panic: sx lock still held cpuid = 1 time = 1572176084 KDB: stack backtrace: db_trace_self_wrapper() at db_trace_self_wrapper+0x47/frame 0xfffffe002436e870 vpanic() at vpanic+0x1c7/frame 0xfffffe002436e8e0 panic() at panic+0x43/frame 0xfffffe002436e940 sx_destroy() at sx_destroy+0x63/frame 0xfffffe002436e960 solisten_proto() at solisten_proto+0xde/frame 0xfffffe002436e9c0 tcp6_usr_listen() at tcp6_usr_listen+0x1dc/frame 0xfffffe002436ea30 solisten() at solisten+0x7a/frame 0xfffffe002436ea70 kern_listen() at kern_listen+0x125/frame 0xfffffe002436eab0 ia32_syscall() at ia32_syscall+0x466/frame 0xfffffe002436ebf0 int0x80_syscall_common() at int0x80_syscall_common+0x9c/frame 0x8142e6d KDB: enter: panic [ thread pid 1821 tid 100853 ] Stopped at kdb_enter+0x67: movq $0,0x1467206(%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 0 rax 0x12 rcx 0xfffffe0024e00000 rdx 0x3ffff rbx 0 rsp 0xfffffe002436e850 rbp 0xfffffe002436e870 rsi 0x40001 rdi 0xffffffff810b4461 vprintf+0xe1 r8 0 r9 0xffffffff r10 0x51b043ad r11 0x722c0816 r12 0xffffffff82068cf0 ddb_dbbe r13 0 r14 0xffffffff81911c94 r15 0xffffffff81911c94 rip 0xffffffff810a96e7 kdb_enter+0x67 rflags 0x200082 kernphys+0x82 kdb_enter+0x67: movq $0,0x1467206(%rip) db> show proc Process 1821 (syz-executor.0) at 0xfffff80036e2fa60: state: NORMAL uid: 0 gids: 0, 0, 5 parent: pid 759 at 0xfffff80003b2ea60 ABI: FreeBSD ELF32 arguments: /root/syz-executor.0 reaper: 0xfffff800031ed530 reapsubtree: 1 sigparent: 20 vmspace: 0xfffff80003c27000 (map 0xfffff80003c27000) (map.pmap 0xfffff80003c270d0) (pmap 0xfffff80003c27130) threads: 4 100553 RunQ syz-executor.0 100844 S accept 0xfffff80003d18168 syz-executor.0 100853 Run CPU 1 syz-executor.0 100854 Run CPU 0 syz-executor.0 db> ps pid ppid pgrp uid state wmesg wchan cmd 1821 759 759 0 R (threaded) syz-executor.0 100553 RunQ syz-executor.0 100844 S accept 0xfffff80003d18168 syz-executor.0 100853 Run CPU 1 syz-executor.0 100854 Run CPU 0 syz-executor.0 1820 760 760 0 S (threaded) syz-executor.1 100080 S nanslp 0xffffffff824f94e0 syz-executor.1 100847 S select 0xfffff80003450840 syz-executor.1 100852 S uwait 0xfffff800038faa00 syz-executor.1 1280 1274 1280 0 Ss select 0xfffff8000343c3c0 dhclient 1277 1 1277 0 Ss select 0xfffff80003450640 dhclient 1274 1267 410 65 S select 0xfffff80003916640 dhclient 1267 410 410 0 S wait 0xfffff80003985a60 sh 1258 1 1258 65 Ss select 0xfffff800034506c0 dhclient 797 756 797 0 Ss piperd 0xfffff80036dd2be0 syz-executor.2 790 756 790 0 Ss piperd 0xfffff80003c252f8 