From ebd4922ecc38e31e662cd641dd04099a9652c9b3 Mon Sep 17 00:00:00 2001 From: Russell King Date: Thu, 24 Oct 2013 08:12:39 +0100 Subject: [PATCH] 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 --- arch/arm/include/asm/mach/map.h | 1 + arch/arm/mm/mmu.c | 55 ++++++++++++++++++++++++++++++--- 2 files changed, 51 insertions(+), 5 deletions(-) diff --git a/arch/arm/include/asm/mach/map.h b/arch/arm/include/asm/mach/map.h index 447be0744a85..f98c7f32c9c8 100644 --- a/arch/arm/include/asm/mach/map.h +++ b/arch/arm/include/asm/mach/map.h @@ -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, 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 #include #include +#include #include #include #include @@ -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); + } + } } } -- 2.30.2