Just play to implement syscall on various OS/ARCH

Supported platforms / build chain :

OS	Arch	nasm/ld	nasm/llvm	llvm/ld	llvm/llvm	Notes
Darwin	x86-64	Yes	No	Yes	No	No llvm-lld support
Linux	x86-64	Yes	Yes	Yes	Yes

C declaration calling convention is used.

Assumption

• syscall convention : All amd64 architectures use the same syscall convention

Some literature

• Architecture
  • https://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-vol-2b-manual.html
  • https://software.intel.com/sites/default/files/article/402129/mpx-linux64-abi.pdf
  • http://courses.cs.washington.edu/courses/cse378/10au/sections/Section1_recap.pdf
• System calls
  • http://www.int80h.org/
  • https://www.freebsd.org/doc/en/books/developers-handbook/x86-system-calls.html
  • https://filippo.io/making-system-calls-from-assembly-in-mac-os-x/
• Assembly
  • http://www.nasm.us/
  • https://en.wikibooks.org/wiki/X86_Assembly
  • https://cs.brown.edu/courses/cs033/docs/guides/x64_cheatsheet.pdf
• MacOS
  • https://opensource.apple.com/source/xnu/xnu-1504.3.12/bsd/kern/syscalls.master