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authorKees Cook <keescook@chromium.org>2013-10-10 17:18:14 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2013-10-13 03:12:07 -0700
commit8ab3820fd5b2896d66da7bb2a906bc382e63e7bc (patch)
tree50f6f4458f86eb66552c13bef81169e44d27dc28 /arch/x86/Kconfig
parentdd78b97367bd575918204cc89107c1479d3fc1a7 (diff)
downloadop-kernel-dev-8ab3820fd5b2896d66da7bb2a906bc382e63e7bc.zip
op-kernel-dev-8ab3820fd5b2896d66da7bb2a906bc382e63e7bc.tar.gz
x86, kaslr: Return location from decompress_kernel
This allows decompress_kernel to return a new location for the kernel to be relocated to. Additionally, enforces CONFIG_PHYSICAL_START as the minimum relocation position when building with CONFIG_RELOCATABLE. With CONFIG_RANDOMIZE_BASE set, the choose_kernel_location routine will select a new location to decompress the kernel, though here it is presently a no-op. The kernel command line option "nokaslr" is introduced to bypass these routines. Signed-off-by: Kees Cook <keescook@chromium.org> Link: http://lkml.kernel.org/r/1381450698-28710-3-git-send-email-keescook@chromium.org Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/Kconfig')
-rw-r--r--arch/x86/Kconfig38
1 files changed, 34 insertions, 4 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ee2fb9d..992701d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1722,16 +1722,46 @@ config RELOCATABLE
Note: If CONFIG_RELOCATABLE=y, then the kernel runs from the address
it has been loaded at and the compile time physical address
- (CONFIG_PHYSICAL_START) is ignored.
+ (CONFIG_PHYSICAL_START) is used as the minimum location.
-# Relocation on x86-32 needs some additional build support
+config RANDOMIZE_BASE
+ bool "Randomize the address of the kernel image"
+ depends on RELOCATABLE
+ depends on !HIBERNATION
+ default n
+ ---help---
+ Randomizes the physical and virtual address at which the
+ kernel image is decompressed, as a security feature that
+ deters exploit attempts relying on knowledge of the location
+ of kernel internals.
+
+ Entropy is generated using the RDRAND instruction if it
+ is supported. If not, then RDTSC is used, if supported. If
+ neither RDRAND nor RDTSC are supported, then no randomness
+ is introduced.
+
+ The kernel will be offset by up to RANDOMIZE_BASE_MAX_OFFSET,
+ and aligned according to PHYSICAL_ALIGN.
+
+config RANDOMIZE_BASE_MAX_OFFSET
+ hex "Maximum ASLR offset allowed"
+ depends on RANDOMIZE_BASE
+ default "0x10000000"
+ range 0x0 0x10000000
+ ---help---
+ Determines the maximal offset in bytes that will be applied to the
+ kernel when Address Space Layout Randomization (ASLR) is active.
+ Must be less than or equal to the actual physical memory on the
+ system. This must be a power of two.
+
+# Relocation on x86 needs some additional build support
config X86_NEED_RELOCS
def_bool y
- depends on X86_32 && RELOCATABLE
+ depends on RANDOMIZE_BASE || (X86_32 && RELOCATABLE)
config PHYSICAL_ALIGN
hex "Alignment value to which kernel should be aligned"
- default "0x1000000"
+ default "0x200000"
range 0x2000 0x1000000 if X86_32
range 0x200000 0x1000000 if X86_64
---help---
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