From: Kees Cook <keescook@chromium.org>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 5/5] arm64: bti: Provide Kconfig for kernel mode BTI
Date: Sat, 28 Mar 2020 14:19:49 -0700 [thread overview]
Message-ID: <202003281419.718CDC24@keescook> (raw)
In-Reply-To: <20200327192107.18394-6-broonie@kernel.org>
On Fri, Mar 27, 2020 at 07:21:07PM +0000, Mark Brown wrote:
> Now that all the code is in place provide a Kconfig option allowing users
> to enable BTI for the kernel if their toolchain supports it, defaulting it
> on since this has security benefits. This is a separate configuration
> option since we currently don't support secondary CPUs that lack BTI if
> the boot CPU supports it.
>
> Current testing appears to show an issue with GCC which causes it to
> emit unsuitable landing pads for function entries in some cases, until
> this issue is understood and either our usage fixed or a suitable
> version of GCC is identified the feature is marked as incompatible with
> GCC. No issues have been identified with clang.
>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
> arch/arm64/Kconfig | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 00cb4db4beab..25bb0931b2ba 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -1607,6 +1607,24 @@ config ARM64_BTI
> BTI, such binaries can still run, but you get no additional
> enforcement of branch destinations.
>
> +config ARM64_BTI_KERNEL
> + bool "Use Branch Target Identification for kernel"
> + default y
> + depends on ARM64_BTI
> + depends on ARM64_PTR_AUTH
> + depends on CC_HAS_BRANCH_PROT_PAC_RET_BTI
(this depend can be dropped with my crazy Makefile suggestion)
> + depends on !CC_IS_GCC
> + depends on (!FUNCTION_GRAPH_TRACER || DYNAMIC_FTRACE_WITH_REGS)
> + help
> + Build the kernel with Branch Target Identification annotations
> + and enable enforcement of this for kernel code. When this option
> + is enabled and the system supports BTI all kernel code including
> + modular code must have BTI enabled.
> +
> +config CC_HAS_BRANCH_PROT_PAC_RET_BTI
> + # GCC 9 or later, clang 8 or later
> + def_bool $(cc-option,-mbranch-protection=pac-ret+leaf+bti)
Exciting! :)
> +
> config ARM64_E0PD
> bool "Enable support for E0PD"
> default y
> --
> 2.20.1
>
--
Kees Cook
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prev parent reply other threads:[~2020-03-28 21:19 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-27 19:21 [PATCH 0/5] arm64: Initial BTI kernel support Mark Brown
2020-03-27 19:21 ` [PATCH 1/5] arm64: bti: Support building kernel C code using BTI Mark Brown
2020-03-28 21:14 ` Kees Cook
2020-03-30 11:33 ` Mark Brown
2020-03-30 18:06 ` Kees Cook
2020-03-31 15:21 ` Mark Brown
2020-03-27 19:21 ` [PATCH 2/5] arm64: asm: Override SYM_FUNC_START when building the kernel with BTI Mark Brown
2020-03-27 19:21 ` [PATCH 3/5] arm64: Set GP bit in kernel page tables to enable BTI for the kernel Mark Brown
2020-03-27 19:21 ` [PATCH 4/5] arm64: mm: Mark module text as guarded pages Mark Brown
2020-03-27 19:21 ` [PATCH 5/5] arm64: bti: Provide Kconfig for kernel mode BTI Mark Brown
2020-03-28 21:19 ` Kees Cook [this message]
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