Messages in this thread Patch in this message |  | | From | Will Deacon <> | Subject | [PATCH 18/18] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0 | Date | Fri, 17 Nov 2017 18:22:01 +0000 |
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Add a Kconfig entry to control use of the entry trampoline, which allows us to unmap the kernel whilst running in userspace and improve the robustness of KASLR.
Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm64/Kconfig | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index f0fcbfc2262e..f99ffb88843a 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -796,6 +796,19 @@ config FORCE_MAX_ZONEORDER However for 4K, we choose a higher default value, 11 as opposed to 10, giving us 4M allocations matching the default size used by generic code. +config UNMAP_KERNEL_AT_EL0 + bool "Unmap kernel when running in userspace (aka \"KAISER\")" + default y + help + Some attacks against KASLR make use of the timing difference between + a permission fault which could arise from a page table entry that is + present in the TLB, and a translation fault which always requires a + page table walk. This option defends against these attacks by unmapping + the kernel whilst running in userspace, therefore forcing translation + faults for all of kernel space. + + If unsure, say Y. + menuconfig ARMV8_DEPRECATED bool "Emulate deprecated/obsolete ARMv8 instructions" depends on COMPAT -- 2.1.4
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