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 17:28:53 UTC
> 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.
> 
> I'll note that, if I reference the wrong kernel file, I get
> the likes of:
> 
> # kgdb /boot/kernel/kernel /var/crash/vmcore.2
> . . .
> Reading symbols from /boot/kernel/kernel...
> Reading symbols from /usr/lib/debug//boot/kernel/kernel.debug...
> /wrkdirs/usr/ports/devel/gdb/work-py311/gdb-15.1/gdb/thread.c:1423: internal-error: switch_to_thread: Assertion `thr != NULL' failed.
> A problem internal to GDB has been detected,
> further debugging may prove unreliable.
> ----- Backtrace -----
> 0x13147fb ???
> 0x1777763 ???
> 0x1777593 ???
> 0x1c09bbf ???
> 0x1733af7 ???
> 0x143c9d3 ???
> 0x1707483 ???
> 0x13468db ???
> 0x17405a3 ???
> 0x1505f7b ???
> 0x1504bd7 ???
> 0x150352f ???
> 0x1226b47 ???
> 0x2ee9ca33 __libc_start1
> /home/pkgbuild/worktrees/main/lib/libc/csu/libc_start1.c:172
> 0x12261cb ???
> ---------------------
> /wrkdirs/usr/ports/devel/gdb/work-py311/gdb-15.1/gdb/thread.c:1423: internal-error: switch_to_thread: Assertion `thr != NULL' failed.
> A problem internal to GDB has been detected,
> further debugging may prove unreliable.
> Quit this debugging session? (y or n) y
> . . .
> 
> 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 
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:
> 
> # uname -apKU
> FreeBSD aarch64-main-PBsmallUFS 15.0-CURRENT FreeBSD 15.0-CURRENT main-n273174-8b2e7da70855 GENERIC arm64 aarch64 1500026 1500026
> 
> # ~/pkgbase-snapshot-list.sh 
> Via pkg-static info -C -x '^FreeBSD-' . . .
> 352 FreeBSD-*-15.snap20241023235252
>  1 FreeBSD-*-15.snap20241022122410
>  1 FreeBSD-*-15.snap20241020224518
>  1 FreeBSD-*-15.snap20241020094723
>  7 FreeBSD-*-15.snap20241015203742
>  1 FreeBSD-*-15.snap20241015145839
>  1 FreeBSD-*-15.snap20241015120827
>  1 FreeBSD-*-15.snap20241014101436
> 34 FreeBSD-*-15.snap20241011184813
> 129 FreeBSD-*-15.snap20241009162208
> Instead via /var/cache/pkg/*.snap*.pkg . . .
> 352 FreeBSD-*-15.snap20241023235252
>  1 FreeBSD-*-15.snap20241022122410
>  1 FreeBSD-*-15.snap20241020224518
>  1 FreeBSD-*-15.snap20241020094723
>  7 FreeBSD-*-15.snap20241015203742
>  1 FreeBSD-*-15.snap20241015145839
>  1 FreeBSD-*-15.snap20241015120827
>  1 FreeBSD-*-15.snap20241014101436
> 34 FreeBSD-*-15.snap20241011184813
> 129 FreeBSD-*-15.snap20241009162208
> 
> # pkg info gdb
> gdb-15.1
> Name           : gdb
> Version        : 15.1
> Installed on   : Mon Oct 14 10:30:51 2024 PDT
> 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: 1500024
> build_timestamp: 2024-10-07T19:01:59+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: 149fe86b8e7
> 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.
> 
> It was from installing an officially built package.
> 
> 
> ===
> Mark Millard
> marklmi at yahoo.com
>