login: panic: tp:0xfffffe0025849000 rc_sacked:1432 > out:1
cpuid = 0
time = 1588695883
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe00037ff5f0
vpanic() at vpanic+0x1c7/frame 0xfffffe00037ff650
panic() at panic+0x43/frame 0xfffffe00037ff6b0
ctf_flight_size() at ctf_flight_size+0x5d/frame 0xfffffe00037ff6e0
bbr_output_wtime() at bbr_output_wtime+0x9801/frame 0xfffffe00037ff990
bbr_output() at bbr_output+0x67/frame 0xfffffe00037ff9c0
tcp_hpts_thread() at tcp_hpts_thread+0xdf7/frame 0xfffffe00037ffb10
ithread_loop() at ithread_loop+0x328/frame 0xfffffe00037ffbb0
fork_exit() at fork_exit+0xb3/frame 0xfffffe00037ffbf0
fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe00037ffbf0
--- trap 0, rip = 0, rsp = 0, rbp = 0 ---
KDB: enter: panic
[ thread pid 12 tid 100072 ]
Stopped at kdb_enter+0x67: movq $0,0x14a8fb6(%rip)
db>
db> set $lines = 0
db> set $maxwidth = 0
db> show registers
cs 0x20
ds 0x3b ll+0x1a
es 0x3b ll+0x1a
fs 0x13
gs 0x1b
ss 0x28 ll+0x7
rax 0x12
rcx 0x80 ll+0x5f
rdx 0xffffffff818a2f1a
rbx 0
rsp 0xfffffe00037ff5d0
rbp 0xfffffe00037ff5f0
rsi 0x1
rdi 0
r8 0
r9 0xffffffff
r10 0
r11 0x2b15173f
r12 0xffffffff82068ec0 ddb_dbbe
r13 0
r14 0xffffffff81942eb6
r15 0xffffffff81942eb6
rip 0xffffffff810ae8b7 kdb_enter+0x67
rflags 0x86 ll+0x65
kdb_enter+0x67: movq $0,0x14a8fb6(%rip)
db> show proc
Process 12 (intr) at 0xfffff80003301520:
state: NORMAL
uid: 0 gids: 0
parent: pid 0 at 0xffffffff8250b710
ABI: null
reaper: 0xffffffff8250b710 reapsubtree: 12
sigparent: 20
vmspace: 0xffffffff8250c350
(map 0xffffffff8250c350)
(map.pmap 0xffffffff8250c410)
(pmap 0xffffffff8250c470)
threads: 23
100010 I [swi6: Giant taskq]
100013 I [swi5: fast taskq]
100016 I [swi6: task queue]
100019 I [swi3: vm]
100020 I [swi4: clock (0)]
100021 I [swi4: clock (1)]
100022 I [swi1: netisr 0]
100034 I [irq24: virtio_pci0]
100035 I [irq25: virtio_pci0]
100036 I [irq26: virtio_pci0]
100037 I [irq27: virtio_pci0]
100038 I [irq28: virtio_pci1]
100039 I [irq29: virtio_pci1]
100040 I [irq30: virtio_pci1]
100041 I [irq31: virtio_pci1]
100042 I [irq32: virtio_pci1]
100047 I [irq10: virtio_pci2]
100049 I [irq1: atkbd0]
100050 I [irq12: psm0]
100051 I [swi0: uart uart++]
100060 I [swi1: pf send]
100072 Run CPU 0 [swi1: hpts]
100073 I [swi1: hpts]
db> ps
pid ppid pgrp uid state wmesg wchan cmd
1581 773 771 0 R CPU 1 syz-executor7370366
773 771 771 0 R syz-executor7370366
771 769 771 0 Ss pause 0xfffff800111cc5c8 csh
