Re: [PATCH] mm/mincore: allow for making sys_mincore() privileged

[Matthew Wilcox]

On Sat, Jan 05, 2019 at 03:39:10PM -0800, Linus Torvalds wrote:
> On Sat, Jan 5, 2019 at 3:16 PM Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > It goes back to forever, it looks like. I can't find a reason.
> 
> mincore() was originally added in 2.3.52pre3, it looks like. Around
> 2000 or so. But sadly before the BK history.
> 
> And that comment about
> 
>   "Later we can get more picky about what "in core" means precisely."
> 
> that still exists above mincore_page() goes back to the original patch.

FreeBSD claims to have a manpage from SunOS 4.1.3 with mincore (!)

https://www.freebsd.org/cgi/man.cgi?query=mincore&apropos=0&sektion=0&manpath=SunOS+4.1.3&arch=default&format=html

DESCRIPTION
       mincore()  returns  the primary memory residency	status of pages	in the
       address space covered by	mappings in the	range [addr, addr + len).  The
       status is returned as a char-per-page in	the character array referenced
       by *vec (which the system assumes to be large enough to	encompass  all
       the  pages  in  the  address range).  The least significant bit of each
       character is set	to 1 to	indicate that the referenced page is  in  pri-
       mary  memory, 0 if it is	not.  The settings of other bits in each char-
       acter is	undefined and may contain other	information in the future.