[PATCH 4/9] x86: Makefile: Add build and config option for CONFIG_FG_KASLR

Kristen Carlson Accardi
2020-04-15T21:06:02Z

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@linux.intel.com>
---
Makefile | 4 ++++
arch/x86/Kconfig | 13 +++++++++++++
2 files changed, 17 insertions(+)

diff --git a/Makefile b/Makefile
index 70def4907036..337b72787200 100644
--- a/Makefile
+++ b/Makefile
@@ -866,6 +866,10 @@ 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 1d6104ea8af0..6aaece89f712 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2182,6 +2182,19 @@ 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