769 682 769 0 Ss select 0xfffff800110c44c0 sshd
748 1 748 0 Ss+ ttyin 0xfffff8000380ccb0 getty
747 1 747 0 Ss+ ttyin 0xfffff800038078b0 getty
746 1 746 0 Ss+ ttyin 0xfffff80003807cb0 getty
745 1 745 0 Ss+ ttyin 0xfffff8000380a0b0 getty
744 1 744 0 Ss+ ttyin 0xfffff8000380a4b0 getty
743 1 743 0 Ss+ ttyin 0xfffff8000380a8b0 getty
742 1 742 0 Ss+ ttyin 0xfffff8000380acb0 getty
741 1 741 0 Ss+ ttyin 0xfffff800038090b0 getty
740 1 740 0 Ss+ ttyin 0xfffff800038094b0 getty
738 1 24 0 S+ piperd 0xfffff80003c782f8 logger
737 736 24 0 S+ nanslp 0xffffffff8252c1e0 sleep
736 1 24 0 S+ wait 0xfffff80003cd5520 sh
686 1 686 0 Ss nanslp 0xffffffff8252c1e0 cron
682 1 682 0 Ss select 0xfffff80003be66c0 sshd
495 1 495 0 Ss select 0xfffff80003be67c0 syslogd
424 1 424 0 Ss select 0xfffff8000308ecc0 devd
423 1 423 65 Ss select 0xfffff800034bc6c0 dhclient
338 1 338 0 Ss select 0xfffff8000308ed40 dhclient
335 1 335 0 Ss select 0xfffff800034bc640 dhclient
23 0 0 0 DL vlruwt 0xfffff80003368a40 [vnlru]
22 0 0 0 DL syncer 0xffffffff82618118 [syncer]
21 0 0 0 DL (threaded) [bufdaemon]
100069 D qsleep 0xffffffff82617430 [bufdaemon]
100076 D - 0xffffffff8200aa00 [bufspacedaemon-0]
100084 D sdflush 0xfffff80003ce1ce8 [/ worker]
20 0 0 0 DL psleep 0xffffffff8263e308 [vmdaemon]
19 0 0 0 DL (threaded) [pagedaemon]
100067 D psleep 0xffffffff826328d8 [dom0]
100074 D launds 0xffffffff826328e4 [laundry: dom0]
100075 D umarcl 0xffffffff81545120 [uma]
18 0 0 0 DL - 0xffffffff8235fe20 [rand_harvestq]
17 0 0 0 DL - 0xffffffff82616a2c [soaiod4]
16 0 0 0 DL - 0xffffffff82616a2c [soaiod3]
15 0 0 0 DL - 0xffffffff82616a2c [soaiod2]
9 0 0 0 DL - 0xffffffff82616a2c [soaiod1]
8 0 0 0 DL pftm 0xffffffff82c4e3a0 [pf purge]
7 0 0 0 DL waiting 0xffffffff8261a890 [sctp_iterator]
6 0 0 0 DL (threaded) [cam]
100033 D - 0xffffffff82237b40 [doneq0]
100066 D - 0xffffffff82237a10 [scanner]
5 0 0 0 DL crypto_ 0xfffff800033f2290 [crypto returns 1]
4 0 0 0 DL crypto_ 0xfffff800033f2230 [crypto returns 0]
3 0 0 0 DL crypto_ 0xffffffff826300c0 [crypto]
14 0 0 0 DL seqstat 0xfffff80003390488 [sequencer 00]
13 0 0 0 DL (threaded) [geom]
100024 D - 0xffffffff8250b180 [g_event]
100025 D - 0xffffffff8250b188 [g_up]
100026 D - 0xffffffff8250b190 [g_down]
2 0 0 0 DL (threaded) [KTLS]
100017 D - 0xfffff800032fac80 [thr_0]
100018 D - 0xfffff800032facc0 [thr_1]
12 0 0 0 RL (threaded) [intr]
100010 I [swi6: Giant taskq]
100013 I [swi5: fast taskq]
