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.TH ADB 1 
.SH NAME
adb \- debugger
.SH SYNOPSIS
.B adb
[\fB\-w\fR] [ objfil [ corfil ] ]
.SH DESCRIPTION
.I 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.
.PP
.I Objfil
is normally an executable program file, preferably
containing a symbol table;
if not then the
symbolic features of
.I  adb
cannot be used although the file can still
be examined.
The default for
.I objfil
is
.B  a.out.
.I Corfil
is assumed to be a core image file produced after
executing
.IR objfil ;
the default for
.I corfil
is
.B  core.
.PP
Requests to
.I  adb
are read from the standard input and
responses are to the standard output.
If the
.B  \-w
flag is present then both
.I  objfil
and
.I corfil
are
created if necessary and
opened for reading and writing
so that files can be modified using
.IR adb .
.I Adb
ignores QUIT; INTERRUPT
causes return to the next
.I adb
command.
.PP
In general requests to
.I  adb
are of the form
.PP
.if n .ti 16
.if t .ti 1.6i
[\|\fIaddress\fR\|]  [\|,
.IR count \|]
[\|\fIcommand\fR\|] [\|;\|]
.PP
If
.I address
is present then
.I  dot
is set to
.IR address .
Initially
.I dot
is set to 0.
For most commands
.I count
specifies how many times
the command will be executed.
The default
.I count
is 1.
.I Address
and
.I count
are expressions.
.PP
The interpretation of an address depends
on the context it is used in.
If a subprocess is being debugged then
addresses are interpreted
in the usual way in the address space of the subprocess.
For further details of address mapping see
.SM ADDRESSES.
.SH EXPRESSIONS
.TP 7.2n
.B .
The value of
.IR dot .
.TP 7.2n
+
The value of
.I dot
incremented by the current increment.
.TP 7.2n
^
The value of
.I dot
decremented by the current increment.
.TP 7.2n
"
The last
.I address
typed.
.TP 7.2n
.I integer
An octal number if
.I integer
begins with a 0;
a hexadecimal number if preceded by
.BR # ;
otherwise a decimal number.
.TP 7.2n
.IB integer . fraction
A 32 bit floating point number.
.TP 7.2n
.I \'cccc\|\'
The ASCII value of up to 4 characters.
\\ may be used to escape a \'.
.TP 7.2n
.I \*(LT name
The value of
.IR name ,
which is either a variable name or a register name.
.I Adb
maintains a number of variables
(see
.SM VARIABLES\*S)
named by single letters or digits.
If
.I name
is a register name then
the value of the register is obtained from
the system header in
.IR corfil .
The register names are
.BR "r0 ... r5 sp pc ps" "."
.TP 7.2n
.I symbol
A
.I symbol
is a sequence
of upper or lower case letters, underscores or
digits, not starting with a digit.
.BR \\ " may be used to escape other characters."
The value of the
.I symbol
is taken from the symbol table
in
.IR objfil .
An initial \_ or \*(TW will be prepended to
.I symbol
if needed.
.TP
.I _ 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.
.TP 7.2n
.IB routine . name
The address of the variable
.I name
in the specified
C routine.
Both
.I routine
and
.I name
are
.IR symbols .
If
.I name
is omitted the value is the address of the
most recently activated C stack frame
corresponding to
.IR routine .
.TP 7.2n
.RI ( exp \|)
The value of the expression
.IR exp .
.LP
.SM
.B  "Monadic\ operators"
.TP 7.2n
.RI \*(ST exp
The contents of the location addressed
by
.I exp
in
.IR corfil .
.TP 7.2n
.RI @ exp
The contents of the location addressed by
.I exp
in
.IR objfil .
.TP 7.2n
.RI \- exp
Integer negation.
.TP 7.2n
.RI \*(TW exp
Bitwise complement.
.LP
.B  "Dyadic\ operators"
are left associative
and are less binding than monadic operators.
