login: panic: ffs_read: type 0
Stopped at      db_enter+0xa:   popq    %rbp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*126903  41537      0         0x2          0    0  dhclient
db_enter() at db_enter+0xa
panic() at panic+0x147
ffs_read(0) at ffs_read+0x382
VOP_READ(ffff80000e2bd498,ffffff0016c351e0,ffffff001f3fc4b0,0) at VOP_READ+0x5e
vn_read(ffffff001f3fc4b0,ffff80000e290bc0,a1e8) at vn_read+0x130
dofilereadv(ffff80000e290bc0,ffff80000e2bd540,a1e8,ffff80000e2bd550,7f7ffffcc908) at dofilereadv+0x14f
sys_read(ffff80000e2bd5e0,ffff80000e290bc0,ffff80000e27cfd0) at sys_read+0x6e
syscall(0) at syscall+0x3e4
Xsyscall(6,3,9,3,1b3d32cca000,1b3d284e3000) at Xsyscall+0x128
end of kernel
end trace frame: 0x7f7ffffcc920, count: 6
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> 
ddb> set $lines = 0
ddb> show panic
ffs_read: type 0
ddb> trace
db_enter() at db_enter+0xa
panic() at panic+0x147
ffs_read(0) at ffs_read+0x382
VOP_READ(ffff80000e2bd498,ffffff0016c351e0,ffffff001f3fc4b0,0) at VOP_READ+0x5evn_read(ffffff001f3fc4b0,ffff80000e290bc0,a1e8) at vn_read+0x130
dofilereadv(ffff80000e290bc0,ffff80000e2bd540,a1e8,ffff80000e2bd550,7f7ffffcc908) at dofilereadv+0x14f
sys_read(ffff80000e2bd5e0,ffff80000e290bc0,ffff80000e27cfd0) at sys_read+0x6e
syscall(0) at syscall+0x3e4
Xsyscall(6,3,9,3,1b3d32cca000,1b3d284e3000) at Xsyscall+0x128
end of kernel
end trace frame: 0x7f7ffffcc920, count: -9
ddb> show registers
rdi               0xffffffff81e17b60    kprintf_mutex
rsi                              0x5
rbp               0xffff80000e2bd250
rbx               0xffff80000e2bd2f0
rdx                            0x3fd
rcx                                0
rax                                0
r8                0xffff80000e2bd220
r9                                 0
r10                                0
r11               0xffffffff8168bd40    x86_bus_space_io_read_1
r12                     0x3000000008
r13               0xffff80000e2bd260
r14                            0x100
r15               0xffffffff81c5971a    apollo_udma133_tim+0x2b40
rip               0xffffffff8150bbba    db_enter+0xa
cs                               0x8
rflags                         0x246
rsp               0xffff80000e2bd250
ss                              0x10
db_enter+0xa:   popq    %rbp