HI Xuerui: This must be a *HUGE* project and gonna put lots of effort in to it! So, first, good luck to you with all my best wishes!~
On 00:39 Thu 12 Aug , WANG Xuerui wrote: > Hi everyone, > > I'm your average Gentoo user who obviously thought his sleeping time is more > than enough, and just decided to start porting Gentoo to LoongArch. As this > is such a niche architecture with no upstreamed support so far, I'm posting > this to announce my intent and gather advice on how to best push this. > > I'll first give some background material to help people gain context, then > describe my porting plan. This is going to be a bit long; apologizes for > that. > > > Note: I'm not affiliated with Loongson in any way; I'm just doing this in my > spare time (once meant for some quality sleep). > > > ## A bit of introduction on the LoongArch > > LoongArch, as its name implies, is the brand-new ISA developed by the > Loongson Corporation, incompatible with MIPS which was implemented by > all previous Loongson processors. Currently only the base ISA specification > is publicly available; it has fixed-length 32-bit instructions, vastly more > instruction formats (39 distinct formats in the base ISA alone!), and its > instruction semantics mostly resemble RISC-V, with a bit of MIPS R6 here and > there. It is capable of 64-bit operations, obviously. > > ISA documentation: https://github.com/loongson/LoongArch-Documentation > ELF psABI draft: https://github.com/loongson/LoongArch-Documentation/pull/3 > > The draft ABI is undergoing fierce review, and is subject to change, > especially the relocation types. Other parts like the register > convention and > data layout is unlikely to change much, though. > > There is little code upstreamed for basic software (GNU toolchain, QEMU, > Linux and the like), but many are open-sourced already. Nevertheless, the > code quality is still very much inferior, and much of it is obviously based > on respective MIPS support. There is continuous debate inside and outside > Loongson on this matter, too. > Didn't do any investigation, but if I read correctly, also see here [1] The fundamental pieces of softwares are open-sourced but *NOT* yet upstreamed So, I'd say, let's wait till it's actually accepted by upstream, before pushing to downsteam (Gentoo here). Sure, you're free to send a pull-request for review/comment, but collect peices under your own overlay would be a good idea ( in my humble opition ). > Kernel ABI and glibc code seems to be inspired by RISC-V, but still some > parts show MIPS heritage. The kernel bits are being reviewed on the > linux-arch > mailing list. > > All of the projects above can be accessed at https://github.com/loongson. > > Loongson 3A5000 is the first LoongArch CPU; the Lemote A2101 board with this > CPU can be bought in China for ~4000 CNY already. > > > ## Gentoo porting plans > > I'm planning to take ARCH=loongarch for the port; and support the LP64 ABI > first. I'd like to support both LP64 and ILP32 ABIs, but that's not a > priority. > start with LP64 would be good idea, so same as RISC-V here. > The ABI flag might be named "ABI_LOONGARCH" but that's IMO a bit long (pun > semi-intended); ARCH=loong and ABI_LOONG might be better, I'm open to > suggestions. > > Because much of the ABI and even some toolchain internals are going through > VERY fierce debate and rework, obviously the port will remain experimental > for a long time. Some minimal support should get in tree though; doing so > would ease a lot of pain for experimentation. I already hacked my way to > generate working crossdev toolchains, and is halfway towards a rootfs with > working Python (and Portage). I've already independently ported strace, and > plan to do the same to libffi in the coming days which would give me Python. > > I'll do all work in my own loongson-overlay first, and upstream these when > appropriate. Eventually I hope to have working crossdev, qemu-user emulation > and proper catalyst support. > > sounds a good plan, first start with making cross compiling work, then try to populate a mini rootfs (kernel, glibc, base system), then python, portage > And that's about all; the message is getting long! Your opinions are > welcome, > and thanks again for following along. > > [1] https://github.com/gentoo/portage/pull/740#issuecomment-895021854 -- Yixun Lan (dlan) Gentoo Linux Developer GPG Key ID AABEFD55