.TP 7.2n
.IR e1 + e2
Integer addition.
.TP 7.2n
.IR e1 \- e2
Integer subtraction.
.TP 7.2n
.IR e1 \*(ST e2
Integer multiplication.
.TP 7.2n
.IR e1 % e2
Integer division.
.TP 7.2n
.IR e1 & e2
Bitwise conjunction.
.TP 7.2n
.IR e1 \(bv e2
Bitwise disjunction.
.TP 7.2n
.IR e1 # e2
.I E1
rounded up to the next multiple of
.IR e2 .
.DT
.SH 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 `\*(ST';
see
.SM ADDRESSES
for further details.)
.TP .5i
.RI ? f
Locations starting at
.I address
in
.I  objfil
are printed according to the format
.IR f .
.TP
.RI / f
Locations starting at
.I address
in
.I  corfil
are printed according to the format
.IR f .
.TP
.RI  = f
The value of
.I address
itself is printed in the
styles indicated by the format
.IR f .
(For
.B i 
format `?' is printed for the parts of the instruction that reference
subsequent words.)
.PP
A
.I 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
.I dot
is incremented temporarily
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.
.ta 2.5n .5i
.RS
.TP
.BR o "	2"
Print 2 bytes in octal.
All octal numbers output by
.I adb
are preceded by 0.
.br
.ns
.TP
.BR O "	4"
Print 4 bytes in octal.
.br
.ns
.TP
.BR q "	2"
Print in signed octal.
.br
.ns
.TP
.BR Q "	4"
Print long signed octal.
.br
.ns
.TP
.BR d "	2"
Print in decimal.
.br
.ns
.TP
.BR D "	4"
Print long decimal.
.br
.ns
.TP
.BR x "	2"
Print 2 bytes in hexadecimal.
.br
.ns
.TP
.BR X "	4"
Print 4 bytes in hexadecimal.
.br
.ns
.TP
.BR u "	2"
Print as an unsigned decimal number.
.br
.ns
.TP
.BR U "	4"
Print long unsigned decimal.
.br
.ns
.TP
.BR f "	4"
Print the 32 bit value
as a floating point number.
.br
.ns
.TP
.BR F "	8"
Print double floating point.
.br
.ns
.TP
.BR b "	1"
Print the addressed byte in octal.
.br
.ns
.TP
.BR c "	1"
Print the addressed character.
.br
.ns
.TP
.BR C "	1"
Print the addressed character using
the following escape convention.
Character values 000 to 040 are printed as @ followed by the corresponding
character in the range 0100 to 0140.
The character @ is printed as @@.
.br
.ns
.TP
.BI s "	n"
Print the addressed characters until a zero character
is reached.
.br
.ns
.TP
.BI S "	n"
Print a string using 
the @ escape convention.
.I n
is the length of the string including its zero terminator.
.br
.ns
.TP
.BR Y "	4"
Print 4 bytes in date format (see
.IR ctime (3)).
.br
.ns
.TP
.BR i "	n"
Print as PDP11 instructions.
.I n
is the number of bytes occupied by the instruction.
This style of printing causes variables 1 and 2 to be set
to the offset parts of the source and destination respectively.
.br
.ns
.TP
.BR a "	0"
Print the value of
.I dot
in symbolic form.
Symbols are checked to ensure that they have an appropriate
type as indicated below.
.LP
	/	local or global data symbol
.br
	?	local or global text symbol
.br
	=	local or global absolute symbol
.TP
.BR p "	2"
Print the addressed value in symbolic form using
the same rules for symbol lookup as
.BR a .
.br
.ns
.TP
.BR t "	0"
When preceded by an integer tabs to the next
appropriate tab stop.
For example,
.B 8t 
moves to the next 8-space tab stop.
.br
.ns
.TP
.BR r "	0"
Print a space.
.br
.ns
.TP
.BR n "	0"
Print a newline.
