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Message-Id: <20210305005327.405365-1-jiancai@google.com>
Date: Thu, 4 Mar 2021 16:53:18 -0800
From: Jian Cai <jiancai@...gle.com>
To: unlisted-recipients:; (no To-header on input)
Cc: ndesaulniers@...gle.com, manojgupta@...gle.com, llozano@...gle.com,
clang-built-linux@...glegroups.com, Jian Cai <jiancai@...gle.com>,
Nathan Chancellor <nathan@...nel.org>,
David Laight <David.Laight@...lab.com>,
Will Deacon <will@...nel.org>,
Russell King <rmk+kernel@...linux.org.uk>,
Linus Walleij <linus.walleij@...aro.org>,
Russell King <linux@...linux.org.uk>,
Catalin Marinas <catalin.marinas@....com>,
James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>,
Arnd Bergmann <arnd@...db.de>,
Masahiro Yamada <masahiroy@...nel.org>,
Kees Cook <keescook@...omium.org>,
"Andreas Färber" <afaerber@...e.de>,
Daniel Palmer <daniel@...f.com>,
Ard Biesheuvel <ardb@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Vladimir Murzin <vladimir.murzin@....com>,
Marc Zyngier <maz@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Mike Rapoport <rppt@...nel.org>,
"Uwe Kleine-König"
<u.kleine-koenig@...gutronix.de>,
Mark Rutland <mark.rutland@....com>,
David Brazdil <dbrazdil@...gle.com>,
Joey Gouly <joey.gouly@....com>,
James Morse <james.morse@....com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-security-module@...r.kernel.org
Subject: [PATCH v6] ARM: Implement SLS mitigation
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@...gle.com>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Suggested-by: Nathan Chancellor <nathan@...nel.org>
Suggested-by: David Laight <David.Laight@...lab.com>
Suggested-by: Will Deacon <will@...nel.org>
Suggested-by: Russell King <rmk+kernel@...linux.org.uk>
Suggested-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Jian Cai <jiancai@...gle.com>
---
Changes v1 -> v2:
Update the description and patch based on Nathan and David's comments.
Changes v2 -> v3:
Modify linker scripts as Nick suggested to address boot failure
(verified with qemu). Added more details in Kconfig.hardening
description. Disable the config by default.
Changes v3 -> v4:
Address Nathan's comment and replace def_bool with depends on in
HARDEN_SLS_ALL.
Changes v4 -> v5:
Removed "default n" and made the description target indepdent in
Kconfig.hardening.
Changes v5 -> v6:
Add select HARDEN_SLS_ALL under config HARDEN_BRANCH_PREDICTOR. This
turns on HARDEN_SLS_ALL by default where applicable.
arch/arm/Makefile | 4 ++++
arch/arm/include/asm/vmlinux.lds.h | 4 ++++
arch/arm/kernel/vmlinux.lds.S | 1 +
arch/arm/mm/Kconfig | 1 +
arch/arm64/Makefile | 4 ++++
arch/arm64/kernel/vmlinux.lds.S | 5 +++++
security/Kconfig.hardening | 8 ++++++++
7 files changed, 27 insertions(+)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index dad5502ecc28..54f9b5ff9682 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -48,6 +48,10 @@ CHECKFLAGS += -D__ARMEL__
KBUILD_LDFLAGS += -EL
endif
+ifeq ($(CONFIG_HARDEN_SLS_ALL), y)
+KBUILD_CFLAGS += -mharden-sls=all
+endif
+
#
# The Scalar Replacement of Aggregates (SRA) optimization pass in GCC 4.9 and
# later may result in code being generated that handles signed short and signed
diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h
index 4a91428c324d..c7f9717511ca 100644
--- a/arch/arm/include/asm/vmlinux.lds.h
+++ b/arch/arm/include/asm/vmlinux.lds.h
@@ -145,3 +145,7 @@
__edtcm_data = .; \
} \
. = __dtcm_start + SIZEOF(.data_dtcm);
+
+#define SLS_TEXT \
+ ALIGN_FUNCTION(); \
+ *(.text.__llvm_slsblr_thunk_*)
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index f7f4620d59c3..e71f2bc97bae 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -63,6 +63,7 @@ SECTIONS
.text : { /* Real text segment */
_stext = .; /* Text and read-only data */
ARM_TEXT
+ SLS_TEXT
}
#ifdef CONFIG_DEBUG_ALIGN_RODATA
diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig
index 35f43d0aa056..bdb63e7b1bec 100644
--- a/arch/arm/mm/Kconfig
+++ b/arch/arm/mm/Kconfig
@@ -837,6 +837,7 @@ config HARDEN_BRANCH_PREDICTOR
bool "Harden the branch predictor against aliasing attacks" if EXPERT
depends on CPU_SPECTRE
default y
+ select HARDEN_SLS_ALL
help
Speculation attacks against some high-performance processors rely
on being able to manipulate the branch predictor for a victim
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 5b84aec31ed3..e233bfbdb1c2 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -34,6 +34,10 @@ $(warning LSE atomics not supported by binutils)
endif
endif
+ifeq ($(CONFIG_HARDEN_SLS_ALL), y)
+KBUILD_CFLAGS += -mharden-sls=all
+endif
+
cc_has_k_constraint := $(call try-run,echo \
'int main(void) { \
asm volatile("and w0, w0, %w0" :: "K" (4294967295)); \
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 7eea7888bb02..d5c892605862 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -103,6 +103,10 @@ jiffies = jiffies_64;
#define TRAMP_TEXT
#endif
+#define SLS_TEXT \
+ ALIGN_FUNCTION(); \
+ *(.text.__llvm_slsblr_thunk_*)
+
/*
* The size of the PE/COFF section that covers the kernel image, which
* runs from _stext to _edata, must be a round multiple of the PE/COFF
@@ -154,6 +158,7 @@ SECTIONS
HIBERNATE_TEXT
TRAMP_TEXT
*(.fixup)
+ SLS_TEXT
*(.gnu.warning)
. = ALIGN(16);
*(.got) /* Global offset table */
diff --git a/security/Kconfig.hardening b/security/Kconfig.hardening
index 269967c4fc1b..db76ad732c14 100644
--- a/security/Kconfig.hardening
+++ b/security/Kconfig.hardening
@@ -121,6 +121,14 @@ choice
endchoice
+config HARDEN_SLS_ALL
+ bool "enable SLS vulnerability hardening"
+ depends on $(cc-option,-mharden-sls=all)
+ help
+ Enables straight-line speculation vulnerability hardening. This inserts
+ speculation barrier instruction sequences after certain unconditional jumps
+ to prevent speculative execution past those barriers.
+
config GCC_PLUGIN_STRUCTLEAK_VERBOSE
bool "Report forcefully initialized variables"
depends on GCC_PLUGIN_STRUCTLEAK
--
2.30.1.766.gb4fecdf3b7-goog
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