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Rust in the kernel is no longer experimental (lwn.net)
341 points by rascul 4 hours ago | hide | past | favorite | 160 comments




  > Mike: rachel and i are no longer dating
  >
  > rachel: mike that's a horrible way of telling people we're married
from the meme section on that page.

> same Mike in an org wide email: thank you all for your support. Starting next week I will no longer be a developer here. I thank my manager blah blah... I will be starting my dream role as Architect and I hope to achieve success.

> Mike's colleagues: Aww.. We'll miss you.

> Mike's manager: Is this your one week's notice? Did you take up an architect job elsewhere immediately after I promoted you to architect ?!


Does the removal of “experimental” now mean that all maintainers are now obligated to not break Rust code?

Rust in the kernel feels like a red herring. For fault tolerance and security, wouldn’t it be a superior solution to migrate Linux to a microkernel architecture? That way, drivers and various other components could be isolated in sandboxes.

I am not a system programmer but, from my understanding, Torvalds has expressed strong opinions about microkernels over a long period of time. The concept looks cleaner on paper but the complexity simply outweighs all the potential benefits. The debate, from what I have followed, expressed similar themes as monolithic vs microservices in the wider software development arena.

You should develop a small experimental kernel with that architecture and publish it on a mailing list.

Just use MINIX, or GNU Hurd.

Go ahead and do it!

This seems big. Is this big?

Yup.

Not a system programmer -- at this point, does C hold any significant advantage over Rust? Is it inevitable that everything written in C is going to be gradually converted to safer languages?

C currently remains the language of system ABIs, and there remains functionality that C can express that Rust cannot (principally bitfields).

Furthermore, in terms of extensions to the language to support more obtuse architecture, Rust has made a couple of decisions that make it hard for some of those architectures to be supported well. For example, Rust has decided that the array index type, the object size type, and the pointer size type are all the same type, which is not the case for a couple of architectures; it's also the case that things like segmented pointers don't really work in Rust (of course, they barely work in C, but barely is more than nothing).


Can you expand on bitfields? There’s crates that implement bitfield structs via macros so while not being baked into the language I’m not sure what in practice Rust isn’t able to do on that front.

Yeah, not sure what they're saying... I use bitfields in multiple of my rust projects using those macros.

I'm not a rust or systems programmer but I think it meant that as an ABI or foreign function interface bitfields are not stable or not intuitive to use, as they can't be declared granularily enough.

That first sentence though. Bitfields and ABI alongside each other.

Bitfield packing rules get pretty wild. Sure the user facing API in the language is convenient, but the ABI it produces is terrible (particularly in evolution).


I would like a revision to bitfields and structs to make them behave the way a programmer things, with the compiler free to suggest changes which optimize the layout. As well as some flag that indicates the compiler should not, it's a finalized structure.

I'm genuinely surprised that usize <=> pointer convertibility exists. Even Go has different types for pointer-width integers (uintptr) and sizes of things (int/uint). I can only guess that Rust's choice was seen as a harmless simplification at the time. Is it something that can be fixed with editions? My guess is no, or at least not easily.

There is a cost to having multiple language-level types that represent the exact same set of values, as C has (and is really noticeable in C++). Rust made an early, fairly explicit decision that a) usize is a distinct fundamental type from the other types, and not merely a target-specific typedef, and b) not to introduce more types for things like uindex or uaddr or uptr, which are the same as usize on nearly every platform.

Rust worded in its initial guarantee that usize was sufficient to roundtrip a pointer (making it effectively uptr), and there remains concern among several of the maintainers about breaking that guarantee, despite the fact that people on the only target that would be affected basically saying they'd rather see that guarantee broken. Sort of the more fundamental problem is that many crates are perfectly happy opting out of compiling for weirder platform--I've designed some stuff that relies on 64-bit system properties, and I'd rather like to have the ability to say "no compile for you on platform where usize-is-not-u64" and get impl From<usize> for u64 and impl From<u64> for usize. If you've got something like that, it also provides a neat way to say "I don't want to opt out of [or into] compiling for usize≠uptr" and keeping backwards compatibility.

If you want to see some long, gory debates on the topic, https://internals.rust-lang.org/t/pre-rfc-usize-is-not-size-... is a good starting point.


> Is it something that can be fixed with editions? My guess is no, or at least not easily.

Assuming I'm reading these blog posts [0, 1] correctly, it seems that the size_of::<usize>() == size_of::<*mut u8>() assumption is changeable across editions.

