This part tells you a number of issues it’s good to know earlier than you get began, equivalent 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 software named Alerts, an Goal-C/Swift software that illustrates how Unix indicators might be processed inside an software. You’ll study some methods to search out and create Swift syntax-style breakpoints in addition to Goal-C type breakpoints. By the top of this part, you’ll have the ability to wield the debugger to carry out many of the primary duties wanted for debugging, in addition to create your individual 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 instrument, LLDB ships with a wholesome quantity of documentation. Understanding find out how to navigate by way of this documentation — together with a few of the extra obscure command flags — is important to mastering LLDB.
Now that you have 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 totally different language in your know-how stack, you’ll have to discover ways to create breakpoints. It’s straightforward to click on on the aspect panel in Xcode to create a breakpoint utilizing the GUI, however the LLDB console may give you way more management over breakpoints.
Learn to question and manipulate the software program you’re debugging. On this chapter, you’ll study concerning the **`expression`** command, which lets you question variables and execute arbitrary code.
You’ve discovered find out how to create breakpoints, find out how to print and modify values, in addition to find out how to execute code whereas paused within the debugger. However thus far you’ve been left excessive and dry on find out how to transfer round within the debugger and examine knowledge past the speedy. 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 probably the greatest instruments for locating code of curiosity by way of the powers of lldb. On this chapter, you will take a deep dive into the picture command.
Study 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.
Understanding what the pc is doing with all these 1s and 0s beneath your code is a wonderful ability to have when digging for helpful details about a program. This part will set you up with the idea you’ll want for the rest of this guide as a way to create complicated debugging scripts — and introduce you to the essential idea behind reverse-engineering code.
Now you’ve gained a primary understanding of find out how to 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 give attention to the low-level elements of debugging.
On this chapter, you’ll discover how a program executes. You’ll take a look at a particular register used to inform the processor the place it ought to learn the subsequent instruction from, in addition to how totally different sizes and groupings of reminiscence can produce very totally 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 known as 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 elements 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 find out how to write code that makes use of private and non-private APIs.
It’s time to study concerning the complementary abilities of creating with these frameworks. On this chapter, you’re going to study strategies and techniques 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 find out how to learn this info.
Now that you have discovered the idea, 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 primary overview of how code signing works by having you choose aside an iOS software and discover ways to re-sign and set up it onto your iOS gadget.
You’ve discovered the essential 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 information 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 lets you entry most elements of the debugger by way 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 desires.
You want a methodical approach to determine what went fallacious in your LLDB script so that you don’t pull your hair out. On this chapter, you’ll discover find out how to 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 find out how to right any errors utilizing Python’s PDB debugging module. Now you’ll discover the principle gamers throughout the lldb Python module for an excellent overview of the principle elements. 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.
While you’re making a customized debugging command, you’ll typically wish 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 approach is a boring one-trick pony. On this chapter, you’ll discover find out how to go 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 date, when evaluating JIT code (i.e. Goal-C, Swift, C, and many others. code that’s executed by way of your Python script), you’ve used a small set of APIs to guage the code. It’s time to speak a couple of 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 give attention to Python scripts. As alluded to within the earlier chapter, the picture lookup -rn command is on its approach out. While you end this chapter, you’ll have a brand new script named “lookup” which queries in a a lot cleaner approach.
When LLDB comes up towards a stripped executable (an executable devoid of DWARF
debugging info), LLDB received’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 personally took to know how the MallocStackLogging atmosphere 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 instrument that allows you to discover code in dynamic & static methods.
http://dtrace.org/information/preface.html
You’ll be able to 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 instrument: it may be a profiler, an analyzer, a debugger or something you need.
I typically will use DTrace to forged a wide-reaching internet over code I wish 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 look at 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 find out how to use DTrace with Swift. On this chapter, you will study further methods DTrace can profile code, in addition to find out how to increase present code with out laying a finger on the precise executable itself.
