.org <tuexen@FreeBSD.org> wrote:
>>> 
>>>> is debugging a kernel panic by using kgdb or lldb on a core file
>>>> supposed to work? At least it is not right now for me...
>>> 
>>> # kgdb /boot/kernel.GENERIC-NODEBUG/kernel /var/crash/vmcore.2
>>> GNU gdb (GDB) 15.1 [GDB v15.1 for FreeBSD]
>>> Copyright (C) 2024 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 "aarch64-portbld-freebsd15.0".
>>> Type "show configuration" for configuration details.
>>> For bug reporting instructions, please see:
>>> <https://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 /boot/kernel.GENERIC-NODEBUG/kernel...
>>> Reading symbols from /usr/lib/debug//boot/kernel.GENERIC-NODEBUG/kernel.debug...
>>> 
>>> Unread portion of the kernel message buffer:
>>> KDB: enter: manual escape to debugger
>>> 
>>> Reading symbols from /boot/kernel.GENERIC-NODEBUG/uhid.ko...
>>> Reading symbols from /usr/lib/debug//boot/kernel.GENERIC-NODEBUG/uhid.ko.debug...
>>> Reading symbols from /boot/kernel.GENERIC-NODEBUG/wmt.ko...
>>> Reading symbols from /usr/lib/debug//boot/kernel.GENERIC-NODEBUG/wmt.ko.debug...
>>> Reading symbols from /boot/kernel.GENERIC-NODEBUG/ums.ko...
>>> Reading symbols from /usr/lib/debug//boot/kernel.GENERIC-NODEBUG/ums.ko.debug...
>>> Reading symbols from /boot/kernel.GENERIC-NODEBUG/zfs.ko...
>>> Reading symbols from /usr/lib/debug//boot/kernel.GENERIC-NODEBUG/zfs.ko.debug...
>>> 0xffff00000050f3f0 in doadump (textdump=0, textdump@entry=212431136) at /home/pkgbuild/worktrees/main/sys/kern/kern_shutdown.c:404
>>> warning: 404 /home/pkgbuild/worktrees/main/sys/kern/kern_shutdown.c: No such file or directory
>>> (kgdb) bt
>>> #0  0xffff00000050f3f0 in doadump (textdump=0, textdump@entry=212431136) at /home/pkgbuild/worktrees/main/sys/kern/kern_shutdown.c:404
>>> #1  0xffff0000000ee6a8 in db_dump (dummy=<optimized out>, dummy2=<optimized out>, dummy3=<optimized out>, dummy4=<optimized out>) at /home/pkgbuild/worktrees/main/sys/ddb/db_command.c:596
>>> #2  0xffff0000000ee478 in db_command (last_cmdp=<optimized out>, cmd_table=<optimized out>, dopager=true) at /home/pkgbuild/worktrees/main/sys/ddb/db_command.c:508
>>> #3  0xffff0000000ee150 in db_command_loop () at /home/pkgbuild/worktrees/main/sys/ddb/db_command.c:555
>>> #4  0xffff0000000f1ff4 in db_trap (type=<optimized out>, code=<optimized out>) at /home/pkgbuild/worktrees/main/sys/ddb/db_main.c:267
>>> #5  0xffff000000568b0c in kdb_trap (type=60, code=0, tf=<optimized out>) at /home/pkgbuild/worktrees/main/sys/kern/subr_kdb.c:790
>>> #6  <signal handler called>
>>> #7  kdb_enter (why=<optimized out>, msg=<optimized out>) at /home/pkgbuild/worktrees/main/sys/kern/subr_kdb.c:556
>>> #8  0xffff0000003625cc in vt_machine_kbdevent (vd=<optimized out>, c=<optimized out>) at /home/pkgbuild/worktrees/main/sys/dev/vt/vt_core.c:761
>>> #9  vt_processkey (kbd=0xffffa000803caa80, vd=0xffff000000d24360 <vt_consdev>, c=-2147483514) at /home/pkgbuild/worktrees/main/sys/dev/vt/vt_core.c:903
>>> #10 vt_kbdevent (kbd=0xffffa000803caa80, event=<optimized out>, arg=0xffff000000d24360 <vt_consdev>) at /home/pkgbuild/worktrees/main/sys/dev/vt/vt_core.c:1030
>>> #11 0xffff0000001ea048 in kbdmux_intr (kbd=0xffffa000803caa80, arg=<optimized out>) at /home/pkgbuild/worktrees/main/sys/dev/kbdmux/kbdmux.c:565
