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| author | Jim Ingham <jingham@apple.com> | 2012-01-24 02:44:07 +0000 |
|---|---|---|
| committer | Jim Ingham <jingham@apple.com> | 2012-01-24 02:44:07 +0000 |
| commit | 6ae0f99f590131fd7557e00f044ecd23c0747315 (patch) | |
| tree | 7da636abd8445b6d49ca4d12eb0067d002a41d4c /lldb/www/python-reference.html | |
| parent | 87a593687cd4a67801149e4cc7aa6727f3fd41df (diff) | |
| download | bcm5719-llvm-6ae0f99f590131fd7557e00f044ecd23c0747315.tar.gz bcm5719-llvm-6ae0f99f590131fd7557e00f044ecd23c0747315.zip | |
Better name for the python reference.
llvm-svn: 148769
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| -rwxr-xr-x | lldb/www/python-reference.html | 457 |
1 files changed, 457 insertions, 0 deletions
diff --git a/lldb/www/python-reference.html b/lldb/www/python-reference.html new file mode 100755 index 00000000000..c5736cb1653 --- /dev/null +++ b/lldb/www/python-reference.html @@ -0,0 +1,457 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml">
+<head>
+<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
+<link href="style.css" rel="stylesheet" type="text/css" />
+<title>LLDB Python FAQ</title>
+</head>
+
+<body>
+ <div class="www_title">
+ LLDB Python FAQ
+ </div>
+
+<div id="container">
+ <div id="content">
+ <!--#include virtual="sidebar.incl"-->
+ <div id="middle">
+ <div class="post">
+ <h1 class ="postheader">Introduction</h1>
+ <div class="postcontent">
+
+ <p>The entire LLDB API is available as Python functions through a script bridging interface.
+ This means the LLDB API's can be used directly from python either interactively or to build python apps that
+ provide debugger features. </p>
+ <p>Additionally, Python can be used as a programmatic interface within the
+ lldb command interpreter (we refer to this for brevity as the embedded interpreter). Of course,
+ in this context it has full access to the LLDB API - with some additional conveniences we will
+ call out in the FAQ.</p>
+
+ </div>
+ <div class="postfooter"></div>
+
+ <div class="post">
+ <h1 class ="postheader">Embedded Python Interpreter</h1>
+ <div class="postcontent">
+
+ <p>The embedded python interpreter can be accessed in a variety of ways from within LLDB. The
+ easiest way is to use the lldb command <b>script</b> with no arguments at the lldb command prompt:</p>
+<code><pre><tt>(lldb) <strong>script</strong>
+Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
+>>> 2+3
+5
+>>> hex(12345)
+'0x3039'
+>>>
+</tt></pre></code>
+
+ <p>This drops you into the embedded python interpreter. When running under the <b>script</b> command,
+ lldb sets some convenience variables that give you quick access to the currently selected entities that characterize
+ the program and debugger state. In each case, if there is no currently selected entity of the appropriate
+ type, the variable's <b>IsValid</b> method will return false.
+ <p>Note also, these variables hold the values
+ of the selected objects on entry to the embedded interpreter. They do not update as you use the LLDB
+ API's to change, for example, the currently selected stack frame or thread.</p>
+ These are all global variables contained in the <b>lldb</b> python namespace :</p>
+ <table class="stats" width="620" cellspacing="0">
+ <tr>
+ <td class="hed" width="20%">Variable</td>
+ <td class="hed" width="10%">Type</td>
+ <td class="hed" width="70%">Description</td>
+ </tr>
+
+ <tr>
+ <td class="content">
+ <b>lldb.debugger</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBDebugger</b>
+ </td>
+ <td class="content">
+ Contains the debugger object whose <b>script</b> command was invoked.
+ The <b>lldb.SBDebugger</b> object owns the command interpreter
+ and all the targets in your debug session. There will always be a
+ Debugger in the embedded interpreter.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>lldb.target</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBTarget</b>
+ </td>
+ <td class="content">
+ Contains the currently selected target - for instance the one made with the
+ <b>file</b> or selected by the <b>target select <target-index></b> command.
+ The <b>lldb.SBTarget</b> manages one running process, and all the executable
+ and debug files for the process.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>lldb.process</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBProcess</b>
+ </td>
+ <td class="content">
+ Contains the process of the currently selected target.
+ The <b>lldb.SBProcess</b> object manages the threads and allows access to
+ memory for the process.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>lldb.thread</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBThread</b>
+ </td>
+ <td class="content">
+ Contains the currently selected thread.
+ The <b>lldb.SBThread</b> object manages the stack frames in that thread.
