On Fri, Sep 4, 2020 at 10:58 AM Alexey Dobriyan <adobriyan@xxxxxxxxx> wrote:
>
> set_fs() is older than some kernel hackers!
>
> $ cd linux-0.11/
> $ find . -type f -name '*.h' | xargs grep -e set_fs -w -n -A3
Oh, it's older than that. It was there (as set_fs) in 0.10, and may
even predate that. But sadly, I don't have tar-balls for 0.02 and
0.03, so can't check.
The actual use of %fs as the user space segment is already there in
0.01, but there was no 'set_fs()'. That was a simpler and more direct
time, and "get_fs()" looked like this back then:
#define _fs() ({ \
register unsigned short __res; \
__asm__("mov %%fs,%%ax":"=a" (__res):); \
__res;})
and all the setting was basically part of the kernel entry asm and. Lovely.
Linus
