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The World of Linux System Calls

137 points by nkurz 12y ago

Rapzid 12y ago
For anyone craving more on syscalls, I can't recommend "The Linux Programming Interface" enough.
- rubiquity 12y ago
  Ditto. I love this book. It's full of all sorts of wonderful knowledge about how Linux works. It has also served as a great way to prop my monitor up higher from time to time! Here's a link: http://man7.org/tlpi/ http://man7.org/tlpi/
justincormack 12y ago
If you want to explore system calls without C or assembler, I wrote a LuaJIT library [1]. You could port it to another language too. [1] https://github.com/justincormack/ljsyscall https://github.com/justincormack/ljsyscall
- walterbell 12y ago
  Is this comparable to Erlang on Xen and OpenMirage (ocaml)? Are there any examples of network-facing services which use this library to execute on a minimal Linux kernel+userspace? What do you think of supporting MiniOS in the future?
  - justincormack 12y ago
    It runs on Xen via the rump kernel http://rumpkernel.org http://rumpkernel.org. it should run on OSv too but will need some work as that uses the glibc ABI not the kernel ABI which differ slightly.
    - fit2rule 12y ago
      Wow, thank you for this work - I'm very interested in using LuaJIT and kernel services in this way, so I will spend some research hours this week reading it and running it .. and using it for things. I guess I'll PM you with a report from the field at some point ..
      - justincormack 12y ago
        Get in touch if you need help or to let me know what you get up to with it - email is in profile, or via github...
deleted 12y ago
[deleted]
frou_dh 12y ago
Learning the general idea of system calls was a revelation to me since it implied that, in a sense, every language was ultimately a scripting language for the kernel.
JoeAltmaier 12y ago
I wrote Linux kernel code years ago. I was struck with how similar the APIs were for compiled-in drivers, loadable drivers and applications. They were almost identical, with small variations in spelling and parameters. It seemed to me that, with only a little more effort, they could have been nearly identical. That would have greatly helped make code portable and reusable e.g. write a library that could be used by apps and drivers both.
- fit2rule 12y ago
  IMHO, portable code is the reason for the different nomenclature. There is also something to be said for the cognizant development of those API's in such a manner .. new words control ownership.
greenleafjacob 12y ago
Nitpick: > For example, x86 processors usually call interrupt 80, while x64 processors use the syscall processor instruction. It's 0x80, or 128 in decimal.
- chjj 12y ago
  Further Nitpick: Nowdays they don't use INT 0x80 for syscalls anymore. It's faster to use something called "virtual system calls" from what I understand (I am not a kernel dev, so don't quote me). It's just what it sounds like. If you ldd a linux binary, you'll see a shared object called `linux-gate.so` or `linux-vdso.so` (it's been renamed a few times). This file doesn't actually exist. It's an imaginary library that exists as the doorway into the kernel for making these calls. I tried to dig up something I read on this. This is what I found if anyone is interested: http://www.trilithium.com/johan/2005/08/linux-gate/ http://www.trilithium.com/johan/2005/08/linux-gate/

137 points by nkurz 12y ago

Rapzid 12y ago

For anyone craving more on syscalls, I can't recommend "The Linux Programming Interface" enough.

rubiquity 12y ago
Ditto. I love this book. It's full of all sorts of wonderful knowledge about how Linux works. It has also served as a great way to prop my monitor up higher from time to time! Here's a link: http://man7.org/tlpi/ http://man7.org/tlpi/

justincormack 12y ago

If you want to explore system calls without C or assembler, I wrote a LuaJIT library [1]. You could port it to another language too. [1] https://github.com/justincormack/ljsyscall https://github.com/justincormack/ljsyscall

walterbell 12y ago
Is this comparable to Erlang on Xen and OpenMirage (ocaml)? Are there any examples of network-facing services which use this library to execute on a minimal Linux kernel+userspace? What do you think of supporting MiniOS in the future?
- justincormack 12y ago
  It runs on Xen via the rump kernel http://rumpkernel.org http://rumpkernel.org. it should run on OSv too but will need some work as that uses the glibc ABI not the kernel ABI which differ slightly.
  - fit2rule 12y ago
    Wow, thank you for this work - I'm very interested in using LuaJIT and kernel services in this way, so I will spend some research hours this week reading it and running it .. and using it for things. I guess I'll PM you with a report from the field at some point ..
    - justincormack 12y ago
      Get in touch if you need help or to let me know what you get up to with it - email is in profile, or via github...

deleted 12y ago

[deleted]

frou_dh 12y ago

Learning the general idea of system calls was a revelation to me since it implied that, in a sense, every language was ultimately a scripting language for the kernel.

JoeAltmaier 12y ago

I wrote Linux kernel code years ago. I was struck with how similar the APIs were for compiled-in drivers, loadable drivers and applications. They were almost identical, with small variations in spelling and parameters. It seemed to me that, with only a little more effort, they could have been nearly identical. That would have greatly helped make code portable and reusable e.g. write a library that could be used by apps and drivers both.

fit2rule 12y ago
IMHO, portable code is the reason for the different nomenclature. There is also something to be said for the cognizant development of those API's in such a manner .. new words control ownership.

greenleafjacob 12y ago

Nitpick: > For example, x86 processors usually call interrupt 80, while x64 processors use the syscall processor instruction. It's 0x80, or 128 in decimal.

chjj 12y ago
Further Nitpick: Nowdays they don't use INT 0x80 for syscalls anymore. It's faster to use something called "virtual system calls" from what I understand (I am not a kernel dev, so don't quote me). It's just what it sounds like. If you ldd a linux binary, you'll see a shared object called `linux-gate.so` or `linux-vdso.so` (it's been renamed a few times). This file doesn't actually exist. It's an imaginary library that exists as the doorway into the kernel for making these calls. I tried to dig up something I read on this. This is what I found if anyone is interested: http://www.trilithium.com/johan/2005/08/linux-gate/ http://www.trilithium.com/johan/2005/08/linux-gate/