syz-executor.3 788 1 788 0 Ss select 0xfffff80003916cc0 dhclient 785 1 785 0 Ss select 0xfffff80003916e40 dhclient 760 756 760 0 Ss nanslp 0xffffffff824f94e0 syz-executor.1 759 756 759 0 Ss nanslp 0xffffffff824f94e0 syz-executor.0 756 754 754 0 S (threaded) syz-fuzzer 100076 S uwait 0xfffff800038f7800 syz-fuzzer 100103 S uwait 0xfffff800038f4c00 syz-fuzzer 100104 S kqread 0xfffff80003dd3300 syz-fuzzer 100105 S uwait 0xfffff800036d7d80 syz-fuzzer 100106 S uwait 0xfffff80003ca9e80 syz-fuzzer 100107 S uwait 0xfffff800036d7e80 syz-fuzzer 100108 S uwait 0xfffff80003ca9380 syz-fuzzer 100109 S uwait 0xfffff800038f4000 syz-fuzzer 100110 S uwait 0xfffff800038f4100 syz-fuzzer 100115 S uwait 0xfffff80003ca9480 syz-fuzzer 754 752 754 0 Ss pause 0xfffff800039850a8 csh 752 668 752 0 Ss select 0xfffff8000343ccc0 sshd 734 1 734 0 Ss+ ttyin 0xfffff800032cdcb0 getty 733 1 733 0 Ss+ ttyin 0xfffff800032cb0b0 getty 732 1 732 0 Ss+ ttyin 0xfffff800032cb4b0 getty 731 1 731 0 Ss+ ttyin 0xfffff800032cb8b0 getty 730 1 730 0 Ss+ ttyin 0xfffff800032cbcb0 getty 729 1 729 0 Ss+ ttyin 0xfffff800032cc0b0 getty 728 1 728 0 Ss+ ttyin 0xfffff800032cc4b0 getty 727 1 727 0 Ss+ ttyin 0xfffff800032cc8b0 getty 726 1 726 0 Ss+ ttyin 0xfffff800032cccb0 getty 672 1 672 0 Ss nanslp 0xffffffff824f94e1 cron 668 1 668 0 Ss select 0xfffff800039171c0 sshd 481 1 481 0 Ss select 0xfffff8000343c5c0 syslogd 410 1 410 0 Ss wait 0xfffff80003c1da60 devd 409 1 409 65 Ss select 0xfffff8000343c440 dhclient 324 1 324 0 Ss select 0xfffff80003917440 dhclient 321 1 321 0 Ss select 0xfffff800039175c0 dhclient 21 0 0 0 DL vlruwt 0xfffff80003b33a60 [vnlru] 20 0 0 0 DL syncer 0xffffffff825cf9b0 [syncer] 19 0 0 0 DL (threaded) [bufdaemon] 100063 D qsleep 0xffffffff825cee58 [bufdaemon] 100065 D - 0xffffffff8200a900 [bufspacedaemon-0] 100079 D sdflush 0xfffff80003b360e8 [/ worker] 18 0 0 0 DL psleep 0xffffffff825ea308 [vmdaemon] 17 0 0 0 DL (threaded) [pagedaemon] 100061 D psleep 0xffffffff82616098 [dom0] 100067 D launds 0xffffffff826160a4 [laundry: dom0] 100068 D umarcl 0xffffffff8152b080 [uma] 16 0 0 0 DL - 0xffffffff82355120 [rand_harvestq] 15 0 0 0 DL waiting 0xffffffff8265b670 [sctp_iterator] 9 0 0 0 DL - 0xffffffff825ce85c [soaiod4] 8 0 0 0 DL - 0xffffffff825ce85c [soaiod3] 7 0 0 0 DL - 0xffffffff825ce85c [soaiod2] 6 0 0 0 DL - 0xffffffff825ce85c [soaiod1] 5 0 0 0 DL (threaded) [cam] 100031 D - 0xffffffff822304c0 [doneq0] 100060 D - 0xffffffff82230388 [scanner] 4 0 0 0 DL crypto_ 0xfffff800032d7090 [crypto returns 1] 3 0 0 0 