+ A thread is always selected in the command interpreter when a target stops.
+ The <b>thread select <thread-index></b> commmand can be used to change the
+ currently selected thread. So as long as you have a stopped process, there will be
+ some selected thread.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>lldb.frame</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBFrame</b>
+ </td>
+ <td class="content">
+ Contains the currently selected stack frame.
+ The <b>lldb.SBFrame</b> object manage the stack locals and the register set for
+ that stack.
+ A stack frame is always selected in the command interpreter when a target stops.
+ The <b>frame select <frame-index></b> commmand can be used to change the
+ currently selected frame. So as long as you have a stopped process, there will
+ be some selected frame.
+ </td>
+ </tr>
+ </table>
+
+ <p>Once in the embedded interpreter, these objects can be used. To get started, note that almost
+ all of the <b>lldb</b> Python objects are able to briefly describe themselves when you pass them
+ to the Python <b>print</b> function:
+<code><pre><tt>(lldb) <b>script</b>
+Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
+>>> <strong>print lldb.debugger</strong>
+Debugger (instance: "debugger_1", id: 1)
+>>> <strong>print lldb.target</strong>
+a.out
+>>> <strong>print lldb.process</strong>
+SBProcess: pid = 59289, state = stopped, threads = 1, executable = a.out
+>>> <strong>print lldb.thread</strong>
+SBThread: tid = 0x1f03
+>>> <strong>print lldb.frame</strong>
+frame #0: 0x0000000100000bb6 a.out main + 54 at main.c:16
+</tt></pre></code>
+
+ </div>
+ <div class="postfooter"></div>
+
+ </div>
+ <div class="post">
+ <h1 class ="postheader">Running a Python script when a breakpoint gets hit</h1>
+ <div class="postcontent">
+
+ <p>One very powerful use of the lldb Python API is to have a python script run when a breakpoint gets hit. Adding python
+ scripts to breakpoints provides a way to create complex breakpoint
+ conditions and also allows for smart logging and data gathering.</p>
+ <p>When your process hits a breakpoint to which you have attached some python code, the code is executed as the
+ body of a function which takes two arguments:</p>
+ <p>
+<code><pre><tt>def breakpoint_function_wrapper(<b>frame</b>, <b>bp_loc</b>):
+ <font color=green># Your code goes here</font>
+</tt></pre></code>
+ <p><table class="stats" width="620" cellspacing="0">
+ <tr>
+ <td class="hed" width="10%">Argument</td>
+ <td class="hed" width="10%">Type</td>
+ <td class="hed" width="80%">Description</td>
+ </tr>
+
+ <tr>
+ <td class="content">
+ <b>frame</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBFrame</b>
+ </td>
+ <td class="content">
+ The current stack frame where the breakpoint got hit.
+ The object will always be valid.
+ This <b>frame</b> argument might <i>not</i> match the currently selected stack frame found in the <b>lldb</b> module global variable <b>lldb.frame</b>.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>bp_loc</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBBreakpointLocation</b>
+ </td>
+ <td class="content">
+ The breakpoint location that just got hit. Breakpoints are represented by <b>lldb.SBBreakpoint</b>
+ objects. These breakpoint objects can have one or more locations. These locations
+ are represented by <b>lldb.SBBreakpointLocation</b> objects.
+ </td>
+ </tr>
+ </table>
+ <p>An example will show how simple it is to write some python code and attach it to a breakpoint.
+ The following example will allow you to track the order in which the functions in a given shared library
+ are first executed during one run of your program. This is a simple method to gather an order file which
+ can be used to optimize function placement within a binary for execution locality.</p>
+ <p>We do this by setting a regular expression breakpoint
+ that will match every function in the shared library. The regular expression '.' will match
+ any string that has at least one character in it, so we will use that.
+ This will result in one <b>lldb.SBBreakpoint</b> object
+ that contains an <b>lldb.SBBreakpointLocation</b> object for each function. As the breakpoint gets
+ hit, we use a counter to track the order in which the function at this particular breakpoint location got hit.
+ Since our code is passed the location that was hit, we can get the name of the function from the location,
+ disable the location so we won't count this function again; then log some info and continue the process.</p>
+ <p>Note we also have to initialize our counter, which we do with the simple one-line version of the <b>script</b>
+ command.
+ <p>Here is the code:
+
+<code><pre><tt>(lldb) <strong>breakpoint set --func-regex=. --shlib=libfoo.dylib</strong>
+Breakpoint created: 1: regex = '.', module = libfoo.dylib, locations = 223
+(lldb) <strong>script counter = 0</strong>
+(lldb) <strong>breakpoint command add --script-type python 1</strong>
+Enter your Python command(s). Type 'DONE' to end.