Or at the very least, if that change (or a similarly workable one) isn't possible, both blog posts do a pretty good job of pointedly not saying so.

[0]: https://faultlore.com/blah/fix-rust-pointers/#redefining-usi...

[1]: https://tratt.net/laurie/blog/2022/making_rust_a_better_fit_...


In what architecture are those types different? Is there a good reason for it there architecturally, or is it just a toolchain idiosyncrasy in terms of how it's exposed (like LP64 vs. LLP64 etc.)?

CHERI has 64-bit object size but 128-bit pointers (because the pointer values also carry pointer provenance metadata in addition to an address). I know some of the pointer types on GPUs (e.g., texture pointers) also have wildly different sizes for the address size versus the pointer size. Far pointers on segmented i386 would be 16-bit object and index size but 32-bit address and pointer size.

There was one accelerator architecture we were working that discussed making the entire datapath be 32-bit (taking less space) and having a 32-bit index type with a 64-bit pointer size, but this was eventually rejected as too hard to get working.


Also you can't do self-referential strutcs.

Double-linked lists are also pain to implement, and they're are heavily used in kernel.


There are certain styles of programming and data structure implementations that end up requiring you to fight Rust at almost every step. Things like intrusive data structures, pointer manipulation and so on. Famously there is an entire book online on how to write a performant linked list in idiomatic Rust - something that is considered straightforward in C.

For these cases you could always use Zig instead of C


Or just build a tested unsafe implementation as a library. For example the Linked List in the standard library.

https://doc.rust-lang.org/src/alloc/collections/linked_list....


what is an intrusive data structure?

Every system under the Sun has a C compiler. This isn't remotely true for Rust. Rust is more modern than C, but has it's own issues, among others very slow compilation times. My guess is that C will be around long after people will have moved on from Rust to another newfangled alternative.

> My guess is that C will be around long after people will have moved on from Rust to another newfangled alternative.

if only due to the Lindy Effect

https://en.wikipedia.org/wiki/Lindy_effect


There is a set of languages which are essentially required to be available on any viable system. At present, these are probably C, C++, Perl, Python, Java, and Bash (with a degree of asterisks on the last two). Rust I don't think has made it through that door yet, but on current trends, it's at the threshold and will almost certainly step through. Leaving this set of mandatory languages is difficult (I think Fortran, and BASIC-with-an-asterisk, are the only languages to really have done so), and Perl is the only one I would risk money on departing in my lifetime.

I do firmly expect that we're less than a decade out from seeing some reference algorithm be implemented in Rust rather than C, probably a cryptographic algorithm or a media codec. Although you might argue that the egg library for e-graphs already qualifies.


A system only needs one programming language to be useful, and when there's only one it's basically always C.

We're already at the point where in order to have a "decent" desktop software experience you _need_ Rust too. For instance, Rust doesn't support some niche architectures because LLVM doesn't support them (those architectures are now exceedingly rare) and this means no Firefox for instance.

What other newfangled alternative to C was ever adopted in the Linux kernel?

I have no doubt C will be around for a long time, but I think Rust also has a lot of staying power and won’t soon be replaced.


I wouldn't be surprised to see zig in the kernel at some point

IMHO Zig doesn't bring enough value of its own to be worth bearing the cost of another language in the kernel.

Rust is different because it both:

- significantly improve the security of the kernel by removing the nastiest class of security vulnerabilities.

- And reduce cognitive burden for contributors by allowing to encode in thr typesystem the invariants that must be upheld.

That doesn't mean Zig is a bad language for a particular project, just that it's not worth adding to an already massive project like the Linux kernel. (Especially a project that already have two languages, C and now Rust).


Zig as a language is not worth, but as a build system it's amazing. I wouldn't be surprised if Zig gets in just because of the much better build system than C ever had (you can cross compile not only across OS, but also across architecture and C stlib versions, including musl). And with that comes the testing system and seamless interop with C, which make it really easy to start writing some auxiliary code in Zig... and eventually it may just be accepted for any development.

Pardon my ignorance but I find the claim "removing the nastiest cla ss of security vulnerabilities" to be a bold claim. Is there ZERO use of "unsafe" rust in kernel code??

Aside from the minimal use of unsafe being heavily audited and the only entry point for those vulnerabilities, it allows for expressing kernel rules explicitly and structurally whereas at best there was a code comment somewhere on how to use the API correctly. This was true because there was discussion precisely about how to implement Rust wrappers for certain APIs because it was ambiguous how those APIs were intended to work.

