From: Will Deacon <will@kernel.org>
To: Jian Cai <jiancai@google.com>
Cc: ndesaulniers@google.com, manojgupta@google.com,
llozano@google.com, clang-built-linux@googlegroups.com,
"Nathan Chancellor" <nathan@kernel.org>,
"David Laight" <David.Laight@aculab.com>,
"Russell King" <rmk+kernel@armlinux.org.uk>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Russell King" <linux@armlinux.org.uk>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"James Morris" <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Andreas Färber" <afaerber@suse.de>,
"Daniel Palmer" <daniel@0x0f.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Ingo Molnar" <mingo@kernel.org>,
"Vladimir Murzin" <vladimir.murzin@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mike Rapoport" <rppt@kernel.org>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Mark Rutland" <mark.rutland@arm.com>,
"David Brazdil" <dbrazdil@google.com>,
"Joey Gouly" <joey.gouly@arm.com>,
"James Morse" <james.morse@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH v6] ARM: Implement SLS mitigation
Date: Fri, 5 Mar 2021 09:52:56 +0000 [thread overview]
Message-ID: <20210305095256.GA22536@willie-the-truck> (raw)
In-Reply-To: <20210305005327.405365-1-jiancai@google.com>
On Thu, Mar 04, 2021 at 04:53:18PM -0800, Jian Cai wrote:
> This patch adds CONFIG_HARDEN_SLS_ALL that can be used to turn on
> -mharden-sls=all, which mitigates the straight-line speculation
> vulnerability, speculative execution of the instruction following some
> unconditional jumps. Notice -mharden-sls= has other options as below,
> and this config turns on the strongest option.
>
> all: enable all mitigations against Straight Line Speculation that are implemented.
> none: disable all mitigations against Straight Line Speculation.
> retbr: enable the mitigation against Straight Line Speculation for RET and BR instructions.
> blr: enable the mitigation against Straight Line Speculation for BLR instructions.
>
> Links:
> https://reviews.llvm.org/D93221
> https://reviews.llvm.org/D81404
> https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/downloads/straight-line-speculation
> https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/frequently-asked-questions#SLS2
>
> Suggested-by: Manoj Gupta <manojgupta@google.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Suggested-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: David Laight <David.Laight@aculab.com>
> Suggested-by: Will Deacon <will@kernel.org>
I'm still reasonably opposed to this patch, so please don't add my
"Suggested-by" here as, if I were to suggest anything, it would be not
to apply this patch :)
I still don't see why SLS is worth a compiler mitigation which will affect
all CPUs that run the kernel binary, but Spectre-v1 is not. In other words,
the big thing missing from this is a justification as to why SLS is a
problem worth working around for general C code.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will@kernel.org>
To: Jian Cai <jiancai@google.com>
Cc: ndesaulniers@google.com, manojgupta@google.com,
llozano@google.com, clang-built-linux@googlegroups.com,
"Nathan Chancellor" <nathan@kernel.org>,
"David Laight" <David.Laight@aculab.com>,
"Russell King" <rmk+kernel@armlinux.org.uk>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Russell King" <linux@armlinux.org.uk>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"James Morris" <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Masahiro Yamada" <masahiroy@kernel.org>,
"Kees Cook" <keescook@chromium.org>,
"Andreas Färber" <afaerber@suse.de>,
"Daniel Palmer" <daniel@0x0f.com>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Ingo Molnar" <mingo@kernel.org>,
"Vladimir Murzin" <vladimir.murzin@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Mike Rapoport" <rppt@kernel.org>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Mark Rutland" <mark.rutland@arm.com>,
"David Brazdil" <dbrazdil@google.com>,
"Joey Gouly" <joey.gouly@arm.com>,
"James Morse" <james.morse@arm.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
linux-security-module@vger.kernel.org
Subject: Re: [PATCH v6] ARM: Implement SLS mitigation
Date: Fri, 5 Mar 2021 09:52:56 +0000 [thread overview]
Message-ID: <20210305095256.GA22536@willie-the-truck> (raw)
In-Reply-To: <20210305005327.405365-1-jiancai@google.com>
On Thu, Mar 04, 2021 at 04:53:18PM -0800, Jian Cai wrote:
> This patch adds CONFIG_HARDEN_SLS_ALL that can be used to turn on
> -mharden-sls=all, which mitigates the straight-line speculation
> vulnerability, speculative execution of the instruction following some
> unconditional jumps. Notice -mharden-sls= has other options as below,
> and this config turns on the strongest option.
