Re: [PATCH v2 05/12] arm64: Basic Branch Target Identification support

From: Dave Martin <Dave.Martin@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: "Paul Elliott" <paul.elliott@arm.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Will Deacon" <will.deacon@arm.com>,
	"Andrew Jones" <drjones@redhat.com>,
	"Amit Kachhap" <amit.kachhap@arm.com>,
	"Vincenzo Frascino" <vincenzo.frascino@arm.com>,
	linux-arch@vger.kernel.org,
	"Eugene Syromiatnikov" <esyr@redhat.com>,
	"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
	"H.J. Lu" <hjl.tools@gmail.com>,
	"Yu-cheng Yu" <yu-cheng.yu@intel.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Arnd Bergmann" <arnd@arndb.de>, "Jann Horn" <jannh@google.com>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	"Kristina Martšenko" <kristina.martsenko@arm.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	linux-arm-kernel@lists.infradead.org,
	"Florian Weimer" <fweimer@redhat.com>,
	linux-kernel@vger.kernel.org, "Sudakshina Das" <sudi.das@arm.com>
Subject: Re: [PATCH v2 05/12] arm64: Basic Branch Target Identification support
Date: Fri, 18 Oct 2019 14:37:40 +0100	[thread overview]
Message-ID: <20191018133739.GD27757@arm.com> (raw)
In-Reply-To: <20191018111003.GC27759@lakrids.cambridge.arm.com>

On Fri, Oct 18, 2019 at 12:10:03PM +0100, Mark Rutland wrote:
> On Fri, Oct 11, 2019 at 06:20:15PM +0100, Dave Martin wrote:
> > On Fri, Oct 11, 2019 at 04:10:29PM +0100, Mark Rutland wrote:
> > > On Thu, Oct 10, 2019 at 07:44:33PM +0100, Dave Martin wrote:
> > > > +#define arch_calc_vm_prot_bits(prot, pkey) arm64_calc_vm_prot_bits(prot)
> > > > +static inline unsigned long arm64_calc_vm_prot_bits(unsigned long prot)
> > > > +{
> > > > +	if (system_supports_bti() && (prot & PROT_BTI))
> > > > +		return VM_ARM64_BTI;
> > > > +
> > > > +	return 0;
> > > > +}
> > > 
> > > Can we call this arch_calc_vm_prot_bits() directly, with all the
> > > arguments:
> > > 
> > > static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
> > > 						   unsigned long pkey)
> > > {
> > > 	...
> > > }
> > > #define arch_calc_vm_prot_bits arch_calc_vm_prot_bits
> > > 
> > > ... as that makes it a bit easier to match definition with use, and just
> > > definign the name makes it a bit clearer that that's probably for the
> > > benefit of some ifdeffery.
> > > 
> > > Likewise for the other functions here.
> > > 
> > > > +#define arch_vm_get_page_prot(vm_flags) arm64_vm_get_page_prot(vm_flags)
> > > > +static inline pgprot_t arm64_vm_get_page_prot(unsigned long vm_flags)
> > > > +{
> > > > +	return (vm_flags & VM_ARM64_BTI) ? __pgprot(PTE_GP) : __pgprot(0);
> > > > +}
> > > > +
> > > > +#define arch_validate_prot(prot, addr) arm64_validate_prot(prot, addr)
> > > > +static inline int arm64_validate_prot(unsigned long prot, unsigned long addr)
> > 
> > Can do, though it looks like a used sparc as a template, and that has a
> > sparc_ prefix.
> > 
> > powerpc uses the generic name, as does x86 ... in its UAPI headers.
> > Odd.
> > 
> > I can change the names here, though I'm not sure it adds a lot of value.
> > 
> > If you feel strongly I can do it.
> 
> I'd really prefer it because it minimizes surprises, and makes it much
> easier to hop around the codebase and find the thing you're looking for.

OK, I've no objection in that case.  I'll make the change.

[...]

Cheers
---Dave