So aside from being like 1-5% unsafe code vs 100% unsafe for C, it’s also more difficult to misuse existing abstractions than it was in the kernel (not to mention that in addition to memory safety you also get all sorts of thread safety protections).

In essence it’s about an order of magnitude fewer defects of the kind that are particularly exploitable (based on research in other projects like Android)


You can absolutely write drivers with zero unsafe Rust. The bridge from Rust to C is where unsafe code lies.

Not zero, but Rust-based kernels (see redox, hubris, asterinas, or blog_os) have demonstrated that you only need a small fraction of unsafe code to make a kernel (3-10%) and it's also the least likely places to make a memory-related error in a C-based kernel in the first place (you're more likely to make a memory-related error when working on the implementation of an otherwise challenging algorithm that has nothing to do with memory management itself, than you are when you are explicitly focused on the memory-management part).

So while there could definitely be an exploitable memory bug in the unsafe part of the kernel, expect those to be at least two orders of magnitude less frequent than with C (as an anecdotal evidence, the Android team found memory defects to be between 3 and 4 orders of magnitude less in practice over the past few years).


I can’t think of many real world production systems which don’t have a rust target. Also I’m hopeful the GCC backend for rustc makes some progress and can become an option for the more esoteric ones

There aren't really any "systems programming" platforms anywhere near production that doesn't have a workable rust target.

It's "embedded programming" where you often start to run into weird platforms (or sub-platforms) that only have a c compiler, or the rust compiler that does exist is somewhat borderline. We are sometimes talking about devices which don't even have a gcc port (or the port is based on a very old version of gcc). Which is a shame, because IMO, rust actually excels as an embedded programming language.

Linux is a bit marginal, as it crosses the boundary and is often used as a kernel for embedded devices (especially ones that need to do networking). The 68k people have been hit quite hard by this, linux on 68k is still a semi-common usecase, and while there is a prototype rust back end, it's still not production ready.


There’s also I believe an effort to target C as the mid level although I don’t know the state / how well it’ll work in an embedded space anyway where performance really matters and these compilers have super old optimizers that haven’t been updated in 3 decades.

It's mostly embedded / microcontroller stuff. Things that you would use something like SDCC or a vendor toolchain for. Things like the 8051, stm8, PIC or oddball things like the 4 cent Padauk micros everyone was raving about a few years ago. 8051 especially still seems to come up from time to time in things like the ch554 usb controller, or some NRF 2.4ghz wireless chips.

Those don’t really support C in any real stretch, talking about general experience with microcontrollers and closed vendor toolchains; it’s a frozen dialect of C from decades ago which isn’t what people think of when they say C (usually people mean at least the 26 year old C99 standard but these often at best support C89 or even come with their own limitations)

> very slow compilation times

That isn't always the case. Slow compilations are usually because of procedural macros and/or heavy use of generics. And even then compile times are often comparable to languages like typescript and scala.


typescript transpilation to js is nearly instant, it's not comparable

> Every system under the Sun has a C compiler... My guess is that C will be around long after people will have moved on from Rust to another newfangled alternative.

This is still the worst possible argument for C. If C persists in places no one uses, then who cares?


I think you didn't catch their drift

C will continue to be used because it always has been and always will be available everywhere, not only places no one uses :/


> C will continue to be used because it always has been and always will be available everywhere

Yes, you can use it everywhere. Is that what you consider a success?


... yes?

You almost certainly have a bunch of devices containing a microcontroller that runs an architecture not targeted by LLVM. The embedded space is still incredibly fragmented.

That said, only a handful of those architectures are actually so weird that they would be hard to write a LLVM backend for. I understand why the project hasn’t established a stable backend plugin API, but it would help support these ancillary architectures that nobody wants to have to actively maintain as part of the LLVM project. Right now, you usually need to use a fork of the whole LLVM project when using experimental backends.


> You almost certainly have a bunch of devices containing a microcontroller that runs an architecture not targeted by LLVM.

This is exactly what I'm saying. Do you think HW drives SW or the other way around? When Rust is in the Linux kernel, my guess is it will be very hard to find new HW worth using, which doesn't have some Rust support.


Doesn’t rustc emit LLVM IR? Are there a lot of systems that LLVM doesn’t support?

There are a number of oddball platforms LLVM doesn't support, yeah.

rustc can use a few different backends. By my understanding, the LLVM backend is fully supported, the Cranelift backend is either fully supported or nearly so, and there's a GCC backend in the works. In addition, there's a separate project to create an independent Rust frontend as part of GCC.

