adb(1) adb(1)
NAME
adb - debugger
SYNOPSIS
adb [-w] [-k] [-Idir] [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
examined. 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 option
is present then both objfil and corfil are created if
necessary and opened for reading and writing so that files
can be modified using adb.
The -k flag option makes adb do UNIX kernel memory mapping;
it should be used when core is a UNIX crash dump or
/dev/mem.
The -I flag option specifies a directory where files to be
read with $< or $<< (see below) will be sought; the default
is /usr/lib/adb.
adb ignores QUIT; INTERRUPT causes return to the next adb
command.
In general, requests to adb are of the form:
[address] [, count] [command] [;]
If address is present then dot is set to address. Initially
dot is set to 0. For most commands count specifies how many
times the command will be executed. The default count is 1.
address and count are expressions.
The interpretation of an address depends on the context it
is used in. If a subprocess is being debugged then
addresses are interpreted in the usual way in the address
space of the subprocess. If the operating system is being
debugged either post-mortem or using the special file
/dev/mem to interactively examine and/or modify memory, the
maps are set to map the kernel virtual addresses which start
at 0x80000000 (on the VAX). (See ADDRESSES).
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adb(1) adb(1)
EXPRESSIONS
. The value of dot.
+ The value of dot incremented by the current
increment.
^ The value of dot decremented by the current
increment.
" The last address typed.
integer
A number. The prefixes 0o and 0O (``zero oh'') force
interpretation in octal radix; the prefixes 0t and 0T
force interpretation in decimal radix; the prefixes
0x and 0X force interpretation in hexadecimal radix.
Thus 0o20 = 0t16 = 0x10 = sixteen. If no prefix
appears, then the default radix is used; see the
``$d'' command. The default radix is initially
hexadecimal. The hexadecimal digits are
0123456789abcdefABCDEF with the obvious values. Note
that a hexadecimal number whose most significant
digit would otherwise be an alphabetic 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
register is obtained from the system header in
corfil. The register names are those printed by the
``$r'' command.
symbol A symbol is a sequence of upper or lower case
letters, underscores or digits, not starting with a
digit. The backslash character \ may be used to
escape other characters. The value of the symbol is
taken from the symbol table in objfil. An initial _
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
distinguish it from internal or hidden variables of a
program.
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adb(1) adb(1)
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. (This form is currently broken on the VAX;
local variables can be examined only with dbx(1).)
(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
objfil.
-exp Integer negation.
~exp Bitwise complement.
#exp Logical negation.
Dyadic operators
are left associative and are less binding than monadic
operators.
e1+e2 Integer addition.
e1-e2 Integer subtraction.
e1*e2 Integer multiplication.
e1%e2 Integer division.
e1&e2 Bitwise conjunction.
e1|e2 Bitwise disjunction.
e1#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
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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
subsequent 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
incremented 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.
o 2 Print 2 bytes in octal. All octal numbers output
by adb are preceded by 0.
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 as an unsigned decimal number.
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
character 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 machine instructions. 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.
a 0 Print the value of dot in symbolic form. Symbols
are checked to ensure that they have an
appropriate type as indicated below.
/ local or global data symbol
? local or global text symbol
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= local or global absolute symbol
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 IR 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
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. Odd addresses are not
allowed when writing to the subprocess address space.
[?/]m b1 e1 f1[?/]
New values for (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 `*' then the second segment (b2,e2,f2) 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 (/bin/sh) is called to read the rest of the
line following ``!''.
$modifier
Miscellaneous commands. The available modifiers are:
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<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 stoppage
or termination, as well as the registers as $r.
This is the default if modifier is omitted.
r Print the general registers and the instruction
addressed by pc. dot is set to pc.
b Print all breakpoints and their associated counts
and commands.
c C stack backtrace. If address is given then it is
taken as the address of the current frame instead
of the contents of the frame-pointer register. If
C is used then the names and (32 bit) values of
all automatic and static variables are printed for
each active function. (broken on the VAX). If
count is given then only the first count frames
are printed.
d Set the default radix to address and report the
new value. Note that address is interpreted in
the (old) current radix. Thus ``10$d'' never
changes the default radix. To make decimal the
default radix, use ``0t10$d''.
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).
o All integers input are regarded as octal.
q Exit from adb.
v Print all non zero variables in octal.
m Print the address map.
p (Kernel debugging) Change the current kernel
memory mapping to map the designated user
structure to the address given by the symbol _u.
The address argument is the address of the user's
user page table entries (on the VAX).
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:modifier
Manage a subprocess. Available modifiers are:
bc Set breakpoint at address. The breakpoint is
executed 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 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.
cs The subprocess is continued with signal s, see
sigvec(2). If 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 r.
ss As for c except that the subprocess is single
stepped count times. 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 The last value printed.
1 The last offset part of an instruction source.
2 The previous value of variable 1.
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.
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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
mapping is represented by two triples (b1, e1, f1) and (b2,
e2, f2) and the file address corresponding to a written
address is calculated as follows.
b1<address<e1 => file address=address+f1-b1, otherwise,
b2<address<e2 => file address=address+f2-b2,
otherwise, the requested 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 ? or / is
followed by an * then 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 then, for that file, b1 is set to 0, e1 is set to
the maximum file size and f1 is set to 0; in this way the
whole file can be examined with no address translation.
FILES
/bin/adb
a.out
core
SEE ALSO
cc(1), dbx(1), ptrace(2), a.out(5), core(5).
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.
BUGS
Since no shell is invoked to interpret the arguments of the
:r command, the customary wild-card and variable expansions
cannot occur.
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