Re: remove the last set_fs() in common code, and remove it for x86 and powerpc v3

[Christophe Leroy]

Le 04/09/2020 à 23:01, David Laight a écrit :
> From: Alexey Dobriyan
> > Sent: 04 September 2020 18:58
> >
> > On Fri, Sep 04, 2020 at 08:00:24AM +0200, Ingo Molnar wrote:
> > > * Christoph Hellwig <hch@xxxxxx> wrote:
> > > > this series removes the last set_fs() used to force a kernel address
> > > > space for the uaccess code in the kernel read/write/splice code, and then
> > > > stops implementing the address space overrides entirely for x86 and
> > > > powerpc.
> > >
> > > Cool! For the x86 bits:
> > >
> > >    Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
> >
> > 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
> > 	./include/asm/segment.h:61:extern inline void set_fs(unsigned long val)
> > 	./include/asm/segment.h-62-{
> > 	./include/asm/segment.h-63-     __asm__("mov %0,%%fs"::"a" ((unsigned short) val));
> > 	./include/asm/segment.h-64-}
>
> What is this strange %fs register you are talking about.
> Figure 2-4 only has CS, DS, SS and ES.

Intel added registers FS and GS in the i386

Christophe