From: Will Deacon <will@kernel.org>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] arm64: bti: Fix support for userspace only BTI
Date: Tue, 12 May 2020 12:42:44 +0100 [thread overview]
Message-ID: <20200512114243.GC3021@willie-the-truck> (raw)
In-Reply-To: <20200512110502.GC5110@sirena.org.uk>
On Tue, May 12, 2020 at 12:05:02PM +0100, Mark Brown wrote:
> On Tue, May 12, 2020 at 11:39:09AM +0100, Will Deacon wrote:
>
> > Might be worth a comment here in case somebody tries to "clean this up"
> > later on!
>
> > > +#ifdef CONFIG_ARM64_BTI_KERNEL
> > > #define PTE_MAYBE_GP (system_supports_bti() ? PTE_GP : 0)
> > > +#else
> > > +#define PTE_MAYBE_GP 0
> > > +#endif
>
> Sure.
>
> > I also notice we have a funny check in the vdso code:
>
> > if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti())
>
> > but why do we care about CONFIG_ARM64_BTI_KERNEL for the vdso pages?
>
> To enable BTI for the vDSO we need the vDSO to be built with BTI
> annotations. Currently the CFLAGS are the same for the vDSO and the
> kernel, we could arrange to allow them to differ but since the most
> likely reason why the user has userspace but not kernel BTI is that
> their compiler isn't suitable it seemed like disproportionate effort
> for a most likely small audience.
I was thinking of using CC_HAS_BRANCH_PROT_PAC_RET_BTI instead, but I'd
forgotten about that GCC bug. Oh well.
Will
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next prev parent reply other threads:[~2020-05-12 11:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-12 9:21 [PATCH] arm64: bti: Fix support for userspace only BTI Mark Brown
2020-05-12 10:39 ` Will Deacon
2020-05-12 11:05 ` Mark Brown
2020-05-12 11:42 ` Will Deacon [this message]
2020-05-13 14:46 ` Dave Martin
2020-05-13 15:08 ` Mark Brown
2020-05-13 16:49 ` Dave Martin
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