Loading carp module crash i386 (12-ALPHA2), seems VNET related

Olivier Cochard-Labbé olivier at freebsd.org
Mon Aug 20 14:26:44 UTC 2018

Just loading carp kernel module is enough to panic it:

[root at router]~# uname -a
FreeBSD router.bsdrp.net 12.0-ALPHA2 FreeBSD 12.0-ALPHA2  r338100M  i386
[root at router]~# kldload carp
Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0x14de0f4c
fault code              = supervisor write, page not present
instruction pointer     = 0x20:0x1201657c
stack pointer           = 0x28:0x11f3e804
frame pointer           = 0x28:0x11f3e80c
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 55291 (kldload)
[ thread pid 55291 tid 100070 ]
Stopped at      vnet_carpstats_init+0x2c:       movl

A backtrace on kgdb gives this output:

(kgdb) bt
#0  __curthread () at ./machine/pcpu.h:226
#1  doadump (textdump=<optimized out>) at
#2  0x009f69ee in db_dump (dummy=302081404, dummy2=false, dummy3=-1,
dummy4=0x11f3e4fc "") at
#3  0x009f67c7 in db_command (last_cmdp=<optimized out>,
cmd_table=<optimized out>, dopager=<optimized out>) at
#4  0x009f6520 in db_command_loop () at
#5  0x009f978d in db_trap (type=12, code=0) at
#6  0x0113e29e in kdb_trap (type=12, code=0, tf=0x11f3e7c4) at
#7  0x016d593c in trap_fatal (frame=0x11f3e7c4, eva=<optimized out>) at
#8  0x016d5a43 in trap_pfault (frame=<optimized out>, usermode=0,
eva=350097228) at
#9  0x016d508f in trap (frame=0x11f3e7c4) at
#10 0xffc0315d in ?? ()
#11 0x11f3e7c4 in ?? ()
#12 0x0121c7ef in vnet_register_sysinit (arg=0x120182cc
<vnet_carpstats_init_vnet_init>) at
#13 0x010c18f0 in linker_file_sysinit (lf=<optimized out>) at
#14 linker_load_file (filename=<optimized out>, result=<optimized out>) at
#15 linker_load_module (kldname=<optimized out>, modname=0x11449c00 "carp",
parent=0x0, verinfo=0x0, lfpp=0x11f3ea6c) at
#16 0x010c30d1 in kern_kldload (td=0x1157c380, file=0x11449c00 "carp",
fileid=0x11f3ea98) at
#17 0x010c31ee in sys_kldload (td=0x1157c380, uap=0x1157c604) at
#18 0x016d6217 in syscallenter (td=<optimized out>) at
#19 syscall (frame=0x11f3eba8) at
#20 0xffc033a7 in ?? ()
#21 0x11f3eba8 in ?? ()
Backtrace stopped: Cannot access memory at address 0xffbfecec
(kgdb) frame 12
#12 0x0121c7ef in vnet_register_sysinit (arg=0x120182cc
<vnet_carpstats_init_vnet_init>) at
500                     vs->func(vs->arg);



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