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Subject: Re: [PATCH 2/5] powerpc/futex: GUAP support for futex ops
From: Russell Currey <ruscur@russell.cc>
To: LEROY Christophe <christophe.leroy@c-s.fr>
Date: Mon, 29 Oct 2018 12:08:01 +1100
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On Fri, 2018-10-26 at 18:32 +0200, LEROY Christophe wrote:
> Russell Currey <ruscur@russell.cc> a écrit :
> 
> > Wrap the futex operations in GUAP locks and unlocks.
> 
> Does it means futex doesn't work anymore once only patch 1 is
> applied  
> ? If so, then you should split patch 1 in two parts and reorder  
> patches so that guap can only be activated once all necessary
> changes  
> are done. Otherwise the serie won't be bisectable

Yeah, I agree.  I just wanted to remove some amount of breadth from
what already is one gigantic patch.  Bisectability is more important
than that, however.

- Russell

> 
> Christophe
> 
> > Signed-off-by: Russell Currey <ruscur@russell.cc>
> > ---
> >  arch/powerpc/include/asm/futex.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/arch/powerpc/include/asm/futex.h  
> > b/arch/powerpc/include/asm/futex.h
> > index 94542776a62d..3aed640ee9ef 100644
> > --- a/arch/powerpc/include/asm/futex.h
> > +++ b/arch/powerpc/include/asm/futex.h
> > @@ -35,6 +35,7 @@ static inline int
> > arch_futex_atomic_op_inuser(int  
> > op, int oparg, int *oval,
> >  {
> >  	int oldval = 0, ret;
> > 
> > +	unlock_user_access();
> >  	pagefault_disable();
> > 
> >  	switch (op) {
> > @@ -62,6 +63,7 @@ static inline int
> > arch_futex_atomic_op_inuser(int  
> > op, int oparg, int *oval,
> >  	if (!ret)
> >  		*oval = oldval;
> > 
> > +	lock_user_access();
> >  	return ret;
> >  }
> > 
> > @@ -75,6 +77,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32
> > __user *uaddr,
> >  	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
> >  		return -EFAULT;
> > 
> > +	unlock_user_access();
> >          __asm__ __volatile__ (
> >          PPC_ATOMIC_ENTRY_BARRIER
> >  "1:     lwarx   %1,0,%3         # futex_atomic_cmpxchg_inatomic\n\
> > @@ -95,6 +98,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32
> > __user *uaddr,
> >          : "cc", "memory");
> > 
> >  	*uval = prev;
> > +	lock_user_access();
> >          return ret;
> >  }
> > 
> > --
> > 2.19.1
> 
>