From 1d4d37159d013a4c54d785407dd8902f901d7bc5 Mon Sep 17 00:00:00 2001 From: Jungseung Lee Date: Sat, 29 Nov 2014 02:33:30 +0100 Subject: ARM: 8235/1: Support for the PXN CPU feature on ARMv7 Modern ARMv7-A/R cores optionally implement below new hardware feature: - PXN: Privileged execute-never(PXN) is a security feature. PXN bit determines whether the processor can execute software from the region. This is effective solution against ret2usr attack. On an implementation that does not include the LPAE, PXN is optionally supported. This patch set PXN bit on user page table for preventing user code execution with privilege mode. Reviewed-by: Catalin Marinas Signed-off-by: Jungseung Lee Signed-off-by: Russell King --- arch/arm/mm/mmu.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'arch/arm/mm/mmu.c') diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index d028dc74a9d5..b590a4c92462 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -52,6 +52,8 @@ EXPORT_SYMBOL(empty_zero_page); */ pmd_t *top_pmd; +pmdval_t user_pmd_table = _PAGE_USER_TABLE; + #define CPOLICY_UNCACHED 0 #define CPOLICY_BUFFERED 1 #define CPOLICY_WRITETHROUGH 2 @@ -528,14 +530,23 @@ static void __init build_mem_type_table(void) hyp_device_pgprot = mem_types[MT_DEVICE].prot_pte; s2_device_pgprot = mem_types[MT_DEVICE].prot_pte_s2; +#ifndef CONFIG_ARM_LPAE /* * We don't use domains on ARMv6 (since this causes problems with * v6/v7 kernels), so we must use a separate memory type for user * r/o, kernel r/w to map the vectors page. */ -#ifndef CONFIG_ARM_LPAE if (cpu_arch == CPU_ARCH_ARMv6) vecs_pgprot |= L_PTE_MT_VECTORS; + + /* + * Check is it with support for the PXN bit + * in the Short-descriptor translation table format descriptors. + */ + if (cpu_arch == CPU_ARCH_ARMv7 && + (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xF) == 4) { + user_pmd_table |= PMD_PXNTABLE; + } #endif /* @@ -605,6 +616,11 @@ static void __init build_mem_type_table(void) } kern_pgprot |= PTE_EXT_AF; vecs_pgprot |= PTE_EXT_AF; + + /* + * Set PXN for user mappings + */ + user_pgprot |= PTE_EXT_PXN; #endif for (i = 0; i < 16; i++) { -- cgit v1.2.3