>>> #12 0xffff0000005839ac in taskqueue_run_locked (queue=queue@entry=0xffffa000803c9c00) at /home/pkgbuild/worktrees/main/sys/kern/subr_taskqueue.c:517
>>> #13 0xffff000000583714 in taskqueue_run (queue=0xffffa000803c9c00) at /home/pkgbuild/worktrees/main/sys/kern/subr_taskqueue.c:532
>>> #14 0xffff0000004bc114 in intr_event_execute_handlers (ie=0xffffa0008028ec00, p=<optimized out>) at /home/pkgbuild/worktrees/main/sys/kern/kern_intr.c:1183
>>> #15 ithread_execute_handlers (ie=0xffffa0008028ec00, p=<optimized out>) at /home/pkgbuild/worktrees/main/sys/kern/kern_intr.c:1196
>>> #16 ithread_loop (arg=<optimized out>, arg@entry=0xffffa000803de5a0) at /home/pkgbuild/worktrees/main/sys/kern/kern_intr.c:1289
>>> #17 0xffff0000004b700c in fork_exit (callout=0xffff0000004bbd78 <ithread_loop>, arg=0xffffa000803de5a0, frame=0xffff00010ca97a00) at /home/pkgbuild/worktrees/main/sys/kern/kern_fork.c:1151
>>> #18 <signal handler called>
>>> 
>>> The context here was from an official PkgBase kernel and world
>>> installation.
>>> 
>>> . . . (deletion) . . .
>>> 
>>> You may have to be more explicit about the specific of the
>>> problem(s) you are seeing.
>> OK. Here is what I am referring to:
>> 
>> tuexen@head:~ % sudo kgdb -c /var/crash/vmcore.last /boot/kernel/kernel
> 
> That command does not match the parameter order in the man page or
> in my example.
> 
> man kgdb output shows kernel first, then core:
> 
> SYNOPSIS
>    kgdb [-a | -f | -fullname] [-b rate] [-q | -quiet] [-v] [-w]
>         [-d crashdir] [-c core | -n dumpnr | -r device] [kernel [core]]
> 
> My example: # kgdb /boot/kernel.GENERIC-NODEBUG/kernel /var/crash/vmcore.2
> 
> You might want to see if using the other order makes a difference.
No it doesn't. I'm specifying the core via the -c core option instead of 
the second argument...

Best regards
Michael
> 
>> Password:
>> GNU gdb (GDB) 15.1 [GDB v15.1 for FreeBSD]
>> Copyright (C) 2024 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 "aarch64-portbld-freebsd15.0".
>> Type "show configuration" for configuration details.
>> For bug reporting instructions, please see:
>> <https://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 /boot/kernel/kernel...
>> Reading symbols from /usr/lib/debug//boot/kernel/kernel.debug...
>> 
>> Unread portion of the kernel message buffer:
>> panic: tcp_do_segment: sent too much
>> cpuid = 1
>> time = 1730910226
>> KDB: stack backtrace:
>> db_trace_self() at db_trace_self
>> db_trace_self_wrapper() at db_trace_self_wrapper+0x38
>> vpanic() at vpanic+0x1a0
>> panic() at panic+0x48
>> tcp_do_segment() at tcp_do_segment+0x2794
>> tcp_input_with_port() at tcp_input_with_port+0xcbc
>> tcp_input() at tcp_input+0x10
>> ip_input() at ip_input+0x35c
>> netisr_dispatch_src() at netisr_dispatch_src+0xd8
>> tunwrite() at tunwrite+0x2a8
>> devfs_write_f() at devfs_write_f+0x108
>> dofilewrite() at dofilewrite+0x7c
>> kern_writev() at kern_writev+0x4c
>> sys_writev() at sys_writev+0x40
>> do_el0_sync() at do_el0_sync+0x60c
>> handle_el0_sync() at handle_el0_sync+0x4c
>> --- exception, esr 0x56000000
>> KDB: enter: panic
>> 
>> Reading symbols from /boot/kernel/tcp_rack.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/tcp_rack.ko.debug...
