Re: SYS_sbrk removal proposal

[Anders Magnusson <ragge%ludd.ltu.se@localhost>]

Den 2017-12-19 kl. 10:53, skrev Kamil Rytarowski:
> I propose to remove the sbrk(2) syscall "change data segment size".
>
> It has never been implemented by the NetBSD kernel since the inception
> of the project and it is emulated in libc with SYS_brk (break, obreak).
>
> This interface is a remnant from the old UNIX and has been marked
> obsolete since the the advent of mmap(2) memory management.
>
> I don't intend to remove the libc's sbrk(2) emulation.
Sounds good :-)

Just a note here:

about 15-20 years ago I did a test by removing the brk(2) syscall and 
replacing its use
in malloc() by mmap(), and also add a libc wrapper for brk() that 
mmap'ed MAXDSIZ/2 if ever called (as a fallback).

This approach worked very well for everything tested _except_ emacs.
There were something in emacs dump logic that seemed to expect that 
brk() were continuing just above bss, or something.
I didn't go deeper into this back then.

Anyway, it might be an idea to revisit this.  IMHO it would be really 
nice if brk(2) could be declared obsolete :-)

-- Ragge