Skip to content
Linux shell for iOS
Branch: master
Clone or download
Pull request Compare This branch is 3 commits ahead, 1 commit behind tbodt:master.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
app
emu
fastlane
fs
iSH.xcodeproj
jit
kernel
platform
subprojects
tests
tools
util
vdso
.editorconfig
.gitignore
.lvimrc
.travis.yml
CHANGELOG.md
ISSUE_TEMPLATE.md
LICENSE
LICENSE.IOS
README.md
debug.h
ish-gdb.gdb
main.c
meson.build
meson_options.txt
misc.h
xX_main_Xx.h
xcode-meson.sh

README.md

iSH

Build Status goto counter fuck counter

A project to get a Linux shell running on iOS, using usermode x86 emulation and syscall translation.

For the current status of the project, check the issues tab, and the commit logs.

You can join the Testflight beta now. There's also a Discord server.

Hacking

You'll need these things to build the project:

  • Python 3
  • Ninja
  • Yarn (only when building for iOS)
  • Meson (pip install meson)
  • Clang and LLD (on mac, brew install llvm, on linux, sudo apt install clang lld or sudo pacman -S clang lld or whatever)
  • sqlite3 (this is so common it may already be installed on linux and is definitely already installed on mac. if not, do something like sudo apt install libsqlite3-dev)

Build for iOS

Open the project in Xcode and click Run. If you're not me, first open the project build settings and change the Product Bundle Identifier to something unique. There are scripts that should do everything else automatically. If you run into any problems, open an issue and I'll try to help.

Build command line tool for testing

To set up your environment, cd to the project and run meson build to create a build directory in build. Then cd to the build directory and run ninja.

To set up a self-contained Alpine linux filesystem, download the Alpine minirootfs tarball for i386 from the Alpine website and run the tools/fakefsify.py script. Specify the minirootfs tarball as the first argument and the name of the output directory as the second argument. Then you can run things inside the Alpine filesystem with ./ish -f alpine /bin/login -f root, assuming the output directory is called alpine.

You can replace ish with tools/ptraceomatic to run the program in a real process and single step and compare the registers at each step. I use it for debugging. Requires 64-bit Linux 4.11 or later.

A note on the JIT

Possibly the most interesting thing I wrote as part of iSH is the JIT. It's not actually a JIT since it doesn't target machine code. Instead it generates an array of pointers to functions called gadgets, and each gadget ends with a tailcall to the next function; like the threaded code technique used by some Forth interpreters. The result is a speedup of roughly 3-5x compared to pure emulation.

Unfortunately, I made the decision to write nearly all of the gadgets in assembly language. This was probably a good decision with regards to performance (though I'll never know for sure), but a horrible decision with regards to readability, maintainability, and my sanity. The amount of bullshit I've had to put up with from the compiler/assembler/linker is insane. It's like there's a demon in there that makes sure my code is sufficiently deformed, and if not, makes up stupid reasons why it shouldn't compile. In order to stay sane while writing this code, I've had to ignore best practices in code structure and naming. You'll find macros and variables with such descriptive names as ss and s and a. Assembler macros nested beyond belief. And to top it off, there are almost no comments.

So a warning: Long-term exposure to this code may cause loss of sanity, nightmares about GAS macros and linker errors, or any number of other debilitating side effects. This code is known to the State of California to cause cancer, birth defects, and reproductive harm.

You can’t perform that action at this time.