4 ms·

RISC-V 64-bit Linux in JavaScript

98 points by mbroncano 10y ago

alpb 10y ago
This was discussed last month. https://news.ycombinator.com/item?id=13210711 https://news.ycombinator.com/item?id=13210711
- bobajeff 10y ago
  Except this is the JavaScript version.
  - Narishma 10y ago
    Which was already available at that time, as you can see some commenters discussing it in that story.
bobajeff 10y ago
Wow, I'm running Linux on top of RISC-V in an emulator in my browser on my phone!
- agumonkey 10y ago
  Babel tower reemerges from the memories of Boole
  - Senji 10y ago
    Our hubris will be our undoing.
- hajile 10y ago
  https://www.destroyallsoftware.com/talks/the-birth-and-death-of-javascript https://www.destroyallsoftware.com/talks/the-birth-and-death...
ramblenode 10y ago
~# date Thu Jan 1 00:03:09 UTC 1970
chris_wot 10y ago
Silly question, but is there an x86 instruction set emulator written in JavaScript? Not even Linux, just something that takes x86 instructions into a "virtual CPU" and lets you run the assembly statements?
- kbeckmann 10y ago
  Not a silly question at all. I would also like to know this. Would be a fun way to play around with assembly without the need of a tool chain etc. Maybe even on your phone while on the train. If this doesn't exist already, I'd be happy to start working on something like this.
  - pmjordan 10y ago
    You could probably start from here: x86 Linux running in a web browser, also by Fabrice Bellard. http://bellard.org/jslinux/ http://bellard.org/jslinux/
- kyberias 10y ago
  Well, each and every PC emulator implemented in Javascript contains an x86 instruction emulator. For example: http://copy.sh/v86/ http://copy.sh/v86/ And many others...
- prashnts 10y ago
  Yep, v86 [0] is what you're looking for! There's even a demo with Linux 3. [1] [0] https://github.com/copy/v86 https://github.com/copy/v86 [1] https://copy.sh/v86/?profile=linux3 https://copy.sh/v86/?profile=linux3
netheril96 10y ago
So, how do you do 64-bit arithmetic in JavaScript? Emulate with two 32-bit number? Won't that be a huge performance bottleneck, one that cannot be optimized by JIT?
- sjrd 10y ago
  Yes, you emulate them with 32-bit numbers. It is a huge performance bottleneck if you do it naively, which most compile-to-JS languages that support 64-bit integers do. Emscripten even has a flag to let you choose between correct-but-slow 64-bit integers and fast-but-incorrect (drops to 53 bits). It is possible to get fast longs in JS, though, if you push your optimizer far enough. This is what we have done in Scala.js. I wrote a paper about this, but it is still under submission so I cannot disclose it just yet. However, I can point to the implementation: * The user-land implementation of `Long`s in Scala.js: https://github.com/scala-js/scala-js/blob/master/library/src/main/scala/scala/scalajs/runtime/RuntimeLong.scala https://github.com/scala-js/scala-js/blob/master/library/src... * The PR that made the performance breakthrough in the optimizer, by stack-allocating all instances of `RuntimeLong`: https://github.com/scala-js/scala-js/pull/2488 https://github.com/scala-js/scala-js/pull/2488
  - bogomipz 10y ago
    I just had to look this up, the limitation is that JS has a max int of 2^53? Do you know what the reasons were for JS not implementing full 2^64? Also I noticed theres a JS C-types that has 64 bit ints, would that not help here?
    - anewhnaccount 10y ago
      All numbers in Javascript are IEEE 754 64-bit double precision floating point numbers. The significand precision is 53 bits (see here https://en.wikipedia.org/wiki/Double-precision_floating-point_format https://en.wikipedia.org/wiki/Double-precision_floating-poin...).
      - bogomipz 10y ago
Yan_Coutinho 10y ago
Architeture doesn't have kernel memory protection? Seems risky...
- orbifold 10y ago
  There is a specification of privileged extensions, I think it was stabilised fairly recently: https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-spec-1.7.pdf https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-sp... The rocket chip generator https://github.com/ucb-bar/rocket-chip https://github.com/ucb-bar/rocket-chip and boom both have support for it, as far as I know.
bogomipz 10y ago
Tangentially related this is a great talk about RISC-V architecture: https://www.youtube.com/watch?v=vB0FC1DZqUM&feature=youtu.be https://www.youtube.com/watch?v=vB0FC1DZqUM&feature=youtu.be