DL crypto_ 0xfffff800032d7030 [crypto returns 0] 2 0 0 0 DL crypto_ 0xffffffff825e4948 [crypto] 14 0 0 0 DL seqstat 0xfffff80003257c88 [sequencer 00] 13 0 0 0 DL (threaded) [geom] 100022 D - 0xffffffff82614690 [g_event] 100023 D - 0xffffffff826146a0 [g_up] 100024 D - 0xffffffff82614698 [g_down] 12 0 0 0 WL (threaded) [intr] 100005 I [swi6: Giant taskq] 100007 I [swi5: fast taskq] 100011 I [swi6: task queue] 100017 I [swi4: clock (0)] 100018 I [swi4: clock (1)] 100019 I [swi3: vm] 100020 I [swi1: netisr 0] 100032 I [irq24: virtio_pci0] 100033 I [irq25: virtio_pci0] 100034 I [irq26: virtio_pci0] 100035 I [irq27: virtio_pci0] 100036 I [irq28: virtio_pci1] 100037 I [irq29: virtio_pci1] 100038 I [irq30: virtio_pci1] 100039 I [irq31: virtio_pci1] 100040 I [irq32: virtio_pci1] 100045 I [irq1: atkbd0] 100046 I [irq12: psm0] 100047 I [swi0: uart uart++] 11 0 0 0 RL (threaded) [idle] 100003 CanRun [idle: cpu0] 100004 CanRun [idle: cpu1] 1 0 1 0 SLs wait 0xfffff800031ed530 [init] 10 0 0 0 DL audit_w 0xffffffff8265c300 [audit] 0 0 0 0 DLs (threaded) [kernel] 100000 D swapin 0xffffffff82603e58 [swapper] 100006 D - 0xfffff800031d7400 [thread taskq] 100008 D - 0xfffff800031e2600 [config_0] 100009 D - 0xfffff800031d7100 [kqueue_ctx taskq] 100010 D - 0xfffff800031d7000 [aiod_kick taskq] 100012 D - 0xfffff800031e2100 [if_config_tqg_0] 100013 D - 0xfffff800031e1e00 [softirq_0] 100014 D - 0xfffff800031e1c00 [softirq_1] 100015 D - 0xfffff800031e1a00 [if_io_tqg_0] 100016 D - 0xfffff800031e1800 [if_io_tqg_1] 100021 D - 0xfffff800031d6800 [firmware taskq] 100026 D - 0xfffff800031d6700 [crypto_0] 100027 D - 0xfffff800031d6700 [crypto_1] 100041 D - 0xfffff800031d6100 [vtnet0 rxq 0] 100042 D - 0xfffff800031d6000 [vtnet0 txq 0] 100043 D - 0xfffff800031d5e00 [vtnet0 rxq 1] 100044 D - 0xfffff800031d5d00 [vtnet0 txq 1] 100048 D - 0xfffff800031d5600 [mca taskq] 100052 D - 0xffffffff824f8260 [deadlkres] 100056 D - 0xfffff800039ad100 [acpi_task_0] 100057 D - 0xfffff800039ad100 [acpi_task_1] 100058 D - 0xfffff800039ad100 [acpi_task_2] 100059 D - 0xfffff800031d6600 [CAM taskq] db> show all locks Process 1821 (syz-executor.0) thread 0xfffff8004d25c000 (100853) exclusive sleep mutex socket (socket) r = 0 (0xfffff80003d13a98) locked @ /syzkaller/managers/i386/kernel/sys/netinet/tcp_usrreq.c:479 exclusive rw tcpinp (tcpinp) r = 0 (0xfffff800363993f0) locked @ /syzkaller/managers/i386/kernel/sys/netinet/tcp_usrreq.c:471 db> show malloc Type InUse MemUse Requests devbuf 4200 4764K 4227 vtbuf 24 1968K 46 