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Annotation of 43BSDReno/share/man/man8/man8.hp300/crash.8, revision 1.1

1.1     ! root        1: .\" Copyright (c) 1990 Regents of the University of California.
        !             2: .\" All rights reserved.  The Berkeley software License Agreement
        !             3: .\" specifies the terms and conditions for redistribution.
        !             4: .\"
        !             5: .\"    @(#)crash.8     5.1 (Berkeley) 6/29/90
        !             6: .\"
        !             7: .TH CRASH 8 "June 29, 1990"
        !             8: .UC 7
        !             9: .SH NAME
        !            10: crash \- what happens when the system crashes
        !            11: .SH DESCRIPTION
        !            12: This section explains what happens when the system crashes
        !            13: and (very briefly) how to analyze crash dumps.
        !            14: .PP
        !            15: When the system crashes voluntarily it prints a message of the form
        !            16: .IP
        !            17: panic: why i gave up the ghost
        !            18: .LP
        !            19: on the console, takes a dump on a mass storage peripheral,
        !            20: and then invokes an automatic reboot procedure as
        !            21: described in
        !            22: .IR reboot (8).
        !            23: Unless some unexpected inconsistency is encountered in the state
        !            24: of the file systems due to hardware or software failure, the system
        !            25: will then resume multi-user operations.
        !            26: .PP
        !            27: The system has a large number of internal consistency checks; if one
        !            28: of these fails, then it will panic with a very short message indicating
        !            29: which one failed.
        !            30: In many instances, this will be the name of the routine which detected
        !            31: the error, or a two-word description of the inconsistency.
        !            32: A full understanding of most panic messages requires perusal of the
        !            33: source code for the system.
        !            34: .PP
        !            35: The most common cause of system failures is hardware failure, which
        !            36: can reflect itself in different ways.  Here are the messages which
        !            37: are most likely, with some hints as to causes.
        !            38: Left unstated in all cases is the possibility that hardware or software
        !            39: error produced the message in some unexpected way.
        !            40: .TP
        !            41: .B iinit
        !            42: This cryptic panic message results from a failure to mount the root filesystem
        !            43: during the bootstrap process.
        !            44: Either the root filesystem has been corrupted,
        !            45: or the system is attempting to use the wrong device as root filesystem.
        !            46: Usually, an alternate copy of the system binary or an alternate root
        !            47: filesystem can be used to bring up the system to investigate.
        !            48: .TP
        !            49: .B Can't exec /etc/init
        !            50: This is not a panic message, as reboots are likely to be futile.
        !            51: Late in the bootstrap procedure, the system was unable to locate
        !            52: and execute the initialization process,
        !            53: .IR init (8).
        !            54: The root filesystem is incorrect or has been corrupted, or the mode
        !            55: or type of /etc/init forbids execution.
        !            56: .TP
        !            57: .B IO err in push
        !            58: .ns
        !            59: .TP
        !            60: .B hard IO err in swap
        !            61: The system encountered an error trying to write to the paging device
        !            62: or an error in reading critical information from a disk drive.
        !            63: The offending disk should be fixed if it is broken or unreliable.
        !            64: .TP
        !            65: .B realloccg: bad optim
        !            66: .ns
        !            67: .TP
        !            68: .B ialloc: dup alloc
        !            69: .ns
        !            70: .TP
        !            71: .B alloccgblk: cyl groups corrupted
        !            72: .ns
        !            73: .TP
        !            74: .B ialloccg: map corrupted
        !            75: .ns
        !            76: .TP
        !            77: .B free: freeing free block
        !            78: .ns
        !            79: .TP
        !            80: .B free: freeing free frag
        !            81: .ns
        !            82: .TP
        !            83: .B ifree: freeing free inode
        !            84: .ns
        !            85: .TP
        !            86: .B alloccg: map corrupted
        !            87: These panic messages are among those that may be produced
        !            88: when filesystem inconsistencies are detected.
        !            89: The problem generally results from a failure to repair damaged filesystems
        !            90: after a crash, hardware failures, or other condition that should not
        !            91: normally occur.
        !            92: A filesystem check will normally correct the problem.
        !            93: .TP
        !            94: .B timeout table overflow
        !            95: .ns
        !            96: This really shouldn't be a panic, but until the data structure
        !            97: involved is made to be extensible, running out of entries causes a crash.
