panic:W AkReNrInNGel: dSPiLag nNoOsTt iLcO aWEssReEDr tOioN n S"YSpgC-AL>wL ir2 e1_c12ou9n7t4 4=7=9 30 "E XfIaiTle d0: d f
ilStopped at savectx+0xae: movl $0,%gs:0x688
TID PID UID PRFLAGS PFLAGS CPU COMMAND
* 75834 91650 0 0x2 0 1 syz-executor
savectx() at savectx+0xae
end of kernel
end trace frame: 0x7f4b09e082b0, count: 14
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports. Insufficient info makes it difficult to find and fix bugs.
ddb{1}>
ddb{1}> set $lines = 0
ddb{1}> set $maxwidth = 0
ddb{1}> show panic
*cpu0: kernel diagnostic assertion "pg->wire_count == 0" failed: file "/syzkaller/managers/multicore/kernel/sys/uvm/uvm_page.c", line 1326
ddb{1}> trace
savectx() at savectx+0xae
end of kernel
end trace frame: 0x7f4b09e082b0, count: -1
ddb{1}> show registers
rdi 0
rsi 0
rbp 0xffff80003c46bf30
rbx 0
rdx 0
rcx 0xffff80003c3ff248
rax 0x3a
r8 0xffff80003c46be60
r9 0xffff8000fffeefa8
r10 0x1867bac8d9a21fe5
r11 0xc837f88598e1a5ef
r12 0
r13 0
r14 0xffff80003c3ff248
r15 0
rip 0xffffffff829fa3ee savectx+0xae
cs 0x8
rflags 0x46
rsp 0xffff80003c46beb0
ss 0x10
savectx+0xae: movl $0,%gs:0x688
ddb{1}> show proc
PROC (syz-executor) tid=75834 pid=91650 tcnt=1 stat=onproc
flags process=2<EXEC> proc=0
runpri=17, usrpri=50, slppri=17, nice=20
wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
forw=0xffffffffffffffff, list=0xffff80003c453a28,0xffff8000333d6568
process=0xffff80003c4ca1d8 user=0xffff80003c466000, vmspace=0xfffffd8075c5f018
estcpu=36, cpticks=31, pctcpu=0.18, user=1, sys=28, intr=2
ddb{1}> ps
PID TID PPID UID S FLAGS WAIT COMMAND
16150 453827 91650 0 2 0 syz-executor
52234 184537 85949 0 3 0x80 nanoslp syz-executor
52234 411273 85949 0 3 0x4000080 fsleep syz-executor
52234 465963 85949 0 3 0x4000080 fsleep syz-executor
52234 408233 85949 0 3 0x4000080 fsleep syz-executor
35189 6338 14536 0 3 0x80 nanoslp syz-executor
35189 190265 14536 0 3 0x4000080 netacc syz-executor
35189 480324 14536 0 3 0x4000080 fsleep syz-executor
67484 119930 42540 0 3 0x80 nanoslp syz-executor
67484 173220 42540 0 3 0x4000080 fsleep syz-executor
67484 115502 42540 0 3 0x4000080 ttyout syz-executor
67484 66846 42540 0 3 0x4000080 fsleep syz-executor
30558 138202 85315 60929 3 0x90 nanoslp syz-executor
30558 352028 85315 60929 3 0x4000090 ttyout syz-executor
30558 399721 85315 60929 3 0x4000090 fsleep syz-executor
66845 191928 50492 0 3 0x80 nanoslp syz-executor
66845 503326 50492 0 3 0x4000080 ttyin syz-executor
*91650 75834 85407 0 7 0x2 syz-executor
61254 191807 0 0 3 0x14200 acct acct
