Merge pull request #486 from phil-opp/building-on-android

Add extra post about building on Android

blog/content/second-edition/extra/building-on-android/index.md

@@ -0,0 +1,107 @@
++++
+title = "Building on Android"
+order = 3
+template = "second-edition/extra.html"
++++
+
+I finally managed to get `blog_os` building on my Android phone using [termux](https://termux.com/). This post explains the necessary steps to set it up.
+
+<img src="building-on-android.png" alt="Screenshot of the compilation output from android" style="height: 50rem;" >
+
+
+### Install Termux and Nightly Rust
+
+First, install [termux](https://termux.com/) from the [Google Play Store](https://play.google.com/store/apps/details?id=com.termux) or from [F-Droid](https://f-droid.org/packages/com.termux/). After installing, open it and perform the following steps:
+
+- Install fish shell, set as default shell, and launch it:
+    ```
+    pkg install fish
+    chsh -s fish
+    fish
+    ```
+
+    This step is of course optional. However, if you continue with bash you will need to adjust some of the following commands to bash syntax.
+
+- Install some basic tools:
+    ```
+    pkg install wget tar
+    ```
+
+- Add the [community repository by its-pointless](https://wiki.termux.com/wiki/Package_Management#By_its-pointless_.28live_the_dream.29:):
+    ```
+    wget https://its-pointless.github.io/setup-pointless-repo.sh
+    bash setup-pointless-repo.sh
+    ```
+
+- Install cargo and a nightly version of rustc:
+    ```
+    pkg install rustc cargo rustc-nightly
+    ```
+
+- Prepend the nightly rustc path to your `PATH` in order to use nightly (fish syntax):
+    ```
+    set -U fish_user_paths $PREFIX/opt/rust-nightly/bin/ $fish_user_paths
+    ```
+
+Now `rustc --version` should work and output a nightly version number.
+
+### Install Git and Clone blog_os
+
+We need something to compile, so let's download the `blog_os` repository:
+
+- Install git:
+    ```
+    pkg install git
+    ```
+
+- Clone the `blog_os` repository:
+    ```
+    git clone https://github.com/phil-opp/blog_os.git
+    ```
+
+If you want to clone/push via SSH, you need to install the `openssh` package: `pkg install openssh`.
+
+### Install Xbuild and Bootimage
+
+Now we're ready to install `cargo xbuild` and `bootimage`
+
+- Run `cargo install`:
+    ```
+    cargo install cargo-xbuild bootimage
+    ```
+
+- Add the cargo bin directory to your `PATH` (fish syntax):
+    ```
+    set -U fish_user_paths ~/.cargo/bin/ $fish_user_paths
+    ```
+
+Now `cargo xbuild` and `bootimage` should be available. It does not work yet because `cargo xbuild` needs access to the rust source code. By default it tries to use rustup for this, but we have no rustup support so we need a different way.
+
+### Providing the Rust Source Code
+
+The Rust source code corresponding to our installed nightly is available in the [`its-pointless` repository](https://github.com/its-pointless/its-pointless.github.io):
+
+- Download a tar containing the source code:
+    ```
+    wget https://github.com/its-pointless/its-pointless.github.io/raw/master/rust-src-nightly.tar.xz
+    ```
+
+- Extract it:
+    ```
+    tar xf rust-src-nightly.tar.xz
+    ```
+
+- Set the `XARGO_RUST_SRC` environment variable to tell cargo-xbuild the source path (fish syntax):
+    ```
+    set -Ux XARGO_RUST_SRC ~/rust-src-nightly/rust-src/lib/rustlib/src/rust/src
+    ```
+
+Now cargo-xbuild should no longer complain about a missing `rust-src` component. However it will throw an I/O error after building the sysroot. The problem is that the downloaded Rust source code has a different structure than the source provided by rustup. We can fix this by adding a symbolic link:
+
+```
+ln -s ~/../usr/opt/rust-nightly/bin ~/../usr/opt/rust-nightly/lib/rustlib/aarch64-linux-android/bin
+```
+
+Now `cargo xbuild --target x86_64-blog_os.json` and `bootimage build` should both work!
+
+I couldn't get QEMU to run yet, so you won't be able to run your kernel. If you manage to get it working, please tell me :).

blog/templates/second-edition/index.html

@@ -70,6 +70,18 @@
     You are viewing the second edition of “Writing an OS in Rust”, which is still in progress. The <a href="{{ get_url(path = "/first-edition") }}">first edition</a> has more content, but is no longer updated. We try our best to incorporate the missing content soon.
 </div>
 
+<hr>
+{% set extra = get_section(path = "second-edition/extra/_index.md") %}
+<h1>{{ extra.title }}</h1>
+<ul>
+    {% for subsection in extra.subsections|reverse %}
+        <li><a href="/{{ subsection.path | safe }}">{{ subsection.title }}</a></li>
+    {% endfor %}
+    {% for page in extra.pages|reverse %}
+        <li><a href="/{{ page.path | safe }}">{{ page.title }}</a></li>
+    {% endfor %}
+</ul>
+
 <aside id="recent-updates">
     <h2>Recent Updates</h2>
     {% include "recent-updates.html" %}