.br
.ns
.tr '"
.TP
.BR '...' " 0"
Print the enclosed string.
.br
.tr ''
.br
.ns
.TP
.B ^
.I Dot
is decremented by the current increment.
Nothing is printed.
.br
.ns
.TP
+
.I Dot
is incremented by 1.
Nothing is printed.
.br
.ns
.TP
\-
.I Dot
is decremented by 1.
Nothing is printed.
.RE
.TP
newline
If the previous command temporarily incremented
.IR dot ,
make the increment permanent.
Repeat the previous command with a
.I count
of 1.
.TP
.RB [ ?/ ] l "\fI value mask\fR"
Words starting at
.I  dot
are masked with
.I mask
and compared with
.I value
until
a match is found.
If
.B L
is used then the match is for 4 bytes at a time instead of 2.
If no match is found then
.I dot
is unchanged; otherwise
.I dot
is set to the matched location.
If
.I mask
is omitted then \-1 is used.
.TP
.RB [ ?/ ] w "\fI value ...\fR"
Write the 2-byte
.I value
into the addressed
location.
If the command is
.BR W ,
write 4 bytes.
Odd addresses are not allowed when writing to the subprocess
address space.
.TP
[\fB?/\fR]\fBm\fI b1 e1 f1\fR[\fB?/\fR]
.br
New values for
.RI ( b1,\ e1,\ f1 )
are recorded.
If less than three expressions are given then
the remaining map parameters are left unchanged.
If the `?' or `/' is followed by `\*(ST' then
the second segment (\fIb2\fR\|,\|\fIe2\fR\|,\|\fIf2\fR)
of the mapping is changed.
If the list is terminated by `?' or `/' then the file
(\fIobjfil\fR or
.I corfil
respectively) is used
for subsequent requests.
(So that, for example, `/m?' will cause `/' to refer to
.IR objfil .)
.TP
.BI \*(GT name
.I Dot
is assigned to the variable or register named.
.TP
.B !
A shell is called to read the
rest of the line following `!'.
.TP
.RI $ modifier
Miscellaneous commands.
The available 
.I modifiers 
are:
.RS
.TP
.BI < f
Read commands from the file
.I f
and return.
.br
.ns
.TP
.BI > f
Send output to the file
.I  f,
which is created if it does not exist.
.br
.ns
.TP
.B r
Print the general registers and
the instruction addressed by
.BR pc .
.I Dot
is set to \fBpc\fR.
.br
.ns
.TP
.B f
Print the floating registers in
single or double length.
If the floating point status of
.B ps
is set to double (0200 bit)
then double length is used anyway.
.br
.ns
.TP
.B b
Print all breakpoints
and their associated counts and commands.
.br
.ns
.TP
.B a
ALGOL 68 stack backtrace.
If
.I address
is given then it is taken to be the
address of the current frame (instead of
.BR r4 ).
If
.I count
is given then only the first
.I count
frames are printed.
.br
.ns
.TP
.B c
C stack backtrace.
If
.I address
is given then it is taken as the
address of the current frame (instead of
.BR r5 ).
If
.B C 
is used then the names and (16 bit) values of all automatic
and static variables are printed for each active function.
If
.I count
is given then only the first
.I count
frames are printed.
.br
.ns
.TP
.B e
The names and values of
external variables are printed.
.br
.ns
.TP
.B w
Set the page width for output to
.I address
(default 80).
.br
.ns
.TP
.B s
Set the limit for symbol matches to
.I address
(default 255).
.br
.ns
.TP
.B o
All integers input are regarded as octal.
.br
.ns
.TP
.B d
Reset integer input as described in
.SM EXPRESSIONS.
.br
.ns
.TP
.B q
Exit from
.IR adb .
.br
.ns
.TP
.B v
Print all non zero variables in octal.
.br
.ns
.TP
.B m
Print the address map.