42540 147013 85407 0 3 0x82 nanoslp syz-executor
14536 308690 85407 0 3 0x82 nanoslp syz-executor
85949 373482 85407 0 3 0x82 nanoslp syz-executor
48041 223871 85407 0 3 0x82 nanoslp syz-executor
50492 302694 85407 0 3 0x82 nanoslp syz-executor
94137 27800 85407 0 3 0x82 wait syz-executor
85315 65798 85407 0 3 0x82 nanoslp syz-executor
85407 225401 66730 0 3 0x82 kqread syz-executor
66730 138756 66504 0 3 0x10008a sigsusp ksh
66504 109705 8602 0 3 0x98 kqread sshd-session
8602 229518 56579 0 3 0x92 kqread sshd-session
93799 457114 1 0 3 0x100083 ttyopn getty
56579 302647 1 0 3 0x88 kqread sshd
55079 363191 97172 74 3 0x1100092 bpf pflogd
97172 163067 1 0 3 0x80 sbwait pflogd
60369 367516 9466 73 3 0x1100090 kqread syslogd
9466 302051 1 0 3 0x100082 sbwait syslogd
43523 255198 1 0 3 0x100080 kqread resolvd
99796 318930 94665 77 3 0x100092 kqread dhcpleased
54553 349321 94665 77 3 0x100092 kqread dhcpleased
94665 402926 1 0 3 0x80 kqread dhcpleased
25592 366838 0 0 3 0x14200 bored smr
37956 99218 0 0 2 0x14200 zerothread
39630 307919 0 0 3 0x14200 aiodoned aiodoned
98689 476689 0 0 3 0x14200 syncer update
22537 42805 0 0 3 0x14200 cleaner cleaner
10376 486320 0 0 3 0x14200 reaper reaper
53604 148356 0 0 3 0x14200 pgdaemon pagedaemon
33365 513860 0 0 3 0x14200 bored viomb
5065 188631 0 0 3 0x40014200 acpi0 acpi0
36504 216666 0 0 3 0x40014200 idle1
13494 444909 0 0 3 0x14200 bored softnet1
75525 523497 0 0 3 0x14200 bored softnet0
77518 244010 0 0 3 0x14200 bored systqmp
65458 164208 0 0 3 0x14200 bored systq
33899 248702 0 0 3 0x14200 tmoslp softclockmp
13329 520574 0 0 3 0x40014200 tmoslp softclock
92957 249955 0 0 3 0x40014200 idle0
1 277840 0 0 3 0x82 wait init
0 0 -1 0 3 0x10010200 scheduler swapper
ddb{1}> show all locks
CPU 0:
exclusive mutex &uvm.pageqlock r = 0 (0xffffffff838cfbc8)
#0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160
#1 mtx_enter+0x4b4 sys/kern/kern_lock.c:487
#2 uvm_pageclean+0x29c sys/uvm/uvm_page.c:980
#3 uvm_pagefree+0x26 sys/uvm/uvm_page.c:1020
#4 uvm_anfree+0xe9 sys/uvm/uvm_anon.c:112
#5 amap_wipeout+0x246 sys/uvm/uvm_amap.c:-1
#6 uvm_unmap_detach+0x8a sys/uvm/uvm_map.c:1353
#7 uvm_map_teardown+0x360 sys/uvm/uvm_map.c:2525
#8 exit1+0x6fc sys/kern/kern_exit.c:260
#9 sys_exit+0x1a sys/kern/kern_exit.c:-1
#10 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#10 syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
#11 Xsyscall+0x128
CPU 1:
exclusive mutex &pr->ps_mtx r = 0 (0xffff80003c4ca2f0)
