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diff --git a/static/v10/man1/db.1 b/static/v10/man1/db.1 new file mode 100644 index 00000000..859bd7e8 --- /dev/null +++ b/static/v10/man1/db.1 @@ -0,0 +1,283 @@ +.pa 1 +.he 'DB (I)'3/15/72'DB (I)' +.ti 0 +NAME db -- debug +.sp +.ti 0 +SYNOPSIS db__ [ core [ namelist ] ] [ -_ ] +.sp +.ti 0 +DESCRIPTION Unlike +many debugging packages (including DEC's ODT, on +which db__ is loosely based) db__ is not loaded as part of the +core image which it is used to examine; instead it examines files. +Typically, the file will be either a core image produced +after a fault or the binary output of +the assembler. +Core____ is the file being debugged; if omitted "core" is assumed. +namelist________ is a file containing a symbol table. +If it is omitted, +the symbol table is obtained from the +file being debugged, +or if not there from a.out_____. +If no appropriate name list file +can be found, db__ can still be used but some of its symbolic +facilities become unavailable. + +For the meaning of the optional third argument, see +the last paragraph below. +.sp +The format for most db__ requests is an address followed +by a one character command. +.sp +Addresses are expressions built up as follows: +.sp +.in +6 +.un 3 +1. A name has the value assigned to it +when the input file was assembled. +It may be relocatable or not depending +on the use of the name during the assembly. +.br +.un 3 +.sp +2. An octal number is an absolute quantity with the appropriate +value. +.br +.un 3 +.sp +3. A decimal number immediately followed by "." is +an absolute quantity with the appropriate value. +.br +.un 3 +.sp +4. An octal number immediately followed by "r" is a relocatable +quantity with the appropriate value. +.br +.un 3 +.sp +5. The symbol "." indicates the current pointer +of db__. The current pointer is set by many db__ requests. + +.ti -3 +6. A "*" before +an expression forms an expression whose value is the +number in the word addressed by the first expression. +A "*" alone is equivalent to "*.". + +.ti -3 +6. Expressions separated by "+" or " " (blank) are expressions +with value equal to the sum of the components. At most +one of the components may be relocatable. +.br +.un 3 +.sp +8. Expressions separated by "-" form an expression +with value equal to the difference to the components. +If the right component is relocatable, the left component +must be relocatable. +.br +.un 3 +.sp +9. Expressions are evaluated left to right. +.sp 1 +.in -6 +Names for registers are +built in: +.sp + r0 ... r5 + sp + pc + fr0 ... fr5 +.sp +These may be examined. +Their values are deduced from the contents +of the stack in a core image file. They are meaningless +in a file that is not a core image. +.sp +If no address is given for a command, the current address +(also specified by ".") is assumed. In general, "." +points to the last word or byte printed by db__. +.sp +There are db__ commands for examining locations +interpreted as octal numbers, machine instructions, +ASCII characters, and addresses. +For numbers and characters, either bytes +or words may be examined. +The following commands are used to examine the specified file. +.sp +.in +6 +.un 3 +/ The addressed word is printed in octal. + +.un 3 +\\ The addressed byte is printed in octal. + +.un 3 +" The addressed word is printed as two ASCII characters. + +.un 3 +' The addressed byte is printed as an ASCII character. +.ti -3 + +` The addressed word is printed in decimal. + +.un 3 +? The addressed word is interpreted as a machine +instruction and a symbolic form of the instruction, +including symbolic addresses, is printed. +Often, the result will appear exactly as it was written +in the source program. +.br +.un 3 + +& The addressed word is interpreted as a symbolic address +and is printed as the name of the symbol whose value is closest +to the addressed word, possibly followed by a signed offset. +.br +.un 3 + +<nl> (i. e., the character "new line") This command advances +the current location counter "." and prints the resulting +location in the mode last specified by +one of the above requests. +.br +.un 3 + +^ This character decrements "." and prints the +resulting location in the mode last selected +one of the above requests. It is a converse to <nl>. + +.un 3 +% Exit. +.sp +.in -6 +Odd addresses to word-oriented commands are rounded +down. +The incrementing and decrementing +of "." done by the <nl> and ^ requests is by one or +two depending on whether the last command +was word or byte oriented. +.sp +The address portion of any of the above commands +may be followed by a comma and then by an +expression. In this case that number of sequential +words or bytes specified by the expression is printed. +"." is advanced so that it points at the +last thing printed. +.sp +There are two commands to interpret the value +of expressions. +.sp +.in +6 +.un 3 += When preceded by an expression, the value of the expression +is typed in octal. +When not preceded by an expression, the value of "." is +indicated. +This command does not change the value of ".". +.br +.un 3 + +: An attempt is made to print the given expression +as a symbolic address. If the expression is relocatable, +that symbol is found whose value is nearest +that of the expression, and the symbol is typed, followed by +a sign and the appropriate offset. +If the value of the expression is absolute, a symbol +with exactly the indicated value is sought and +printed if found; if no matching symbol is discovered, the +octal value of the expression is given. +.sp +.in -6 +The following command may be used to patch the file being debugged. +.sp +.in +6 +.un 3 +! This command must be preceded by an expression. +The value of the expression is stored at the location +addressed by the current value of ".". +The opcodes do not appear in the symbol +table, so the user must assemble them by hand. + +.sp +.in -6 +The following command is used after a fault has caused +a core image file to be produced. +.sp +.in +6 +.un 3 +$ causes the fault type and +the contents of the general registers and +several other registers to be printed both in octal and symbolic +format. +The values are as they were at the time of the fault. +.sp +.in -6 +Db__ should not be used to examine special files, +for example disks and tapes, since it reads one byte +at a time. +Use od(I) instead. + +For some purposes, it is important to know how addresses +typed by the user correspond with +locations in the file being debugged. +The mapping algorithm employed by db__ is non-trivial +for two reasons: +First, in an a.out_____ file, there is a 20(8) byte header +which will not appear when the file is loaded into +core for execution. +Therefore, apparent location 0 should correspond +with actual file offset 20. +Second, some systems cause a "squashed" core +image to be written. +In such a core +image, addresses in the stack must be mapped +according to the degree of squashing +which has been employed. +Db__ obeys the following rules: + +If exactly one argument is given, and if it appears +to be an a.out_____ file, the 20-byte header is skipped +during addressing, i.e., 20 is added to all addresses typed. +As a consequence, the header can be examined +beginning at location -20. + +If exactly one argument is given and if the file does +not appear to be an a.out_____ file, no mapping is done. + +If zero or two arguments are given, +the mapping appropriate to a core image file is employed. +This means that locations above the program break +and below the stack +effectively do not exist (and are not, in fact, recorded +in the core file). +Locations above the user's stack pointer are mapped, +in looking at the core file, to +the place where they are really stored. +The per-process data kept by the +system, which is stored in the last 512(10) bytes +of the core file, +can be addressed at apparent locations 160000-160777. + +If one wants to examine +a file which has an associated name list, +but is not a core image file, the last argument "-" +can be used (actually the only purpose of the +last argument is to make the number of +arguments not equal to two). +This feature is used most frequently in +examining the memory file /dev/mem. + +.ti 0 +FILES -- +.sp +.ti 0 +SEE ALSO as(I), core(V), a.out(V), od(I) +.sp +.ti 0 +DIAGNOSTICS "File not found" if the first argument +cannot be read; otherwise "?". +.sp +.ti 0 +BUGS -- |