Date: Sat, 5 Dec 2015 11:00:27 +0000
From: Catalin Marinas <catalin.marinas@arm.com>
To: Yury Norov <ynorov@caviumnetworks.com>
Cc: arnd@arndb.de, pinskia@gmail.com, Prasun.Kapoor@caviumnetworks.com,
        schwab@suse.de, Nathan_Lynch@mentor.com, linux-kernel@vger.kernel.org,
        agraf@suse.de, klimov.linux@gmail.com, broonie@kernel.org,
        jan.dakinevich@gmail.com, joseph@codesourcery.com,
        ddaney.cavm@gmail.com, bamvor.zhangjian@huawei.com,
        philipp.tomsich@theobroma-systems.com, andrey.konovalov@linaro.org,
        linux-arm-kernel@lists.infradead.org,
        christoph.muellner@theobroma-systems.com
Subject: Re: [PATCH v6 07/19] arm64: introduce is_a32_task and is_a32_thread
 (for AArch32 compat)
Message-ID: <20151205110025.GA1978@MBP.local>
References: <1447795019-30176-1-git-send-email-ynorov@caviumnetworks.com>
 <1447795019-30176-8-git-send-email-ynorov@caviumnetworks.com>
 <20151203121303.GK10747@e104818-lin.cambridge.arm.com>
 <20151204170523.GA2791@yury-N73SV>
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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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