This part tells you just a few issues it’s essential know earlier than you get began, corresponding to what you’ll want for {hardware} and software program, the place to search out the undertaking recordsdata for this guide, and extra.
This part will cowl the fundamentals of utilizing LLDB, Apple’s software program debugger. You’ll discover an utility named Alerts, an Goal-C/Swift utility that illustrates how Unix indicators could be processed inside an utility. You’ll be taught some methods to search out and create Swift syntax-style breakpoints in addition to Goal-C fashion breakpoints. By the tip of this part, you’ll be capable of wield the debugger to carry out a lot of the primary duties wanted for debugging, in addition to create your personal easy customized instructions.
On this chapter, you’re going to get acquainted with LLDB and examine the method of introspecting and debugging a program. You’ll begin off by introspecting a program you didn’t even write — Xcode!
Identical to any respectable developer device, LLDB ships with a wholesome quantity of documentation. Realizing how you can navigate by means of this documentation — together with a few of the extra obscure command flags — is crucial to mastering LLDB.
Now that you have discovered in regards to the two most important instructions, assist and apropos, it is time to examine all of the methods LLDB can connect itself to a course of.
Whether or not you’re utilizing Swift, Goal-C, C++, C, or a completely completely different language in your expertise stack, you’ll must discover ways to create breakpoints. It’s simple to click on on the aspect panel in Xcode to create a breakpoint utilizing the GUI, however the LLDB console may give you far more management over breakpoints.
Discover ways to question and manipulate the software program you’re debugging. On this chapter, you’ll be taught in regards to the **`expression`** command, which lets you question variables and execute arbitrary code.
You’ve discovered how you can create breakpoints, how you can print and modify values, in addition to how you can execute code whereas paused within the debugger. However to this point you’ve been left excessive and dry on how you can transfer round within the debugger and examine knowledge past the fast. On this chapter, you’ll discover ways to transfer the debugger out and in of code whereas `lldb` has suspended a program.
It is time to discover top-of-the-line instruments for locating code of curiosity by means of the powers of lldb. On this chapter, you will take a deep dive into the picture command.
Be taught a beautiful various to creating breakpoints by monitoring reads or writes to reminiscence.
On this chapter, you’ll discover ways to create easy, customized instructions after which persist them for utilizing each time you launch `lldb`.
On this chapter, you’ll discover ways to create instructions that may take inputs.
Realizing what the pc is doing with all these 1s and 0s beneath your code is a superb ability to have when digging for helpful details about a program. This part will set you up with the speculation you’ll want for the rest of this guide as a way to create complicated debugging scripts — and introduce you to the fundamental idea behind reverse-engineering code.
Now you’ve gained a primary understanding of how you can maneuver across the debugger, it’s time to take a step down the executable Jenga tower and discover the 1s and 0s that make up your supply code. This part will deal with the low-level facets of debugging.
On this chapter, you’ll discover how a program executes. You’ll have a look at a particular register used to inform the processor the place it ought to learn the following instruction from, in addition to how completely different sizes and groupings of reminiscence can produce very completely different outcomes.
What does being “handed on the stack” imply precisely? It’s time to take a deeper dive into what occurs when a perform is named from an meeting standpoint by exploring some “stack associated” registers in addition to the contents within the stack.
With a basis of assembler idea solidly beneath you, it’s time to discover different facets of how applications work. This part is an eclectic grab-bag of bizarre and enjoyable research into reverse engineering, seldom-used APIs and debugging methods.
On this chapter, you’ll study a particular API that allows debugging and even disables different processes from debugging the calling course of.
Shared libraries are important for any program to run. This chapter focuses on the compilation and linking course of, highlighting how you can write code that makes use of private and non-private APIs.
It’s time to be taught in regards to the complementary expertise of creating with these frameworks. On this chapter, you’re going to study strategies and methods to “hook” into Swift and C code in addition to execute strategies you wouldn’t usually have entry to.
The file format used for a compiled program working on any Apple {hardware}. This chapter discusses how you can learn this info.
Now that you have discovered the speculation, it is time to have some enjoyable. Discover ways to seek for curse phrases in Apple frameworks and cheat at playing video games.
