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General Programming Concepts: Writing and Debugging Programs
The adb debug program uses addresses, expressions, operators,
subcommands, and variables to organize and manipulate data.
The address in a file associated
with a written address is determined by a mapping associated with that
file. Each mapping is represented by two triples (B1,
E1, F1) and (B2, E2,
F2). The FileAddress parameter that corresponds
to a written Address parameter is calculated as follows:
B1<=Address<E1=>FileAddress=Address+F1-B1
OR
B2<=Address<E2=>FileAddress=Address+F2-B2
If the requested
Address parameter is neither between B1 and
E1 nor between B2 and E2, the
Address parameter is not valid. In some cases, such as
programs with separated I and D space, the two segments for a file may
overlap. If a ? (question mark) or / (slash)
subcommand is followed by an * (asterisk), only the second triple
is used.
The initial setting of both
mappings is suitable for normal a.out and core
files. If either file is not of the kind expected, the B1
parameter for that file is set to a value of 0, the E1 parameter is
set to the maximum file size, and the F1 parameter is set to a
value of 0. In this way, the whole file can be examined with no address
translation.
The following expressions are
supported by the adb debug program:
| . (period)
| Specifies the last address used by a subcommand. The last address
is also known as the current address.
|
| + (plus)
| Increases the value of . (period) by the current increment.
|
| ^ (caret)
| Decreases the value of . (period) by the current increment.
|
| " (double quotes)
| Specifies the last address typed by a command.
|
| Integer
| Specifies an octal number if this parameter begins with 0o, a
hexadecimal number if preceded by 0x or #, or a decimal
number if preceded by 0t. Otherwise, this expression
specifies a number interpreted in the current radix. Initially, the
radix is 16.
|
| `Cccc'
| Specifies the ASCII value of up to 4 characters. A \ (backslash)
can be used to escape an ' (apostrophe).
|
| < Name
| Reads the current value of the Name parameter. The
Name parameter is either a variable name or a register name.
The adb command maintains a number of
variables named by single letters or digits. If the Name
parameter is a register name, the value of the register is obtained from the
system header in the CoreFile parameter. Use the
$r subcommand to see the valid register names.
|
| Symbol
| Specifies a sequence of uppercase or lowercase letters, underscores, or
digits, though the sequence cannot start with a digit. The value of the
Symbol parameter is taken from the symbol table in the
ObjectFile parameter. An initial _ (underscore) is prefixed
to the Symbol parameter, if needed.
|
| .Symbol
| Specifies the entry point of the function named by the Symbol
parameter.
|
| Routine.Name
| Specifies the address of the Name parameter in the specified C
language routine. Both the Routine and Name
parameters are Symbol parameters. If the Name
parameter is omitted, the value is the address of the most recently activated
C stack frame corresponding to the Routine parameter.
|
| (Expression)
| Specifies the value of the expression.
|
Integers, symbols, variables, and
register names can be combined with the following operators:
| Unary Operators
|
| *Expression
| Returns contents of the location addressed by the Expression
parameter in the CoreFile parameter.
|
| @Expression
| Returns contents of the location addressed by the Expression
parameter in the ObjectFile parameter.
|
| -Expression
| Performs integer negation.
|
| ~Expression
| Performs bit-wise complement.
|
| #Expression
| Performs logical negation.
|
| Binary Operators
|
| Expression1+Expression2
| Performs integer addition.
|
| Expression1-Expression2
| Performs integer subtraction.
|
| Expression1*Expression2
| Performs integer multiplication.
|
| Expression1%Expression2
| Performs integer division.
|
| Expression1&Expression2
| Performs bit-wise conjunction.
|
| Expression1|Expression2
| Performs bit-wise disjunction.
|
| Expression1#Expression2
| Rounds up the Expression1 parameter to the next multiple of
the Expression2 parameter.
|
Binary operators are
left-associative and are less binding than unary operators.
You can display the contents of a
text or data segment with the ? (question mark) or the /
(slash) subcommand. The = (equal sign) subcommand displays a
given address in the specified format. The ? and
/ subcommands can be followed by an * (asterisk).
| ?Format
| Displays the contents of the ObjectFile parameter starting at
the Address parameter. The value of .
(period) increases by the sum of the increment for each format letter.
|
| /Format
| Displays the contents of the CoreFile parameter starting at
the Address parameter. The value of .
