Re: [PATCH v9 09/12] mm/kasan: kasan specific map populate function
From: Mark Rutland <mark.rutland@arm.com>
Date: 2017-10-03 14:50:20
Also in:
linux-arm-kernel, linux-mm, lkml, sparclinux
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.
quoted hunk ↗ jump to hunk
Signed-off-by: Pavel Tatashin <redacted> --- 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