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Re: [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat)

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  Re: [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread  (for AArch32 compat) Catalin Marinas <catalin.marinas@arm.com> - 2015-12-03 13:20 +0100
    Re: [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread  (for AArch32 compat) Yury Norov <ynorov@caviumnetworks.com> - 2015-12-04 18:10 +0100
      Re: [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread  (for AArch32 compat) Catalin Marinas <catalin.marinas@arm.com> - 2015-12-05 12:10 +0100

#1282987 — Re: [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread (for AArch32 compat)

On Wed, Nov 18, 2015 at 12:16:47AM +0300, Yury Norov wrote:
> diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
> index 7fbed69..9700e5e 100644
> --- a/arch/arm64/include/asm/compat.h
> +++ b/arch/arm64/include/asm/compat.h
> @@ -299,19 +299,44 @@ struct compat_shmid64_ds {
>  	compat_ulong_t __unused5;
>  };
>  
> -static inline int is_compat_task(void)
> +#ifdef CONFIG_AARCH32_EL0
> +
> +static inline int is_a32_compat_task(void)
>  {
>  	return test_thread_flag(TIF_32BIT);
>  }
>  
> -static inline int is_compat_thread(struct thread_info *thread)
> +static inline int is_a32_compat_thread(struct thread_info *thread)
>  {
>  	return test_ti_thread_flag(thread, TIF_32BIT);
>  }
>  
> +#else
> +
> +static inline int is_a32_compat_task(void)
> +{
> +	return 0;
> +}
> +
> +static inline int is_a32_compat_thread(struct thread_info *thread)
> +{
> +	return 0;
> +}
> +#endif
> +
> +static inline int is_compat_task(void)
> +{
> +	return is_a32_compat_task();
> +}
> +
>  #else /* !CONFIG_COMPAT */
>  
> -static inline int is_compat_thread(struct thread_info *thread)
> +static inline int is_a32_compat_thread(struct thread_info *thread)
> +{
> +	return 0;
> +}
> +
> +static inline int is_a32_compat_task(void)
>  {
>  	return 0;
>  }

My main worry with this patch is a potential #include mess. I can see
that you already had to include asm/compat.h explicitly in
hw_breakpoint.c even though linux/compat.h was already included. In
subsequent files (asm/elf.h, asm/memory.h) you check is_compat_task()
without explicitly including asm/compat.h and hope that it won't break.

A solution would be to add these functions in a separate header file
that gets included where needed (also by asm/compat.h).

-- 
Catalin
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#1284050

On Thu, Dec 03, 2015 at 12:13:03PM +0000, Catalin Marinas wrote:
> On Wed, Nov 18, 2015 at 12:16:47AM +0300, Yury Norov wrote:
> > diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
> > index 7fbed69..9700e5e 100644
> > --- a/arch/arm64/include/asm/compat.h
> > +++ b/arch/arm64/include/asm/compat.h
> > @@ -299,19 +299,44 @@ struct compat_shmid64_ds {
> >  	compat_ulong_t __unused5;
> >  };
> >  
> > -static inline int is_compat_task(void)
> > +#ifdef CONFIG_AARCH32_EL0
> > +
> > +static inline int is_a32_compat_task(void)
> >  {
> >  	return test_thread_flag(TIF_32BIT);
> >  }
> >  
> > -static inline int is_compat_thread(struct thread_info *thread)
> > +static inline int is_a32_compat_thread(struct thread_info *thread)
> >  {
> >  	return test_ti_thread_flag(thread, TIF_32BIT);
> >  }
> >  
> > +#else
> > +
> > +static inline int is_a32_compat_task(void)
> > +{
> > +	return 0;
> > +}
> > +
> > +static inline int is_a32_compat_thread(struct thread_info *thread)
> > +{
> > +	return 0;
> > +}
> > +#endif
> > +
> > +static inline int is_compat_task(void)
> > +{
> > +	return is_a32_compat_task();
> > +}
> > +
> >  #else /* !CONFIG_COMPAT */
> >  
> > -static inline int is_compat_thread(struct thread_info *thread)
> > +static inline int is_a32_compat_thread(struct thread_info *thread)
> > +{
> > +	return 0;
> > +}
> > +
> > +static inline int is_a32_compat_task(void)
> >  {
> >  	return 0;
> >  }
> 
> My main worry with this patch is a potential #include mess. I can see
> that you already had to include asm/compat.h explicitly in
> hw_breakpoint.c even though linux/compat.h was already included. In
> subsequent files (asm/elf.h, asm/memory.h) you check is_compat_task()
> without explicitly including asm/compat.h and hope that it won't break.
> 
> A solution would be to add these functions in a separate header file
> that gets included where needed (also by asm/compat.h).

