From 1e6b48116a95046ec51f3d40f83aff8b006674d7 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Thu, 3 Apr 2014 17:28:11 -0700 Subject: ARM: mm: allow non-text sections to be non-executable Adds CONFIG_ARM_KERNMEM_PERMS to separate the kernel memory regions into section-sized areas that can have different permisions. Performs the NX permission changes during free_initmem, so that init memory can be reclaimed. This uses section size instead of PMD size to reduce memory lost to padding on non-LPAE systems. Based on work by Brad Spengler, Larry Bassel, and Laura Abbott. Signed-off-by: Kees Cook Tested-by: Laura Abbott Acked-by: Nicolas Pitre --- arch/arm/mm/Kconfig | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/arm/mm/Kconfig') diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index ae69809a9e47..7a0756df91a2 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -1008,3 +1008,12 @@ config ARCH_SUPPORTS_BIG_ENDIAN help This option specifies the architecture can support big endian operation. + +config ARM_KERNMEM_PERMS + bool "Restrict kernel memory permissions" + help + If this is set, kernel memory other than kernel text (and rodata) + will be made non-executable. The tradeoff is that each region is + padded to section-size (1MiB) boundaries (because their permissions + are different and splitting the 1M pages into 4K ones causes TLB + performance problems), wasting memory. -- cgit v1.2.3