This chapter provides you with a primary overview of how code signing works by having you decide aside an iOS utility and discover ways to re-sign and set up it onto your iOS gadget.
You’ve discovered the fundamental LLDB instructions, the meeting that goes into code and the miscellaneous low-level ideas that make a program…effectively, a program.
It’s time to place that information collectively to create some very highly effective and sophisticated debugging scripts. As you’ll quickly see, you’re solely restricted by your ability and creativeness — and discovering the proper class (or header file) to do your debugging bidding.
LLDB ships with an built-in Python module that lets you entry most elements of the debugger by means of Python. This allows you to leverage all the ability of Python (and its modules) to assist uncover no matter darkish secrets and techniques vex you.
Subsequent up within the tradeoff between comfort and complexity is LLDB’s script bridging. With script bridging, you are able to do almost something you want. Script bridging is a Python interface LLDB makes use of to assist prolong the debugger to perform your wildest debugging desires.
You want a methodical manner to determine what went fallacious in your LLDB script so that you don’t pull your hair out. On this chapter, you’ll discover how you can examine your LLDB Python scripts utilizing the Python pdb module, which is used for debugging Python scripts.
You’ve discovered the necessities of working with LLDB’s Python module, in addition to how you can appropriate any errors utilizing Python’s PDB debugging module. Now you’ll discover the principle gamers throughout the lldb Python module for a great overview of the principle elements. On this chapter, you’ll add some arguments to this script and take care of some annoying edge instances, such dealing with instructions in another way between Goal-C and Swift.
Once you’re making a customized debugging command, you’ll usually need to barely tweak performance based mostly upon choices or arguments equipped to your command. A customized LLDB command that may do a job just one manner is a boring one-trick pony. On this chapter, you’ll discover how you can cross optionally available parameters (aka choices) in addition to arguments (parameters that are anticipated) to your customized command to change performance or logic in your customized LLDB scripts.
To this point, when evaluating JIT code (i.e. Goal-C, Swift, C, and so on. code that’s executed by means of your Python script), you’ve used a small set of APIs to guage the code. It’s time to speak a few new class within the lldb Python module, SBValue, and the way it can simplify the parsing of JIT code output.
For the remainder of the chapters on this part, you will deal with Python scripts. As alluded to within the earlier chapter, the picture lookup -rn command is on its manner out. Once you end this chapter, you’ll have a brand new script named “lookup” which queries in a a lot cleaner manner.
When LLDB comes up towards a stripped executable (an executable devoid of DWARF
debugging info), LLDB gained’t have the image info to provide the stack hint. As a substitute, LLDB will generate an artificial identify for a way it acknowledges as a way, however doesn’t know what to name it. On this chapter, you’ll construct an LLDB script that may resymbolicate stripped Goal-C capabilities in a stack hint.
For the ultimate chapter on this part, you’ll undergo the identical steps I actually took to grasp how the MallocStackLogging surroundings variable is used to get the stack hint when an object is created. From there, you’ll create a customized LLDB command which supplies you the stack hint of when an object was allotted or deallocated in reminiscence — even after the stack hint is lengthy gone from the debugger.
What? Youve by no means heard of DTrace?! It’s AWESOME! DTrace is a device that allows you to discover code in dynamic & static methods.
http://dtrace.org/information/preface.html
You possibly can create DTrace probes to be compiled into your code (static), or you possibly can examine any code that’s already compiled and working (dynamic). DTrace is a flexible device: it may be a profiler, an analyzer, a debugger or something you need.
I usually will use DTrace to solid a wide-reaching internet over code I need to discover, when I’ve no clue the place I ought to begin.
You’ll discover a really small part of what DTrace is able to doing by tracing Goal-C code in already compiled functions. Utilizing DTrace to watch iOS frameworks (like UIKit) may give you an unbelievable perception into how the authors designed their code.
This chapter will act as a grab-bag of extra DTrace fundamentals, harmful actions (yay!), in addition to how you can use DTrace with Swift. On this chapter, you will be taught further methods DTrace can profile code, in addition to how you can increase present code with out laying a finger on the precise executable itself.