100016 I [swi6: task queue]
100019 I [swi3: vm]
100020 I [swi4: clock (0)]
100021 I [swi4: clock (1)]
100022 I [swi1: netisr 0]
100034 I [irq24: virtio_pci0]
100035 I [irq25: virtio_pci0]
100036 I [irq26: virtio_pci0]
100037 I [irq27: virtio_pci0]
100038 I [irq28: virtio_pci1]
100039 I [irq29: virtio_pci1]
100040 I [irq30: virtio_pci1]
100041 I [irq31: virtio_pci1]
100042 I [irq32: virtio_pci1]
100047 I [irq10: virtio_pci2]
100049 I [irq1: atkbd0]
100050 I [irq12: psm0]
100051 I [swi0: uart uart++]
100060 I [swi1: pf send]
100072 Run CPU 0 [swi1: hpts]
100073 I [swi1: hpts]
11 0 0 0 RL (threaded) [idle]
100003 CanRun [idle: cpu0]
100004 CanRun [idle: cpu1]
1 0 1 0 SLs wait 0xfffff80003304000 [init]
10 0 0 0 DL audit_w 0xffffffff82630598 [audit]
0 0 0 0 DLs (threaded) [kernel]
100000 D swapin 0xffffffff8250b710 [swapper]
100005 D - 0xfffff80003325000 [if_config_tqg_0]
100006 D - 0xfffff80003326e00 [softirq_0]
100007 D - 0xfffff80003326d00 [softirq_1]
100008 D - 0xfffff80003326c00 [if_io_tqg_0]
100009 D - 0xfffff80003326b00 [if_io_tqg_1]
100011 D - 0xfffff80003333600 [in6m_free taskq]
100012 D - 0xfffff80003333500 [thread taskq]
100014 D - 0xfffff80003333200 [kqueue_ctx taskq]
100015 D - 0xfffff80003333100 [aiod_kick taskq]
100023 D - 0xfffff80003383d00 [firmware taskq]
100028 D - 0xfffff80003383200 [crypto_0]
100029 D - 0xfffff80003383200 [crypto_1]
100043 D - 0xfffff800037dc400 [vtnet0 rxq 0]
100044 D - 0xfffff800037dc300 [vtnet0 txq 0]
100045 D - 0xfffff800037dc200 [vtnet0 rxq 1]
100046 D - 0xfffff800037dc100 [vtnet0 txq 1]
100048 D vtbslp 0xfffff800035b1780 [virtio_balloon]
100052 D - 0xfffff800037dae00 [mca taskq]
100053 D - 0xffffffff81ce6631 [deadlkres]
100061 D - 0xfffff800037dac00 [acpi_task_0]
100062 D - 0xfffff800037dac00 [acpi_task_1]
100063 D - 0xfffff800037dac00 [acpi_task_2]
100065 D - 0xfffff80003384a00 [CAM taskq]
db> show all locks
Process 1581 (syz-executor7370366) thread 0xfffffe001d9f2e00 (100105)
exclusive rw tcpinp (tcpinp) r = 0 (0xfffff8001187b020) locked @ /syzkaller/managers/main/kernel/sys/netinet/tcp_usrreq.c:1756
Process 12 (intr) thread 0xfffffe001d9f3c00 (100072)
exclusive rw tcpinp (tcpinp) r = 0 (0xfffff800115333f0) locked @ /syzkaller/managers/main/kernel/sys/netinet/tcp_hpts.c:1539
db> show malloc
Type InUse MemUse Requests
pf_hash 5 11524K 5
devbuf 4213 4851K 4238
tcp_hpts 5 3201K 5
vtbuf 24 1968K 46
sysctloid 27747 1619K 27811
kobj 332 1328K 488