#0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160
#1 mtx_enter+0x4b4 sys/kern/kern_lock.c:487
#2 lim_fork+0x40 sys/kern/kern_resource.c:692
#3 process_new+0x2db sys/kern/kern_fork.c:238
#4 fork1+0x3f6 sys/kern/kern_fork.c:-1
#5 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#5 syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
#6 Xsyscall+0x128
Process 91650 (syz-executor) thread 0xffff80003c3ff248 (75834)
exclusive kernel_lock &kernel_lock r = 0 (0xffffffff838bcc48)
#0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160
#1 syscall+0xaf4 mi_syscall sys/sys/syscall_mi.h:175 [inline]
#1 syscall+0xaf4 sys/arch/amd64/amd64/trap.c:775
#2 Xsyscall+0x128
exclusive mutex &pr->ps_mtx r = 0 (0xffff80003c4ca2f0)
#0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160
#1 mtx_enter+0x4b4 sys/kern/kern_lock.c:487
#2 lim_fork+0x40 sys/kern/kern_resource.c:692
#3 process_new+0x2db sys/kern/kern_fork.c:238
#4 fork1+0x3f6 sys/kern/kern_fork.c:-1
#5 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#5 syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
#6 Xsyscall+0x128
ddb{1}> show malloc
Type InUse MemUse HighUse Limit Requests Type Lim
devbuf 10253 11189K 11432K 166960K 13788 0
pcb 19 13K 14K 166960K 329 0
rtable 211 10K 11K 166960K 614 0
pf 39 18K 82K 166960K 184 0
ifaddr 37 6K 7K 166960K 122 0
ifgroup 62 2K 3K 166960K 222 0
sysctl 4 1K 9K 166960K 83 0
counters 72 37K 38K 166960K 318 0
ioctlops 0 0K 8K 166960K 1869 0
iov 1 1K 16K 166960K 183 0
mount 1 1K 1K 166960K 1 0
log 0 0K 0K 166960K 4 0
vnodes 1455 91K 92K 166960K 3092 0
UFS quota 1 32K 32K 166960K 1 0
UFS mount 5 36K 36K 166960K 5 0
shm 2 1K 5K 166960K 26 0
VM map 2 1K 1K 166960K 2 0
sem 12 0K 0K 166960K 63 0
dirhash 12 2K 2K 166960K 30 0
ACPI 1692 195K 286K 166960K 12470 0
file desc 17 61K 110K 166960K 1505 0
sigio 0 0K 0K 166960K 31 0
proc 73 115K 163K 166960K 734 0
subproc 72 4K 4K 166960K 90 0
NFS srvsock 1 0K 0K 166960K 1 0
NFS daemon 1 16K 16K 166960K 1 0
ip_moptions 0 0K 0K 166960K 141 0
in_multi 74 5K 7K 166960K 161 0
ether_multi 1 0K 0K 166960K 13 0
mrt 0 0K 0K 166960K 9 0
ISOFS mount 1 32K 32K 166960K 1 0
MSDOSFS mount 1 16K 16K 166960K 1 0
ttys 241 1076K 1076K 166960K 241 0
exec 0 0K 1K 166960K 593 0
fusefs mount 1 32K 32K 166960K 1 0
pfkey data 0 0K 0K 166960K 2 0
tdb 3 0K 0K 166960K 3 0
VM swap 8 62K 64K 166960K 10 0
UVM amap 261 172K 190K 166960K 15519 0
UVM aobj 52 17K 19K 166960K 59 0
pinsyscall 42 84K 108K 166960K 2707 0
memdesc 1 4K 4K 166960K 1 0
crypto data 1 1K 1K 166960K 1 0
ip6_options 0 0K 1K 166960K 167 0
