Commit ebd4922e authored by Russell King's avatar Russell King
Browse files

ARM: implement basic NX support for kernel lowmem mappings 



Add basic NX support for kernel lowmem mappings.  We mark any section
which does not overlap kernel text as non-executable, preventing it
from being used to write code and then execute directly from there.

This does not change the alignment of the sections, so the kernel
image doesn't grow significantly via this change, so we can do this
without needing a config option.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 2e2c9de2

arch/arm/include/asm/mach/map.h

+1 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ enum { 
	MT_LOW_VECTORS,

	MT_HIGH_VECTORS,

	MT_MEMORY_RWX,

	MT_MEMORY_RW,

	MT_ROM,

	MT_MEMORY_RWX_NONCACHED,

	MT_MEMORY_RW_DTCM,

arch/arm/mm/mmu.c

+50 −5
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <asm/cputype.h>

#include <asm/sections.h>

#include <asm/cachetype.h>

#include <asm/sections.h>

#include <asm/setup.h>

#include <asm/smp_plat.h>

#include <asm/tlb.h>
@@ -293,6 +294,13 @@ static struct mem_type mem_types[] = { 
		.prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,

		.domain    = DOMAIN_KERNEL,

	},

	[MT_MEMORY_RW] = {

		.prot_pte  = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY |

			     L_PTE_XN,

		.prot_l1   = PMD_TYPE_TABLE,

		.prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE,

		.domain    = DOMAIN_KERNEL,

	},

	[MT_ROM] = {

		.prot_sect = PMD_TYPE_SECT,

		.domain    = DOMAIN_KERNEL,
@@ -410,6 +418,9 @@ static void __init build_mem_type_table(void) 
			mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_XN;

			mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_XN;

			mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_XN;



			/* Also setup NX memory mapping */

			mem_types[MT_MEMORY_RW].prot_sect |= PMD_SECT_XN;

		}

		if (cpu_arch >= CPU_ARCH_ARMv7 && (cr & CR_TRE)) {

			/*
@@ -489,6 +500,8 @@ static void __init build_mem_type_table(void) 
			mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED;

			mem_types[MT_MEMORY_RWX].prot_sect |= PMD_SECT_S;

			mem_types[MT_MEMORY_RWX].prot_pte |= L_PTE_SHARED;

			mem_types[MT_MEMORY_RW].prot_sect |= PMD_SECT_S;

			mem_types[MT_MEMORY_RW].prot_pte |= L_PTE_SHARED;

			mem_types[MT_MEMORY_DMA_READY].prot_pte |= L_PTE_SHARED;

			mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= PMD_SECT_S;

			mem_types[MT_MEMORY_RWX_NONCACHED].prot_pte |= L_PTE_SHARED;
@@ -545,6 +558,8 @@ static void __init build_mem_type_table(void) 
	mem_types[MT_HIGH_VECTORS].prot_l1 |= ecc_mask;

	mem_types[MT_MEMORY_RWX].prot_sect |= ecc_mask | cp->pmd;

	mem_types[MT_MEMORY_RWX].prot_pte |= kern_pgprot;

	mem_types[MT_MEMORY_RW].prot_sect |= ecc_mask | cp->pmd;

	mem_types[MT_MEMORY_RW].prot_pte |= kern_pgprot;

	mem_types[MT_MEMORY_DMA_READY].prot_pte |= kern_pgprot;

	mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= ecc_mask;

	mem_types[MT_ROM].prot_sect |= cp->pmd;
@@ -1296,6 +1311,8 @@ static void __init kmap_init(void) 
static void __init map_lowmem(void)

{

	struct memblock_region *reg;

	unsigned long kernel_x_start = round_down(__pa(_stext), SECTION_SIZE);

	unsigned long kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE);



	/* Map all the lowmem memory banks. */

	for_each_memblock(memory, reg) {
@@ -1308,12 +1325,40 @@ static void __init map_lowmem(void) 
		if (start >= end)

			break;



		if (end < kernel_x_start || start >= kernel_x_end) {

			map.pfn = __phys_to_pfn(start);

			map.virtual = __phys_to_virt(start);

			map.length = end - start;

		map.type = MT_MEMORY;

			map.type = MT_MEMORY_RWX;



			create_mapping(&map);

		} else {

			/* This better cover the entire kernel */

			if (start < kernel_x_start) {

				map.pfn = __phys_to_pfn(start);

				map.virtual = __phys_to_virt(start);

				map.length = kernel_x_start - start;

				map.type = MT_MEMORY_RW;



				create_mapping(&map);

			}



			map.pfn = __phys_to_pfn(kernel_x_start);

			map.virtual = __phys_to_virt(kernel_x_start);

			map.length = kernel_x_end - kernel_x_start;

			map.type = MT_MEMORY_RWX;



			create_mapping(&map);



			if (kernel_x_end < end) {

				map.pfn = __phys_to_pfn(kernel_x_end);

				map.virtual = __phys_to_virt(kernel_x_end);

				map.length = end - kernel_x_end;

				map.type = MT_MEMORY_RW;



				create_mapping(&map);

			}

		}

	}

}

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