newblk 451 1137K 508
vfscache 4 1025K 4
pcb 828 587K 882
inodedep 26 525K 71
ufs_quota 1 512K 1
vfs_hash 1 512K 1
callout 2 512K 2
intr 4 388K 4
subproc 114 222K 1649
acpica 1674 185K 52709
vnet_data 1 168K 1
pagedep 8 130K 18
tfo_ccache 1 128K 1
sem 4 106K 4
DEVFS1 101 101K 110
linker 237 91K 265
bus 964 78K 3344
mtx_pool 2 72K 2
syncache 1 68K 1
acpitask 1 64K 1
ddb_capture 1 64K 1
module 496 62K 496
temp 18 33K 1534
hostcache 1 32K 1
shm 1 32K 1
msg 4 30K 4
DEVFS3 120 30K 130
umtx 234 30K 234
kdtrace 148 29K 3218
DEVFS_RULE 56 27K 56
gtaskqueue 18 26K 18
inpcbpolicy 814 26K 937
vmem 3 22K 4
kbdmux 6 22K 6
BPF 10 18K 10
ufs_mount 3 17K 4
proc 3 17K 3
tty 16 16K 16
tidhash 1 16K 1
ithread 98 16K 98
bus-sc 30 14K 1431
ifaddr 32 13K 32
KTRACE 100 13K 100
kenv 95 12K 99
eventhandler 132 12K 132
pfs_nodes 20 10K 20
GEOM 60 10K 487
rman 82 10K 423
bmsafemap 2 9K 41
UART 12 9K 12
devstat 4 9K 4
rpc 2 8K 2
shmfd 1 8K 1
pfs_vncache 1 8K 1
audit_evclass 233 8K 291
CAM DEV 3 6K 510
vt 11 6K 11
cred 21 6K 234
sglist 5 6K 5
CAM queue 5 6K 1528
taskqueue 45 5K 45
ufs_dirhash 24 5K 24
routetbl 28 5K 32
plimit 17 5K 322
ifnet 3 5K 3
memdesc 1 4K 1
MCA 32 4K 32
evdev 4 4K 4
filedesc 1 4K 1
UMA 247 4K 247
lltable 11 4K 11
hhook 13 4K 13
ether_multi 40 4K 45
pf_ifnet 5 3K 6
in6_multi 25 3K 25
kqueue 47 3K 1584
acpisem 22 3K 22
terminal 11 3K 11
session 20 3K 31
pgrp 20 3K 31
uidinfo 3 3K 8
local_apic 1 2K 1
io_apic 1 2K 1
ipsec-saq 2 2K 2
select 15 2K 15
proc-args 39 2K 472
freefile 13 2K 22
CAM XPT 22 2K 543
lockf 15 2K 22
Unitno 25 2K 37
acpidev 20 2K 20
msi 9 2K 9
softdep 1 1K 1
dirrem 4 1K 28
ipsecpolicy 1 1K 1
sahead 1 1K 1
secasvar 1 1K 1
clone 8 1K 8
vnodemarker 2 1K 8
NFSD session 1 1K 1
CAM periph 4 1K 271
diradd 7 1K 36
indirdep 3 1K 3
nhops 6 1K 6
toponodes 6 1K 6
isadev 6 1K 6
mount 16 1K 86
pci_link 10 1K 10
ip6ndp 4 1K 5
sctp_ifa 5 1K 5
crypto 3 1K 3
newdirblk 4 1K 8
mkdir 4 1K 16
in_multi 2 1K 3
pfil 4 1K 4
chacha20random 1 1K 1
CAM SIM 2 1K 2
epoch 4 1K 4
cdev 2 1K 2
encap_export_host 8 1K 8
osd 3 1K 9
mld 2 1K 2
sctp_ifn 2 1K 2
igmp 2 1K 2
vnodes 1 1K 1
NFSD lckfile 1 1K 1
NFSD V4client 1 1K 1
DEVFS 9 1K 10
feeder 7 1K 7
loginclass 3 1K 7
CAM dev queue 2 1K 2
CAM I/O Scheduler 1 1K 1
apmdev 1 1K 1
atkbddev 2 1K 2
CAM path 4 1K 1034
tcpfunc 2 1K 2
ktls 1 1K 1
pmchooks 1 1K 1
prison 4 1K 4
DEVFSP 2 1K 2
soname 4 1K 6595
filecaps 4 1K 66
tun 3 1K 3
nexusdev 5 1K 5
entropy 2 1K 35
freework 1 1K 26