        !            98: If this happens, make the timeout table bigger.
        !            99: .TP
        !           100: .B "trap type %d, code = %x, v = %x"
        !           101: An unexpected trap has occurred within the system; the trap types are:
        !           102: .sp
        !           103: .nf
        !           104: 0      bus error
        !           105: 1      address error
        !           106: 2      illegal instruction
        !           107: 3      divide by zero
        !           108: 4      \fIchk\fP instruction
        !           109: 5      \fItrapv\fP instruction
        !           110: 6      privileged instruction
        !           111: 7      trace trap
        !           112: 8      MMU fault
        !           113: 9      simulated software interrupt
        !           114: 10     format error
        !           115: 11     FP coprocessor fault
        !           116: 12     coprocessor fault
        !           117: 13     simulated AST
        !           118: .fi
        !           119: .sp
        !           120: The favorite trap type in system crashes is trap type 8,
        !           121: indicating a wild reference.
        !           122: ``code'' (hex) is the concatenation of the MMU status register
        !           123: (see <hp300/cpu.h>)
        !           124: in the high 16 bits and the 68020 special status word
        !           125: (see the 68020 manual, page 6-17)
        !           126: in the low 16.
        !           127: ``v'' (hex) is the virtual address which caused the fault.
        !           128: Additionally, the kernel will dump about a screenful of semi-useful
        !           129: information.
        !           130: ``pid'' (decimal) is the process id of the process running at the
        !           131: time of the exception.
        !           132: Note that if we panic in an interrupt routine,
        !           133: this process may not be related to the panic.
        !           134: ``ps'' (hex) is the 68020 processor status register ``ps''.
        !           135: ``pc'' (hex) is the value of the program counter saved
        !           136: on the hardware exception frame.
        !           137: It may
        !           138: .I not
        !           139: be the PC of the instruction causing the fault.
        !           140: ``sfc'' and ``dfc'' (hex) are the 68020 source/destination function codes.
        !           141: They should always be one.
        !           142: ``p0'' and ``p1'' are the VAX-like region registers.
        !           143: They are of the form:
        !           144: .sp
        !           145:        <length> '@' <kernel VA>
        !           146: .sp
        !           147: where both are in hex.
        !           148: Following these values are a dump of the processor registers (hex).
        !           149: Finally, is a dump of the stack (user/kernel) at the time of the offense.
        !           150: .TP
        !           151: .B init died
        !           152: The system initialization process has exited.  This is bad news, as no new
        !           153: users will then be able to log in.  Rebooting is the only fix, so the
        !           154: system just does it right away.
        !           155: .TP
        !           156: .B out of mbufs: map full
        !           157: The network has exhausted its private page map for network buffers.
        !           158: This usually indicates that buffers are being lost, and rather than
        !           159: allow the system to slowly degrade, it reboots immediately.
        !           160: The map may be made larger if necessary.
        !           161: .PP
        !           162: That completes the list of panic types you are likely to see.
        !           163: .PP
        !           164: When the system crashes it writes (or at least attempts to write)
        !           165: an image of memory into the back end of the dump device,
        !           166: usually the same as the primary swap
        !           167: area.  After the system is rebooted, the program
        !           168: .IR savecore (8)
        !           169: runs and preserves a copy of this core image and the current
        !           170: system in a specified directory for later perusal.  See
        !           171: .IR savecore (8)
        !           172: for details.
        !           173: .PP
        !           174: To analyze a dump you should begin by running
        !           175: .IR adb (1)
        !           176: with the 
        !           177: .B \-k
        !           178: flag on the system load image and core dump.
        !           179: If the core image is the result of a panic,
        !           180: the panic message is printed.
        !           181: Normally the command
        !           182: ``$c''
        !           183: will provide a stack trace from the point of
        !           184: the crash and this will provide a clue as to
        !           185: what went wrong.
        !           186: A more complete discussion
        !           187: of system debugging is impossible here.
        !           188: See, however,
        !           189: ``Using ADB to Debug the UNIX Kernel''.
        !           190: .SH "SEE ALSO"
        !           191: adb(1),
        !           192: reboot(8)
        !           193: .br
        !           194: .I "MC68020 32-bit Microprocessor User's Manual"
        !           195: .br
        !           196: .I "Using ADB to Debug the UNIX Kernel"
        !           197: .br
        !           198: .I "4.3BSD for the HP300"

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