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Rust doesn't support the same amount of architectures C and Linux do, hopefully either Rust learns to support more architectures, or this stays confined to just

by chomp 6y ago

Rust doesn't support the same amount of architectures C and Linux do, hopefully either Rust learns to support more architectures, or this stays confined to just driver code because I'd hate to see Linux disappear from some of the more esoteric architectures.

dralley 6y ago
> Another point is taking on drivers first for "any initial trials to drivers is simply the architecture side," said Torvalds. "Lots of drivers are only relevant on a couple of target architectures, so the whole issue with Rust code not being supported on some architectures is less of an issue."
tambourine_man 6y ago
Linus is very proud of Linux running on anything, from toasters to HPC, so I think it's safe to assume less common architectures aren't going away.
- steveklabnik 6y ago
  Linux removes platform support from time to time, like any project. IA64 was a recent, notable example. That being said, it is true that Rust doesn't yet support all the platforms that are important to the kernel. That's one of the reasons this is starting with drivers, and is one of the reasons why some folks are pursuing a Rust frontend for gcc.
- pm215 6y ago
  It depends entirely on whether there are still developers interested in maintaining support for those architectures. It seems pretty safe to assume that Torvalds isn't going to be in favour of "we drop anything without a rust backend tomorrow"; but on the other hand 8 archs were dropped in 2018 -- https://lwn.net/Articles/749292/ https://lwn.net/Articles/749292/ -- essentially for lack of any active interest in them. It's possible that eventually "set of archs with a rust backend" and "set of archs which people care about enough to keep alive in the kernel" converge to the same set. It's even possible that one day "does this even have a rust backend?" becomes a marker of "is this thing really of use to anybody" in the same way that in 2018 "does this thing have support in upstream gcc" was a marker for "maybe we can drop this". That would be years from now, if ever, though, IMHO.
- Hublium 6y ago
  I thought that was NetBSD's thing?
  - throwaway0x1 6y ago
    Indeed it was, two decades ago... Linux has taken the pole position in supported architectures now though.
- Narishma 6y ago
  Plenty of them have already gone away. If they don't have people maintaining them, they get dropped over time.
brundolf 6y ago
Or maybe this would inspire people to expand LLVM support? There's nothing fundamental that prevents Rust from running on those architectures (as far as I know)
- willcipriano 6y ago
  I don't believe there is anything fundamentally preventing any language from running on any architecture other than "we haven't gotten around to it yet". Can't you emulate any Turing machine inside of any other Turing machine? I'd guess you could run the latest version of Python on anything more advanced than a abacus if you had a couple of lifetimes to waste on the project.
  - brundolf 6y ago
    My point is that a) half of the work doesn't have to happen because of LLVM's back-/front-end split, and b) if these are architectures that people care about keeping around and investing in, the benefits of adding LLVM support will go beyond just Rust
bitwize 6y ago
Weird architectures weren't supported to begin with: https://blog.yossarian.net/2021/02/28/Weird-architectures-werent-supported-to-begin-with https://blog.yossarian.net/2021/02/28/Weird-architectures-we... If you're still running a system with an arcane ISA, support it yourself. 99% of the people running modern Linux are interested in three CPU architectures (four or five once RISC-V gains traction), all of them supported by Rust. Supporting old or obscure ISAs is not a priority at this point compared to bringing kernel memory safety into the 21st century, which Rust helps a lot with.
- Gaelan 6y ago
  While I think I agree with this article, that isn't the case here. That article is talking about taking C code that happens to be portable to an obscure architecture, but never officially supported it, then complaining when the never-official support breaks for some reason. We're talking here about the Linux kernel, which (by necessity) was explicitly ported to every architecture it works on, so any lost architecture support would be an explicitly removed feature.
xiphias2 6y ago
I think adding new targets to LLVM is an infititely easier task than writing safe C code (as long as the LLVM team is open to it)
- Blikkentrekker 6y ago
  Rustc's lack of architecture support is purely an LLVM issue/ A far as I know, the latter supports many architectures the former does not.
  - steveklabnik 6y ago
    It is true that Rust supports a subset of the architectures LLVM supports, but to be honest, I am not sure if "many" is the right adjective. I mean that in a literal sense, I don't have a good handle on the list. For Rust, the list is https://doc.rust-lang.org/nightly/rustc/platform-support.html https://doc.rust-lang.org/nightly/rustc/platform-support.htm..., but I'm not sure if there's such a list for LLVM, other than looking at something like https://llvm.org/doxygen/Triple_8h_source.html https://llvm.org/doxygen/Triple_8h_source.html and figuring it out?
- junon 6y ago
  This is false equivalency.
- justaguy88 6y ago
  The other avenue is adding a Rust frontend to GCC
perryizgr8 6y ago
We actually ran against this problem when I tried to get a rust toolchain up and running for our ARM v6 based product. I think that support has been added now, but it's a harder sell now because people wonder what other incompatibilities might be there, hidden, and waiting to bite us later.

