第10章 内核调试

# kgdb -n N

# kgdb -n last

# kgdb /boot/kernel/kernel /var/crash/vmcore.0

 1:# cd /usr/obj/usr/src/sys/KERNCONF
 2:# kgdb kernel.debug /var/crash/vmcore.0
 3:GNU gdb 5.2.1 (FreeBSD)
 4:Copyright 2002 Free Software Foundation, Inc.
 5:GDB is free software, covered by the GNU General Public License, and you are
 6:welcome to change it and/or distribute copies of it under certain conditions.
 7:Type "show copying" to see the conditions.
 8:There is absolutely no warranty for GDB.  Type "show warranty" for details.
 9:This GDB was configured as "i386-undermydesk-freebsd"...
10:panic: page fault
11:panic messages:
12:---
13:Fatal trap 12: page fault while in kernel mode
14:cpuid = 0; apic id = 00
15:fault virtual address   = 0x300
16:fault code:             = supervisor read, page not present
17:instruction pointer     = 0x8:0xc0713860
18:stack pointer           = 0x10:0xdc1d0b70
19:frame pointer           = 0x10:0xdc1d0b7c
20:code segment            = base 0x0, limit 0xfffff, type 0x1b
21:                        = DPL 0, pres 1, def32 1, gran 1
22:processor eflags        = resume, IOPL = 0
23:current process         = 14394 (uname)
24:trap number             = 12
25:panic: page fault
26      cpuid = 0;
27:Stack backtrace:
28
29:syncing disks, buffers remaining... 2199 2199 panic: mi_switch: switch in a critical section
30:cpuid = 0;
31:Uptime: 2h43m19s
32:Dumping 255 MB
33: 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240
34:---
35:Reading symbols from /boot/kernel/snd_maestro3.ko...done.
36:Loaded symbols for /boot/kernel/snd_maestro3.ko
37:Reading symbols from /boot/kernel/snd_pcm.ko...done.
38:Loaded symbols for /boot/kernel/snd_pcm.ko
39:#0  doadump () at /usr/src/sys/kern/kern_shutdown.c:240
40:240             dumping++;
41:(kgdb) list *0xc0713860
42:0xc0713860 is in lapic_ipi_wait (/usr/src/sys/i386/i386/local_apic.c:663).
43:658                     incr = 0;
44:659                     delay = 1;
45:660             } else
46:661                     incr = 1;
47:662             for (x = 0; x < delay; x += incr) {
48:663                     if ((lapic->icr_lo & APIC_DELSTAT_MASK) == APIC_DELSTAT_IDLE)
49:664                             return (1);
50:665                     ia32_pause();
51:666             }
52:667             return (0);
53:(kgdb) backtrace
54:#0  doadump () at /usr/src/sys/kern/kern_shutdown.c:240
55:#1  0xc055fd9b in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:372
56:#2  0xc056019d in panic () at /usr/src/sys/kern/kern_shutdown.c:550
57:#3  0xc0567ef5 in mi_switch () at /usr/src/sys/kern/kern_synch.c:470
58:#4  0xc055fa87 in boot (howto=256) at /usr/src/sys/kern/kern_shutdown.c:312
59:#5  0xc056019d in panic () at /usr/src/sys/kern/kern_shutdown.c:550
60:#6  0xc0720c66 in trap_fatal (frame=0xdc1d0b30, eva=0)
61:    at /usr/src/sys/i386/i386/trap.c:821
62:#7  0xc07202b3 in trap (frame=
63:      {tf_fs = -1065484264, tf_es = -1065484272, tf_ds = -1065484272, tf_edi = 1, tf_esi = 0, tf_ebp = -602076292, tf_isp = -602076324, tf_ebx = 0, tf_edx = 0, tf_ecx = 1000000, tf_eax = 243, tf_trapno = 12, tf_err = 0, tf_eip = -1066321824, tf_cs = 8, tf_eflags = 65671, tf_esp = 243, tf_ss = 0})
64:    at /usr/src/sys/i386/i386/trap.c:250
65:#8  0xc070c9f8 in calltrap () at {standard input}:94
66:#9  0xc07139f3 in lapic_ipi_vectored (vector=0, dest=0)
67:    at /usr/src/sys/i386/i386/local_apic.c:733
68:#10 0xc0718b23 in ipi_selected (cpus=1, ipi=1)
69:    at /usr/src/sys/i386/i386/mp_machdep.c:1115
70:#11 0xc057473e in kseq_notify (ke=0xcc05e360, cpu=0)
71:    at /usr/src/sys/kern/sched_ule.c:520
72:#12 0xc0575cad in sched_add (td=0xcbcf5c80)
73:    at /usr/src/sys/kern/sched_ule.c:1366
74:#13 0xc05666c6 in setrunqueue (td=0xcc05e360)
75:    at /usr/src/sys/kern/kern_switch.c:422
76:#14 0xc05752f4 in sched_wakeup (td=0xcbcf5c80)
77:    at /usr/src/sys/kern/sched_ule.c:999
78:#15 0xc056816c in setrunnable (td=0xcbcf5c80)
79:    at /usr/src/sys/kern/kern_synch.c:570
80:#16 0xc0567d53 in wakeup (ident=0xcbcf5c80)
81:    at /usr/src/sys/kern/kern_synch.c:411
82:#17 0xc05490a8 in exit1 (td=0xcbcf5b40, rv=0)
83:    at /usr/src/sys/kern/kern_exit.c:509
84:#18 0xc0548011 in sys_exit () at /usr/src/sys/kern/kern_exit.c:102
85:#19 0xc0720fd0 in syscall (frame=
86:      {tf_fs = 47, tf_es = 47, tf_ds = 47, tf_edi = 0, tf_esi = -1, tf_ebp = -1077940712, tf_isp = -602075788, tf_ebx = 672411944, tf_edx = 10, tf_ecx = 672411600, tf_eax = 1, tf_trapno = 12, tf_err = 2, tf_eip = 671899563, tf_cs = 31, tf_eflags = 642, tf_esp = -1077940740, tf_ss = 47})
87:    at /usr/src/sys/i386/i386/trap.c:1010
88:#20 0xc070ca4d in Xint0x80_syscall () at {standard input}:136
89:---Can't read userspace from dump, or kernel process---
90:(kgdb) quit

# sysctl debug.kdb.enter=1

 break function-name address

 continue

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 del
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 s

 n

 x/wx 0xf0133fe0,40
 x/hd db_symtab_space
 x/bc termbuf,10
 x/s stringbuf

 x ,10

 x/ia foofunc,10

 w/b termbuf 0xa 0xb 0
 w/w 0xf0010030 0 0

 show reg

 p $eax

 set $eax new-value

 call func(arg1, arg2, ...)

 ps

 panic

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# sysctl debug.kdb.current=gdb
debug.kdb.current: ddb -> gdb

# sysctl debug.kdb.enter=1
debug.kdb.enter: 0KDB: enter: sysctl debug.kdb.enter

# cd /usr/obj/usr/src/amd64.amd64/sys/GENERIC/
# kgdb kernel
GNU gdb (GDB) 10.2 [GDB v10.2 for FreeBSD]
Copyright (C) 2021 Free Software Foundation, Inc.
...
Reading symbols from kernel...
Reading symbols from /usr/obj/usr/src/amd64.amd64/sys/GENERIC/kernel.debug...
(kgdb)

(kgdb) target remote /dev/cuau0

Remote debugging using /dev/cuau0
kdb_enter (why=<optimized out>, msg=<optimized out>) at /usr/src/sys/kern/subr_kdb.c:506
506                     kdb_why = KDB_WHY_UNSET;
(kgdb)