callout 3 1672K 3 kobj 331 1324K 488 newblk 45 1035K 4096 vfscache 4 1025K 4 inodedep 270 647K 1317 pcb 36 548K 771 ufs_quota 1 512K 1 vfs_hash 1 512K 1 intr 4 388K 4 subproc 127 253K 1900 acpica 1674 185K 48775 vnet_data 1 168K 1 pagedep 15 132K 1022 tfo_ccache 1 128K 1 filedesc 17 117K 2037 sysctloid 2038 107K 2098 sem 4 106K 4 DEVFS1 105 105K 122 bus 962 77K 2947 linker 204 76K 230 mtx_pool 2 72K 2 UMAHash 3 69K 5 syncache 1 68K 1 acpitask 1 64K 1 ddb_capture 1 64K 1 module 492 62K 493 BPF 30 53K 30 umtx 300 38K 300 gtaskqueue 22 34K 22 kdtrace 170 33K 5471 hostcache 1 32K 1 shm 1 32K 36 freefile 255 32K 1235 dirrem 254 32K 1237 DEVFS3 124 31K 134 msg 4 30K 4 DEVFS_RULE 56 27K 56 ifaddr 74 25K 74 kbdmux 6 22K 6 vmem 3 19K 4 lltable 46 17K 47 temp 34 17K 1920 ufs_mount 3 17K 4 proc 3 17K 3 tty 16 16K 16 tidhash 1 16K 1 ithread 87 15K 87 ether_multi 172 14K 177 bus-sc 26 13K 1146 KTRACE 100 13K 100 ifnet 7 13K 7 kenv 95 12K 99 in6_multi 89 11K 89 eventhandler 122 11K 122 pfs_nodes 20 10K 20 GEOM 60 10K 489 rman 77 9K 418 bmsafemap 3 9K 1338 devstat 4 9K 4 UART 12 9K 12 rpc 2 8K 2 sctp_timw 32 8K 32 shmfd 1 8K 1 pfs_vncache 1 8K 1 cred 30 8K 226 audit_evclass 230 8K 288 routetbl 58 7K 62 select 54 7K 54 CAM DEV 3 6K 508 kqueue 56 6K 1831 plimit 22 6K 394 vt 11 6K 11 sglist 5 6K 5 CAM queue 5 6K 1522 ufs_dirhash 24 5K 24 DEVFSP 74 5K 78 freework 19 5K 2049 taskqueue 42 5K 42 memdesc 1 4K 1 MCA 32 4K 32 evdev 4 4K 4 kcovinfo 64 4K 68 sctp_atcl 7 4K 549 session 28 4K 40 pgrp 28 4K 40 hhook 13 4K 13 terminal 11 3K 11 lockf 24 3K 56 proc-args 47 3K 563 acpisem 20 3K 20 uidinfo 5 3K 6 sctp_ifa 17 3K 17 local_apic 1 2K 1 io_apic 1 2K 1 ipsec-saq 2 2K 2 sctp_stro 2 2K 210 ip6ndp 12 2K 21 Unitno 30 2K 1509 diradd 13 2K 1273 CAM XPT 22 2K 542 freeblks 6 2K 1160 in_multi 6 2K 7 acpidev 20 2K 20 crypto 2 2K 2 msi 9 2K 9 tun 7 2K 7 mkdir 8 1K 2012 ipsecpolicy 1 1K 1 sahead 1 1K 1 secasvar 1 1K 1 clone 8 1K 8 cdev 4 1K 4 NFSD session 1 1K 1 CAM periph 4 1K 270 mld 6 1K 6 sctp_ifn 6 1K 6 igmp 6 1K 6 toponodes 6 1K 6 isadev 6 1K 6 mount 16 1K 86 pci_link 10 1K 10 CAM SIM 2 1K 2 softdep 1 1K 1 chacha20random 1 1K 1 epoch 4 1K 4 encap_export_host 8 1K 8 pfil 3 1K 3 inpcbpolicy 11 1K 193 sctp_atky 9 1K 759 osd 3 1K 9 newdirblk 4 1K 1006 indirdep 1 1K 1564 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 3 atkbddev 2 1K 2 apmdev 1 1K 1 pmchooks 1 1K 1 prison 4 1K 4 CAM dev queue 2 1K 2 CAM I/O Scheduler 1 1K 1 CAM path 4 1K 1030 sctp_athm 7 1K 549 soname 4 1K 5745 nexusdev 5 1K 5 