+> <font color=green># Increment our counter. Since we are in a function, this must be a global python variable</font>
+> <strong>global counter</strong>
+> <strong>counter += 1</strong>
+> <font color=green># Get the name of the function</font>
+> <strong>name = frame.GetFunctionName()</strong>
+> <font color=green># Print the order and the function name</font>
+> <strong>print '[%i] %s' % (counter, name)</strong>
+> <font color=green># Disable the current breakpoint location so it doesn't get hit again</font>
+> <strong>bp_loc.SetEnabled(False)</strong>
+> <font color=green># How continue the process</font>
+> <strong>frame.GetThread().GetProcess().Continue()</strong>
+> <strong>DONE</strong>
+</tt></pre></code>
+ <p>The <b>breakpoint command add</b> command above attaches a python script to breakpoint 1.
+ To remove the breakpoint command:
+ <p><code>(lldb) <strong>breakpoint command delete 1</strong></code>
+ </div>
+ </div>
+ <div class="post">
+ <h1 class ="postheader">Create a new LLDB command using a python function</h1>
+ <div class="postcontent">
+
+ <p>Python functions can be used to create new LLDB command interpreter commands, which will work
+ like all the natively defined lldb commands. This provides a very flexible and easy way to extend LLDB to meet your
+ debugging requirements. </p>
+ <p>To write a python function that implements a new LDB command define the function to take four arguments as follows:</p>
+
+ <code><pre><tt>def command_function(<b>debugger</b>, <b>command</b>, <b>result</b>, <b>dict</b>):
+ <font color=green># Your code goes here</font>
+ </tt></pre></code>
+ <p><table class="stats" width="620" cellspacing="0">
+ <tr>
+ <td class="hed" width="10%">Argument</td>
+ <td class="hed" width="10%">Type</td>
+ <td class="hed" width="80%">Description</td>
+ </tr>
+
+ <tr>
+ <td class="content">
+ <b>debugger</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBDebugger</b>
+ </td>
+ <td class="content">
+ The current debugger object.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>command</b>
+ </td>
+ <td class="content">
+ <b>python string</b>
+ </td>
+ <td class="content">
+ A python string containing all arguments for your command. If you need to chop up the arguments
+ try using the <b>shlex</b> module's <code>shlex.split(command)</code> to properly extract the
+ arguments.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>result</b>
+ </td>
+ <td class="content">
+ <b>lldb.SBCommandReturnObject</b>
+ </td>
+ <td class="content">
+ A return object where you can indicate the success or failure of your command. You can also
+ provide information for the command result by printing data into it. You can also just print
+ data as you normally would in a python script and the output will show up; this is useful for
+ logging, but the real output for your command should go in the result object.
+ </td>
+ </tr>
+ <tr>
+ <td class="content">
+ <b>dict</b>
+ </td>
+ <td class="content">
+ <b>python dict object</b>
+ </td>
+ <td class="content">
+ The dictionary for the current embedded script session which contains all variables
+ and functions.
+ </td>
+ </tr>
+ </table>
+ <p>One other handy convenience when defining lldb command-line commands is the command
+ <b>command script import</b> which will import a module specified by file path - so you
+ don't have to change your PYTHONPATH for temporary scripts. It also has another convenience
+ that if your new script module has a function of the form:</p>
+
+ <code><pre><tt>def __lldb_module_init(<b>debugger</b>, <b>dict</b>):
+ <font color=green># Command Initialization code goes here</font>
+ </tt></pre></code>
+
+ <p>where <b>debugger</b> and <b>dict</b> are as above, that function will get run when the module is loaded
+ allowing you to add whatever commands you want into the current debugger.</p>
+ <p>Now we can create a module called <b>ls.py</b> that will implement a function that
+ can be used by LLDB's python command code:</p>
+
+<code><pre><tt><font color=green>#!/usr/bin/python</font>
+
+import lldb
+import commands
+import optparse
+import shlex
+
+def ls(debugger, command, result, dict):
+ result.PutCString(commands.getoutput('/bin/ls %s' % command))
+
+<font color=green># And the initialization code to add your commands </font>
+def __lldb_module_init(debugger, dict):
+ debugger.HandleCommand('command script add -f ls.ls ls')
+ print 'The "ls" python command has been installed and is ready for use.'
+</tt></pre></code>
+ <p>Now we can load the module into LLDB and use it</p>
+<code><pre><tt>% lldb
+(lldb) <strong>command script import ls</strong>
+The "ls" python command has been installed and is ready for use.
