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    SubjectRe: [PATCH v9 09/12] mm/kasan: kasan specific map populate function
    Hi Pavel,

    On Wed, Sep 20, 2017 at 04:17:11PM -0400, Pavel Tatashin wrote:
    > During early boot, kasan uses vmemmap_populate() to establish its shadow
    > memory. But, that interface is intended for struct pages use.
    >
    > Because of the current project, vmemmap won't be zeroed during allocation,
    > but kasan expects that memory to be zeroed. We are adding a new
    > kasan_map_populate() function to resolve this difference.

    Thanks for putting this together.

    I've given this a spin on arm64, and can confirm that it works.

    Given that this involes redundant walking of page tables, I still think
    it'd be preferable to have some common *_populate() helper that took a
    gfp argument, but I guess it's not the end of the world.

    I'll leave it to Will and Catalin to say whether they're happy with the
    page table walking and the new p{u,m}d_large() helpers added to arm64.

    Thanks,
    Mark.

    >
    > Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
    > ---
    > arch/arm64/include/asm/pgtable.h | 3 ++
    > include/linux/kasan.h | 2 ++
    > mm/kasan/kasan_init.c | 67 ++++++++++++++++++++++++++++++++++++++++
    > 3 files changed, 72 insertions(+)
    >
    > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
    > index bc4e92337d16..d89713f04354 100644
    > --- a/arch/arm64/include/asm/pgtable.h
    > +++ b/arch/arm64/include/asm/pgtable.h
    > @@ -381,6 +381,9 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
    > PUD_TYPE_TABLE)
    > #endif
    >
    > +#define pmd_large(pmd) pmd_sect(pmd)
    > +#define pud_large(pud) pud_sect(pud)
    > +
    > static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
    > {
    > *pmdp = pmd;
    > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
    > index a5c7046f26b4..7e13df1722c2 100644
    > --- a/include/linux/kasan.h
    > +++ b/include/linux/kasan.h
    > @@ -78,6 +78,8 @@ size_t kasan_metadata_size(struct kmem_cache *cache);
    >
    > bool kasan_save_enable_multi_shot(void);
    > void kasan_restore_multi_shot(bool enabled);
    > +int __meminit kasan_map_populate(unsigned long start, unsigned long end,
    > + int node);
    >
    > #else /* CONFIG_KASAN */
    >
    > diff --git a/mm/kasan/kasan_init.c b/mm/kasan/kasan_init.c
    > index 554e4c0f23a2..57a973f05f63 100644
    > --- a/mm/kasan/kasan_init.c
    > +++ b/mm/kasan/kasan_init.c
    > @@ -197,3 +197,70 @@ void __init kasan_populate_zero_shadow(const void *shadow_start,
    > zero_p4d_populate(pgd, addr, next);
    > } while (pgd++, addr = next, addr != end);
    > }
    > +
    > +/* Creates mappings for kasan during early boot. The mapped memory is zeroed */
    > +int __meminit kasan_map_populate(unsigned long start, unsigned long end,
    > + int node)
    > +{
    > + unsigned long addr, pfn, next;
    > + unsigned long long size;
    > + pgd_t *pgd;
    > + p4d_t *p4d;
    > + pud_t *pud;
    > + pmd_t *pmd;
    > + pte_t *pte;
    > + int ret;
    > +
    > + ret = vmemmap_populate(start, end, node);
    > + /*
    > + * We might have partially populated memory, so check for no entries,
    > + * and zero only those that actually exist.
    > + */
    > + for (addr = start; addr < end; addr = next) {
    > + pgd = pgd_offset_k(addr);
    > + if (pgd_none(*pgd)) {
    > + next = pgd_addr_end(addr, end);
    > + continue;
    > + }
    > +
    > + p4d = p4d_offset(pgd, addr);
    > + if (p4d_none(*p4d)) {
    > + next = p4d_addr_end(addr, end);
    > + continue;
    > + }
    > +
    > + pud = pud_offset(p4d, addr);
    > + if (pud_none(*pud)) {
    > + next = pud_addr_end(addr, end);
    > + continue;
    > + }
    > + if (pud_large(*pud)) {
    > + /* This is PUD size page */
    > + next = pud_addr_end(addr, end);
    > + size = PUD_SIZE;
    > + pfn = pud_pfn(*pud);
    > + } else {
    > + pmd = pmd_offset(pud, addr);
    > + if (pmd_none(*pmd)) {
    > + next = pmd_addr_end(addr, end);
    > + continue;
    > + }
    > + if (pmd_large(*pmd)) {
    > + /* This is PMD size page */
    > + next = pmd_addr_end(addr, end);
    > + size = PMD_SIZE;
    > + pfn = pmd_pfn(*pmd);
    > + } else {
    > + pte = pte_offset_kernel(pmd, addr);
    > + next = addr + PAGE_SIZE;
    > + if (pte_none(*pte))
    > + continue;
    > + /* This is base size page */
    > + size = PAGE_SIZE;
    > + pfn = pte_pfn(*pte);
    > + }
    > + }
    > + memset(phys_to_virt(PFN_PHYS(pfn)), 0, size);
    > + }
    > + return ret;
    > +}
    > --
    > 2.14.1
    >

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