ADB(1) ADB(1) NAME adb - debugger SYNOPSIS adb [-w] [ objfil [ corfil ] ] DESCRIPTION Adb is a general purpose debugging program. It may be used to examine files and to provide a controlled environment for the execution of UNIX programs. Objfil is normally an executable program file, preferably containing a symbol table; if not then the symbolic features of adb cannot be used although the file can still be exam- ined. The default for objfil is `a.out'. Corfil is assumed to be a core image file produced after executing objfil; the default for corfil is `core'. Requests to adb are read from the standard input and responses are to the standard output. If the -w flag is present then both objfil and corfil are created if necessary and opened for reading and writing so that files can be mod- ified using adb. Adb ignores QUIT; INTERRUPT causes return to the next adb command. In general requests to adb have the form [address] [, count] [command] [;] If address is present then dot is set to address. Initially dot is set to 0. For most commands count specifies how many times the command will be executed. The default count is 1. Address and count are expressions. EXPRESSIONS . The value of dot. + The value of dot incremented by the current incre- ment. ^ The value of dot decremented by the current incre- ment. " The last address typed. integer A number. The prefixes 0o and 0O (zero oh) force interpretation in octal radix; the prefixes 0t and 0T force interpretation in decimal radix; the prefixes 0x and 0X or a leading sharp-sign `#' force ADB(1) ADB(1) interpretation in hexadecimal radix. Thus 0o20 = 0t16 = 0x10 = sixteen. If no prefix appears, then the default radix is used; see the $d command. The default radix is initially hexadecimal. The hexadec- imal digits are 0123456789abcdefABCDEF with the obvi- ous values. Note that a hexadecimal number whose most significant digit would otherwise be an alpha- betic character must have a 0x (or 0X) prefix (or a leading zero if the default radix is hexadecimal). integer.fraction A 32 bit floating point number. 'cccc' The ASCII value of up to 4 characters. \ may be used to escape a '. < name The value of name, which is either a variable name or a register name. Adb maintains a number of variables (see VARIABLES) named by single letters or digits. If name is a register name then the value of the reg- ister is obtained from the system header in corfil. The register names are those printed by the $r com- mand. symbol A symbol is a sequence of upper or lower case let- ters, underscores or digits, not starting with a digit. The value of the symbol is taken from the symbol table in objfil. An initial _ or ~ will be prepended to symbol if needed. _ symbol In C, the `true name' of an external symbol begins with _. It may be necessary to utter this name to disinguish it from internal or hidden variables of a program. routine.name The address of the variable name in the specified C routine. Both routine and name are symbols. If name is omitted the value is the address of the most recently activated C stack frame corresponding to routine; if routine is omitted, the active procedure is assumed. (exp) The value of the expression exp. Monadic operators *exp The contents of the location addressed by exp in corfil. @exp The contents of the location addressed by exp in ADB(1) ADB(1) objfil. -exp Integer negation. ~exp Bitwise complement.' %exp If exp is used as an address, it is in register space; see ADDRESSES . Dyadic operators are left associative and are less binding than monadic operators. e2 Integer addition. e2 Integer subtraction. e2 Integer multiplication. e2 Integer division. e2 Bitwise conjunction. e2 Bitwise disjunction. e2 E1 rounded up to the next multiple of e2. COMMANDS Most commands consist of a verb followed by a modifier or list of modifiers. The following verbs are available. (The commands `?' and `/' may be followed by `*'; see ADDRESSES for further details.) ?f Locations starting at address in objfil are printed according to the format f. dot is incremented by the sum of the increments for each format letter (q.v.). /f Locations starting at address in corfil are printed according to the format f and dot is incremented as for `?'