NDP 13 0K 1K 166960K 87 0
temp 79 8680K 8794K 166960K 65089 0
kqueue 17 28K 32K 166960K 267 0
SYN cache 2 16K 16K 166960K 2 0
ddb{1}> show all pools
Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle
plcache 128 26 0 0 1 0 1 1 0 8 0
rtpcb 120 130 0 127 1 0 1 1 0 8 0
rtentry 176 163 0 84 6 0 6 6 0 8 0
unpcb 144 929 0 906 7 3 4 4 0 8 3
syncache 336 9 0 9 3 2 1 1 0 8 1
tcpqe 32 2 0 2 2 1 1 1 0 8 1
tcpcb 736 412 0 405 13 6 7 7 0 8 5
arp 136 26 0 13 1 0 1 1 0 8 0
inpcb 328 1407 0 1393 16 9 7 7 0 8 5
nd6 152 33 0 13 1 0 1 1 0 8 0
pkpcb 40 10 0 10 1 0 1 1 0 8 1
kcovpl 48 10 0 2 1 0 1 1 0 8 0
mppekey 1024 2 0 2 2 2 0 1 0 8 0
ppxss 1192 103 0 103 1 0 1 1 0 8 1
pppxif 1504 8 0 8 2 1 1 1 0 8 1
pfstscr 40 2 0 2 1 1 0 1 0 8 0
pffrag 232 10 0 2 1 0 1 1 0 482 0
pffrnode 88 10 0 2 1 0 1 1 0 8 0
pffrent 40 19 0 11 1 0 1 1 0 8 0
pfosfp 40 1428 0 1005 5 0 5 5 0 8 0
pfosfpen 112 1428 0 714 21 0 21 21 0 8 0
pfrktable 1344 3 0 3 2 2 0 1 0 8 0
pfstitem 24 91 0 25 1 0 1 1 0 8 0
pfstkey 128 92 0 26 3 0 3 3 0 8 0
pfstate 448 91 0 26 8 0 8 8 0 8 0
pfrule 1344 27 0 21 2 1 1 2 0 8 0
rttmr 136 1 0 1 1 0 1 1 0 8 1
art_heap8 4096 4 0 0 4 0 4 4 0 8 0
art_heap4 256 688 0 325 32 8 24 31 0 8 0
art_table 40 692 0 325 6 0 6 6 0 8 0
art_node 32 162 0 92 1 0 1 1 0 8 0
sysvmsgpl 40 17 0 11 1 0 1 1 0 8 0
semapl 112 57 0 47 1 0 1 1 0 8 0
shmpl 112 45 0 3 2 0 2 2 0 8 0
dirhash 1024 29 0 12 3 0 3 3 0 8 0
dino2pl 256 4309 0 2801 95 0 95 95 0 8 0
ffsino 296 4309 0 2801 117 0 117 117 0 8 0
nchpl 144 6376 0 4667 64 0 64 64 0 8 0
rtmask 32 17 0 17 3 2 1 1 0 8 1
vnodes 216 5472 0 0 304 0 304 304 0 8 0
namei 1024 22074 0 22074 2 1 1 2 0 8 1
percpumem 16 174 0 123 1 0 1 1 0 8 0
vcpupl 3968 8 0 1 1 0 1 1 0 8 0
vmpool 848 11 0 4 1 0 1 1 0 8 0
kstatmem 264 140 0 108 3 0 3 3 0 8 0
scsiplug 72 6 0 6 3 2 1 1 0 8 1
scxspl 216 33829 0 33829 7 5 2 5 1 8 2
plimitpl 152 379 0 361 1 0 1 1 0 8 0
sigapl 424 1831 0 1782 9 3 6 8 0 8 0
knotepl 120 825 0 0 25 0 25 25 0 8 0
kqueuepl 224 612 0 598 11 6 5 5 0 8 3
pipepl 344 300 0 273 9 6 3 9 0 8 0
fdescpl 528 1793 0 1762 4 1 3 4 0 8 0
filepl 160 11937 0 11694 24 8 16 21 0 8 4
lockfpl 104 744 0 741 2 1 1 2 0 8 0
lockfspl 48 287 0 284 1 0 1 1 0 8 0
sessionpl 144 30 0 21 1 0 1 1 0 8 0
pgrppl 48 47 0 30 1 0 1 1 0 8 0
ucredpl 104 2018 0 2004 1 0 1 1 0 8 0
zombiepl 144 1784 0 1782 1 0 1 1 0 8 0
processpl 1232 1831 0 1782 6 0 6 6 0 8 0
procpl 664 4186 0 4126 8 1 7 8 0 8 0
sosppl 176 16 0 16 3 2 1 1 0 8 1
sockpl 752 2549 0 2508 25 13 12 17 0 8 7
mcl64k 65536 18 0 0 3 0 3 3 0 8 0
