[kernel-hardening] [PATCH v6 02/11] arm64: mmu: move TLB maintenance from callers to create_mapping_late()

Ard Biesheuvel
2017-03-09T20:52:00Z

In preparation of refactoring the kernel mapping logic so that text regions
are never mapped writable, which would require adding explicit TLB
maintenance to new call sites of create_mapping_late() (which is currently
invoked twice from the same function), move the TLB maintenance from the
call site into create_mapping_late() itself, and change it from a full
TLB flush into a flush by VA, which is more appropriate here.

Also, given that create_mapping_late() has evolved into a routine that only
updates protection bits on existing mappings, rename it to
update_mapping_prot()

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/mm/mmu.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index d28dbcf596b6..6cafd8723d1a 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -319,17 +319,20 @@ void __init create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
pgd_pgtable_alloc, page_mappings_only);
}

-static void create_mapping_late(phys_addr_t phys, unsigned long virt,
- phys_addr_t size, pgprot_t prot)
+static void update_mapping_prot(phys_addr_t phys, unsigned long virt,
+ phys_addr_t size, pgprot_t prot)
{
if (virt < VMALLOC_START) {
- pr_warn("BUG: not creating mapping for %pa at 0x%016lx - outside kernel range\n",
+ pr_warn("BUG: not updating mapping for %pa at 0x%016lx - outside kernel range\n",
&phys, virt);
return;
}

__create_pgd_mapping(init_mm.pgd, phys, virt, size, prot,
NULL, debug_pagealloc_enabled());
+
+ /* flush the TLBs after updating live kernel mappings */
+ flush_tlb_kernel_range(virt, virt + size);
}

static void __init __map_memblock(pgd_t *pgd, phys_addr_t start, phys_addr_t end)
@@ -402,19 +405,16 @@ void mark_rodata_ro(void)
unsigned long section_size;

section_size = (unsigned long)_etext - (unsigned long)_text;
- create_mapping_late(__pa_symbol(_text), (unsigned long)_text,
+ update_mapping_prot(__pa_symbol(_text), (unsigned long)_text,
section_size, PAGE_KERNEL_ROX);
/*
* mark .rodata as read only. Use __init_begin rather than __end_rodata
* to cover NOTES and EXCEPTION_TABLE.
*/
section_size = (unsigned long)__init_begin - (unsigned long)__start_rodata;
- create_mapping_late(__pa_symbol(__start_rodata), (unsigned long)__start_rodata,
+ update_mapping_prot(__pa_symbol(__start_rodata), (unsigned long)__start_rodata,
section_size, PAGE_KERNEL_RO);

- /* flush the TLBs after updating live kernel mappings */
- flush_tlb_all();
-
debug_checkwx();
}

--
2.7.4