. =f The value of address itself is printed in the styles indicated by the format f. (For i format `?' is printed for the parts of the instruction that reference subse- quent words.) A format consists of one or more characters that specify a style of printing. Each format character may be preceded by a decimal integer that is a repeat count for the format character. While stepping through a format dot is incre- mented by the amount given for each format letter. If no format is given then the last format is used. The format letters available are as follows. ADB(1) ADB(1) o 2 Print 2 bytes in octal. O 4 Print 4 bytes in octal. q 2 Print in signed octal. Q 4 Print long signed octal. d 2 Print in decimal. D 4 Print long decimal. x 2 Print 2 bytes in hexadecimal. X 4 Print 4 bytes in hexadecimal. u 2 Print unsigned decimal. U 4 Print long unsigned decimal. f 4 Print the 32 bit value as a floating point number. F 8 Print double floating point. b 1 Print the addressed byte in octal. c 1 Print the addressed character. C 1 Print the addressed character using the standard escape convention where control characters are printed as ^X and the delete character is printed as ^?. s n Print the addressed characters until a zero char- acter is reached. S n Print a string using the ^X escape convention (see C above). n is the length of the string including its zero terminator. Y 4 Print 4 bytes in date format (see ctime(3)). i n Print as VAX instructions. n is the number of bytes occupied by the instruction. This style of printing causes variables 0, (1, ...) to be set to the offset parts of the first (second, ...) operand of the instruction. a 0 Print the value of dot in symbolic form. p 4 Print the addressed value in symbolic form using the same rules for symbol lookup as a. t 0 When preceded by an integer tabs to the next appropriate tab stop. For example, 8t moves to the next 8-space tab stop. r 0 Print a space. n 0 Print a newline. "..." 0 Print the enclosed string. ^ Dot is decremented by the current increment. Nothing is printed. + Dot is incremented by 1. Nothing is printed. - Dot is decremented by 1. Nothing is printed. newline Repeat the previous command with a count of 1. [?/]l value mask Words starting at dot are masked with mask and compared with value until a match is found. If L is used then the match is for 4 bytes at a time instead of 2. If no match is found then dot is unchanged; otherwise dot is ADB(1) ADB(1) set to the matched location. If mask is omitted then -1 is used. [?/]w value ... Write the 2-byte value into the addressed location. If the command is W, write 4 bytes. [?/]m b e f[?/] New values for (b, e, f) in the first map entry are recorded. If less than three expressions are given then the remaining map parameters are left unchanged. The address type (instruction or data) is unchanged in any case. If the `?' or `/' is followed by `*' then the second segment of the mapping is changed. If the list is terminated by `?' or `/' then the file (objfil or corfil respectively) is used for subsequent requests. (So that, for example, `/m?' will cause `/' to refer to objfil.) >name Dot is assigned to the variable or register named. ! A shell is called to read the rest of the line follow- ing `!'. $modifier Miscellaneous commands. The available modifiers are: <f Read commands from the file f. If this command is executed in a file, further commands in the file are not seen. If f is omitted, the current input stream is terminated. If a count is given, and is zero, the command will be ignored. The value of the count will be placed in variable 9 before the first command in f is executed. <<f Similar to < except it can be used in a file of commands without causing the file to be closed. Variable 9 is saved during the execution of this command, and restored when it completes. There is a (small) finite limit to the number of << files that can be open at once. >f Append output to the file f, which is created if it does not exist. If f is omitted, output is returned to the terminal. ? Print process id, the signal which caused stopping or termination, as well as the registers. This is the default if modifier is omitted. r Print the general registers and the instruction addressed by pc. Dot is set to pc. R Like $r, but include boring registers like the kernel stack pointer. b Print all breakpoints and their associated counts ADB(1) ADB(1) and commands. c C stack backtrace. If address is given then it is taken as the address of the current frame (instead of fp). If C is used then the names and (32 bit) values of all parameters, automatic and static variables are printed for each active function. If count is given then only the first count frames are printed. d Set the default radix to address and report the new value. Address is interpreted in the (old) current radix; `10$d' never changes the default radix. To make decimal the default radix, use `0t10$d'. A radix of zero is a special case: input with a leading zero is octal, that with a leading sharp-sign `#' is hexadecimal, other num- bers are decimal; output is hexadecimal by default; hex and octal numbers are printed with a leading # and 0 respectively. e The names and values of external variables are printed. w Set the page width for output to address (default 80). s Set the limit for symbol matches to address (default 255). q Exit from adb. v Print all non zero variables in the current radix. m Print the address maps. k Simulated VAX memory management: set the system base register pointer to address. System space addresses will hereafter be mapped according to the system page table. If address is zero, map- ping is turned