%title: Free Software on ARM Hardwares
%author: Icenowy Zheng
%date 2017-07-15

-> Contents <-

- Current Status on Free Software on ARM Hardwares

- Benefits for Free Software on ARM Hardwares

- Non-free Softwares' Status on ARM Hardwares

- Totally Free non-x86 non-ARM Platforms

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-> Current Status on Free Software on ARM Hardwares <-

- Most ARMv{7,8}-A systems use Linux kernel.

- Some systems use U-Boot as the bootloader.

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-> Linux on ARM Hardwares <-

- Some vendors (e.g. Rockchip) joins the Linux mainline development actively.

- Some vendors still make ugly BSP (e.g. Qualcomm).

- Some vendors not only make ugly BSP, but also don't want to update it (e.g. Allwinner).

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-> U-Boot on ARM Hardwares <-

- U-Boot is a kind of bootloader for ARM.

- Some platforms also use U-Boot SPL (which is a small version of U-Boot designed to work as first-stage firmware to init basical hardwares).

- Unfortunately Android devices usually don't use U-Boot -- usually the used bootloader is modified "Little Kernel".

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-> ARM Trusted Firmware <-

- ARM Trusted Firmware is an implementation of the ARM firmware.

- Usual platforms only use the BL3-1 part, which is the AArch64 EL3 monitor.

- It's BSD licensed, which means that vendors have the possibility not to release the source.

- From U-Boot 2017.05 on, U-Boot SPL can load ATF with the main U-Boot binary via FIT, and this feature is used by mainlined booting firmware of Allwinner and Rockchip SoCs.

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-> Benefits for Free Systems with ARM Hardwares <-

- Usually cheap devices

- Less anti-feature

- Simple designs

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-> Some ARM devices are quite cheap <-

- Chinese SoC vendors, e.g. Allwinner, Amlogic and Rockchip, makes cheap chips available for several dollars. For example, Allwinner A64 is availble for only *$5*.

- SBC vendors use these cheap SoCs to make cheap boards. The most cheap Orange Pi can be get for *$10*.

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-> Less anti-feature and simple design <-

- There's no Intel ME on ARM platforms ;-)

- Some ARM SoCs can let the software on the ARM core fully control the hardware.

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-> Status on non-free softwares on ARM hardwares <-

- Some processors still have high-permission "monitors".

- Proprietary bootloaders

- Peripherals' firmware.

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-> ARM SoCs' design can also be evil <-

- For some ARM SoCs, there's still a processor that has higher permission than the main application processor.

- Qualcomm SoCs often start from their Modem or DSP, and these co-processors can access all memory of main application processor. The firmwares are even signed!

- Broadcom SoCs (e.g. BCM283x) have a VC4 core controlling all things.

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-> Proprietary bootloaders <-

- Not all SoCs have their bootloaders open-sourced.

- Some vendors do not want to open the details of the DRAM controllers, and DRAM initialization is one of the most important functions of the first-stage bootloader.

- Some SoCs with co-processor starts at the co-processor.

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-> Peripherals' firmwares <-

- Some external peripherals on ARM hardwares have also firmwares, and usually they're proprietary.

- Broadcomm BCM43xx Wi-Fi chips' firmwares have already discovered CVE: *CVE-2017-9417*.

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-> Free systems with non-x86 non-ARM architectures <-

- MIPS: Loongson-2E/2F, Atheros ar71xx

- RISC-V: still ongoing

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-> MIPS totally free systems <-

- Loongson-2E/2F uses the PMON firmware.

- Atheros ar71xx routers use U-Boot as boot firmware, and have a wireless MAC without blobs needed (totally free routers platform certified by FSF).

- Disadvantages on MIPS systems: they don't have a unified bootloader-kernel protocol.

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-> Further views on RISC-V <-

- RISC-V is a new ISA by UCB, which needs no license fee.

- Only one hardware implementation is on the market now, and it has only RV32IMA.

- Still *no* proper Linux support (the "official" riscv-linux is only a simple homework of some UCB students). FreeBSD is WIP on RISC-V, and using a more clean design.

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-> Thanks for listening! <-

- Icenowy Zheng from AOSC

- Developer in Linux mainline, mainly for Allwinner SoCs