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SubjectRe: [PATCH v2 5/5] x86/kasan: Populate shadow for shared chunk of the CPU entry area
On Mon, Nov 14, 2022, Peter Zijlstra wrote:
> On Mon, Nov 14, 2022 at 05:44:00PM +0300, Andrey Ryabinin wrote:
> > Going back kasan_populate_shadow() seems like safer and easier choice.
> > The only disadvantage of it that we might waste 1 page, which is not
> > much compared to the KASAN memory overhead.
>
> So the below delta?
>
> ---
> --- a/arch/x86/mm/kasan_init_64.c
> +++ b/arch/x86/mm/kasan_init_64.c
> @@ -388,7 +388,7 @@ void __init kasan_init(void)
> shadow_cea_end = kasan_mem_to_shadow_align_up(CPU_ENTRY_AREA_BASE +
> CPU_ENTRY_AREA_MAP_SIZE);
>
> - kasan_populate_early_shadow(
> + kasan_populate_shadow(
> kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
> kasan_mem_to_shadow((void *)VMALLOC_START));

Wrong one, that's the existing mapping. To get back to v1:

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index af82046348a0..0302491d799d 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -416,8 +416,8 @@ void __init kasan_init(void)
* area is randomly placed somewhere in the 512GiB range and mapping
* the entire 512GiB range is prohibitively expensive.
*/
- kasan_populate_early_shadow((void *)shadow_cea_begin,
- (void *)shadow_cea_per_cpu_begin);
+ kasan_populate_shadow(shadow_cea_begin,
+ shadow_cea_per_cpu_begin, 0);

kasan_populate_early_shadow((void *)shadow_cea_end,
kasan_mem_to_shadow((void *)__START_KERNEL_map));
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