[PATCH] arm64: kasan: Use actual memory node when populating the kernel image shadow

[Ard Biesheuvel]

On 11 March 2016 at 01:57, Catalin Marinas <catalin.marinas at arm.com> wrote:
> With the 16KB or 64KB page configurations, the generic
> vmemmap_populate() implementation warns on potential offnode
> page_structs via vmemmap_verify() because the arm64 kasan_init() passes
> NUMA_NO_NODE instead of the actual node for the kernel image memory.
>
> Fixes: f9040773b7bb ("arm64: move kernel image to base of vmalloc area")
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> Reported-by: James Morse <james.morse at arm.com>

I still think using vmemmap_populate() is somewhat of a hack here, and
the fact that we have different versions for 4k pages and !4k pages,
while perhaps justified for the actual real purpose of allocating
struct page arrays, makes this code more fragile than it needs to be.
How difficult would it be to simply have a kasan specific
vmalloc_shadow() function that performs a
memblock_alloc/create_mapping, and does the right thing wrt aligning
the edges, rather than putting knowledge about how vmemmap_populate
happens to align its allocations into the kasan code?

Regardless,

Acked-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>

> ---
>  arch/arm64/mm/kasan_init.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 56e19d150c21..a164183f3481 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -152,7 +152,8 @@ void __init kasan_init(void)
>
>         clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
>
> -       vmemmap_populate(kimg_shadow_start, kimg_shadow_end, NUMA_NO_NODE);
> +       vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
> +                        pfn_to_nid(virt_to_pfn(_text)));
>
>         /*
>          * vmemmap_populate() has populated the shadow region that covers the