by chomp 6y ago

dralley 6y ago

> Another point is taking on drivers first for "any initial trials to drivers is simply the architecture side," said Torvalds. "Lots of drivers are only relevant on a couple of target architectures, so the whole issue with Rust code not being supported on some architectures is less of an issue."

tambourine_man 6y ago

Linus is very proud of Linux running on anything, from toasters to HPC, so I think it's safe to assume less common architectures aren't going away.

steveklabnik 6y ago
Linux removes platform support from time to time, like any project. IA64 was a recent, notable example. That being said, it is true that Rust doesn't yet support all the platforms that are important to the kernel. That's one of the reasons this is starting with drivers, and is one of the reasons why some folks are pursuing a Rust frontend for gcc.
pm215 6y ago
It depends entirely on whether there are still developers interested in maintaining support for those architectures. It seems pretty safe to assume that Torvalds isn't going to be in favour of "we drop anything without a rust backend tomorrow"; but on the other hand 8 archs were dropped in 2018 -- https://lwn.net/Articles/749292/ https://lwn.net/Articles/749292/ -- essentially for lack of any active interest in them. It's possible that eventually "set of archs with a rust backend" and "set of archs which people care about enough to keep alive in the kernel" converge to the same set. It's even possible that one day "does this even have a rust backend?" becomes a marker of "is this thing really of use to anybody" in the same way that in 2018 "does this thing have support in upstream gcc" was a marker for "maybe we can drop this". That would be years from now, if ever, though, IMHO.
Hublium 6y ago
I thought that was NetBSD's thing?
- throwaway0x1 6y ago
  Indeed it was, two decades ago... Linux has taken the pole position in supported architectures now though.
Narishma 6y ago
Plenty of them have already gone away. If they don't have people maintaining them, they get dropped over time.

brundolf 6y ago

Or maybe this would inspire people to expand LLVM support? There's nothing fundamental that prevents Rust from running on those architectures (as far as I know)

willcipriano 6y ago
I don't believe there is anything fundamentally preventing any language from running on any architecture other than "we haven't gotten around to it yet". Can't you emulate any Turing machine inside of any other Turing machine? I'd guess you could run the latest version of Python on anything more advanced than a abacus if you had a couple of lifetimes to waste on the project.
- brundolf 6y ago
  My point is that a) half of the work doesn't have to happen because of LLVM's back-/front-end split, and b) if these are architectures that people care about keeping around and investing in, the benefits of adding LLVM support will go beyond just Rust

bitwize 6y ago

Weird architectures weren't supported to begin with: https://blog.yossarian.net/2021/02/28/Weird-architectures-werent-supported-to-begin-with https://blog.yossarian.net/2021/02/28/Weird-architectures-we... If you're still running a system with an arcane ISA, support it yourself. 99% of the people running modern Linux are interested in three CPU architectures (four or five once RISC-V gains traction), all of them supported by Rust. Supporting old or obscure ISAs is not a priority at this point compared to bringing kernel memory safety into the 21st century, which Rust helps a lot with.

Gaelan 6y ago
While I think I agree with this article, that isn't the case here. That article is talking about taking C code that happens to be portable to an obscure architecture, but never officially supported it, then complaining when the never-official support breaks for some reason. We're talking here about the Linux kernel, which (by necessity) was explicitly ported to every architecture it works on, so any lost architecture support would be an explicitly removed feature.

xiphias2 6y ago

I think adding new targets to LLVM is an infititely easier task than writing safe C code (as long as the LLVM team is open to it)

Blikkentrekker 6y ago
Rustc's lack of architecture support is purely an LLVM issue/ A far as I know, the latter supports many architectures the former does not.
- steveklabnik 6y ago
  It is true that Rust supports a subset of the architectures LLVM supports, but to be honest, I am not sure if "many" is the right adjective. I mean that in a literal sense, I don't have a good handle on the list. For Rust, the list is https://doc.rust-lang.org/nightly/rustc/platform-support.html https://doc.rust-lang.org/nightly/rustc/platform-support.htm..., but I'm not sure if there's such a list for LLVM, other than looking at something like https://llvm.org/doxygen/Triple_8h_source.html https://llvm.org/doxygen/Triple_8h_source.html and figuring it out?
junon 6y ago
This is false equivalency.
justaguy88 6y ago
The other avenue is adding a Rust frontend to GCC

perryizgr8 6y ago

We actually ran against this problem when I tried to get a rust toolchain up and running for our ARM v6 based product. I think that support has been added now, but it's a harder sell now because people wonder what other incompatibilities might be there, hidden, and waiting to bite us later.