On Tue, Nov 06, 2018 at 06:30:22PM +0100, Andrey Konovalov wrote:
> A tag-based KASAN shadow memory cell contains a memory tag, that
> corresponds to the tag in the top byte of the pointer, that points to that
> memory. The native top byte value of kernel pointers is 0xff, so with
> tag-based KASAN we need to initialize shadow memory to 0xff.
>
> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> ---
> arch/arm64/mm/kasan_init.c | 16 ++++++++++++++--
> include/linux/kasan.h | 8 ++++++++
> mm/kasan/common.c | 3 ++-
> 3 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 63527e585aac..18ebc8994a7b 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -43,6 +43,15 @@ static phys_addr_t __init kasan_alloc_zeroed_page(int node)
> return __pa(p);
> }
>
> +static phys_addr_t __init kasan_alloc_raw_page(int node)
> +{
> + void *p = memblock_alloc_try_nid_raw(PAGE_SIZE, PAGE_SIZE,
> + __pa(MAX_DMA_ADDRESS),
> + MEMBLOCK_ALLOC_ACCESSIBLE,
> + node);
> + return __pa(p);
> +}
> +
> static pte_t *__init kasan_pte_offset(pmd_t *pmdp, unsigned long addr, int node,
> bool early)
> {
> @@ -88,7 +97,9 @@ static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
>
> do {
> phys_addr_t page_phys = early ? __pa_symbol(kasan_zero_page)
> - : kasan_alloc_zeroed_page(node);
> + : kasan_alloc_raw_page(node);
> + if (!early)
> + memset(__va(page_phys), KASAN_SHADOW_INIT, PAGE_SIZE);
> next = addr + PAGE_SIZE;
> set_pte(ptep, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
> } while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)));
> @@ -138,6 +149,7 @@ asmlinkage void __init kasan_early_init(void)
> KASAN_SHADOW_END - (1UL << (64 - KASAN_SHADOW_SCALE_SHIFT)));
> BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
> BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
> +
> kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
> true);
> }
> @@ -234,7 +246,7 @@ void __init kasan_init(void)
> set_pte(&kasan_zero_pte[i],
> pfn_pte(sym_to_pfn(kasan_zero_page), PAGE_KERNEL_RO));
>
> - memset(kasan_zero_page, 0, PAGE_SIZE);
> + memset(kasan_zero_page, KASAN_SHADOW_INIT, PAGE_SIZE);
If this isn't going to contain zero, can we please have a preparatory
patch renaming this to something which isn't misleading?
Perhaps kasan_common_shadow_page?
Thanks,
Mark.
