Live CD problems.

[Max Herrgaard]

    That is definitely not correct.  If you don't mind burning another dead
    CD could you please try this patch?  It will force the system to panic
    when it tries to do a 0-length I/O.  Then get a backtrace from the DDB
    prompt so we can see the call chain that leads up to the problem.
                                        -Matt
Is this sufficient?

(kgdb) bt
#0  dumpsys () at thread.h:83
#1  0xc02eb11b in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:371
#2  0xc02eb8a4 in panic (fmt=0xc0562c05 "from debugger") at
/usr/src/sys/kern/kern_shutdown.c:796
#3  0xc0166a66 in db_panic (addr=-1068477435, have_addr=0, count=-1,
modif=0xc07d6604 "") at /usr/src/sys/ddb/db_command.c:447
#4  0xc01669fb in db_command (last_cmdp=0xc0634690, cmd_table=0x0,
aux_cmd_tablep=0xc05be6f8, aux_cmd_tablep_end=0xc05be714) at
/usr/src/sys/ddb/db_command.c:343
#5  0xc0166adb in db_command_loop () at /usr/src/sys/ddb/db_command.c:469
#6  0xc0169670 in db_trap (type=3, code=0) at /usr/src/sys/ddb/db_trap.c:71
#7  0xc05050a8 in kdb_trap (type=3, code=0, regs=0xc07d6728) at
/usr/src/sys/platform/pc32/i386/db_interface.c:148
#8  0xc0517f20 in trap (frame=0xc07d6728) at
/usr/src/sys/platform/pc32/i386/trap.c:804
#9  0xc05060f6 in calltrap () at /usr/src/sys/platform/pc32/i386/exception.s:783
#10 0xc0505405 in Debugger (msg=0x12 <Address 0x12 out of bounds>) at
cpufunc.h:73
#11 0xc02eb89c in panic (fmt=0xc05652e4 "zero length DMA transfer") at
/usr/src/sys/kern/kern_shutdown.c:794
#12 0xc01a04c8 in ata_dmaload (dev=0xc622bb28, data=0xc0c14000 "",
count=0, dir=2, addr=0x12, entries=0x0) at
/usr/src/sys/dev/disk/nata/ata-dma.c:230
#13 0xc01a0ca0 in ata_begin_transaction (request=0xc0b2b190) at
/usr/src/sys/dev/disk/nata/ata-lowlevel.c:180
#14 0xc01a4710 in ata_start (dev=0xc622bb28) at
/usr/src/sys/dev/disk/nata/ata-queue.c:214
#15 0xc01a4376 in ata_queue_request (request=0xc0b2b190) at
/usr/src/sys/dev/disk/nata/ata-queue.c:95
#16 0xc01b386d in atapi_action (sim=0xc0b03ba8, ccb=0x0) at
/usr/src/sys/dev/disk/nata/atapi-cam.c:602
#17 0xc014be68 in xpt_run_dev_sendq (bus=0xc0af2c90) at
/usr/src/sys/bus/cam/cam_xpt.c:3640
#18 0xc014b111 in xpt_action (start_ccb=0xca67a140) at
/usr/src/sys/bus/cam/cam_xpt.c:2809
#19 0xc015c90b in cdstart (periph=0xc0b03bf8, start_ccb=0xca67a140) at
/usr/src/sys/bus/cam/scsi/scsi_cd.c:1584
#20 0xc014bbfc in xpt_run_dev_allocq (bus=0xc0af2c90) at
/usr/src/sys/bus/cam/cam_xpt.c:3507
#21 0xc014baa1 in xpt_schedule (perph=0xc0b03bf8,
new_priority=3232705680) at /usr/src/sys/bus/cam/cam_xpt.c:3402
#22 0xc015c5d2 in cdstrategy (ap=0x12) at
/usr/src/sys/bus/cam/scsi/scsi_cd.c:1496
#23 0xc02d456d in dev_dstrategy (dev=0xc0b25fe8, bio=0x20) at
/usr/src/sys/kern/kern_device.c:238
#24 0xc030094e in diskstrategy (ap=0x12) at /usr/src/sys/kern/subr_disk.c:423
#25 0xc02d456d in dev_dstrategy (dev=0xc0b26f18, bio=0x20) at
/usr/src/sys/kern/kern_device.c:238
#26 0xc034824d in spec_strategy (ap=0xc65f5d18) at
/usr/src/sys/vfs/specfs/spec_vnops.c:544
#27 0xc034328b in vop_strategy (ops=0x0, vp=0xc0b6b188,
bio=0xc0ba3e30) at /usr/src/sys/kern/vfs_vopops.c:659
#28 0xc0329357 in vn_strategy (vp=0xc0b6b188, bio=0x20) at
/usr/src/sys/kern/vfs_bio.c:2779
#29 0xc0326140 in bread (vp=0xc0b6b188, loffset=) at
/usr/src/sys/kern/vfs_bio.c:630
#30 0xc02c2f4e in iso_mountfs (devvp=0xc0b6b188, mp=0xc0b84020,
argp=0xc07d6b64) at /usr/src/sys/vfs/isofs/cd9660/cd9660_vfsops.c:321
#31 0xc02c2ad8 in iso_mountroot (mp=0xc0b84020) at
/usr/src/sys/vfs/isofs/cd9660/cd9660_vfsops.c:165
#32 0xc02c2b36 in cd9660_mount (mp=0xc0b84020, path=0x0, data=0x12
<Address 0x12 out of bounds>, cred=0xc0b16120) at
/usr/src/sys/vfs/isofs/cd9660/cd9660_vfsops.c:189
#33 0xc032f650 in vfs_mountroot_try (mountfrom=0xc0577e53
"cd9660:cd0c") at /usr/src/sys/kern/vfs_conf.c:244
#34 0xc032f3f4 in vfs_mountroot (junk=0x0) at /usr/src/sys/kern/vfs_conf.c:143
#35 0xc02c7cd1 in mi_startup () at /usr/src/sys/kern/init_main.c:234
#36 0xc014098b in begin () at /usr/src/sys/platform/pc32/i386/locore.s:337