5 ms·

Using TinyCC to compile Linux (2.4) kernels

103 points by jesprenj 4y ago

bumblebritches5 4y ago
mobilio 4y ago
Original: https://bellard.org/tcc/tccboot.html https://bellard.org/tcc/tccboot.html
lionkor 4y ago
Why is it so fast? 8 seconds seems awfully low for the linux kernel.
- matthews2 4y ago
  The version being built (2.4) is over twenty years old and had much less code. If you take a modern kernel (like 5.x) and build configure it with 'make tinyconfig', it should build similarly quickly.
  - MuffinFlavored 4y ago
    Can TinyCC still compile the 5.x kernel without issues?
    - rurban 4y ago
      No, this is being worked in. The goal should be a -Oboring optimizer without any broken optimizations and aggressive UB assumptions. Something neither gcc nor clang can provide.
    - wrycoder 4y ago
      See bootstrapping.org
      - chexum 4y ago
        http://bootstrappable.org http://bootstrappable.org perhaps?
        wrycoder 4y ago
        oops. Thanks! https://bootstrappable.org/ https://bootstrappable.org/ https://bootstrapping.miraheze.org/wiki/Mes https://bootstrapping.miraheze.org/wiki/Mes https://reproducible-builds.org/ https://reproducible-builds.org/ https://archive.fosdem.org/2021/schedule/event/gnumes/ https://archive.fosdem.org/2021/schedule/event/gnumes/
    - sylware 4y ago
      you cannot, as linux code is using a lot of gcc/clang extensions stuff, namely this is some sort of C dialect, not really C. Almost at every new release of linux, "somebody" did manage to commit into its code the usage of new gcc/clang extensions. The right(TM) way would be to port linux to simple and lean C (like some simple C89 with benign bits of c99/c11): the price is some loss of performance which could be partially mitigated with an assembly port of critical fast-paths (I guess that would show on really loaded servers only). In the end, if RISC-V is a success, namely a world with a pertinent ISA without toxic IP tied to it (like x86/arm), then a full assembly port of linux would be more than interesting in order to rid it from compiler tantrums.
      - MuffinFlavored 4y ago
        > you cannot, as linux code is using a lot of gcc/clang extensions stuff Linux 5.x kernel that is, but not Linux 4.x kernel because that was tcc-compilable?
  - pacetherace 4y ago
    Thanks for making me feel old
- hawski 4y ago
  It is a single pass compiler, that doesn't do many optimizations. Fun factoid: TCC is sort of predecessor to QEMU.
  - phyrex 4y ago
    They’re both from the same guy
    - masklinn 4y ago
      Yes, but beyond that qemu was pretty much fabrice nerdsniping himself: he initially wanted to make the tcc backend more flexible (to support other targets than x86), then started playing with making the frontend more flexible, at one point he started to make the frontend take in compiled machine code, and that's the starting point of qemu: a dynamic recompiler / machine code translator, rather than a traditional emulator.
john-tells-all 4y ago
should be flagged [2016]
- jesprenj 4y ago
  You're right, sorry, I'm not yet used to the HN netiquette. I did specify the kernel version in the title, because the program really can't compile newer kernels. It seems I can't fix the title now. Please flag the OP, after all it would be better to link to the original bellard's site instead of this github repository.
londons_explore 4y ago
You could take this one step further and have some magic filesystem filter such that all binaries are compiled before use. Ie. your hard disk would contain no executable code, only source code. It sounds slow, but it needn't be if you have the right caching in place. Binaries could even be recompiled with better/slower compilers as needed to give better performance too. Now I think about it it isn't so different from the android/java model of shipping applications as bytecode...
- wongarsu 4y ago
  I guess that's the logical extreme of what Gentoo is doing, just without the speed benefits (since the compiler is under time pressure and thus won't do a great job). Maybe if you combine it with profile guided optimization? (Yes, this is basically reinventing Java/.NET)
- jesprenj 4y ago
  tcc has a -run option argument which executes the binary after creating it as a temporary file. This way tcc -run can be specified in the shebang and you can execute c code like a script, which is outright amazing.
- goldsteinq 4y ago
  TempleOS does this

