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| + | ==== 01. The Aarch64 (arm64) toolchain ==== | ||
| + | |||
| + | Well, we want to compile things. | ||
| + | We'll be using the personal PC / laptop, which is probably running on a Intel/AMD-based //x86-64// CPU architecture. | ||
| + | |||
| + | But we want to compile code for a foreign architecture: Aarch64 (also known as arm64). | ||
| + | So we will need a cross compiler: a compiler that runs on your **host** but generates binary code for another **target**. | ||
| + | |||
| + | Cross compilers are usually named using this convention ''<target_arch>-<vendor>-[<os>-]<abi>-gcc''. In our case, it will be ''aarch64-none-linux-gnu-gcc'': | ||
| + | |||
| + | * **aarch64:** The target architecture; ARM 64-bit (why isn't it called this way? don't ask us :( ...). | ||
| + | * **none:** The toolchain supplier. Here, we're dealing with the official cross compiler from ARM so the vendor is not relevant. | ||
| + | * **linux:** The target OS (this filed is optional). | ||
| + | * **gnu:** The Application Binary Interface (ABI) defining how the generated code will interact with other software components. Don't mistake this for **gnueabi**, which is meant to generate bare metal code. | ||
| + | |||
| + | == Step 0. Download the toolchain == | ||
| + | |||
| + | Identify the correct toolchain and download it from [[https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads/|here]]. Yes, you can also install it with your package manger but it's always better to have a project-specific copy. | ||
| + | New compiler releases are known to sometime break the build process. | ||
| + | |||
| + | After extracting it, consider exporting the compiler's **prefix** (''aarch64-none-linux-gnu-'') from your newly downloaded toolchain as the ''CROSS_COMPILE'' environment variable. Otherwise, you will have to specify the full path of the cross compiler every time when invoking a script. E.g.: | ||
| + | <code> | ||
| + | export CROSS_COMPILE=/absolute/path/to/compiler/bin/aarch64-none-linux-gnu- | ||
| + | # now you can use the cross compiler as such: | ||
| + | "${CROSS_COMPILE}gcc" ... | ||
| + | # make will inherit this value, so no need to add a CROSS_COMPILE | ||
| + | # when invoking it from your terminal ;) | ||
| + | make | ||
| + | </code> | ||
| + | But //beware//: export only affects the terminal it's run from (so run it in each one :P)! | ||
| + | |||
| + | <note hint> | ||
| + | Try to download / clone all projects inside a common root directory. | ||
| + | Then, you could create a top-level Makefile with rules for running commands inside each of their subfolder. | ||
| + | Try to keep the project's official git name and unified structure, e.g.: | ||
| + | <code> | ||
| + | /home/user/arm-summer-school/ | ||
| + | ├── toolchain/aarch64-none-linux-gnu/... | ||
| + | ├── imx-atf/ # ARM Trusted Firmware code | ||
| + | ├── firmware/ # NXP IMX proprietary firmware BLOBs | ||
| + | ├── u-boot-tn-imx/ # U-Boot source code | ||
| + | ├── imx-mkimage/ # IMX mkimage scripts | ||
| + | ├── Makefile # your makefile, highly recommended! :P | ||
| + | └── ... # and many others to come! | ||
| + | </code> | ||
| + | </note> | ||
| + | |||