mcl16k 16384 2 0 0 1 0 1 1 0 8 0
mcl12k 12288 2 0 0 1 0 1 1 0 8 0
mcl9k 9216 2 0 0 1 0 1 1 0 8 0
mcl8k 8192 4 0 0 1 0 1 1 0 8 0
mcl4k 4096 116 0 0 15 0 15 15 0 8 0
mcl2k2 2112 1 0 0 1 0 1 1 0 8 0
mcl2k 2048 51 0 0 6 0 6 6 0 8 0
mtagpl 96 38 0 0 1 0 1 1 0 8 0
mbufpl 256 228 0 0 13 0 13 13 0 8 0
bufpl 280 13442 0 7306 439 0 439 439 0 8 0
anonpl 32 11889 0 0 97 1 96 96 0 246 0
amapchunkpl 152 53309 0 52730 40 2 38 39 0 158 10
amappl16 200 5853 0 5790 33 18 15 21 0 8 8
amappl15 192 1 0 1 1 1 0 1 0 8 0
amappl14 184 5 0 5 1 1 0 1 0 8 0
amappl13 176 455 0 454 1 0 1 1 0 8 0
amappl12 168 2179 0 2138 3 0 3 3 0 8 0
amappl11 160 5 0 3 1 0 1 1 0 8 0
amappl10 152 72 0 58 1 0 1 1 0 8 0
amappl9 144 245 0 245 1 1 0 1 0 8 0
amappl8 136 36 0 32 1 0 1 1 0 8 0
amappl7 128 107 0 105 1 0 1 1 0 8 0
amappl6 120 309 0 295 1 0 1 1 0 8 0
amappl5 112 90 0 77 1 0 1 1 0 8 0
amappl4 104 455 0 425 1 0 1 1 0 8 0
amappl3 96 10523 0 10415 5 1 4 4 0 8 0
amappl2 88 610 0 550 2 0 2 2 0 8 0
amappl1 80 16371 0 15780 16 1 15 15 0 8 0
amappl 88 14474 0 14293 5 0 5 5 0 92 0
uvmvnodes 80 157 0 0 4 0 4 4 0 8 0
dma65536 65536 2 0 2 1 0 1 1 0 8 1
dma8192 8192 1 0 1 1 1 0 1 0 8 0
dma4096 4096 2 0 2 2 2 0 1 0 8 0
dma1024 1024 1 0 0 1 0 1 1 0 8 0
dma256 256 7 0 7 2 2 0 1 0 8 0
dma128 128 254 0 254 2 2 0 1 0 8 0
dma64 64 7 0 7 2 2 0 1 0 8 0
dma32 32 7 0 7 1 1 0 1 0 8 0
dma16 16 19 0 18 1 0 1 1 0 8 0
aobjpl 72 58 0 7 1 0 1 1 0 8 0
uaddrrnd 24 1793 0 1762 1 0 1 1 0 8 0
uaddrbest 32 2 0 0 1 0 1 1 0 8 0
uaddr 24 1793 0 1762 1 0 1 1 0 8 0
vmmpekpl 168 16322 0 16277 4 1 3 3 0 8 0
vmmpepl 168 119480 0 117495 107 4 103 104 0 357 7
vmsppl 488 1792 0 1761 6 1 5 5 0 8 0
rwobjpl 80 33328 0 32136 35 4 31 31 0 8 2
pdppl 4096 3616 0 3537 120 39 81 88 0 8 2
pvpl 32 22032 0 0 178 0 178 178 0 265 0
pmappl 256 1803 0 1765 3 0 3 3 0 8 0
extentpl 40 45 0 27 1 0 1 1 0 8 0
phpool 112 331 0 63 8 0 8 8 0 8 0
ddb{1}> machine ddbcpu 0
Stopped at x86_ipi_db+0x27: addq $0x8,%rsp
x86_ipi_db(ffffffff837c5ff0) at x86_ipi_db+0x27 sys/arch/amd64/amd64/db_interface.c:394
x86_ipi_handler() at x86_ipi_handler+0xd9 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
x86_bus_space_io_write_1(3f8,0,6c) at x86_bus_space_io_write_1+0x40 sys/arch/amd64/amd64/bus_space.c:790
comcnputc(800,6c) at comcnputc+0x1ab bus_space_barrier sys/dev/ic/com.c:-1 [inline]
comcnputc(800,6c) at comcnputc+0x1ab sys/dev/ic/com.c:1263
cnputc(6c) at cnputc+0x67 sys/dev/cons.c:218
db_putchar(6c) at db_putchar+0x36d sys/ddb/db_output.c:155
kprintf() at kprintf+0x29c5 sys/kern/subr_prf.c:-1
