crate start

Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "gba"
+version = "0.0.1"
+authors = ["Lokathor <zefria@gmail.com>", "Ketsuban"]
+edition = "2018"
+license = "Apache2"
+
+[dependencies]
+
+[profile.release]
+lto = true
+panic = "abort"

README.md

@@ -1,2 +1,57 @@
+[![License:Apache2](https://img.shields.io/badge/License-Apache2-green.svg)](https://www.apache.org/licenses/LICENSE-2.0)
+
 # gba
+
 A crate that helps you make GBA games
+
+# First Time Setup
+
+[ketsuban](https://github.com/ketsuban) is the wizard who explained to me how to
+do this stuff.
+
+1) Install `devkitpro`. They have a graphical installer for Windows, or you can
+   use pacman or whatever for linux things I guess. The goal here, among other
+   things, is to have a `binutils` setup that's targeting `arm-none-eabi`. We'll
+   also use some of their tools that are specific to GBA development so if you
+   for some reason already have the appropriate `binutils` then you probably
+   still want devkitpro.
+   * On Windows you'll want something like `C:\devkitpro\devkitARM\bin` and
+     `C:\devkitpro\tools\bin` to be added to your PATH. I'm not sure on the
+     directories for other systems. If you know then file a PR with the info.
+
+2) Next we use `cargo install cargo-xbuild` to get that all setup.
+
+3) Create a binary project. We're going to want nightly rust for this, so if you
+   don't already have it set to default to nightly you should [set that
+   up](https://github.com/rust-lang-nursery/rustup.rs#the-toolchain-file) for
+   this project.
+
+4) Clone this repo. It has an appropriate `main.rs` that will draw three test
+   dots as well as other support files:
+  * crt0.s
+  * linker.ld
+  * thumbv4-none-eabi.json
+  * build.rs
+
+5) Run `arm-none-eabi-as crt0.s -o crt0.o` to build the `crt0.s` into a `crt0.o`
+   file. You could theoretically to it only when `crt0.s` changes, but in out
+   `build.bat` file it's set to simply run every single time because it's a
+   cheap enough operation.
+
+6) Build with `cargo xbuild --target thumbv4-none-eabi.json`
+  * The file extension is significant, and `cargo xbuild` takes it as a flag to
+    compile dependencies with the same sysroot, so you can include crates
+    normally. Well, crates that can run inside a GBA at least (Which means they
+    have to be `no_std`, and even `no_alloc`).
+  * This generates an ELF binary that some emulators can run directly (which is
+    helpful because it has debug symbols).
+
+7) Also you can patch up the output to be a "real" ROM file:
+  * `arm-none-eabi-objcopy -O binary target/thumbv4-none-eabi/debug/gbatest target/output.gba`
+  * `gbafix target/output.gba`
+
+8) Alternately, you can use the provided `build.bat` file (or write a similar
+   `build.sh` file of course), which does all four steps above.
+
+9) Time to read the [Tonc](https://www.coranac.com/tonc/text/toc.htm) tutorial
+   and convert all the C code you see into rust code.

build.bat

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+@echo off
+REM It could work to only rebuild the `crt0.o` file when `crt0.s` actually
+REM changes, but it's actually a super cheap operation so we'll just do it
+REM every single time to avoid any mix ups.
+@echo on
+
+arm-none-eabi-as crt0.s -o crt0.o
+
+@echo off
+REM This builds our program for the GBA. Note that the extension here is
+REM important, because it causes all crates that we might import to also
+REM use the correct target.
+@echo on
+
+cargo xbuild --target thumbv4-none-eabi.json
+
+@echo off
+REM Some emulators can use cargo's output directly (which is cool, because then
+REM you can keep debug symbols and stuff), but to make a "real" ROM we have to
+REM also use the devkitpro tools to patch up the file a bit.
+@echo on
+
+arm-none-eabi-objcopy -O binary target/thumbv4-none-eabi/debug/main target/output.gba
+gbafix target/output.gba
+
+@echo off
+REM Now all the same for release mode too!
+@echo on
+
+cargo xbuild --target thumbv4-none-eabi.json --release
+arm-none-eabi-objcopy -O binary target/thumbv4-none-eabi/release/main target/output-release.gba
+gbafix target/output-release.gba

crt0.s

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+    .arm
+__start:
+    b .Linit
+
+    @ ROM header will be filled in by gbafix
+    .fill 188, 1, 0
+
+.Linit:
+    @ set IRQ stack pointer
+    mov r0, #0x12
+    msr CPSR_cf, r0
+    ldr sp, =0x3007fa0
+
+    @ set user stack pointer
+    mov r0, #0x1f
+    msr CPSR_cf, r0
+    ldr sp, =0x3007f00
+
+    @ copy .data section to IWRAM
+    ldr r0, =__data_lma     @ source address
+    ldr r1, =__data_start   @ destination address
+    ldr r3, =__data_end
+    sub r2, r3, r1
+    beq .Lskip              @ don't try to copy an empty .data section
+    add r2, #3
+    mov r2, r2, asr #2      @ length (in words)
+    add r2, #0x04000000     @ copy by words
+    swi 0xb0000
+
+.Lskip:
+    @ jump to user code
+    ldr r0, =main
+    bx r0
+    .pool

rustfmt.toml

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+error_on_line_overflow = false
+fn_args_density = "Compressed"
+reorder_imported_names = true
+reorder_imports = true
+reorder_imports_in_group = true
+use_try_shorthand = true
+write_mode = "Overwrite"
+tab_spaces = 2
+max_width = 150
+color = "Never"

src/lib.rs

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+#![no_std]

thumbv4-none-eabi.json

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+{
+  "abi-blacklist": [
+    "stdcall",
+    "fastcall",
+    "vectorcall",
+    "thiscall",
+    "win64",
+    "sysv64"
+  ],
+  "arch": "arm",
+  "atomic-cas": false,
+  "cpu": "arm7tdmi",
+  "data-layout": "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64",
+  "emit-debug-gdb-scripts": false,
+  "env": "",
+  "executables": true,
+  "features": "+soft-float,+strict-align",
+  "linker": "arm-none-eabi-ld",
+  "linker-flavor": "ld",
+  "linker-is-gnu": true,
+  "llvm-target": "thumbv4-none-eabi",
+  "os": "none",
+  "panic-strategy": "abort",
+  "pre-link-args": {
+    "ld": [
+      "-Tlinker.ld"
+    ]
+  },
+  "relocation-model": "static",
+  "target-c-int-width": "32",
+  "target-endian": "little",
+  "target-pointer-width": "32",
+  "vendor": ""
+}