ACID(1) ACID(1)
NAME
acid, acidtypes - debugger
SYNOPSIS
acid [ -l library ] [ -wq ] [ -m machine ] [ pid | core ] [
textfile ]
acidtypes [ -p prefix ] file ...
DESCRIPTION
Acid is a programmable symbolic debugger. It can inspect
one or more processes that share an address space. A pro-
gram to be debugged may be specified by the process id of a
running or defunct process, or by the name of the program's
text file (a.out by default). At the prompt, acid will
store function definitions or print the value of expres-
sions. Options are
-w Allow the textfile to be modified.
-q Print variable renamings at startup.
-l library
Load from library at startup; see below.
-m machine
Assume instructions are for the given CPU type (see
mach(3)) instead of using the executable header to
select the CPU type.
-k Debug the kernel state for the process, rather than
the user state.
At startup, acid obtains standard function definitions from
the library file /usr/local/plan9/acid/port, architecture-
dependent functions from /usr/local/plan9/acid/$objtype,
user-specified functions from $home/lib/acid, and further
functions from -l files. Definitions in any file may over-
ride previously defined functions. If the function
acidinit() is defined, it will be invoked after all modules
have been loaded. Then the function acidmap() will be
invoked if defined. /usr/local/plan9/acid/port provides a
definition of acidmap that attaches all the shared libraries
being used by the target process and then runs acidtypes
(q.v.) to create acid functions for examining data struc-
tures.
Language
Symbols of the program being debugged become integer vari-
ables whose values are addresses. Contents of addresses are
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ACID(1) ACID(1)
obtained by indirection. Local variables are qualified by
function name, for example main:argv. When program symbols
conflict with acid words, distinguishing $ signs are pre-
fixed. Such renamings are reported at startup; option -q
suppresses them.
Variable types (integer, float, list, string) and formats
are inferred from assignments. Truth values false/true are
attributed to zero/nonzero integers or floats and to
empty/nonempty lists or strings. Lists are sequences of
expressions surrounded by {} and separated by commas.
Expressions are much as in C, but yield both a value and a
format. Casts to complex types are allowed. Lists admit
the following operators, with subscripts counted from 0.
head list
tail list
append list, element
delete list, subscript
Format codes are the same as in db(1). Formats may be
attached to (unary) expressions with \, e.g. (32*7)\D.
There are two indirection operators, * to address a core
image, @ to address a text file. The type and format of the
result are determined by the format of the operand, whose
type must be integer.
Statements are
if expr then statement [ else statement ]
while expr do statement
loop expr, expr do statement
defn name(args) { statement }
defn name
name(args)
builtin name(args)
local name
return expr
whatis [ name ]
The statement defn name clears the definition for name. A
defn may override a built-in function; prefixing a function
call with builtin ignores any overriding defn, forcing the
use of the built-in function.
Here is a partial list of functions; see the manual for a
complete list.
stk() Print a stack trace for current process.
lstk() Print a stack trace with values of local vari-
ables.
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ACID(1) ACID(1)
gpr() Print general registers. Registers can also
be accessed by name, for example *R0.
spr() Print special registers such as program
counter and stack pointer.
fpr() Print floating-point registers.
regs() Same as spr();gpr().
fmt(expr,format)
Expression expr with format given by the char-
acter value of expression format.
src(address) Print 10 lines of source around the program
address.
Bsrc(address) Get the source line for the program address
into a window of a running sam(1) and select
it.
line(address) Print source line nearest to the program
address.
source() List current source directories.
addsrcdir(string)
Add a source directory to the list.
filepc(where) Convert a string of the form
sourcefile:linenumber to a machine address.
pcfile(address)
Convert a machine address to a source file
name.
pcline(address)
Convert a machine address to a source line
number.
bptab() List breakpoints set in the current process.
bpset(address)
Set a breakpoint in the current process at the
given address. (Doesn't work on Unix yet.)
bpdel(address)
Delete a breakpoint from the current process.
cont() Continue execution of current process and wait
for it to stop.
step() Execute a single machine instruction in the
current process. (Doesn't work on Unix yet.)
func() Step repeatedly until after a function return.
stopped(pid) This replaceable function is called automati-
cally when the given process stops. It nor-
mally prints the program counter and returns
to the prompt.
asm(address) Disassemble 30 machine instructions beginning
at the given address.
mem(address,string)
Print a block of memory interpreted according
to a string of format codes.
dump(address,n,string)
Like mem(), repeated for n consecutive blocks.
print(expr,...)
