This part tells you just a few issues you have to know earlier than you get began, corresponding to what you’ll want for {hardware} and software program, the place to seek out the mission information 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 may be processed inside an utility. You’ll study 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 of 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 device, LLDB ships with a wholesome quantity of documentation. Realizing navigate by way of this documentation — together with a number of the extra obscure command flags — is important to mastering LLDB.
Now that you have realized 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 totally different language in your expertise stack, you’ll have to discover ways to create breakpoints. It’s straightforward to click on on the facet panel in Xcode to create a breakpoint utilizing the GUI, however the LLDB console can provide you way more management over breakpoints.
Discover ways to question and manipulate the software program you’re debugging. On this chapter, you’ll study in regards to the **`expression`** command, which lets you question variables and execute arbitrary code.
You’ve realized create breakpoints, print and modify values, in addition to execute code whereas paused within the debugger. However thus far you’ve been left excessive and dry on transfer round within the debugger and examine information 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 the most effective 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.
Be taught a pretty different 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 wonderful talent 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 advanced 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 deal with the low-level points 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 following 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 operate is 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 principle solidly under you, it’s time to discover different points of how packages 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 study in regards to the complementary expertise of creating 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 working on any Apple {hardware}. This chapter discusses learn this info.
Now that you have realized 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 will provide you with a fundamental 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 machine.
You’ve realized 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 sophisticated debugging scripts. As you’ll quickly see, you’re solely restricted by your talent and creativeness — and discovering the right class (or header file) to do your debugging bidding.
LLDB ships with an built-in Python module that permits you to entry most components of the debugger by way 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 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 means to determine what went incorrect 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 realized 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 throughout the lldb Python module for an excellent overview of the principle components. On this chapter, you’ll add some arguments to this script and take care of some annoying edge circumstances, such dealing with instructions in another way between Goal-C and Swift.
While you’re making a customized debugging command, you’ll typically need to barely tweak performance primarily based upon choices or arguments equipped to your command. A customized LLDB command that may do a job just one means is a boring one-trick pony. On this chapter, you’ll discover move non-obligatory 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.
Thus far, when evaluating JIT code (i.e. Goal-C, Swift, C, and so forth. code that’s executed by way 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 deal with Python scripts. As alluded to within the earlier chapter, the picture lookup -rn command is on its means out. While you end this chapter, you’ll have a brand new script named “lookup” which queries in a a lot cleaner means.
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 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 features in a stack hint.
For the ultimate chapter on this part, you’ll undergo the identical steps I actually took to know how the MallocStackLogging setting 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 may 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 typically will use DTrace to forged 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 functions. 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 study further methods DTrace can profile code, in addition to increase present code with out laying a finger on the precise executable itself.