Even then, there are still some systems that will support C but won't support Rust any time soon. Systems with old compilers/compiler forks, systems with unusual data types which violate Rust's assumptions (like 8 bit bytes IIRC)


C is fun to write. I can write Rust, but I prefer writing C. I prefer compiling C, I prefer debugging C. I prefer C.

It's a bit like asking with the new mustang on the market, with airbags and traction control, why would you ever want to drive a classic mustang?


It’s okay to enjoy driving an outdated and dangerous car for the thrill because it makes pleasing noise, as long as you don’t annoy too much other people with it.

> I prefer debugging C

I prefer not having to debug... I think most people would agree with that.


Before we ask if almost all things old will be rewritten in Rust, we should ask if almost all things new are being written in Rust or other memory-safe languages?

Obviously not. When will that happen? 15 years? Maybe it's generational: How long before developers 'born' into to memory-safe languages as serious choices will be substantially in charge of software development?


I don't know I tend to either come across new tools written in Rust, JavaScript or Python but relatively low amount of C. The times I see some "cargo install xyz" in a git repo of some new tool is definitely noticeable.

> Obviously not

Is it obvious? I haven't heard of new projects in non-memory-safe languages lately, and I would think they would struggle to attract contributors.


New high-scale data infrastructure projects I am aware of mostly seem to be C++ (often C++20). A bit of Rust, which I’ve used, and Zig but most of the hardcore stuff is still done in C++ and will be for the foreseeable future.

It is easy to forget that the state-of-the-art implementations of a lot of systems software is not open source. They don’t struggle to attract contributors because of language choices, being on the bleeding edge of computer science is selling point enough.



Zig at least claims some level of memory safety in their marketing. How real that is I don't know.

About as real as claiming that C/C++ is memory safe because of sanitizers IMHO.

I'm unaware of any such marketing.

Out of curiosity, do the LLMs all use memory safe languages?

Whenever the public has heard about the language it's always been Python.

The language that implements Python's high-speed floating point has often been FORTRAN.

https://fortranwiki.org/fortran/show/Python


Llama.cpp is called Llama.cpp, so there’s that…

I'm a bit wary if this is hiding an agist sentiment, though. I doubt most Rust developers were 'born into' the language, but instead adopted it on top of existing experience in other languages.

People can learn Rust at any age. The reality is that experienced people often are more hesitant to learn new things.

I can think of possible reasons: Early in life, in school and early career, much of what you work on is inevitably new to you, and also authorities (professor, boss) compel you to learn whatever they choose. You become accustomed to and skilled at adapting new things. Later, when you have power to make the choice, you are less likely to make yourself change (and more likely to make the junior people change, when there's a trade-off). Power corrupts, even on that small scale.

There's also a good argument for being stubborn and jaded: You have 30 years perfecting the skills, tools, efficiencies, etc. of C++. For the new project, even if C++ isn't as good a fit as Rust, are you going to be more efficient using Rust? How about in a year? Two years? ... It might not be worth learning Rust at all; ROI might be higher continuing to invest in additional elite C++ skills. Certainly that has more appeal to someone who knows C++ intimately - continue to refine this beautiful machine, or bang your head against the wall?

For someone without that investment, Rust might have higher ROI; that's fine, let them learn it. We still need C++ developers. Morbid but true, to a degree: 'Progress happens one funeral at a time.'


I still think you're off the mark. Again, most existing Rust developers are not "blank slate Rust developers". That they do not rush out to rewrite all of their past projects in C++ may be more about sunk costs, and wanting to solve new problems with from-scratch development.

> most existing Rust developers are not "blank slate Rust developers"

Not most, but the pool of software devs has been doubling every five years, and Rust matches C# on "Learning to Code" votes at Stack Overflow's last survey, which is crazy considering how many people learn C# just to use Unity. I think you underestimate how many developers are Rust blank slates.

Anecdotically, I've recently come across comments from people who've taught themselves Rust but not C or C++.


That's fair; my claims are kept simplistic for purposes of space and time. However, I'm talking about new projects, not rewriting legacy code.

you can look at rust sources of real system programs like framekernel or such things. uefi-rs etc.

there u can likely explore well the boundaries where rust does and does not work.

people have all kind of opinions. mine is this:

if you need unsafe peppered around, the only thing rust offers is being very unergonomic. its hard to write and hard to debug for no reason. Writing memory-safe C code is easy. The problems rust solves arent bad, just solved in a way thats way more complicated than writing same (safe) C code.

a language is not unsafe. you can write perfectly shit code in rust. and you can write perfectly safe code in C.

people need to stop calling a language safe and then reimplementing other peoples hard work in a bad way creating whole new vulnerabilities.


