[PATCH] arm64: mmu: Place guard page after mapping of kernel image
From: mark.rutland@arm.com (Mark Rutland)
Date: 2017-07-31 10:24:14
On Thu, Jul 27, 2017 at 06:03:55PM +0100, Will Deacon wrote:
The vast majority of virtual allocations in the vmalloc region are followed by a guard page, which can help to avoid overruning on vma into another, which may map a read-sensitive device. This patch adds a guard page to the end of the kernel image mapping (i.e. following the data/bss segments). Cc: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <redacted> Signed-off-by: Will Deacon <redacted>
Looks sane to me. Acked-by: Mark Rutland <mark.rutland@arm.com> Mark.
quoted hunk ↗ jump to hunk
--- arch/arm64/mm/mmu.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 23c2d89a362e..f1eb15e0e864 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c@@ -496,7 +496,7 @@ void mark_rodata_ro(void) static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, pgprot_t prot, struct vm_struct *vma, - int flags) + int flags, unsigned long vm_flags) { phys_addr_t pa_start = __pa_symbol(va_start); unsigned long size = va_end - va_start;@@ -507,10 +507,13 @@ static void __init map_kernel_segment(pgd_t *pgd, void *va_start, void *va_end, __create_pgd_mapping(pgd, pa_start, (unsigned long)va_start, size, prot, early_pgtable_alloc, flags); + if (!(vm_flags & VM_NO_GUARD)) + size += PAGE_SIZE; + vma->addr = va_start; vma->phys_addr = pa_start; vma->size = size; - vma->flags = VM_MAP; + vma->flags = VM_MAP | vm_flags; vma->caller = __builtin_return_address(0); vm_area_add_early(vma);@@ -541,14 +544,15 @@ static void __init map_kernel(pgd_t *pgd) * Only rodata will be remapped with different permissions later on, * all other segments are allowed to use contiguous mappings. */ - map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text, 0); + map_kernel_segment(pgd, _text, _etext, text_prot, &vmlinux_text, 0, + VM_NO_GUARD); map_kernel_segment(pgd, __start_rodata, __inittext_begin, PAGE_KERNEL, - &vmlinux_rodata, NO_CONT_MAPPINGS); + &vmlinux_rodata, NO_CONT_MAPPINGS, VM_NO_GUARD); map_kernel_segment(pgd, __inittext_begin, __inittext_end, text_prot, - &vmlinux_inittext, 0); + &vmlinux_inittext, 0, VM_NO_GUARD); map_kernel_segment(pgd, __initdata_begin, __initdata_end, PAGE_KERNEL, - &vmlinux_initdata, 0); - map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data, 0); + &vmlinux_initdata, 0, VM_NO_GUARD); + map_kernel_segment(pgd, _data, _end, PAGE_KERNEL, &vmlinux_data, 0, 0); if (!pgd_val(*pgd_offset_raw(pgd, FIXADDR_START))) { /*-- 2.1.4