Re: [PATCH v4 1/2] powerpc/uaccess: Implement unsafe_put_user() using 'asm goto'

Segher Boessenkool
2020-05-06T22:18:36Z

On Wed, May 06, 2020 at 08:10:57PM +0200, Christophe Leroy wrote:
> Le 06/05/2020 à 19:58, Segher Boessenkool a écrit :
> >> #define __put_user_asm_goto(x, addr, label, op) \
> >> asm volatile goto( \
> >>- "1: " op "%U1%X1 %0,%1 # put_user\n" \
> >>+ "1: " op "%X1 %0,%1 # put_user\n" \
> >> EX_TABLE(1b, %l2) \
> >> : \
> >>- : "r" (x), "m<>" (*addr) \
> >>+ : "r" (x), "m" (*addr) \
> >> : \
> >> : label)
> >
> >Like that. But you will have to do that to *all* places we use the "<>"
> >constraints, or wait for more stuff to fail? And, there probably are
> >places we *do* want update form insns used (they do help in some loops,
> >for example)?
> >
>
> AFAICT, git grep "m<>" provides no result.

Ah, okay.

> However many places have %Ux:

<snip>

Yes, all of those are from when "m" still meant what "m<>" is now. For
seeing how many update form insns can be generated (and how much that
matters), these all should be fixed, at a minimum.

Segher