Apple handled this problem by adding memory safety to C (Firebloom). It seems unlikely they would throw away that investment and move to Rust. I’m sure lots of other companies don’t want to throw away their existing code, and when they write new code there will always be a desire to draw on prior art.

It’s available on more obscure platforms than Rust, and more people are familiar with it.

I wouldn’t say it’s inevitable that everything will be rewritten in Rust, at the very least this will this decades. C has been with us for more than half a century and is the foundation of pretty much everything, it will take a long time to migrate all that.

More likely is that they will live next to each other for a very, very long time.


It's a bit like asking if there is any significant advantage to ICE motors over electric motors. They both have advantages and disadvantages. Every person who uses one or the other, will tell you about their own use case, and why nobody could possibly need to use the alternative.

There's already applications out there for the "old thing" that need to be maintained, and they're way too old for anyone to bother with re-creating it with the "new thing". And the "old thing" has some advantages the "new thing" doesn't have. So some very specific applications will keep using the "old thing". Other applications will use the "new thing" as it is convenient.

To answer your second question, nothing is inevitable, except death, taxes, and the obsolescence of machines. Rust is the new kid on the block now, but in 20 years, everybody will be rewriting all the Rust software in something else (if we even have source code in the future; anyone you know read machine code or punch cards?). C'est la vie.


Rust still compiles into bigger binary sizes than C, by a small amount. Although it’s such a complex thing depending on your code that it really depends case-by-case, and you can get pretty close. On embedded systems with small amounts of ram (think on the order of 64kbytes), a few extra kb still hurts a lot.

A lot of C's popularity is with how standard and simple it is. I doubt Rust will be the safe language of the future, simply because of its complexity. The true future of "safe" software is already here, JavaScript.

There will be small niches leftover:

* Embedded - This will always be C. No memory allocation means no Rust benefits. Rust is also too complex for smaller systems to write compilers.

* OS / Kernel - Nearly all of the relevant code is unsafe. There aren't many real benefits. It will happen anyways due to grant funding requirements. This will take decades, maybe a century. A better alternative would be a verified kernel with formal methods and a Linux compatibility layer, but that is pie in the sky.

* Game Engines - Rust screwed up its standard library by not putting custom allocation at the center of it. Until we get a Rust version of the EASTL, adoption will be slow at best.

* High Frequency Traders - They would care about the standard library except they are moving on from C++ to VHDL for their time-sensitive stuff. I would bet they move to a garbage-collected language for everything else, either Java or Go.

* Browsers - Despite being born in a browser, Rust is unlikely to make any inroads. Mozilla lost their ability to make effective change and already killed their Rust project once. Google has probably the largest C++ codebase in the world. Migrating to Rust would be so expensive that the board would squash it.

* High-Throughput Services - This is where I see the bulk of Rust adoption. I would be surprised if major rewrites aren't already underway.


> No memory allocation means no Rust benefits.

This isn't really true; otherwise, there would be no reason for no_std to exist. Data race safety is independent of whether you allocate or not, lifetimes can be handy even for fixed-size arenas, you still get bounds checks, you still get other niceties like sum types/an expressive type system, etc.

> OS / Kernel - Nearly all of the relevant code is unsafe.

I think that characterization is rather exaggerated. IIRC the proportion of unsafe code in Redox OS is somewhere around 10%, and Steve Klabnik said that Oxide's Hubris has a similarly small proportion of unsafe code (~3% as of a year or two ago) [0]

> Browsers - Despite being born in a browser, Rust is unlikely to make any inroads.

Technically speaking, Rust already has. There has been Rust in Firefox for quite a while now, and Chromium has started allowing Rust for third-party components.

[0]: https://news.ycombinator.com/item?id=42312699

[1]: https://old.reddit.com/r/rust/comments/bhtuah/production_dep...


The Temporal API in Chrome is implemented in Rust. We’re definitely seeing more Rust in browsers including beyond Firefox.

> Google has probably the largest C++ codebase in the world. Migrating to Rust would be so expensive that the board would squash it.

Google is transitioning large parts of Android to Rust and there is now first-party code in Chromium and V8 in Rust. I’m sure they’ll continue to write new C++ code for a good while, but they’ve made substantial investments to enable using Rust in these projects going forward.

Also, if you’re imagining the board of a multi-trillion dollar market cap company is making direct decisions about what languages get used, you may want to check what else in this list you are imagining.