sctp_vrf 1 1K 1
vnet 1 1K 1
acpiintr 1 1K 1
pmc 1 1K 1
cpus 2 1K 2
vnet_data_free 1 1K 1
Per-cpu 1 1K 1
p1003.1b 1 1K 1
pf_table 0 0K 0
pf_rule 0 0K 0
pf_altq 0 0K 0
pf_osfp 0 0K 0
pf_temp 0 0K 0
ath_hal 0 0K 0
madt_table 0 0K 2
athdev 0 0K 0
ata_pci 0 0K 0
ata_dma 0 0K 0
ata_generic 0 0K 0
amr 0 0K 0
scsi_da 0 0K 69
ata_da 0 0K 0
pvscsi 0 0K 0
smartpqi 0 0K 0
scsi_ch 0 0K 0
scsi_cd 0 0K 0
USBdev 0 0K 0
USB 0 0K 0
AHCI driver 0 0K 0
agp 0 0K 0
iavf 0 0K 0
ixl 0 0K 0
nvme_da 0 0K 0
acpipwr 0 0K 0
twsbuf 0 0K 0
twe_commands 0 0K 0
twa_commands 0 0K 0
tcp_log_dev 0 0K 0
midi buffers 0 0K 0
fpukern_ctx 0 0K 0
mixer 0 0K 0
xen_intr 0 0K 0
ac97 0 0K 0
xen_hvm 0 0K 0
legacydrv 0 0K 0
qpidrv 0 0K 0
hdacc 0 0K 0
hdac 0 0K 0
dmar_idpgtbl 0 0K 0
dmar_dom 0 0K 0
dmar_ctx 0 0K 0
dmar_dmamap 0 0K 0
hdaa 0 0K 0
acpi_perf 0 0K 0
acpicmbat 0 0K 0
isci 0 0K 0
bxe_ilt 0 0K 0
xenbus 0 0K 0
SIIS driver 0 0K 0
vm_fictitious 0 0K 0
CAM CCB 0 0K 1824
PUC 0 0K 0
ppbusdev 0 0K 0
agtiapi_MemAlloc malloc 0 0K 0
osti_cacheable 0 0K 0
tempbuff 0 0K 0
tempbuff 0 0K 0
UMAHash 0 0K 0
ag_tgt_map_t malloc 0 0K 0
ag_slr_map_t malloc 0 0K 0
vm_pgdata 0 0K 0
jblocks 0 0K 0
savedino 0 0K 12
sentinel 0 0K 0
jfsync 0 0K 0
jtrunc 0 0K 0
sbdep 0 0K 3
jsegdep 0 0K 0
jseg 0 0K 0
jfreefrag 0 0K 0
jfreeblk 0 0K 0
jnewblk 0 0K 0
jmvref 0 0K 0
jremref 0 0K 0
jaddref 0 0K 0
freedep 0 0K 0
freeblks 0 0K 25
freefrag 0 0K 7
allocindir 0 0K 0
allocdirect 0 0K 0
ufs_trim 0 0K 0
mactemp 0 0K 0
audit_trigger 0 0K 0
audit_pipe_presel 0 0K 0
audit_pipeent 0 0K 0
audit_pipe 0 0K 0
audit_evname 0 0K 0
audit_bsm 0 0K 0
audit_gidset 0 0K 0
audit_text 0 0K 0
audit_path 0 0K 0
audit_data 0 0K 0
audit_cred 0 0K 0
xform 0 0K 0
NLM 0 0K 0
ipsec-spdcache 0 0K 0
ipsec-reg 0 0K 0
ipsec-misc 0 0K 0
ipsecrequest 0 0K 0
ip6opt 0 0K 3
ip6_msource 0 0K 0
ip6_moptions 0 0K 0
in6_mfilter 0 0K 0
frag6 0 0K 0
tcplog 0 0K 0
lDevFlags * malloc 0 0K 0
LRO 0 0K 0
sctp_mcore 0 0K 0
sctp_socko 0 0K 0
sctp_iter 0 0K 3
sctp_mvrf 0 0K 0
sctp_timw 0 0K 0
sctp_cpal 0 0K 0
sctp_cmsg 0 0K 0
sctp_stre 0 0K 0
sctp_athi 0 0K 0
sctp_athm 0 0K 0
sctp_atky 0 0K 0
sctp_atcl 0 0K 0
sctp_a_it 0 0K 3
sctp_aadr 0 0K 0
sctp_stro 0 0K 0
sctp_stri 0 0K 0
sctp_map 0 0K 0
newreno data 0 0K 0
ip_msource 0 0K 0
ip_moptions 0 0K 0
in_mfilter 0 0K 0
ipid 0 0K 0
80211scan 0 0K 0
80211ratectl 0 0K 0
80211power 0 0K 0
80211nodeie 0 0K 0
80211node 0 0K 0
80211mesh_gt 0 0K 0
80211mesh_rt 0 0K 0
