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Annotation of researchv10dc/dist/man/v3/man1/db.1, revision 1.1

1.1     ! root        1: .pa 1
        !             2: .he 'DB (I)'3/15/72'DB (I)'
        !             3: .ti 0
        !             4: NAME           db -- debug
        !             5: .sp
        !             6: .ti 0
        !             7: SYNOPSIS       db__ [ core [ namelist ] ] [ -_ ]
        !             8: .sp
        !             9: .ti 0
        !            10: DESCRIPTION    Unlike
        !            11: many debugging packages (including DEC's ODT, on
        !            12: which db__ is loosely based) db__ is not loaded as part of the
        !            13: core image which it is used to examine; instead it examines files.
        !            14: Typically, the file will be either a core image produced
        !            15: after a fault or the binary output of
        !            16: the assembler.
        !            17: Core____ is the file being debugged; if omitted "core" is assumed.
        !            18: namelist________ is a file containing a symbol table.
        !            19: If it is omitted,
        !            20: the symbol table is obtained from the
        !            21: file being debugged,
        !            22: or if not there from a.out_____.
        !            23: If no appropriate name list file
        !            24: can be found, db__ can still be used but some of its symbolic
        !            25: facilities become unavailable.
        !            26: 
        !            27: For the meaning of the optional third argument, see
        !            28: the last paragraph below.
        !            29: .sp
        !            30: The format for most db__ requests is an address followed
        !            31: by a one character command.
        !            32: .sp
        !            33: Addresses are expressions built up as follows:
        !            34: .sp
        !            35: .in +6
        !            36: .un 3
        !            37: 1. A name has the value assigned to it
        !            38: when the input file was assembled.
        !            39: It may be relocatable or not depending
        !            40: on the use of the name during the assembly.
        !            41: .br
        !            42: .un 3
        !            43: .sp
        !            44: 2. An octal number is an absolute quantity with the appropriate
        !            45: value.
        !            46: .br
        !            47: .un 3
        !            48: .sp
        !            49: 3. A decimal number immediately followed by "." is
        !            50: an absolute quantity with the appropriate value.
        !            51: .br
        !            52: .un 3
        !            53: .sp
        !            54: 4. An octal number immediately followed by "r" is a relocatable
        !            55: quantity with the appropriate value.
        !            56: .br
        !            57: .un 3
        !            58: .sp
        !            59: 5. The symbol "." indicates the current pointer
        !            60: of db__.  The current pointer is set by many db__ requests.
        !            61: 
        !            62: .ti -3
        !            63: 6. A "*" before
        !            64: an expression forms an expression whose value is the
        !            65: number in the word addressed by the first expression.
        !            66: A "*" alone is equivalent to "*.".
        !            67: 
        !            68: .ti -3
        !            69: 6. Expressions separated by "+" or " " (blank) are expressions
        !            70: with value equal to the sum of the components.  At most
        !            71: one of the components may be relocatable.
        !            72: .br
        !            73: .un 3
        !            74: .sp
        !            75: 8. Expressions separated by "-" form an expression
        !            76: with value equal to the difference to the components.
        !            77: If the right component is relocatable, the left component
        !            78: must be relocatable.
        !            79: .br
        !            80: .un 3
        !            81: .sp
        !            82: 9. Expressions are evaluated left to right.
        !            83: .sp 1
        !            84: .in -6
        !            85: Names for registers are
        !            86: built in:
        !            87: .sp
        !            88:    r0 ... r5
        !            89:    sp
        !            90:    pc
        !            91:    fr0 ... fr5
        !            92: .sp
        !            93: These may be examined.
        !            94: Their values are deduced from the contents
        !            95: of the stack in a core image file.  They are meaningless
        !            96: in a file that is not a core image.
        !            97: .sp
        !            98: If no address is given for a command, the current address
        !            99: (also specified by ".") is assumed.  In general, "."
        !           100: points to the last word or byte printed by db__.
        !           101: .sp
        !           102: There are db__ commands for examining locations
        !           103: interpreted as octal numbers, machine instructions,
        !           104: ASCII characters, and addresses.
        !           105: For numbers and characters, either bytes
        !           106: or words may be examined.
        !           107: The following commands are used to examine the specified file.
        !           108: .sp
        !           109: .in +6
        !           110: .un 3
        !           111: /  The addressed word is printed in octal.
        !           112: 
        !           113: .un 3
        !           114: \\  The addressed byte is printed in octal.
        !           115: 
        !           116: .un 3
        !           117: "  The addressed word is printed as two ASCII characters.
        !           118: 
        !           119: .un 3
        !           120: '  The addressed byte is printed as an ASCII character.
        !           121: .ti -3
        !           122: 
        !           123: `  The addressed word is printed in decimal.
        !           124: 
        !           125: .un 3
        !           126: ?  The addressed word is interpreted as a machine
        !           127: instruction and a symbolic form of the instruction,
        !           128: including symbolic addresses, is printed.
        !           129: Often, the result will appear exactly as it was written
        !           130: in the source program.
        !           131: .br
        !           132: .un 3
        !           133: 
        !           134: &  The addressed word is interpreted as a symbolic address
        !           135: and is printed as the name of the symbol whose value is closest
        !           136: to the addressed word, possibly followed by a signed offset.
        !           137: .br
        !           138: .un 3
        !           139: 
        !           140: <nl> (i. e., the character "new line")  This command advances
        !           141: the current location counter "." and prints the resulting
        !           142: location in the mode last specified by
        !           143: one of the above requests.
