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From: Dave Martin <Dave.Martin@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
	Will Deacon <will@kernel.org>, Kees Cook <keescook@chromium.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 01/10] arm64: bti: Support building kernel C code using BTI
Date: Tue, 5 May 2020 17:50:45 +0100	[thread overview]
Message-ID: <20200505165045.GQ30377@arm.com> (raw)
In-Reply-To: <20200429211641.9279-2-broonie@kernel.org>

On Wed, Apr 29, 2020 at 10:16:32PM +0100, Mark Brown wrote:
> When running with BTI enabled we need to ask the compiler to enable
> generation of BTI landing pads beyond those generated as a result of
> pointer authentication instructions being landing pads. Since the two
> features are practically speaking unlikely to be used separately we
> will make kernel mode BTI depend on pointer authentication in order
> to simplify the Makefile.
> 
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  arch/arm64/Makefile | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
> index 85e4149cc5d5..90150b5b180e 100644
> --- a/arch/arm64/Makefile
> +++ b/arch/arm64/Makefile
> @@ -71,7 +71,11 @@ branch-prot-flags-y += $(call cc-option,-mbranch-protection=none)
>  
>  ifeq ($(CONFIG_ARM64_PTR_AUTH),y)
>  branch-prot-flags-$(CONFIG_CC_HAS_SIGN_RETURN_ADDRESS) := -msign-return-address=all
> +ifeq ($(CONFIG_ARM64_BTI_KERNEL),y)
> +branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET_BTI) := -mbranch-protection=pac-ret+leaf+bti
> +else
>  branch-prot-flags-$(CONFIG_CC_HAS_BRANCH_PROT_PAC_RET) := -mbranch-protection=pac-ret+leaf
> +endif

Is it worth a comment to explain how this differs from
-mbranch-protection=standard, and why we're not using that here?

Cheers
---Dave

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  reply	other threads:[~2020-05-05 16:50 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-29 21:16 [PATCH v2 00/10] arm64: BTI kernel and vDSO support Mark Brown
2020-04-29 21:16 ` [PATCH v2 01/10] arm64: bti: Support building kernel C code using BTI Mark Brown
2020-05-05 16:50   ` Dave Martin [this message]
2020-05-05 17:31     ` Mark Brown
2020-05-06 12:24       ` Amit Kachhap
2020-04-29 21:16 ` [PATCH v2 02/10] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI Mark Brown
2020-05-05 14:56   ` Will Deacon
2020-05-05 15:18     ` Mark Brown
2020-05-05 16:08       ` Will Deacon
2020-05-05 17:21         ` Mark Brown
2020-05-06  7:10           ` Will Deacon
2020-05-06 10:41             ` Mark Brown
2020-05-06 10:50               ` Will Deacon
2020-05-06 11:43                 ` Mark Brown
2020-05-06 12:27                   ` Will Deacon
2020-05-06 13:03                     ` Mark Brown
2020-05-06 13:40                 ` Dave Martin
2020-05-06 14:45                   ` Will Deacon
2020-05-06 15:25                     ` Mark Brown
2020-05-06 15:48                       ` Will Deacon
2020-05-06 15:33                     ` Dave Martin
2020-04-29 21:16 ` [PATCH v2 03/10] arm64: Set GP bit in kernel page tables to enable BTI for the kernel Mark Brown
2020-04-29 21:16 ` [PATCH v2 04/10] arm64: bpf: Annotate JITed code for BTI Mark Brown
2020-04-29 21:16 ` [PATCH v2 05/10] arm64: mm: Mark executable text as guarded pages Mark Brown
2020-04-29 21:16 ` [PATCH v2 06/10] arm64: bti: Provide Kconfig for kernel mode BTI Mark Brown
2020-04-29 21:16 ` [PATCH v2 07/10] arm64: asm: Provide a mechanism for generating ELF note for BTI Mark Brown
2020-05-05 14:58   ` Will Deacon
2020-05-05 16:51     ` Dave Martin
2020-05-05 17:06     ` Mark Brown
2020-05-06 11:26       ` Will Deacon
2020-05-06 12:38         ` Mark Brown
2020-05-06 13:44           ` Will Deacon
2020-05-06 15:39             ` Mark Brown
2020-04-29 21:16 ` [PATCH v2 08/10] arm64: vdso: Annotate " Mark Brown
2020-04-29 21:16 ` [PATCH v2 09/10] arm64: vdso: Force the vDSO to be linked as BTI when built " Mark Brown
2020-04-29 21:16 ` [PATCH v2 10/10] arm64: vdso: Map the vDSO text with guarded pages " Mark Brown
2020-04-30 17:18 ` [PATCH v2 00/10] arm64: BTI kernel and vDSO support Catalin Marinas
2020-04-30 17:23   ` Mark Brown

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