> Embedded - This will always be C. No memory allocation means no Rust benefits. Rust is also too complex for smaller systems to write compilers.

Modern embedded isn't your grandpa's embedded anymore. Modern embedded chips have multiple KiB of ram, some even above 1MiB and have been like that for almost a decade (look at ESP32 for instance). I once worked on embedded projects based on ESP32 that used full C++, with allocators, exceptions, ... using SPI RAM and worked great. There's a fantastic port of ESP-IDF on Rust that Espressif themselves is maintaining nowadays, too.


> No memory allocation means no Rust benefits

There are memory safety issues that literally only apply to memory on the stack, like returning dangling pointers to local variables. Not touching the heap doesn't magically avoid all of the potential issues in C.


Rust is already making substantial inroads in browsers, especially for things like codecs. Chrome also recently replaced FreeType with Skrifa (Rust), and the JS Temporal API in V8 is implemented in Rust.

    > Rust is also too complex for smaller systems to write compilers.
I am not a compiler engineer, but I want to tease apart this statement. As I understand, the main Rust compiler uses LLVM framework which uses an intermediate language that is somewhat like platform independent assembly code. As long as you can write a lexer/parser to generate the intermediate language, there will be a separate backend to generate machine code from the intermediate language. In my (non-compiler-engineer) mind, separates the concern of front-end language (Rust) from target platform (embedded). Do you agree? Or do I misunderstand?

> No memory allocation means no Rust benefits.

Memory safety applies to all memory. Not just heap allocated memory.

This is a strange claim because it's so obviously false. Was this comment supposed to be satire and I just missed it?

Anyway, Rust has benefits beyond memory safety.

> Rust is also too complex for smaller systems to write compilers.

Rust uses LLVM as the compiler backend.

There are already a lot of embedded targets for Rust and a growing number of libraries. Some vendors have started adopting it with first-class support. Again, it's weird to make this claim.

> Nearly all of the relevant code is unsafe. There aren't many real benefits.

Unsafe sections do not make the entire usage of Rust unsafe. That's a common misconception from people who don't know much about Rust, but it's not like the unsafe keyword instantly obliterates any Rust advantages, or even all of its safety guarantees.

It's also strange to see this claim under an article about the kernel developers choosing to move forward with Rust.

> High Frequency Traders - They would care about the standard library except they are moving on from C++ to VHDL for their time-sensitive stuff. I would bet they move to a garbage-collected language for everything else, either Java or Go.

C++ and VHDL aren't interchangeable. They serve different purposes for different layers of the system. They aren't moving everything to FPGAs.

Betting on a garbage collected language is strange. Tail latencies matter a lot.

This entire comment is so weird and misinformed that I had to re-read it to make sure it wasn't satire or something.


> Memory safety applies to all memory. Not just heap allocated memory.

> Anyway, Rust has benefits beyond memory safety.

I want to elaborate on this a little bit. Rust uses some basic patterns to ensure memory safety. They are 1. RAII, 2. the move semantics, and 3. the borrow validation semantics.

This combination however, is useful for compile-time-verified management of any 'resource', not just heap memory. Think of 'resources' as something unique and useful, that you acquire when you need it and release/free it when you're done.

For regular applications, it can be heap memory allocations, file handles, sockets, resource locks, remote session objects, TCP connections, etc. For OS and embedded systems, that could be a device buffer, bus ownership, config objects, etc.

> > Nearly all of the relevant code is unsafe. There aren't many real benefits.

Yes. This part is a bit weird. The fundamental idea of 'unsafe' is to limit the scope of unsafe operations to as few lines as possible (The same concept can be expressed in different ways. So don't get offended if it doesn't match what you've heard earlier exactly.) Parts that go inside these unsafe blocks are surprisingly small in practice. An entire kernel isn't all unsafe by any measure.


> The true future of "safe" software is already here, JavaScript.

only in interpreter mode.


Rust isn't that complex unless your pulling in magical macro libraries or dealing with things like pin and that stuff,which you really don't need to.

It's like saying python is complex becasue you have metaclasses, but you'll never need to reach for them.


You mean safer languages like Fil-C.

Shitloads of already existing libraries. For example I'm not going to start using it for Arduino-y things until all the peripherals I want have drivers written in Rust.

Why? You can interact with C libraries from Rust just fine.

But you now have more complexity and no extra safety.

I think it'll be less like telegram lines- which were replaced fully for a major upgrade in functionality, and more like rail lines- which were standardized and ubiquitous, still hold some benefit but mainly only exist in areas people don't venture nearly as much.