tcpfunc 1 1K 1 sctp_vrf 1 1K 1 sctp_map 4 1K 420 vnet 1 1K 1 acpiintr 1 1K 1 pmc 1 1K 1 filecaps 3 1K 80 cpus 2 1K 2 vnet_data_free 1 1K 1 Per-cpu 1 1K 1 entropy 1 1K 38 p1003.1b 1 1K 1 ppbusdev 0 0K 0 agtiapi_MemAlloc malloc 0 0K 0 osti_cacheable 0 0K 0 madt_table 0 0K 2 tempbuff 0 0K 0 tempbuff 0 0K 0 smartpqi 0 0K 0 ag_tgt_map_t malloc 0 0K 0 ag_slr_map_t malloc 0 0K 0 lDevFlags * malloc 0 0K 0 tiDeviceHandle_t * malloc 0 0K 0 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 iavf 0 0K 0 ixl 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 fpukern_ctx 0 0K 0 xen_intr 0 0K 0 CAM ccb queue 0 0K 0 xen_hvm 0 0K 0 legacydrv 0 0K 0 qpidrv 0 0K 0 mrsasbuf 0 0K 0 mpt_user 0 0K 0 dmar_idpgtbl 0 0K 0 dmar_dom 0 0K 0 dmar_ctx 0 0K 0 dmar_dmamap 0 0K 0 mps_user 0 0K 0 MPSSAS 0 0K 0 isci 0 0K 0 bxe_ilt 0 0K 0 xenbus 0 0K 0 vm_fictitious 0 0K 0 mps 0 0K 0 mpr_user 0 0K 0 MPRSAS 0 0K 0 vm_pgdata 0 0K 0 jblocks 0 0K 0 savedino 0 0K 1404 sentinel 0 0K 0 jfsync 0 0K 0 jtrunc 0 0K 0 sbdep 0 0K 10 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 freefrag 0 0K 5 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 nfsclient_nlminfo 0 0K 0 nfsclient_lock 0 0K 0 NFS FHA 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 LRO 0 0K 0 sctp_mcore 0 0K 0 sctp_socko 0 0K 167 sctp_iter 0 0K 12 sctp_mvrf 0 0K 0 sctp_cpal 0 0K 0 sctp_cmsg 0 0K 0 sctp_stre 0 0K 0 sctp_athi 0 0K 0 sctp_a_it 0 0K 12 sctp_aadr 0 0K 0 sctp_stri 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 vnodemarker 0 0K 24 mpr 0 0K 0 statfs 0 0K 1182 export_host 0 0K 0 cl_savebuf 0 0K 2 biobuf 0 0K 0 aios 0 0K 0 lio 0 0K 0 acl 0 0K 0 mfibuf 0 0K 0 mbuf_tag 0 0K 312 accf 0 0K 0 pts 0 0K 0 iov 0 0K 14197 ioctlops 0 0K 104 Witness 0 0K 0 stack 0 0K 0 md_sectors 0 0K 0 sbuf 0 0K 364 md_disk 0 0K 0 compressor 0 0K 0 malodev 0 0K 0 SWAP 0 0K 0 LED 0 0K 0 sysctltmp 0 0K 594 sysctl 0 0K 1 ekcd 0 0K 0 dumper 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 prison_racct 0 0K 0 Fail Points 0 0K 0 sigio 0 0K 1 filedesc_to_leader 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 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 ath_hal 0 0K 0 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 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 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 mixer 0 0K 0 ac97 0 0K 0 hdacc 0 0K 0 hdac 0 0K 0 hdaa 0 0K 0 acpi_perf 0 0K 0 acpicmbat 0 0K 0 SIIS driver 0 0K 0 CAM CCB 0 0K 7358 PUC 0 0K 0 db> show ktr No such command; use "help" to list available commands