>
> all: enable all mitigations against Straight Line Speculation that are implemented.
> none: disable all mitigations against Straight Line Speculation.
> retbr: enable the mitigation against Straight Line Speculation for RET and BR instructions.
> blr: enable the mitigation against Straight Line Speculation for BLR instructions.
>
> Links:
> https://reviews.llvm.org/D93221
> https://reviews.llvm.org/D81404
> https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/downloads/straight-line-speculation
> https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability/frequently-asked-questions#SLS2
>
> Suggested-by: Manoj Gupta <manojgupta@google.com>
> Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
> Suggested-by: Nathan Chancellor <nathan@kernel.org>
> Suggested-by: David Laight <David.Laight@aculab.com>
> Suggested-by: Will Deacon <will@kernel.org>
I'm still reasonably opposed to this patch, so please don't add my
"Suggested-by" here as, if I were to suggest anything, it would be not
to apply this patch :)
I still don't see why SLS is worth a compiler mitigation which will affect
all CPUs that run the kernel binary, but Spectre-v1 is not. In other words,
the big thing missing from this is a justification as to why SLS is a
problem worth working around for general C code.
Will
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next prev parent reply other threads:[~2021-03-05 9:54 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-12 5:14 [PATCH] ARM: Implement Clang's SLS mitigation Jian Cai
2021-02-12 5:14 ` Jian Cai
2021-02-12 5:55 ` Nathan Chancellor
2021-02-12 5:55 ` Nathan Chancellor
2021-02-12 10:41 ` David Laight
2021-02-12 10:41 ` David Laight
2021-02-12 19:52 ` [PATCH v2] " Jian Cai
2021-02-12 19:52 ` Jian Cai
2021-02-17 9:49 ` Will Deacon
2021-02-17 9:49 ` Will Deacon
2021-02-17 11:05 ` David Laight
2021-02-17 11:05 ` David Laight
2021-03-25 14:01 ` Linus Walleij
2021-03-25 14:01 ` Linus Walleij
2021-02-17 18:20 ` Nick Desaulniers
2021-02-17 18:20 ` Nick Desaulniers
2021-02-19 20:18 ` [PATCH v3] ARM: Implement " Jian Cai
2021-02-19 20:18 ` Jian Cai
2021-02-19 20:30 ` Nathan Chancellor
2021-02-19 20:30 ` Nathan Chancellor
2021-02-19 23:08 ` [PATCH v4] " Jian Cai
2021-02-19 23:08 ` Jian Cai
2021-02-21 10:13 ` Russell King - ARM Linux admin
2021-02-21 10:13 ` Russell King - ARM Linux admin
2021-02-22 11:58 ` Will Deacon
2021-02-22 11:58 ` Will Deacon
2021-02-22 21:50 ` Jian Cai
2021-02-22 21:50 ` Jian Cai
2021-02-23 10:04 ` Will Deacon
2021-02-23 10:04 ` Will Deacon
2021-03-03 15:18 ` Linus Walleij
2021-03-03 15:18 ` Linus Walleij
2021-03-03 15:29 ` David Laight
2021-03-03 15:29 ` David Laight
2021-03-03 15:31 ` Linus Walleij
2021-03-03 15:31 ` Linus Walleij
2021-02-23 2:31 ` [PATCH v5] " Jian Cai
2021-02-23 2:31 ` Jian Cai
2021-02-23 2:35 ` Jian Cai
2021-02-23 2:35 ` Jian Cai
2021-03-03 15:04 ` Linus Walleij
2021-03-03 15:04 ` Linus Walleij
2021-03-04 23:22 ` Jian Cai
2021-03-04 23:22 ` Jian Cai
2021-03-06 12:25 ` Linus Walleij
2021-03-06 12:25 ` Linus Walleij
2021-03-10 4:43 ` Jian Cai
2021-03-10 4:43 ` Jian Cai
2021-03-22 11:45 ` Linus Walleij
2021-03-22 11:45 ` Linus Walleij
2021-03-23 22:39 ` Jian Cai
2021-03-23 22:39 ` Jian Cai
2021-03-05 0:53 ` [PATCH v6] " Jian Cai
2021-03-05 0:53 ` Jian Cai
2021-03-05 9:52 ` Will Deacon [this message]
2021-03-05 9:52 ` Will Deacon
2021-03-06 12:27 ` Linus Walleij
2021-03-06 12:27 ` Linus Walleij
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