(period) increases by the sum of the increment for each format letter.
|
| =Format
| Displays the value of the Address parameter. The
i and s format letters are not meaningful for this
command.
|
The Format parameter
consists of one or more characters that specify print style. Each
format character may be preceded by a decimal integer that is a repeat count
for the format character. While stepping through a format, the
. (period) increments by the amount given for each format
letter. If no format is given, the last format is used.
The available format letters are
as follows:
| a
| Prints the value of . (period) in symbolic form.
Symbols are checked to ensure that they have an appropriate type.
|
| b
| Prints the addressed byte in the current radix, unsigned.
|
| c
| Prints the addressed character.
|
| C
| Prints the addressed character using the following escape
conventions:
- Prints control characters as ~ (tilde) followed by the
corresponding printing character.
- Prints nonprintable characters as ~ (tilde)
<Number>, where Number
specifies the hexadecimal value of the character. The ~ character
prints as ~ ~ (tilde tilde).
|
| d
| Prints in decimal.
|
| D
| Prints long decimal.
|
| f
| Prints the 32-bit value as a floating-point number.
|
| F
| Prints double floating point.
|
| i Number
| Prints as instructions. Number is the number of bytes
occupied by the instruction.
|
| n
| Prints a new line.
|
| o
| Prints 2 bytes in octal.
|
| O
| Prints 4 bytes in octal.
|
| p
| Prints the addressed value in symbolic form using the same rules for
symbol lookup as the a format letter.
|
| q
| Prints 2 bytes in the current radix, unsigned.
|
| Q
| Prints 4 unsigned bytes in the current radix.
|
| r
| Prints a space.
|
| s Number
| Prints the addressed character until a zero character is reached.
|
| S Number
| Prints a string using the ~ (tilde) escape convention. The
Number variable specifies the length of the string including its
zero terminator.
|
| t
| Tabs to the next appropriate tab stop when preceded by an integer.
For example, the 8t format command moves to the next 8-space tab
stop.
|
| u
| Prints as an unsigned decimal number.
|
| U
| Prints a long unsigned decimal.
|
| x
| Prints 2 bytes in hexadecimal.
|
| X
| Prints 4 bytes in hexadecimal.
|
| Y
| Prints 4 bytes in date format.
|
| /
| Local or global data symbol.
|
| ?
| Local or global text symbol.
|
| =
| Local or global absolute symbol.
|
| "..."
| Prints the enclosed string.
|
| ^
| Decreases the . (period) by the current
increment. Nothing prints.
|
| +
| Increases the . (period) by a value of 1.
Nothing prints.
|
| -
| Decreases the . (period) decrements by a value of
1. Nothing prints.
|
| newline
| Repeats the previous command incremented with a Count of
1.
|
| [?/]lValue
Mask
| Words starting at the . (period) are
masked with the Mask value and compared with the Value
parameter until a match is found. If L is used, the match is
for 4 bytes at a time instead of 2 bytes. If no match is found, then
. (period) is unchanged; otherwise, .
(period) is set to the matched location. If the Mask
parameter is omitted, a value of -1 is used.
|
| [?/]wValue...
| Writes the 2-byte Value parameter into the addressed
location. If the command is W, write 4 bytes. If the
command is V, write 1 byte. Alignment restrictions may apply
when using the w or W command.
|
| [,Count][?/]m
B1 E1 F1[?/]
| Records new values for the B1, E1, and
F1 parameters. If less than three expressions are given, the
remaining map parameters are left unchanged. If the ?
(question mark) or / (slash) is followed by an *
(asterisk), the second segment (B2, E2, F2) of the mapping is
changed. If the list is terminated by ? or /, the
file (ObjectFile or CoreFile, respectively) is used for
subsequent requests. (For example, the /m? command causes
/ to refer to the ObjectFile) file. If the
Count parameter is specified, the adb command changes
the maps associated with that file or library only. The $m
command shows the count that corresponds to a particular file. If the
Count parameter is not specified, a default value of 0 is
used.
|
| >Name
| Assigns a . (period) to the variable or register specified by the
Name parameter.
|
| !
| Calls a shell to read the line following ! (exclamation
mark).
|
| $Modifier
| Miscellaneous commands. The available values for
Modifier are:
- <File
- Reads commands from the specified file and returns to standard
input. If a count is given as 0, the command will be ignored.
