iOS打的LLDB学习资料-英文版

Section I: Beginning LLDB

Commands

This section will cover the basics of using LLDB, Apple’s software debugger. You’ll

explore an application named Signals, an Objective-C/Swift application that illustrates

how Unix signals can be processed within an application. You’ll learn some strategies to

find and create Swift syntax-style breakpoints as well as Objective-C style breakpoints.

By the end of this section, you’ll be able to wield the debugger to perform most of the

basic tasks needed for debugging, as well as create your own simple custom commands.

Chapter 1: Getting Started

Chapter 8: Persisting & Customizing Commands

Chapter 9: Regex Commands

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In this chapter, you’re going to get acquainted with LLDB and investigate the process of

introspecting and debugging a program. You’ll start off by introspecting a program you

didn’t even write — Xcode!

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Before you can start working with LLDB, you need to learn about a feature introduced

by Apple to thwart malware. Unfortunately, this feature will also thwart your attempts

to introspect and debug using LLDB and other tools like DTrace. Never fear though,

because Apple included a way to turn this feature off — for those who know what

they’re doing. And you’re going to become one of these people who knows what they’re

doing!

The feature blocking your introspection and debugging attempts is System Integrity

Protection, also known as Rootless. This system restricts what programs can do —

even if they have root access — to stop malware from planting itself deep inside your

system.

If you currently have Rootless enabled, you’ll be unable to attach to the majority of

Apple’s programs. There are exceptions however, such as any apps shipped on the iOS

Simulator.

For example, try attaching LLDB to the Finder application.

Open up a Terminal window and look for the Finder process, like so:

You’ll notice the following error:

Note: There are many ways to attach to a process, as well as specific

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2. When the screen turns blank, hold down Command + R until the Apple boot logo

appears. This will put your computer into Recovery Mode.

3. Now, find the Utilities menu from the top and then select Terminal.

4. With the Terminal window open, type:

5. Your computer will restart with Rootless disabled.

Note: A safer way to follow along with this book would be to create a dedicated

virtual machine using VMWare or VirtualBox and only disable Rootless on this.

You can verify if you’ve successfully disabled Rootless by trying the same command in

Terminal again once you log into your account.

LLDB should now attach itself to the current Finder process. The output of a successful

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Now that you’ve disabled Rootless, you can attach LLDB to any process on your macOS

machine (some hurdles may apply, such as with ptrace, but we’ll get to that later).

You’re first going to look into an application you frequently use in your day-to-day

development: Xcode! Make sure you have the latest version of Xcode 9 installed on

your computer before continuing.

of Xcode, which could cause confusion.

In Terminal, type the following:

This launches LLDB.

Create a new Terminal tab by pressing ⌘ + T. Edit the tab’s title again using ⌘ + Shift +

I and name the tab Xcode stderr. This Terminal tab will contain all output when you

print content from the debugger.

Make sure you are on the Xcode stderr Terminal tab and type the following:

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