Self hosting kernel

Last time I talked to Jeremiah Orians about it, the stage0-posix project required only the following system calls of a POSIX kernel, up to M2-Planet+mescc-tools:

• execve(), fork(), waitpid(), exit()
• brk()
• open(), close(), read(), write()
• lseek()
• chmod()

execve(), fork(), waitpid(), and exit() are used in a stereotyped manner for spawning a child process running a new program, then waiting for it to exit(); and chmod() is only used to make a file executable.

He said mescc-tools-extra+Kaem also needs:

• fchmod()
• access()
• chdir(), fchdir()
• mkdir() (in particular for extracting tarballs)
• mknod()
• getcwd() (traditionally a library function implemented with stat())
• umask()
• uname() (to find out what the architecture is)

Mes proper and probably tcc also needs:

• unlink()
• ioctl() (specifically isatty(), to find out whether a shell is interactive)
• stat()
• fsync(), though of course this can be a no-op

In particular it doesn’t require pipes or I/O redirection.