From: Will Deacon <will@kernel.org>
To: Amit Kachhap <amit.kachhap@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Bhupesh Sharma <bhsharma@redhat.com>,
kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
James Morse <james.morse@arm.com>,
Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/2] arm64/crash_core: Export KERNELPACMASK in vmcoreinfo
Date: Wed, 6 May 2020 13:31:12 +0100 [thread overview]
Message-ID: <20200506123112.GF8043@willie-the-truck> (raw)
In-Reply-To: <bc5e6fc5-15f4-40bb-4466-816de5912893@arm.com>
On Wed, May 06, 2020 at 05:32:56PM +0530, Amit Kachhap wrote:
> On 5/4/20 10:47 PM, Will Deacon wrote:
> > On Mon, Apr 27, 2020 at 11:55:01AM +0530, Amit Daniel Kachhap wrote:
> > > diff --git a/arch/arm64/include/asm/compiler.h b/arch/arm64/include/asm/compiler.h
> > > index eece20d..32d5900 100644
> > > --- a/arch/arm64/include/asm/compiler.h
> > > +++ b/arch/arm64/include/asm/compiler.h
> > > @@ -19,6 +19,9 @@
> > > #define __builtin_return_address(val) \
> > > (void *)(ptrauth_clear_pac((unsigned long)__builtin_return_address(val)))
> > > +#else /* !CONFIG_ARM64_PTR_AUTH */
> > > +#define ptrauth_user_pac_mask() 0ULL
> > > +#define ptrauth_kernel_pac_mask() 0ULL
> >
> > This doesn't look quite right to me, since you still have to take into
> > account the case where CONFIG_ARM64_PTR_AUTH=y but the feature is not
> > available at runtime:
>
> Yes agree with you here. However the config gaurd is saving some extra
> computation for __builtin_return_address. There are some compiler
> support being added in __builtin_extract_return_address to mask the PAC.
> Hopefully that will improve this code. In the meantime let it be like this.
Does the extra computation matter? Isn't it just a couple of instructions?
Will
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next prev parent reply other threads:[~2020-05-06 12:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-27 6:25 [PATCH v2 1/2] arm64/crash_core: Export KERNELPACMASK in vmcoreinfo Amit Daniel Kachhap
2020-04-27 6:25 ` [PATCH v2 2/2] Documentation/vmcoreinfo: Add documentation for 'KERNELPACMASK' Amit Daniel Kachhap
2020-05-04 17:34 ` Will Deacon
2020-05-06 12:07 ` Amit Kachhap
2020-04-30 11:35 ` [PATCH v2 1/2] arm64/crash_core: Export KERNELPACMASK in vmcoreinfo Amit Kachhap
2020-04-30 11:44 ` Amit Kachhap
2020-05-04 17:17 ` Will Deacon
2020-05-06 12:02 ` Amit Kachhap
2020-05-06 12:31 ` Will Deacon [this message]
2020-05-06 13:04 ` Amit Kachhap
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