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 <keescook@chromium.org>
Tested-by: Laura Abbott <lauraa@codeaurora.org>
Acked-by: Nicolas Pitre <nico@linaro.org>
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index bdf5c94..1c52c8e 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -1373,13 +1373,20 @@
if (start >= end)
break;
- if (end < kernel_x_start || start >= kernel_x_end) {
+ if (end < kernel_x_start) {
map.pfn = __phys_to_pfn(start);
map.virtual = __phys_to_virt(start);
map.length = end - start;
map.type = MT_MEMORY_RWX;
create_mapping(&map);
+ } else if (start >= kernel_x_end) {
+ map.pfn = __phys_to_pfn(start);
+ map.virtual = __phys_to_virt(start);
+ map.length = end - start;
+ map.type = MT_MEMORY_RW;
+
+ create_mapping(&map);
} else {
/* This better cover the entire kernel */
if (start < kernel_x_start) {