        !           144: .br
        !           145: .un 3
        !           146: 
        !           147: ^  This character decrements "." and prints the
        !           148: resulting location in the mode last selected
        !           149: one of the above requests.  It is a converse to <nl>.
        !           150: 
        !           151: .un 3
        !           152: %  Exit.
        !           153: .sp
        !           154: .in -6
        !           155: Odd addresses to word-oriented commands are rounded
        !           156: down.
        !           157: The incrementing and decrementing
        !           158: of "." done by the <nl> and ^ requests is by one or
        !           159: two depending on whether the last command
        !           160: was word or byte oriented.
        !           161: .sp
        !           162: The address portion of any of the above commands
        !           163: may be followed by a comma and then by an
        !           164: expression.  In this case that number of sequential
        !           165: words or bytes specified by the expression is printed.
        !           166: "." is advanced so that it points at the
        !           167: last thing printed.
        !           168: .sp
        !           169: There are two commands to interpret the value
        !           170: of expressions.
        !           171: .sp
        !           172: .in +6
        !           173: .un 3
        !           174: =  When preceded by an expression, the value of the expression
        !           175: is typed in octal.
        !           176: When not preceded by an expression, the value of "." is
        !           177: indicated.
        !           178: This command does not change the value of ".".
        !           179: .br
        !           180: .un 3
        !           181: 
        !           182: :  An attempt is made to print the given expression
        !           183: as a symbolic address.  If the expression is relocatable,
        !           184: that symbol is found whose value is nearest
        !           185: that of the expression, and the symbol is typed, followed by
        !           186: a sign and the appropriate offset.
        !           187: If the value of the expression is absolute, a symbol
        !           188: with exactly the indicated value is sought and
        !           189: printed if found; if no matching symbol is discovered, the
        !           190: octal value of the expression is given.
        !           191: .sp
        !           192: .in -6
        !           193: The following command may be used to patch the file being debugged.
        !           194: .sp
        !           195: .in +6
        !           196: .un 3
        !           197: !  This command must be preceded by an expression.
        !           198: The value of the expression is stored at the location
        !           199: addressed by the current value of ".".
        !           200: The opcodes do not appear in the symbol
        !           201: table, so the user must assemble them by hand.
        !           202: 
        !           203: .sp
        !           204: .in -6
        !           205: The following command is used after a fault has caused
        !           206: a core image file to be produced.
        !           207: .sp
        !           208: .in +6
        !           209: .un 3
        !           210: $  causes the fault type and
        !           211: the contents of the general registers and
        !           212: several other registers to be printed both in octal and symbolic
        !           213: format.
        !           214: The values are as they were at the time of the fault.
        !           215: .sp
        !           216: .in -6
        !           217: Db__ should not be used to examine special files,
        !           218: for example disks and tapes, since it reads one byte
        !           219: at a time.
        !           220: Use od(I) instead.
        !           221: 
        !           222: For some purposes, it is important to know how addresses
        !           223: typed by the user correspond with
        !           224: locations in the file being debugged.
        !           225: The mapping algorithm employed by db__ is non-trivial
        !           226: for two reasons:
        !           227: First, in an a.out_____ file, there is a 20(8) byte header
        !           228: which will not appear when the file is loaded into
        !           229: core for execution.
        !           230: Therefore, apparent location 0 should correspond
        !           231: with actual file offset 20.
        !           232: Second, some systems cause a "squashed" core
        !           233: image to be written.
        !           234: In such a core
        !           235: image, addresses in the stack must be mapped
        !           236: according to the degree of squashing
        !           237: which has been employed.
        !           238: Db__ obeys the following rules:
        !           239: 
        !           240: If exactly one argument is given, and if it appears
        !           241: to be an a.out_____ file, the 20-byte header is skipped
        !           242: during addressing, i.e., 20 is added to all addresses typed.
        !           243: As a consequence, the header can be examined
        !           244: beginning at location -20.
        !           245: 
        !           246: If exactly one argument is given and if the file does
        !           247: not appear to be an a.out_____ file, no mapping is done.
        !           248: 
        !           249: If zero or two arguments are given,
        !           250: the mapping appropriate to a core image file is employed.
        !           251: This means that locations above the program break
        !           252: and below the stack
        !           253: effectively do not exist (and are not, in fact, recorded
        !           254: in the core file).
        !           255: Locations above the user's stack pointer are mapped,
        !           256: in looking at the core file, to
        !           257: the place where they are really stored.
        !           258: The per-process data kept by the
        !           259: system, which is stored in the last 512(10) bytes
        !           260: of the core file,
        !           261: can be addressed at apparent locations 160000-160777.
        !           262: 
        !           263: If one wants to examine
        !           264: a file which has an associated name list,
        !           265: but is not a core image file, the last argument "-"
        !           266: can be used (actually the only purpose of the
        !           267: last argument is to make the number of
        !           268: arguments not equal to two).
        !           269: This feature is used most frequently in
        !           270: examining the memory file /dev/mem.
        !           271: 
        !           272: .ti 0
        !           273: FILES          --
        !           274: .sp
        !           275: .ti 0
        !           276: SEE ALSO       as(I), core(V), a.out(V), od(I)
        !           277: .sp
        !           278: .ti 0
        !           279: DIAGNOSTICS    "File not found" if the first argument
        !           280: cannot be read; otherwise "?".
        !           281: .sp
        !           282: .ti 0
        !           283: BUGS           --

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