103 points by jesprenj 4y ago

bumblebritches5 4y ago

mobilio 4y ago

Original: https://bellard.org/tcc/tccboot.html https://bellard.org/tcc/tccboot.html

lionkor 4y ago

Why is it so fast? 8 seconds seems awfully low for the linux kernel.

matthews2 4y ago
The version being built (2.4) is over twenty years old and had much less code. If you take a modern kernel (like 5.x) and build configure it with 'make tinyconfig', it should build similarly quickly.
- MuffinFlavored 4y ago
  Can TinyCC still compile the 5.x kernel without issues?
  - rurban 4y ago
    No, this is being worked in. The goal should be a -Oboring optimizer without any broken optimizations and aggressive UB assumptions. Something neither gcc nor clang can provide.
  - wrycoder 4y ago
    See bootstrapping.org
    - chexum 4y ago
      http://bootstrappable.org http://bootstrappable.org perhaps?
      - wrycoder 4y ago
        oops. Thanks! https://bootstrappable.org/ https://bootstrappable.org/ https://bootstrapping.miraheze.org/wiki/Mes https://bootstrapping.miraheze.org/wiki/Mes https://reproducible-builds.org/ https://reproducible-builds.org/ https://archive.fosdem.org/2021/schedule/event/gnumes/ https://archive.fosdem.org/2021/schedule/event/gnumes/
  - sylware 4y ago
    you cannot, as linux code is using a lot of gcc/clang extensions stuff, namely this is some sort of C dialect, not really C. Almost at every new release of linux, "somebody" did manage to commit into its code the usage of new gcc/clang extensions. The right(TM) way would be to port linux to simple and lean C (like some simple C89 with benign bits of c99/c11): the price is some loss of performance which could be partially mitigated with an assembly port of critical fast-paths (I guess that would show on really loaded servers only). In the end, if RISC-V is a success, namely a world with a pertinent ISA without toxic IP tied to it (like x86/arm), then a full assembly port of linux would be more than interesting in order to rid it from compiler tantrums.
    - MuffinFlavored 4y ago
      > you cannot, as linux code is using a lot of gcc/clang extensions stuff Linux 5.x kernel that is, but not Linux 4.x kernel because that was tcc-compilable?
- pacetherace 4y ago
  Thanks for making me feel old
hawski 4y ago
It is a single pass compiler, that doesn't do many optimizations. Fun factoid: TCC is sort of predecessor to QEMU.
- phyrex 4y ago
  They’re both from the same guy
  - masklinn 4y ago
    Yes, but beyond that qemu was pretty much fabrice nerdsniping himself: he initially wanted to make the tcc backend more flexible (to support other targets than x86), then started playing with making the frontend more flexible, at one point he started to make the frontend take in compiled machine code, and that's the starting point of qemu: a dynamic recompiler / machine code translator, rather than a traditional emulator.

john-tells-all 4y ago

should be flagged [2016]

jesprenj 4y ago
You're right, sorry, I'm not yet used to the HN netiquette. I did specify the kernel version in the title, because the program really can't compile newer kernels. It seems I can't fix the title now. Please flag the OP, after all it would be better to link to the original bellard's site instead of this github repository.

londons_explore 4y ago

You could take this one step further and have some magic filesystem filter such that all binaries are compiled before use. Ie. your hard disk would contain no executable code, only source code. It sounds slow, but it needn't be if you have the right caching in place. Binaries could even be recompiled with better/slower compilers as needed to give better performance too. Now I think about it it isn't so different from the android/java model of shipping applications as bytecode...

wongarsu 4y ago
I guess that's the logical extreme of what Gentoo is doing, just without the speed benefits (since the compiler is under time pressure and thus won't do a great job). Maybe if you combine it with profile guided optimization? (Yes, this is basically reinventing Java/.NET)
jesprenj 4y ago
tcc has a -run option argument which executes the binary after creating it as a temporary file. This way tcc -run can be specified in the shebang and you can execute c code like a script, which is outright amazing.
goldsteinq 4y ago
TempleOS does this