This part tells you just a few issues it’s worthwhile to know earlier than you get began, comparable to what you’ll want for {hardware} and software program, the place to seek out the undertaking recordsdata for this e-book, 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 alerts will be processed inside an utility. You’ll be taught some methods to seek out and create Swift syntax-style breakpoints in addition to Goal-C type breakpoints. By the tip of this part, you’ll be capable to wield the debugger to carry out many of the fundamental 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!
Similar to any respectable developer software, LLDB ships with a wholesome quantity of documentation. Figuring out navigate by means of this documentation — together with a few of the extra obscure command flags — is important to mastering LLDB.
Now that you’ve got discovered concerning 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 wholly completely different language in your expertise stack, you’ll have to learn to create breakpoints. It’s simple to click on on the facet panel in Xcode to create a breakpoint utilizing the GUI, however the LLDB console can provide you rather more management over breakpoints.
Learn to question and manipulate the software program you’re debugging. On this chapter, you’ll be taught concerning the **`expression`** command, which lets you question variables and execute arbitrary code.
You’ve discovered create breakpoints, print and modify values, in addition to execute code whereas paused within the debugger. However to this point you’ve been left excessive and dry on transfer round within the debugger and examine knowledge past the instant. On this chapter, you’ll learn to transfer the debugger out and in of code whereas `lldb` has suspended a program.
It is time to discover the most effective 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 gorgeous different to creating breakpoints by monitoring reads or writes to reminiscence.
On this chapter, you’ll learn to create easy, customized instructions after which persist them for utilizing each time you launch `lldb`.
On this chapter, you’ll learn to create instructions that may take inputs.
Figuring out 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 e-book so as to create complicated debugging scripts — and introduce you to the fundamental principle behind reverse-engineering code.
Now you’ve gained a fundamental understanding of 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 concentrate on the low-level features 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 principle solidly beneath you, it’s time to discover different features 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 find out about a particular API that permits 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 write code that makes use of private and non-private APIs.
It’s time to be taught concerning the complementary expertise of growing with these frameworks. On this chapter, you’re going to find out about 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 operating on any Apple {hardware}. This chapter discusses learn this info.
Now that you’ve got discovered the speculation, it is time to have some enjoyable. Learn to seek for curse phrases in Apple frameworks and cheat at playing video games.
This chapter gives you a fundamental overview of how code signing works by having you decide aside an iOS utility and learn to re-sign and set up it onto your iOS machine.
You’ve discovered the fundamental LLDB instructions, the meeting that goes into code and the miscellaneous low-level ideas that make a program…properly, a program.
It’s time to place that data collectively to create some very highly effective and complicated 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 means that you can entry most components of the debugger by means of Python. This allows you to leverage all the facility 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 practically something you want. Script bridging is a Python interface LLDB makes use of to assist prolong the debugger to perform your wildest debugging goals.
You want a methodical method to determine what went fallacious in your LLDB script so that you don’t pull your hair out. On this chapter, you’ll discover 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 appropriate any errors utilizing Python’s PDB debugging module. Now you’ll discover the principle gamers inside the lldb Python module for a superb overview of the principle components. On this chapter, you’ll add some arguments to this script and cope with some annoying edge instances, such dealing with instructions in another way between Goal-C and Swift.
If 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 method is a boring one-trick pony. On this chapter, you’ll discover go elective 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 forth. code that’s executed by means of your Python script), you’ve used a small set of APIs to judge 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 concentrate on Python scripts. As alluded to within the earlier chapter, the picture lookup -rn command is on its method out. If you end this chapter, you’ll have a brand new script named „lookup“ which queries in a a lot cleaner method.
When LLDB comes up in opposition to a stripped executable (an executable devoid of DWARF
debugging info), LLDB gained’t have the image info to provide the stack hint. As an alternative, LLDB will generate an artificial title 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 can 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 provides 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 software that allows you to discover code in dynamic & static methods.
http://dtrace.org/information/preface.html
You may create DTrace probes to be compiled into your code (static), or you may examine any code that’s already compiled and operating (dynamic). DTrace is a flexible software: it may be a profiler, an analyzer, a debugger or something you need.
I usually will use DTrace to solid a wide-reaching web 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 purposes. Utilizing DTrace to watch iOS frameworks (like UIKit) can provide you an unimaginable 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 use DTrace with Swift. On this chapter, you will be taught extra methods DTrace can profile code, in addition to increase current code with out laying a finger on the precise executable itself.
