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authorRussell King <rmk+kernel@arm.linux.org.uk>2013-10-24 08:12:39 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2013-12-11 09:53:16 +0000
commitebd4922ecc38e31e662cd641dd04099a9652c9b3 (patch)
tree9bdeb148dca0324f7c16bf33feee00fe013dcd0f /arch/arm/mm/mmu.c
parent2e2c9de207be043ee80161971c814d740759d3bc (diff)
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: Russell King <rmk+kernel@arm.linux.org.uk>
Diffstat (limited to 'arch/arm/mm/mmu.c')
-rw-r--r--arch/arm/mm/mmu.c55
1 files changed, 50 insertions, 5 deletions
diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index fce2e7388098..9ec715f12224 100644
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -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;
- map.pfn = __phys_to_pfn(start);
- map.virtual = __phys_to_virt(start);
- map.length = end - start;
- map.type = MT_MEMORY;
+ 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_RWX;
- create_mapping(&map);
+ 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);
+ }
+ }
}
}