RISC-V support?

[tommythorn]

Describe the problem you are trying to solve
rustup is wonderful, so it's sad it doesn't support RISC-V, I get "rustup: unknown CPU type: riscv64" which run on Ubuntu 20.04 (which has rustc, cargo, etc).

Describe the solution you'd like
I'd like it to install the latest Rust

Notes
I used the Ubuntu image from https://github.com/carlosedp/riscv-bringup to issue the commands. I assume this is actually blocked on something on rust side, but I didn't see any issues tracking this.

[tesuji]

One could investigate and add risv cpu type to

rustup/rustup-init.sh

Lines 228 to 296 in c022b92

	case "$_cputype" in
	i386 | i486 | i686 | i786 | x86)
	_cputype=i686
	;;
	xscale | arm)
	_cputype=arm
	if [ "$_ostype" = "linux-android" ]; then
	_ostype=linux-androideabi
	fi
	;;
	armv6l)
	_cputype=arm
	if [ "$_ostype" = "linux-android" ]; then
	_ostype=linux-androideabi
	else
	_ostype="${_ostype}eabihf"
	fi
	;;
	armv7l | armv8l)
	_cputype=armv7
	if [ "$_ostype" = "linux-android" ]; then
	_ostype=linux-androideabi
	else
	_ostype="${_ostype}eabihf"
	fi
	;;
	aarch64)
	_cputype=aarch64
	;;
	x86_64 | x86-64 | x64 | amd64)
	_cputype=x86_64
	;;
	mips)
	_cputype=$(get_endianness mips '' el)
	;;
	mips64)
	if [ "$_bitness" -eq 64 ]; then
	# only n64 ABI is supported for now
	_ostype="${_ostype}abi64"
	_cputype=$(get_endianness mips64 '' el)
	fi
	;;
	ppc)
	_cputype=powerpc
	;;
	ppc64)
	_cputype=powerpc64
	;;
	ppc64le)
	_cputype=powerpc64le
	;;
	s390x)
	_cputype=s390x
	;;
	*)
	err "unknown CPU type: $_cputype"

[tommythorn]

Hmm, tried the obvious

--- rustup.sh.org	2020-04-01 17:52:18.571954138 +0000
+++ rustup.sh	2020-04-01 17:34:57.396790022 +0000
@@ -226,6 +226,9 @@
     esac
 
     case "$_cputype" in
+	riscv64)
+	    _cputype=riscv64
+	    ;;
 
         i386 | i486 | i686 | i786 | x86)
             _cputype=i686

but assuming this follows the convention, the failure is

rustup: command failed: downloader https://static.rust-lang.org/rustup/dist/riscv64-unknown-linux-gnu/rustup-init /tmp/tmp.jnFi5770CM/rustup-init

[tesuji]

What is the full target triple of riscv?

[tesuji]

Does riscv has std? rustup depends on std.
Acording to https://forge.rust-lang.org/release/platform-support.html, riscv is bare metal
only.

[tommythorn]

1. I don't know what the convention calls for but poking around I found:

tommy@Ubuntu-riscv64:~$ rustc --print target-list|grep riscv
riscv32i-unknown-none-elf
riscv32imac-unknown-none-elf
riscv32imc-unknown-none-elf
riscv64gc-unknown-linux-gnu
riscv64gc-unknown-none-elf
riscv64imac-unknown-none-elf

2. I don't know how Canonical got their riscv rust binaries.

[tommythorn]

Changing the _cputype=riscv64gc I get

info: downloading installer
curl: (22) The requested URL returned error: 404 
rustup: command failed: downloader https://static.rust-lang.org/rustup/dist/riscv64gc-unknown-linux-gnu/rustup-init /tmp/tmp.PxoInJ2fwo/rustup-init

[kinnison]

There are multiple things at play here.

1. rustup-init.sh needs to know about riscv
2. rustup itself needs to be taught because otherwise it can't recognise it for toolchains (targets are a different matter)
3. rust-lang/rust needs to publish dockers for building targetting riscv
4. our CI needs updating to include riscv as a target
5. rust-lang/rust needs to publish a riscv toolchain, not just a std
6. and finally we can do a release of rustup including riscv linux

If people are serious about assisting with this, then perhaps we might put together a checklist and get it underway; though without support from the main rust-lang/rust repo for the docker and the compiler releases, there's not a lot we can do beyond preparing for the possiblity in the future.

[tommythorn]

Thanks, it was exactly a list like this I was hoping to see. Without a published toolchain there's not much point to the rest. IIUC, this is tracked by rust-lang/rust#62117 which I updated to point back here.

[tblah]

I have a WIP PR for this #2313

It isn't useful yet because there aren't official toolchains for a riscv host. However cross-compilation toolchains can be downloaded for a riscv target today (tested using rustup 1.21.1): see cross-rs/cross#413

[kinnison]

The completed riscvgc support was released today. I'd be interested to know if it works for you or not.

[tommythorn]

Thanks! The script seems to progress on my (fully up-to-date) Ubuntu RISC-V VM. However, it looks like we aren't there yet:

Current installation options:


   default host triple: riscv64gc-unknown-linux-gnu
     default toolchain: stable (default)
               profile: default
  modify PATH variable: yes

1) Proceed with installation (default)
2) Customize installation
3) Cancel installation
>1

info: profile set to 'default'
info: default host triple is riscv64gc-unknown-linux-gnu
info: syncing channel updates for 'stable-riscv64gc-unknown-linux-gnu'
info: latest update on 2020-06-18, rust version 1.44.1 (c7087fe00 2020-06-17)
error: target 'riscv64gc-unknown-linux-gnu' not found in channel.  Perhaps check https://forge.rust-lang.org/release/platform-support.html for available targets

riscv64gc-unknown-linux-gnu is listed under Tier 2 (does that imply not-stable?).