98 points by mbroncano 10y ago

alpb 10y ago

This was discussed last month. https://news.ycombinator.com/item?id=13210711 https://news.ycombinator.com/item?id=13210711

bobajeff 10y ago
Except this is the JavaScript version.
- Narishma 10y ago
  Which was already available at that time, as you can see some commenters discussing it in that story.

bobajeff 10y ago

Wow, I'm running Linux on top of RISC-V in an emulator in my browser on my phone!

agumonkey 10y ago
Babel tower reemerges from the memories of Boole
- Senji 10y ago
  Our hubris will be our undoing.
hajile 10y ago
https://www.destroyallsoftware.com/talks/the-birth-and-death-of-javascript https://www.destroyallsoftware.com/talks/the-birth-and-death...

ramblenode 10y ago

~# date Thu Jan 1 00:03:09 UTC 1970

chris_wot 10y ago

Silly question, but is there an x86 instruction set emulator written in JavaScript? Not even Linux, just something that takes x86 instructions into a "virtual CPU" and lets you run the assembly statements?

kbeckmann 10y ago
Not a silly question at all. I would also like to know this. Would be a fun way to play around with assembly without the need of a tool chain etc. Maybe even on your phone while on the train. If this doesn't exist already, I'd be happy to start working on something like this.
- pmjordan 10y ago
  You could probably start from here: x86 Linux running in a web browser, also by Fabrice Bellard. http://bellard.org/jslinux/ http://bellard.org/jslinux/
kyberias 10y ago
Well, each and every PC emulator implemented in Javascript contains an x86 instruction emulator. For example: http://copy.sh/v86/ http://copy.sh/v86/ And many others...
prashnts 10y ago
Yep, v86 [0] is what you're looking for! There's even a demo with Linux 3. [1] [0] https://github.com/copy/v86 https://github.com/copy/v86 [1] https://copy.sh/v86/?profile=linux3 https://copy.sh/v86/?profile=linux3

netheril96 10y ago

So, how do you do 64-bit arithmetic in JavaScript? Emulate with two 32-bit number? Won't that be a huge performance bottleneck, one that cannot be optimized by JIT?

sjrd 10y ago
Yes, you emulate them with 32-bit numbers. It is a huge performance bottleneck if you do it naively, which most compile-to-JS languages that support 64-bit integers do. Emscripten even has a flag to let you choose between correct-but-slow 64-bit integers and fast-but-incorrect (drops to 53 bits). It is possible to get fast longs in JS, though, if you push your optimizer far enough. This is what we have done in Scala.js. I wrote a paper about this, but it is still under submission so I cannot disclose it just yet. However, I can point to the implementation: * The user-land implementation of `Long`s in Scala.js: https://github.com/scala-js/scala-js/blob/master/library/src/main/scala/scala/scalajs/runtime/RuntimeLong.scala https://github.com/scala-js/scala-js/blob/master/library/src... * The PR that made the performance breakthrough in the optimizer, by stack-allocating all instances of `RuntimeLong`: https://github.com/scala-js/scala-js/pull/2488 https://github.com/scala-js/scala-js/pull/2488
- bogomipz 10y ago
  I just had to look this up, the limitation is that JS has a max int of 2^53? Do you know what the reasons were for JS not implementing full 2^64? Also I noticed theres a JS C-types that has 64 bit ints, would that not help here?
  - anewhnaccount 10y ago
    All numbers in Javascript are IEEE 754 64-bit double precision floating point numbers. The significand precision is 53 bits (see here https://en.wikipedia.org/wiki/Double-precision_floating-point_format https://en.wikipedia.org/wiki/Double-precision_floating-poin...).
    - bogomipz 10y ago

Yan_Coutinho 10y ago

Architeture doesn't have kernel memory protection? Seems risky...

orbifold 10y ago
There is a specification of privileged extensions, I think it was stabilised fairly recently: https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-spec-1.7.pdf https://people.eecs.berkeley.edu/~krste/papers/riscv-priv-sp... The rocket chip generator https://github.com/ucb-bar/rocket-chip https://github.com/ucb-bar/rocket-chip and boom both have support for it, as far as I know.

bogomipz 10y ago

Tangentially related this is a great talk about RISC-V architecture: https://www.youtube.com/watch?v=vB0FC1DZqUM&feature=youtu.be https://www.youtube.com/watch?v=vB0FC1DZqUM&feature=youtu.be