db_printf(ffffffff83389dfa) at db_printf+0x9b sys/kern/subr_prf.c:-1
panic(ffffffff833b2750) at panic+0x103 sys/kern/subr_prf.c:217
__assert(ffffffff833ef9fe,ffffffff833e5731,52e,ffffffff83406f81) at __assert+0x29 sys/kern/subr_prf.c:-1
uvm_pagedequeue(fffffd8008b33c60) at uvm_pagedequeue+0x2dd sys/uvm/uvm_page.c:1324
uvm_pageclean(fffffd8008b33c60) at uvm_pageclean+0x2ad sys/uvm/uvm_page.c:981
uvm_pagefree(fffffd8008b33c60) at uvm_pagefree+0x26 sys/uvm/uvm_page.c:1020
end trace frame: 0xffff80002ffcf8e0, count: 0
ddb{0}> trace
x86_ipi_db(ffffffff837c5ff0) at x86_ipi_db+0x27 sys/arch/amd64/amd64/db_interface.c:394
x86_ipi_handler() at x86_ipi_handler+0xd9 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
x86_bus_space_io_write_1(3f8,0,6c) at x86_bus_space_io_write_1+0x40 sys/arch/amd64/amd64/bus_space.c:790
comcnputc(800,6c) at comcnputc+0x1ab bus_space_barrier sys/dev/ic/com.c:-1 [inline]
comcnputc(800,6c) at comcnputc+0x1ab sys/dev/ic/com.c:1263
cnputc(6c) at cnputc+0x67 sys/dev/cons.c:218
db_putchar(6c) at db_putchar+0x36d sys/ddb/db_output.c:155
kprintf() at kprintf+0x29c5 sys/kern/subr_prf.c:-1
db_printf(ffffffff83389dfa) at db_printf+0x9b sys/kern/subr_prf.c:-1
panic(ffffffff833b2750) at panic+0x103 sys/kern/subr_prf.c:217
__assert(ffffffff833ef9fe,ffffffff833e5731,52e,ffffffff83406f81) at __assert+0x29 sys/kern/subr_prf.c:-1
uvm_pagedequeue(fffffd8008b33c60) at uvm_pagedequeue+0x2dd sys/uvm/uvm_page.c:1324
uvm_pageclean(fffffd8008b33c60) at uvm_pageclean+0x2ad sys/uvm/uvm_page.c:981
uvm_pagefree(fffffd8008b33c60) at uvm_pagefree+0x26 sys/uvm/uvm_page.c:1020
uvm_anfree(fffffd8062b87150) at uvm_anfree+0xe9 sys/uvm/uvm_anon.c:112
amap_wipeout(fffffd806ee63b40) at amap_wipeout+0x246 sys/uvm/uvm_amap.c:-1
uvm_unmap_detach(ffff80002ffcf9a0,0) at uvm_unmap_detach+0x8a sys/uvm/uvm_map.c:1353
uvm_map_teardown(fffffd8075c5f5d0) at uvm_map_teardown+0x360 sys/uvm/uvm_map.c:2525
exit1(ffff8000333d6fb8,0,0,1) at exit1+0x6fc sys/kern/kern_exit.c:260
sys_exit(ffff8000333d6fb8,ffff80002ffcfb70,ffff80002ffcfac0) at sys_exit+0x1a sys/kern/kern_exit.c:-1
syscall(ffff80002ffcfb70) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80002ffcfb70) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x779b1843e8a0, count: -22
ddb{0}> machine ddbcpu 1
Stopped at savectx+0xae: movl $0,%gs:0x688
savectx() at savectx+0xae
end of kernel
end trace frame: 0x7f4b09e082b0, count: 14
ddb{1}> trace
savectx() at savectx+0xae
end of kernel
end trace frame: 0x7f4b09e082b0, count: -1