For my hobby code, I'm not going to start writing Rust anytime soon. My code is safe enough and I like C as it is. I don't write software for martian rovers, and for ordinary tasks, C is more ergonomic than Rust, especially for embedded tasks.

For my work code, it all comes down to SDKs and stuff. For example I'm going to write firmware for Nordic ARM chip. Nordic SDK uses C, so I'm not going to jump through infinite number of hoops and incomplete rust ports, I'll just use official SDK and C. If it would be the opposite, I would be using Rust, but I don't think that would happen in the next 10 years.

Just like C++ never killed C, despite being perfect replacement for it, I don't believe that Rust would kill C, or C++, because it's even less convenient replacement. It'll dilute the market, for sure.


> Just like C++ never killed C, despite being perfect replacement for it

I think c++ didn't replace C because it is a bad language. It did not offer any improvements on the core advantages of C.

Rust however does. It's not perfect, but it has a substantially larger chance of "replacing" C, if that ever happens.


I guess it's time to finally try FreeBSD.

Lua in the kernel!

The title sounded worse than it is.

C++ devs are spinning in their graves now.

Or installing Haiku!

This title is moderately clickbait-y and comes with a subtle implication that Rust might be getting removed from the kernel. IMO it should be changed to "Rust in the kernel is no longer experimental"

I absolutely understand the sentiment, but LWN is a second-to-none publication that on this rare occasion couldn't resist the joke, and also largely plays to an audience who will immediately understand that it's tongue-in-cheek.

Speaking as a subscriber of about two decades who perhaps wouldn't have a career without the enormous amount of high-quality education provided by LWN content, or at least a far lesser one: Let's forgive.


He didn't intend it as a joke and his intent matches the op's title revision request: https://lwn.net/Articles/1049840/

> on this rare occasion couldn't resist the joke

It was unintentional as per author

> Ouch. That is what I get for pushing something out during a meeting, I guess. That was not my point; the experiment is done, and it was a success. I meant no more than that.


The “Ouch.” was in reference to being compared to Phoronix.

Has anyone found them to be inaccurate, or fluffy to the point it degraded the content?

I haven’t - but then again, probably predominantly reading the best posts being shared on aggregators.


Nah I used to read Phoronix and the articles are a bit clickbaity sometimes but mostly it's fine. The real issue is the reader comments. They're absolute trash.

Fair. But there’s even an additional difference between snarky clickbait and “giving the exact opposite impression of the truth in a headline” ;)

Hacker news generally removes Clickbait titles regardless of the provenance

If it was being removed the title would be "An update on rust in the kernel"

I think on HN, people generally want the submission's title to match the page's title.

(I do agree it's clickbait-y though)


Guidelines say fine to editorialize in these cases.

> Otherwise please use the original title, unless it is misleading or linkbait; don't editorialize.

https://news.ycombinator.com/newsguidelines.html


I think on HN, people waste too much time arguing about the phrasing of the headline, whether it is clickbait, etc. and not enough discussing the actual substance of the article.

I prefer improved titles. However, not in this case. It is rather irony, because LWN does not need click-bait.

This one is apparently a genuine mistake from the author. But I think we should leave it as it is. The confusion and the argument about it is interesting in itself.

It’s a bit clickbait-y, but the article is short, to the point, and frankly satisfying. If there is such a thing as good clickbait, then this might be it. Impressive work!

Might as well just post it:

  The topic of the Rust experiment was just discussed at the annual Maintainers Summit. The consensus among the assembled developers is that Rust in the kernel is no longer experimental — it is now a core part of the kernel and is here to stay. So the "experimental" tag will be coming off. Congratulations are in order for all of the Rust-for-Linux team.

This should just be the pinned comment.

Perhaps, except it can have the reverse effect. I was surprised, disappointed, and then almost moved on without clicking the link or the discussion. I'm glad I clicked. But good titles don't mislead! (To be fair, this one didn't mislead, but it was confusing at best.)

i agree and this matches the authors intent: https://lwn.net/Articles/1049840/

Seems you do not understand the concept of fun. You can learn that, makes your life easier.

He didn't mean to! That said, the headline did make me look.

I'm having deja Vu. Was there another quite similar headline here a few weeks or so ago?

Oh dear can you imagine the crushing complexity of a future Rust kernel.

By most accounts the Rust4Linux project has made the kernel less complex by forcing some technical debt to be addressed and bad APIs to be improved.