Print the values of the expressions.
newproc(arguments)
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ACID(1) ACID(1)
Start a new process with arguments given as a
string and halt at the first instruction.
new() Like newproc(), but take arguments (except
argv[0]) from string variable progargs.
win() Like new(), but run the process in a separate
window.
start(pid) Start a stopped process.
kill(pid) Kill the given process.
setproc(pid) Make the given process current.
rc(string) Escape to the shell, rc(1), to execute the
command string.
include(string)
Read acid commands from the named file.
includepipe(string)
Run the command string, reading its standard
output as acid commands.
Shared library segments
When a pid or core file is specified on the command line,
acid will, as part of its startup, determine the set of
shared libraries in use by the process image and map those
at appropriate locations. If acid is started without a pid
or core file and is subsequently attached to a process via
setproc, the shared library maps can be initialized by call-
ing dynamicmap().
Type information
Unix compilers conventionally include detailed type informa-
tion in the debugging symbol section of binaries. The
external program acidtypes extracts this information and
formats it as acid program text. Once the shared libraries
have been mapped, the default acid startup invokes acidtypes
(via includepipe) on the set of currently mapped text files.
The function acidtypes() can be called to rerun the command
after changing the set of mapped text files.
Acid Libraries
There are a number of acid `libraries' that provide higher-
level debugging facilities. One notable example is trump,
which uses acid to trace memory allocation. Trump requires
starting acid on the program, either by attaching to a run-
ning process or by executing new() on a binary (perhaps
after setting progargs), stopping the process, and then run-
ning trump() to execute the program under the scaffolding.
The output will be a trace of the memory allocation and free
calls executed by the program. When finished tracing, stop
the process and execute untrump() followed by cont() to
resume execution.
EXAMPLES
Start to debug /bin/ls; set some breakpoints; run up to the
first one (this example doesn't work on Unix yet):
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ACID(1) ACID(1)
% acid /bin/ls
/bin/ls: mips plan 9 executable
/sys/lib/acid/port
/sys/lib/acid/mips
acid: new()
70094: system call _main ADD $-0x14,R29
70094: breakpoint main+0x4 MOVW R31,0x0(R29)
acid: pid
70094
acid: argv0 = **main:argv\s
acid: whatis argv0
integer variable format s
acid: *argv0
/bin/ls
acid: bpset(ls)
acid: cont()
70094: breakpoint ls ADD $-0x16c8,R29
acid:
Display elements of a linked list of structures:
complex Str { 'D' 0 val; 'X' 4 next; };
s = *headstr;
while s != 0 do{
complex Str s;
print(s.val, "\n");
s = s.next;
}
Note the use of the . operator instead of ->.
Display an array of bytes declared in C as char array[].
*(array\s)
This example gives array string format, then prints the
string beginning at the address (in acid notation) *array.
Trace the system calls executed by ls(1) (neither does this
one):
% acid -l truss /bin/ls
/bin/ls:386 plan 9 executable
/sys/lib/acid/port
/sys/lib/acid/kernel
/sys/lib/acid/truss
/sys/lib/acid/386
acid: progargs = "-l lib/profile"
acid: new()
acid: truss()
open("#c/pid", 0)
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ACID(1) ACID(1)
return value: 3
pread(3, 0x7fffeeac, 20, -1)
return value: 12
data: " 166 "
...
stat("lib/profile", 0x0000f8cc, 113)
return value: 65
open("/env/timezone", 0)
return value: 3
pread(3, 0x7fffd7c4, 1680, -1)
return value: 1518
data: "EST -18000 EDT -14400
9943200 25664400 41392800 57718800 73447200 89168400
104896800 ..."
close(3)
return value: 0
pwrite(1, "--rw-rw-r-- M 9 rob rob 2519 Mar 22 10:29 lib/profile
", 54, -1)
--rw-rw-r-- M 9 rob rob 2519 Mar 22 10:29 lib/profile
return value: 54
...
166: breakpoint _exits+0x5 INTB $0x40
acid: cont()
FILES
/usr/local/plan9/acid/$objtype
/usr/local/plan9/acid/port
/usr/local/plan9/acid/kernel
/usr/local/plan9/acid/trump
/usr/local/plan9/acid/truss
$home/lib/acid
SOURCE
/usr/local/plan9/src/cmd/acid
SEE ALSO
mk(1), db(1)
Phil Winterbottom, ``Acid Manual''.
DIAGNOSTICS
At termination, kill commands are proposed for processes
that are still active.
BUGS
There is no way to redirect the standard input and standard
output of a new process.
Source line selection near the beginning of a file may pick
an adjacent file.
With the extant stepping commands, one cannot step through
instructions outside the text segment and it is hard to
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ACID(1) ACID(1)
debug across process forks.
Breakpoints do not work yet. Therefore, commands such as
step, new, and truss do not work either. New in particular
will need some help to cope with dynamic libraries.
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