80211perr 0 0K 0
80211prep 0 0K 0
80211preq 0 0K 0
80211dfs 0 0K 0
80211crypto 0 0K 0
80211vap 0 0K 0
iflib 0 0K 0
vlan 0 0K 0
gif 0 0K 0
ifdescr 0 0K 0
zlib 0 0K 0
fadvise 0 0K 0
tiDeviceHandle_t * malloc 0 0K 0
statfs 0 0K 196
export_host 0 0K 0
cl_savebuf 0 0K 3
ag_portal_data_t malloc 0 0K 0
ag_device_t malloc 0 0K 0
STLock malloc 0 0K 0
CCB List 0 0K 0
sr_iov 0 0K 0
OCS 0 0K 0
OCS 0 0K 0
nvme 0 0K 0
nvd 0 0K 0
netmap 0 0K 0
mwldev 0 0K 0
MVS driver 0 0K 0
CAM ccb queue 0 0K 0
mrsasbuf 0 0K 0
mpt_user 0 0K 0
mps_user 0 0K 0
biobuf 0 0K 0
aios 0 0K 0
lio 0 0K 0
acl 0 0K 0
MPSSAS 0 0K 0
mbuf_tag 0 0K 25
accf 0 0K 0
pts 0 0K 0
iov 0 0K 12966
ioctlops 0 0K 85
Witness 0 0K 0
stack 0 0K 0
mps 0 0K 0
mpr_user 0 0K 0
MPRSAS 0 0K 0
mpr 0 0K 0
mfibuf 0 0K 0
md_sectors 0 0K 0
sbuf 0 0K 288
md_disk 0 0K 0
compressor 0 0K 0
malodev 0 0K 0
SWAP 0 0K 0
LED 0 0K 0
sysctltmp 0 0K 574
sysctl 0 0K 1
ekcd 0 0K 0
dumper 0 0K 0
sendfile 0 0K 0
rctl 0 0K 0
ix_sriov 0 0K 0
aacraidcam 0 0K 0
ix 0 0K 0
ipsbuf 0 0K 0
iirbuf 0 0K 0
cache 0 0K 0
aacraid_buf 0 0K 0
kcovinfo 0 0K 0
prison_racct 0 0K 0
Fail Points 0 0K 0
sigio 0 0K 1
filedesc_to_leader 0 0K 0
pwd 0 0K 0
tty console 0 0K 0
aaccam 0 0K 0
aacbuf 0 0K 0
zstd 0 0K 0
nvlist 0 0K 0
SCSI ENC 0 0K 0
SCSI sa 0 0K 0
isofs_node 0 0K 0
isofs_mount 0 0K 0
tr_raid5_data 0 0K 0
tr_raid1e_data 0 0K 0
tr_raid1_data 0 0K 0
tr_raid0_data 0 0K 0
tr_concat_data 0 0K 0
md_sii_data 0 0K 0
md_promise_data 0 0K 0
md_nvidia_data 0 0K 0
md_jmicron_data 0 0K 0
md_intel_data 0 0K 0
md_ddf_data 0 0K 0
raid_data 0 0K 72
geom_flashmap 0 0K 0
NFS FHA 0 0K 0
newnfsmnt 0 0K 0
newnfsclient_req 0 0K 0
NFSCL layrecall 0 0K 0
NFSCL session 0 0K 0
NFSCL sockreq 0 0K 0
NFSCL devinfo 0 0K 0
NFSCL flayout 0 0K 0
NFSCL layout 0 0K 0
NFSD rollback 0 0K 0
NFSCL diroffdiroff 0 0K 0
NEWdirectio 0 0K 0
NEWNFSnode 0 0K 0
NFSCL lck 0 0K 0
NFSCL lckown 0 0K 0
NFSCL client 0 0K 0
NFSCL deleg 0 0K 0
NFSCL open 0 0K 0
NFSCL owner 0 0K 0
NFS fh 0 0K 0
NFS req 0 0K 0
NFSD usrgroup 0 0K 0
NFSD string 0 0K 0
NFSD V4lock 0 0K 0
NFSD V4state 0 0K 0
NFSD srvcache 0 0K 0
msdosfs_fat 0 0K 0
msdosfs_mount 0 0K 0
msdosfs_node 0 0K 0
DEVFS4 0 0K 0
DEVFS2 0 0K 0
gntdev 0 0K 0
privcmd_dev 0 0K 0
evtchn_dev 0 0K 0
xenstore 0 0K 0
scsi_pass 0 0K 0
ciss_data 0 0K 0
xnb 0 0K 0
xbbd 0 0K 0
xbd 0 0K 0
Balloon 0 0K 0
sysmouse 0 0K 0
vtfont 0 0K 0
db> show ktr
No such command; use "help" to list available commands