+(lldb) <strong>ls -l /tmp/</strong>
+total 365848
+-rw-r--r--@ 1 someuser wheel 6148 Jan 19 17:27 .DS_Store
+-rw------- 1 someuser wheel 7331 Jan 19 15:37 crash.log
+</tt></pre></code>
+ <p>A template has been created in the source repository that can help you to create
+ lldb command quickly:</p>
+ <a href="http://llvm.org/svn/llvm-project/lldb/trunk/examples/python/cmdtemplate.py">cmdtemplate.py</a>
+ </div>
+ <div class="post">
+ <h1 class ="postheader">Using the lldb.py module in python</h1>
+ <div class="postcontent">
+
+ <p>LLDB has all of its core code build into a shared library which gets
+ used by the <b>lldb</b> command line application. On Mac OS X this
+ shared library is a framework: <b>LLDB.framework</b> and on other
+ unix variants the program is a shared library: <b>lldb.so</b>. LLDB also
+ provides an lldb.py module that contains the bindings from LLDB into Python.
+ To use the
+ <b>LLDB.framework</b> to create your own stand-alone python programs, you will
+ need to tell python where to look in order to find this module. This
+ is done by setting the <b>PYTHONPATH</b> environment variable, adding
+ a path to the directory that contains the <b>lldb.py</b> python module. On
+ Mac OS X, this is contained inside the LLDB.framework, so you would do:
+
+ <p>For csh and tcsh:</p>
+ <p><code>% <b>setenv PYTHONPATH /Developer/Library/PrivateFrameworks/LLDB.framework/Resources/Python</b></code></p>
+ <p>For sh and bash:
+ <p><code>% <b>export PYTHONPATH=/Developer/Library/PrivateFrameworks/LLDB.framework/Resources/Python</b></code></p>
+
+ <p> Alternately, you can append the LLDB Python directory to the <b>sys.path</b> list directly in
+ your Python code before importing the lldb module.</p>
+
+ <p>
+ Now your python scripts are ready to import the lldb module. Below is a
+ python script that will launch a program from the current working directory
+ called "a.out", set a breakpoint at "main", and then run and hit the breakpoint,
+ and print the process, thread and frame objects if the process stopped:
+
+ </p>
+<code><pre><tt><font color=green>#!/usr/bin/python</font>
+
+import lldb
+
+<font color=green># Set the path to the executable to debug</font>
+exe = "./a.out"
+
+<font color=green># Create a new debugger instance</font>
+debugger = lldb.SBDebugger.Create()
+
+<font color=green># When we step or continue, don't return from the function until the process
+# stops. Otherwise we would have to handle the process events ourselves which, while doable is
+#a little tricky. We do this by setting the async mode to false.</font>
+debugger.SetAsync (False)
+
+<font color=green># Create a target from a file and arch</font>
+print "Creating a target for '%s'" % exe
+
+target = debugger.CreateTargetWithFileAndArch (exe, lldb.LLDB_ARCH_DEFAULT)
+
+if target:
+ <font color=green># If the target is valid set a breakpoint at main</font>
+ main_bp = target.BreakpointCreateByName ("main", target.GetExecutable().GetFilename());
+
+ print main_bp
+
+ <font color=green># Launch the process. Since we specified synchronous mode, we won't return
+ # from this function until we hit the breakpoint at main</font>
+ process = target.LaunchSimple (None, None, os.getcwd())
+
+ <font color=green># Make sure the launch went ok</font>
+ if process:
+ <font color=green># Print some simple process info</font>
+ state = process.GetState ()
+ print process
+ if state == lldb.eStateStopped:
+ <font color=green># Get the first thread</font>
+ thread = process.GetThreadAtIndex (0)
+ if thread:
+ <font color=green># Print some simple thread info</font>
+ print thread
+ <font color=green># Get the first frame</font>
+ frame = thread.GetFrameAtIndex (0)
+ if frame:
+ <font color=green># Print some simple frame info</font>
+ print frame
+ function = frame.GetFunction()
+ <font color=green># See if we have debug info (a function)</font>
+ if function:
+ <font color=green># We do have a function, print some info for the function</font>
+ print function
+ <font color=green># Now get all instructions for this function and print them</font>
+ insts = function.GetInstructions(target)
+ disassemble_instructions (insts)
+ else:
+ <font color=green># See if we have a symbol in the symbol table for where we stopped</font>
+ symbol = frame.GetSymbol();
+ if symbol:
+ <font color=green># We do have a symbol, print some info for the symbol</font>
+ print symbol
+</tt></pre></code>
+ </div>
+ <div class="postfooter"></div>
+
+ </div>
+ </div>
+</div>
+</body>
+</html>
|
