TH ACID 1
SH NAME
acid \- debugger
SH SYNOPSIS
B acid
[
BI -l " libfile
]
[
B -wq
] [
B -m
I machine
] [
I pid
]
[
I textfile
]
SH DESCRIPTION
I Acid
is a programmable symbolic debugger.
It can inspect one or more processes that share an address space.
A program 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
RB ( 8.out
by default).
At the prompt,
I acid
will store function definitions or print the value of expressions.
Options are
TP .9i
B -w
Allow the textfile to be modified.
TP
B -q
Don't print variable renamings at startup.
TP
BI -l " library
Load from
I library
at startup; see below.
TP
BI -m " machine
Assume instructions are for the given CPU type
(one of
BR 3210 ,
BR 386 ,
etc., as listed in
IR 2c (1),
or
B sunsparc
or
B mipsco
for the  manufacturer-defined instruction notation for those processors)
instead of using the magic number to select
the CPU type.
TP
BI -k
Debug the kernel state for the process, rather than the user state.
PP
At startup,
I acid
obtains standard function definitions from the library file
BR /sys/lib/acid/port ,
architecture-dependent functions from
BR /sys/lib/acid/$objtype ,
user-specified functions from
BR $home/lib/acid ,
and further functions from
B -l
files.
Definitions in any file may override previously defined functions.
If the function
IR acidinit ()
is defined, it will be invoked after all modules have been loaded.
See
IR 2c (1)
for information about creating
I acid
functions for examining data structures.
SS Language
Symbols of the program being debugged become integer
variables whose values are addresses.
Contents of addresses are obtained by indirection.
Local variables are qualified by
function name, for example
BR main:argv .
When program symbols conflict with
I acid
words, distinguishing
B $
signs are prefixed.
Such renamings are reported at startup; option
B -q
suppresses them.
PP
Variable types
RI ( "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
BR {\^}
and separated by commas.
PP
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.
IP
BI head " list
br
BI tail " list
br
BI append " list", " element
br
BI delete " list", " subscript
PP
Format codes are the same as in
IR db (1).
Formats may be attached to (unary) expressions with
BR \e ,
e.g.
BR (32*7)\eD .
There are two indirection operators,
B *
to address a core image,
B @
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.
PP
Statements are
IP
BI if " expr " then " statement " "\fR[ \fPelse\fI statement \fR]
br
BI while " expr " do " statement
br
BI loop " expr" , " expr " do " statement
br
BI defn " name" ( args ") {" " statement \fP}
br
BI local " name
br
BI return " expr
br
BR whatis " [ \fI name \fP]
PP
Here is a partial list of functions; see the manual for a complete list.
TF asm(address)
TP
B stk()
Print a stack trace for current process.
TP
B lstk()
Print a stack trace with values of local variables.
TP
B gpr()
Print general registers.
Registers can also be accessed by name, for example
BR *R0 .
TP
B spr()
Print special registers such as program counter and stack pointer.
TP
B fpr()
Print floating-point registers.
TP
B regs()
Same as
BR spr();gpr() .
TP
BI fmt( expr , format )
Expression
I expr
with format given by the character value of expression
IR format .
TP
BI src( address )
Print 10 lines of source around the program address.
TP
BI Bsrc( address )
Get the source line for the program address
into a window of a running
IR sam (1)
and select it.
TP
BI line( address )
Print source line nearest to the program address.
TP
B source()
List current source directories.
TP
BI addsrcdir( string )
Add a source directory to the list.
TP
BI filepc( where )
Convert a string of the form
IB sourcefile : linenumber
to a machine address.
TP
BI pcfile( address )
Convert a machine address to a source file name.
TP
BI pcline( address )
Convert a machine address to a source line number.
TP
BI bptab()
List breakpoints set in the current process.
TP
BI bpset( address )
Set a breakpoint in the current process at the given address.
TP
BI bpdel( address )
Delete a breakpoint from the current process.
TP
B cont()
Continue execution of current process and wait for it to stop.
TP
B step()
Execute a single machine instruction in the current process.
TP
B func()
Step repeatedly until after a function return.
TP
BI stopped( pid )
This replaceable function is called automatically when the given process
stops.
It normally prints the program counter and returns to the prompt.
TP
BI asm( address )
Disassemble 30 machine instructions beginning at the given address.
TP
BI mem( address , string )
Print a block of memory
interpreted according to a string of format codes.
TP
BI dump( address , n , string\fP)
Like
BR mem (),
repeated for
I n
consecutive blocks.
TP
BI print( expr , ... )
Print the values of the expressions.
TP
BI newproc( arguments )
Start a new process with arguments given as a string
and halt at the first instruction.
TP
B new()
Like
IR newproc (),
but take arguments (except
BR argv[0] )
from string variable
BR progargs .
TP
B win()
Like
IR new (),
but run the process in a separate window.
TP
BI start( pid )
Start a stopped process.
TP
BI kill( pid )
Kill the given process.
TP
BI setproc( pid )
Make the given process current.
TP
BI rc( string )
Escape to the shell,
IR rc (1),
to execute the command string.
SH EXAMPLES
Start to debug
BR /bin/ls ;
set some breakpoints; run up to the first one:
IP
EX
% 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\es
acid: whatis argv0
integer variable format s
acid: *argv0
/bin/ls
acid: bpset(ls)
acid: cont()
70094: breakpoint  ls   ADD     $-0x16c8,R29
acid:
EE
PP
Display elements of a linked list of structures:
IP
EX
complex Str { 'D' 0 val; 'X' 4 next; };
complex Str s;
s = *headstr;
while s != 0 do{
       print(s.val, "\en");
       s = s.next;
}
EE
PP
Note the use of the
B .
operator instead of
BR -> .
PP
Display an array of bytes declared in C as
BR "char array[]" .
IP
EX
*(array\es)
EE
PP
This example gives
B array
string format, then prints the string beginning at the address (in
I acid
notation)
BR *array .
SH FILES
B /proc/*/text
br
B /proc/*/mem
br
B /proc/*/ctl
br
B /proc/*/note
br
B /sys/lib/acid/$objtype
br
B /sys/lib/acid/port
br
B $home/lib/acid
SH SOURCE
B /sys/src/cmd/acid
SH "SEE ALSO"
IR 2a (1),
IR 2c (1),
IR 2l (1),
IR mk (1),
IR db (1)
br
Phil Winterbottom,
``Acid Manual''.
SH DIAGNOSTICS
At termination, kill commands are proposed
for processes that are still active.
SH BUGS
There is no way to redirect the standard input and standard output
of a new process.
br
Source line selection near the beginning of a file may pick
an adjacent file.
br
With the extant stepping commands, one cannot step through instructions
outside the text segment and it is hard to debug across process forks.

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