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SubjectRe: [PATCH v2] mm/memblock: skip kmemleak for kasan_init()
On Wed, Nov 28, 2018 at 05:08:45PM -0500, Qian Cai wrote:
> Kmemleak does not play well with KASAN (tested on both HPE Apollo 70 and
> Huawei TaiShan 2280 aarch64 servers).
>
> After calling start_kernel()->setup_arch()->kasan_init(), kmemleak early
> log buffer went from something like 280 to 260000 which caused kmemleak
> disabled and crash dump memory reservation failed. The multitude of
> kmemleak_alloc() calls is from nested loops while KASAN is setting up
> full memory mappings, so let early kmemleak allocations skip those
> memblock_alloc_internal() calls came from kasan_init() given that those
> early KASAN memory mappings should not reference to other memory.
> Hence, no kmemleak false positives.
>
> kasan_init
> kasan_map_populate [1]
> kasan_pgd_populate [2]
> kasan_pud_populate [3]
> kasan_pmd_populate [4]
> kasan_pte_populate [5]
> kasan_alloc_zeroed_page
> memblock_alloc_try_nid
> memblock_alloc_internal
> kmemleak_alloc
>
> [1] for_each_memblock(memory, reg)
> [2] while (pgdp++, addr = next, addr != end)
> [3] while (pudp++, addr = next, addr != end && pud_none(READ_ONCE(*pudp)))
> [4] while (pmdp++, addr = next, addr != end && pmd_none(READ_ONCE(*pmdp)))
> [5] while (ptep++, addr = next, addr != end && pte_none(READ_ONCE(*ptep)))
>
> Signed-off-by: Qian Cai <cai@gmx.us>

Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> # memblock parts

> ---
>
> Changes since v1:
> * only skip memblock_alloc_internal() calls came from kasan_int().
>
> arch/arm64/mm/kasan_init.c | 2 +-
> include/linux/memblock.h | 1 +
> mm/memblock.c | 19 +++++++++++--------
> 3 files changed, 13 insertions(+), 9 deletions(-)
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index 63527e5..fcb2ca3 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -39,7 +39,7 @@ static phys_addr_t __init kasan_alloc_zeroed_page(int node)
> {
> void *p = memblock_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
> __pa(MAX_DMA_ADDRESS),
> - MEMBLOCK_ALLOC_ACCESSIBLE, node);
> + MEMBLOCK_ALLOC_KASAN, node);
> return __pa(p);
> }
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index aee299a..3ef3086 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -320,6 +320,7 @@ static inline int memblock_get_region_node(const struct memblock_region *r)
> /* Flags for memblock allocation APIs */
> #define MEMBLOCK_ALLOC_ANYWHERE (~(phys_addr_t)0)
> #define MEMBLOCK_ALLOC_ACCESSIBLE 0
> +#define MEMBLOCK_ALLOC_KASAN 1
>
> /* We are using top down, so it is safe to use 0 here */
> #define MEMBLOCK_LOW_LIMIT 0
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 9a2d5ae..abb9f7f 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -262,7 +262,8 @@ phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
> phys_addr_t kernel_end, ret;
>
> /* pump up @end */
> - if (end == MEMBLOCK_ALLOC_ACCESSIBLE)
> + if (end == MEMBLOCK_ALLOC_ACCESSIBLE ||
> + end == MEMBLOCK_ALLOC_KASAN)
> end = memblock.current_limit;
>
> /* avoid allocating the first page */
> @@ -1412,13 +1413,15 @@ static void * __init memblock_alloc_internal(
> done:
> ptr = phys_to_virt(alloc);
>
> - /*
> - * The min_count is set to 0 so that bootmem allocated blocks
> - * are never reported as leaks. This is because many of these blocks
> - * are only referred via the physical address which is not
> - * looked up by kmemleak.
> - */
> - kmemleak_alloc(ptr, size, 0, 0);
> + /* Skip kmemleak for kasan_init() due to high volume. */
> + if (max_addr != MEMBLOCK_ALLOC_KASAN)
> + /*
> + * The min_count is set to 0 so that bootmem allocated
> + * blocks are never reported as leaks. This is because many
> + * of these blocks are only referred via the physical
> + * address which is not looked up by kmemleak.
> + */
> + kmemleak_alloc(ptr, size, 0, 0);
>
> return ptr;
> }
> --
> 1.8.3.1
>

--
Sincerely yours,
Mike.

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