Add basic support for RISC-V 64bit architecture

[ldevulder]

Basic support of riscv64 architecture.

TODO:

• shim is not supported yet, package is not available in Tumbleweed but could be compiled. More work needed, but not something that should block this PR, will be done when shim will be available in openSUSE.
• Remove the hardcoded x86_64 path for GRUB loader directory.
• Maybe find an elegant way to add DTB in EFI partition (/EFI/dtb/ for SUSE based distributions), could be useful for arm64 too. Followed in Find a way to add DTB in EFI partition (for ARM and RISC-V) #1861.

[codecov-commenter]

Codecov Report

Attention: 27 lines in your changes are missing coverage. Please review.

Comparison is base (6358862) 75.29% compared to head (34d2031) 75.09%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
pkg/live/green.go	63.63%	11 Missing and 1 partial ⚠️
pkg/utils/grub.go	53.33%	7 Missing ⚠️
pkg/constants/constants.go	73.33%	4 Missing ⚠️
pkg/types/v1/platform.go	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1856      +/-   ##
==========================================
- Coverage   75.29%   75.09%   -0.21%     
==========================================
  Files          67       67              
  Lines        6825     6869      +44     
==========================================
+ Hits         5139     5158      +19     
- Misses       1315     1340      +25     
  Partials      371      371              

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[kkaempf]

lgtm

[frelon]

Really nice work, psyched to see riscv support!

That said, this PR breaks current multi-platform workflow. I would like to be able to write make PLATFORM=linux/amd64,linux/arm64,linux/riscv64 build and get a multi-platform image that can be pushed and has all dependencies needed to build other systems.

[ldevulder]

Here the grub entry with the latest fixes, no more hardcoded x86_64 (checked on x86_64 and riscv64):

$ sudo mount -o loop build/elemental-tumbleweed.riscv64.iso /mnt
mount: /mnt: WARNING: source write-protected, mounted read-only.
$ ls /mnt
boot  EFI  rootfs.squashfs
$ ls /mnt/boot/
grub2  riscv64
$ cat /mnt/boot/grub2/grub.cfg
[...]
menuentry "Elemental" --class os --unrestricted {
		echo Loading kernel...
		$linux ($root)/boot/riscv64/loader/linux cdroot root=live:CDLABEL=COS_LIVE rd.live.dir=/ rd.live.squashimg=rootfs.squashfs console=tty1 console=ttyS0 rd.cos.disable cos.setup=/run/initramfs/live/iso-config
		echo Loading initrd...
		$initrd ($root)/boot/riscv64/loader/initrd
	}
[...]

[ldevulder]

I would like to be able to write make PLATFORM=linux/amd64,linux/arm64,linux/riscv64 build

It should be doable, but keep in mind that qemu docker configuration will be needed to be able to build the full OS stack (or native client on docker).

But the CLI can be compiled for all supported arch directly (thanks to cross-compiling) from x86_64 (test on my laptop) with the build-cli-with-docker target.

[davidcassany]

LGTM 👍 Cool too see riscv

I think this PR should be merged before #1858

[frelon]

Very nice! 👍