>> Reading symbols from /boot/kernel/tcphpts.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/tcphpts.ko.debug...
>> Reading symbols from /boot/kernel/if_bridge.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/if_bridge.ko.debug...
>> Reading symbols from /boot/kernel/bridgestp.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/bridgestp.ko.debug...
>> Reading symbols from /boot/kernel/uhid.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/uhid.ko.debug...
>> Reading symbols from /boot/kernel/wmt.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/wmt.ko.debug...
>> Reading symbols from /boot/kernel/cc_newreno.ko...
>> Reading symbols from /usr/lib/debug//boot/kernel/cc_newreno.ko.debug...
>> 0xffff0000004b5644 in doadump (textdump=0) at /usr/home/tuexen/freebsd-src/sys/kern/kern_shutdown.c:404
>> 404 dump_savectx();
>> (kgdb) up
>> #1  0x3fdb0000000e99f0 in ?? ()
>> (kgdb)  Initial frame selected; you cannot go up.
>> (kgdb)  Initial frame selected; you cannot go up.
>> (kgdb) quit
>> tuexen@head:~ % pkg info gdb  gdb-15.1
>> Name           : gdb
>> Version        : 15.1
>> Installed on   : Thu Oct 24 10:32:17 2024 CEST
>> Origin         : devel/gdb
>> Architecture   : FreeBSD:15:aarch64
>> Prefix         : /usr/local
>> Categories     : devel
>> Licenses       : GPLv3
>> Maintainer     : pizzamig@FreeBSD.org
>> WWW            : https://www.gnu.org/software/gdb/
>> Comment        : GNU Project Debugger
>> Options        :
>> BUNDLED_READLINE: off
>> BUNDLED_ZLIB   : off
>> DEBUGINFOD     : off
>> GDB_LINK       : on
>> GUILE          : off
>> KGDB           : on
>> NLS            : on
>> PORT_ICONV     : on
>> PORT_READLINE  : on
>> PYTHON         : on
>> SOURCE_HIGHLIGHT: on
>> SYSTEM_ICONV   : off
>> SYSTEM_ZLIB    : on
>> TUI            : on
>> XXHASH         : on
>> Shared Libs required:
>> libzstd.so.1
>> libxxhash.so.0
>> libsource-highlight.so.4
>> libreadline.so.8
>> libpython3.11.so.1.0
>> libmpfr.so.6
>> libintl.so.8
>> libiconv.so.2
>> libgmp.so.10
>> libexpat.so.1
>> libboost_regex.so.1.85.0
>> Annotations    :
>> FreeBSD_version: 1500025
>> build_timestamp: 2024-10-16T20:27:27+0000
>> built_by       : poudriere-git-3.4.2
>> cpe            : cpe:2.3:a:gnu:gdb:15.1:::::freebsd15:aarch64
>> flavor         : py311
>> port_checkout_unclean: no
>> port_git_hash  : 82beca9e630
>> ports_top_checkout_unclean: no
>> ports_top_git_hash: 94c4ac6b071
>> repo_type      : binary
>> repository     : FreeBSD
>> Flat size      : 58.5MiB
>> Description    :
>> GDB is a source-level debugger for Ada, C, C++, Objective-C, Pascal and
>> many other languages.  GDB can target (i.e., debug programs running on)
>> more than a dozen different processor architectures, and GDB itself can
>> run on most popular GNU/Linux, Unix and Microsoft Windows variants.
>> tuexen@head:~ % 
>> 
>> Using kgdb from "pkg install gdb" and locally built world and kernel.
>> 
>> Best regards
>> Michael
>>> 
>>> For reference:
>>> 
>>> . . . (deletion) . . .
> 
> 
> 
> ===
> Mark Millard
> marklmi at yahoo.com
>