Thank you for pointing that. I don't see big advantage in moving that
to new file, only if you insist. What about just fixing that mess?

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#1284529

On Fri, Dec 04, 2015 at 08:05:23PM +0300, Yury Norov wrote:
> On Thu, Dec 03, 2015 at 12:13:03PM +0000, Catalin Marinas wrote:
> > On Wed, Nov 18, 2015 at 12:16:47AM +0300, Yury Norov wrote:
> > > diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
> > > index 7fbed69..9700e5e 100644
> > > --- a/arch/arm64/include/asm/compat.h
> > > +++ b/arch/arm64/include/asm/compat.h
> > > @@ -299,19 +299,44 @@ struct compat_shmid64_ds {
> > >  	compat_ulong_t __unused5;
> > >  };
> > >  
> > > -static inline int is_compat_task(void)
> > > +#ifdef CONFIG_AARCH32_EL0
> > > +
> > > +static inline int is_a32_compat_task(void)
> > >  {
> > >  	return test_thread_flag(TIF_32BIT);
> > >  }
> > >  
> > > -static inline int is_compat_thread(struct thread_info *thread)
> > > +static inline int is_a32_compat_thread(struct thread_info *thread)
> > >  {
> > >  	return test_ti_thread_flag(thread, TIF_32BIT);
> > >  }
> > >  
> > > +#else
> > > +
> > > +static inline int is_a32_compat_task(void)
> > > +{
> > > +	return 0;
> > > +}
> > > +
> > > +static inline int is_a32_compat_thread(struct thread_info *thread)
> > > +{
> > > +	return 0;
> > > +}
> > > +#endif
> > > +
> > > +static inline int is_compat_task(void)
> > > +{
> > > +	return is_a32_compat_task();
> > > +}
> > > +
> > >  #else /* !CONFIG_COMPAT */
> > >  
> > > -static inline int is_compat_thread(struct thread_info *thread)
> > > +static inline int is_a32_compat_thread(struct thread_info *thread)
> > > +{
> > > +	return 0;
> > > +}
> > > +
> > > +static inline int is_a32_compat_task(void)
> > >  {
> > >  	return 0;
> > >  }
> > 
> > My main worry with this patch is a potential #include mess. I can see
> > that you already had to include asm/compat.h explicitly in
> > hw_breakpoint.c even though linux/compat.h was already included. In
> > subsequent files (asm/elf.h, asm/memory.h) you check is_compat_task()
> > without explicitly including asm/compat.h and hope that it won't break.
> > 
> > A solution would be to add these functions in a separate header file
> > that gets included where needed (also by asm/compat.h).
> 
> Thank you for pointing that. I don't see big advantage in moving that
> to new file, only if you insist. What about just fixing that mess?

As I said above, you use is_compat_task() in asm/elf.h for example
without including asm/compat.h. At some point, you may get a build error
in some unrelated C file. You could wait until it happens and then sort
it out (by either including asm/compat.h in asm/elf.h or creating a new
header file). My preference is to prevent such build errors early.

-- 
Catalin
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