The Linux kernel is already very complex, and I expect that replacing much or all of it with Rust code will be good for making it more tractable to understand. Because you can represent complex states with more sophisticated types than in C, if nothing else.

Complexity of Rust is just codifying existing complexity.

There’s one already — they seem to be doing decently well.

https://www.redox-os.org/


Safety is good.

Unless it means sacrificing freedom.

freedom to shoot yourself in the foot?

how much?

That is why most of the world has not been using c/c++ for decades.

I'm not on the Rust bandwagon, but statements like this make absolutely no sense.

A lot of software was written in C and C++ because they were the only option for decades. If you couldn't afford garbage collection and needed direct control of the hardware there wasn't much of a choice. Had their been "safer" alternatives, it's possible those would have been used instead.

It's only been in the last few years we've seen languages emerge that could actually replace C/C++ with projects like Rust, Zig and Odin. I'm not saying they will, or they should, but just that we actually have alternatives now.


One could rewrite curl with Perl 30 years ago. Or with Java, Golang, Python, you name it. Yet it stays written with C even today.

Your comment comes across disingenuous to me. Writing it in, for example, Java would have limited it to situations where you have the JVM available, which is a minuscule subset of the situations that curl is used in today, especially if we're not talking "curl, the CLI tool" but libcurl. I have a feeling you know that already and mostly want to troll people. And Golang is only 16 years old according to Wikipedia, by the way.

That's not true when the topic is operating system kernels.

OS kernels? Everything from numpy to CUDA to NCCL is using C/C++ (doing all the behind the scene heavy lifting), never mind the classic systems software like web browsers, web servers, networking control plane (the list goes on).

Newer web servers have already moved away from C/C++.

Web browsers have been written in restricted subsets of C/C++ with significant additional tooling for decades at this point, and are already beginning to move to Rust.


> Web browsers have been written in restricted subsets of C/C++ with significant additional tooling for decades at this point

So, written in C/C++? It seems to me you're trying to make a point that reality doesn't agree with but you stubbornly keep pushing it.


> So, written in C/C++?

Not in the sense that people who are advocating writing new code in C/C++ generally mean. If someone is advocating following the same development process as Chrome does, then that's a defensible position. But if someone is advocating developing in C/C++ without any feature restrictions or additional tooling and arguing "it's fine because Chrome uses C/C++", no, it isn't.


There is not a single major browser written in Rust. Even Ladybird, a new project, adopted C++.

Firefox and Chrome already contain significant amounts of Rust code, and the proportion is increasing.

https://github.com/chromium/chromium : C++ 74.0%, Java 8.8%, Objective-C++ 4.8%, TypeScript 4.2%, HTML 2.5%, Python 2.4%, Other 3.3%

https://github.com/mozilla-firefox/firefox : JavaScript 28.9%, C++ 27.9%, HTML 21.8%, C 10.4%, Python 2.9%, Kotlin 2.7%, Other 5.4%

How significant?


According to https://4e6.github.io/firefox-lang-stats/, 12%.

I would love an updated version of https://docs.google.com/spreadsheets/d/1flUGg6Ut4bjtyWdyH_9e... (which stops in 2020).

For Chrome, I don't know if anyone has compiled the stats, but navigating from https://chromium.googlesource.com/chromium/src/+/refs/heads/... I see at least a bunch of vendored crates, so there's some use, which makes sense since in 2023 they announced that they would support it.


People didn't use seatbelts before seatbelts were invented.

Most software development these days is JS/Typescript slop, popular doesn't equal better

You can write slop in any language. And good software for that matter.

Most of the world uses other languages because they’re easier, not because they’re safer.

They're easier because, amongst other improvements, they are safer.

They had me in the first half of the article, not gonna lie. I thought they resigned because Rust was so complicated and unsuitable, but it's the opposite

This is great because it means someday (possibly soon) Linux development will slowly grind to a halt and become unmaintainable, so we can start from scratch and write a new kernel.

I’m curious how they’ll manage long term safety without the guarantees Rust brought. That tradeoff won’t age well.

You may want to read the article.

(Spoiler alert: Rust graduated to a full, first-class part of the kernel; it isn't being removed.)


It's late, but I'm having a hell of a time parsing this. Could you explain what you meant?

I think they read the title but not the article and assumed Rust was being removed, and (rightfully, if that were true) opined that that was a shortsighted decision.

(Of course, that's not what's happening at all.)


Ah! I hadn't considered that, thanks. That makes way more sense - having read the article I couldn't figure out what was being said here otherwise.



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