.RE
.TP
.BI : modifier
Manage a subprocess.
Available modifiers are:
.RS
.TP
.BI b c
Set breakpoint at
.IR address .
The breakpoint is executed
.IR count \-1
times before
causing a stop.
Each time the breakpoint is encountered
the command
.I c
is executed.
If this command sets
.I dot
to zero
then the breakpoint causes a stop.
.TP
.B d
Delete breakpoint at
.IR address .
.TP
.B r
Run
.I objfil
as a subprocess.
If
.I address
is given explicitly then the
program is entered at this point; otherwise
the program is entered at its standard entry point.
.I 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.
.TP
.BI c s
The subprocess is continued
with signal
.I s
c
.I s,
see
.IR signal (2).
If
.I address
is given then the subprocess
is continued at this address.
If no signal is specified then the signal
that caused the subprocess to stop is sent.
Breakpoint skipping is the same
as for
.BR r .
.TP
.BI s s
As for
.B c 
except that
the subprocess is single stepped
.I count
times.
If there is no current subprocess then
.I objfil
is run
as a subprocess as for
.BR r .
In this case no signal can be sent; the remainder of the line
is treated as arguments to the subprocess.
.TP
.B k
The current subprocess, if any, is terminated.
.RE
.SH VARIABLES
.I Adb
provides a number of variables.
Named variables are set initially by
.I  adb
but are not used subsequently.
Numbered variables are reserved for communication
as follows.
.TP
0
The last value printed.
.br
.ns
.TP
1
The last offset part of an instruction source.
.br
.ns
.TP
2
The previous value of variable 1.
.PP
On entry the following are set
from the system header in the
.IR corfil .
If
.I corfil
does not appear to be a
.B core 
file then
these values are set from
.IR objfil .
.TP
b
The base address of the data segment.
.br
.ns
.TP
d
The data segment size.
.br
.ns
.TP
e
The entry point.
.br
.ns
.TP
m
The `magic' number (0405, 0407, 0410 or 0411).
.br
.ns
.TP
s
The stack segment size.
.br
.ns
.TP
t
The text segment size.
.SH ADDRESSES
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
.RI ( "b1, e1, f1" )
and
.RI ( "b2, e2, f2" )
and the
.I file address
corresponding to a written
.I address
is calculated as follows.
.PP
.if t .ti 1.5i
.if n .ti 8
.IR b1 \*(LE address < e1
\*(IM
.IR "file address" = address + f1\-b1,
otherwise,
.PP
.if t .ti 1.5i
.if n .ti 8
.IR b2 \*(LE address < e2
\*(IM
.IR "file address" = address + f2\-b2,
.PP
otherwise, the requested
.I address
is not legal.
In some cases (e.g. for programs with separated I and D
space) the two segments for a file may overlap.
If a
.B ? 
or
.B / 
is followed by an
.B \*(ST 
then only the second
triple is used.
.PP
The initial setting of both mappings is suitable for
normal
.B a.out 
and
.B core 
files.
If either file is not of the kind expected then, for that file,
.I b1
is set to 0,
.I e1
is set to
the maximum file size
and
.I f1
is set to 0; in this way the whole
file can be examined with no address translation.
.PP
So that
.I adb
may be used on large files
all appropriate values are kept as signed 32 bit integers.
.SH FILES
/dev/mem
.br
/dev/swap
.br
a.out
.br
core
.SH SEE\ ALSO
ptrace(2),
a.out(5),
core(5)
.SH DIAGNOSTICS
`Adb' when there is no current command or format.
Comments about inaccessible files, syntax errors,
abnormal termination of commands, etc.
Exit status is 0, unless last command failed or
returned nonzero status.
.SH BUGS
A breakpoint set at the entry point is not effective
on initial entry to the program.
.br
When single stepping, system calls do not count as an
executed instruction.
.br
Local variables whose names are the same as an external
variable may foul up the accessing of the external.