The value of the count is placed in the adb 9 variable
before the first command in the File parameter is executed.
- <<File
- Reads commands from the specified file and returns to standard
input. The <<File command can be used in a
file without causing the file to be closed. If a count is given as 0,
the command is ignored. The value of the count is placed in the
adb 9 variable before the first command in
File is executed. The adb 9 variable
is saved during the execution of the <<File
command and restored when <<File completes.
There is a limit to the number of <<File commands
that can be open at once.
- >File
- Sends output to the specified file. If the File
parameter is omitted, output returns to standard output. The
File parameter is created if it does not exist.
- b
- Prints all breakpoints and their associated counts and commands.
- c
- Stacks back trace. If the Address parameter is given, it
is taken as the address of the current frame (instead of using the frame
pointer register). If the format letter C is used, the names
and values of all automatic and static variables are printed for each active
function. If the Count parameter is given, only the number
of frames specified by the Count parameter are printed.
- d
- Sets the current radix to the Address value or a value of 16 if
no address is specified.
- e
- Prints the names and values of external variables. If a count is
specified, only the external variables associated with that file are
printed.
- f
- Prints the floating-point registers in hexadecimal.
- i instruction set
- Selects the instruction set to be used for disassembly.
- I
- Changes the default directory as specified by the -I flag to
the Name parameter value.
- m
- Prints the address map.
- n mnem_set
- Selects the mnemonics to be used for disassembly.
- o
- Sets the current radix to a value of 8.
- q
- Exits the adb command.
- r
- Prints the general registers and the instruction addressed by
iar and sets the . (period) to
iar. The Number$r parameter prints the
register specified by the Number variable. The
Number,Count$r parameter prints registers
Number+Count-1,...,Number.
- s
- Sets the limit for symbol matches to the Address value.
The default is a value of 255.
- v
- Prints all non-zero variables in octal.
- w
- Sets the output page width for the Address parameter.
The default is 80.
- P Name
- Uses the Name value as a prompt string.
- ?
- Prints the process ID, the signal that caused stoppage or termination, and
the registers of $r.
|
| :Modifier
| Manages a subprocess. Available modifiers are:
- bCommand
- Sets the breakpoint at the Address parameter. The
breakpoint runs the Count parameter -1 times before causing a
stop. Each time the breakpoint is encountered, the specified command
runs. If this command sets . (period) to a value of
0, the breakpoint causes a stop.
- cSignal
- Continues the subprocess with the specified signal. If the
Address parameter is given, the subprocess is continued at this
address. If no signal is specified, the signal that caused the
subprocess to stop is sent. Breakpoint skipping is the same as for the
r modifier.
- d
- Deletes the breakpoint at the Address parameter.
- k
- Stops the current subprocess, if one is running.
- r
- Runs the ObjectFile parameter as a subprocess. If the
Address parameter is given explicitly, the program is entered at
this point. Otherwise, the program is entered at its standard entry
point. The Count parameter specifies how many breakpoints
are to be ignored before stopping. Arguments to the subprocess can be
supplied on the same line as the command. An argument starting with
< or > establishes standard input or output for
the command. On entry to the subprocess, all signals are turned
on.
- sSignal
- Continues the subprocess in single steps up to the number specified in the
Count parameter. If there is no current subprocess, the
ObjectFile parameter is run as a subprocess. In this case no
signal can be sent. The remainder of the line is treated as arguments
to the subprocess.
|
The adb command
provides a number of variables. When the adb program is
started, the following variables are set from the system header in the
specified core file. If the CoreFile parameter does not
appear to be a core file, these values are set from the
ObjectFile parameter:
| 0
| Last value printed
|
| 1
| Last displacement part of an instruction source
|
| 2
| Previous value of the 1 variable
|
| 9
| Count on the last $< or $<< subcommand
|
| b
| Base address of the data segment
|
| d
| Size of the data segment
|
| e
| Entry address of the program
|
| m
| "Magic" number
|
| s
| Size of the stack segment
|
| t
| Size of the text segment
|
The adb command
adb Debug Program Overview
Using adb Expressions
Displaying and Manipulating the Source File with the adb Program
adb Debug Program Expressions
adb Debug Program Operators
adb Debug Program Subcommands
adb Debug Program Variables
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