off. p Set the PCB base pointer to address, which may be either the physical address of a process control block (as found in the PCBB register) or the sys- tem space address of a page table entry which points to a PCB (as found in p_addr). User space addresses will hereafter be translated according to the user page tables pointed to by the PCB. Kernel mapping ($k) must already be in effect. If address is zero, user mapping is turned off; addresses less than 0x80000000 will be treated as physical addresses. $k and $p are useful for system debugging. :modifier Manage a subprocess. Available modifiers are: bc Set breakpoint at address. The breakpoint is exe- cuted count-1 times before causing a stop. Each time the breakpoint is encountered the command c is executed. If this command is omitted or sets ADB(1) ADB(1) dot to zero then the breakpoint causes a stop. d Delete breakpoint at address. r Run objfil as a subprocess. If address is given explicitly then the program is entered at this point; otherwise the program is entered at its standard entry point. count specifies how many breakpoints are to be ignored before stopping. Arguments to the subprocess may be supplied on the same line as the command. An argument starting with < or > causes the standard input or output to be established for the command. All signals are turned on on entry to the subprocess. cs The subprocess is continued. If s is omitted or nonzero, the subprocess is sent the signal that caused it to stop; if 0 is specified, no signal is sent. Breakpoints and single-stepping don't count as signals. Breakpoint skipping is the same as for r. ss As for c except that the subprocess is single stepped count times. If a signal is sent, it is received before the first instruction is executed. If there is no current subprocess then objfil is run as a subprocess as for r. In this case no signal can be sent; the remainder of the line is treated as arguments to the subprocess. k The current subprocess, if any, is terminated. VARIABLES Adb provides a number of variables. Named variables are set initially by adb but are not used subsequently. Numbered variables are reserved for communication as follows. 0, 1, ... The offset parts of the first, second, ... operands of the last instruction printed. Meaningless if the operand was a register. 9 The count on the last $< or $<< command. On entry the following are set from the system header in the corfil. If corfil does not appear to be a core file then these values are set from objfil. b The base address of the data segment. d The data segment size. e The entry point. m The `magic' number (0407, 0410 or 0413). s The stack segment size. t The text segment size. ADDRESSES The address in a file associated with a written address is determined by a mapping associated with that file. Each ADB(1) ADB(1) mapping is represented by one or more quadruples (t, b, e, f), each mapping addresses of type t (instruction, data, user block) in the range b through e to the part of the file beginning at address f. An address a of type t is mapped to a file address by finding a quadruple of type t, for which b≦a<e; the file address is address+f-b. As a special case, if an instruction space address is not found, a second search is made for the same address in data space. Typically, the text segment of a program is mapped as instruction space, the data and bss segments as data space. If objfil is an a.out, or if corfil is a core image or pro- cess file, maps are set accordingly. Otherwise, a single `data space' map is set up, with b and f set to zero, and e set to a huge number; thus the entire file can be examined without address translation. The ? and / commands attempt to examine instruction and data space respectively. ?* tries for data space (in objfil); /* accesses instruction space (in corfil). Registers in process and core images are a special case; they live in a special `register' address space. The con- tents of register 0 are located at address %0; register 1 at %4 (registers are 4 bytes long); and so on. % addresses are mapped to the registers for the `current frame,' set by local variable references, and reset to the outermost frame (the `real' registers) whenever a process runs or a stack trace is requested. Simulated memory management translations (the $k and $p com- mands) are done before the mapping described above. So that adb may be used on large files all appropriate val- ues are kept as signed 32 bit integers. FILES a.out core /usr/lib/adb/* parameter files SEE ALSO pi(9.1), sdb(1), proc(4), a.out(5), core(5) DIAGNOSTICS `Adb' when there is no current command or format. Comments about inaccessible files, syntax errors, abnormal termina- tion of commands, etc. Exit status is 0, unless last com- mand failed or returned nonzero status. BUGS Either the explanation or the implementation of register ADB(1) ADB(1) variables is too complex and arcane. 0$d should probably be the default.