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ARM: mm: allow non-text sections to be non-executable

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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>
This commit is contained in:
Kees Cook
2014-04-03 17:28:11 -07:00
parent 23a4e4050b
commit 1e6b48116a
4 changed files with 133 additions and 2 deletions
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9
arch/arm/mm/mmu.c
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@@ -1373,12 +1373,19 @@ static void __init map_lowmem(void)
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 */