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Date: Thu, 21 May 2020 09:56:35 -0700
From: Kristen Carlson Accardi <kristen@...ux.intel.com>
To: keescook@...omium.org,
tglx@...utronix.de,
mingo@...hat.com,
bp@...en8.de,
Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
x86@...nel.org,
"H. Peter Anvin" <hpa@...or.com>
Cc: arjan@...ux.intel.com,
linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com,
rick.p.edgecombe@...el.com,
Kristen Carlson Accardi <kristen@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>,
linux-kbuild@...r.kernel.org
Subject: [PATCH v2 4/9] x86: Makefile: Add build and config option for CONFIG_FG_KASLR
Allow user to select CONFIG_FG_KASLR if dependencies are met. Change
the make file to build with -ffunction-sections if CONFIG_FG_KASLR
Signed-off-by: Kristen Carlson Accardi <kristen@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Tested-by: Tony Luck <tony.luck@...el.com>
---
Makefile | 4 ++++
arch/x86/Kconfig | 13 +++++++++++++
2 files changed, 17 insertions(+)
diff --git a/Makefile b/Makefile
index 04f5662ae61a..28e515baa824 100644
--- a/Makefile
+++ b/Makefile
@@ -862,6 +862,10 @@ ifdef CONFIG_LIVEPATCH
KBUILD_CFLAGS += $(call cc-option, -flive-patching=inline-clone)
endif
+ifdef CONFIG_FG_KASLR
+KBUILD_CFLAGS += -ffunction-sections
+endif
+
# arch Makefile may override CC so keep this after arch Makefile is included
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2d3f963fd6f1..50e83ea57d70 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2183,6 +2183,19 @@ config RANDOMIZE_BASE
If unsure, say Y.
+config FG_KASLR
+ bool "Function Granular Kernel Address Space Layout Randomization"
+ depends on $(cc-option, -ffunction-sections)
+ depends on RANDOMIZE_BASE && X86_64
+ help
+ This option improves the randomness of the kernel text
+ over basic Kernel Address Space Layout Randomization (KASLR)
+ by reordering the kernel text at boot time. This feature
+ uses information generated at compile time to re-layout the
+ kernel text section at boot time at function level granularity.
+
+ If unsure, say N.
+
# Relocation on x86 needs some additional build support
config X86_NEED_RELOCS
def_bool y
--
2.20.1
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