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[PATCH v8 09/11] x86/kasan: explicitly zero kasan shadow memory

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To optimize the performance of struct page initialization,
vmemmap_populate() will no longer zero memory.

We must explicitly zero the memory that is allocated by vmemmap_populate()
for kasan, as this memory does not go through struct page initialization
path.

Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Steven Sistare <steven.sistare@oracle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Reviewed-by: Bob Picco <bob.picco@oracle.com>
---
 arch/x86/mm/kasan_init_64.c | 66 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index bc84b73684b7..cc0399032673 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -84,6 +84,66 @@ static struct notifier_block kasan_die_notifier = {
 };
 #endif
 
+/*
+ * x86 variant of vmemmap_populate() uses either PMD_SIZE pages or base pages
+ * to map allocated memory.  This routine determines the page size for the given
+ * address from vmemmap.
+ */
+static u64 get_vmemmap_pgsz(u64 addr)
+{
+	pgd_t *pgd;
+	p4d_t *p4d;
+	pud_t *pud;
+	pmd_t *pmd;
+
+	pgd = pgd_offset_k(addr);
+	BUG_ON(pgd_none(*pgd) || pgd_large(*pgd));
+
+	p4d = p4d_offset(pgd, addr);
+	BUG_ON(p4d_none(*p4d) || p4d_large(*p4d));
+
+	pud = pud_offset(p4d, addr);
+	BUG_ON(pud_none(*pud) || pud_large(*pud));
+
+	pmd = pmd_offset(pud, addr);
+	BUG_ON(pmd_none(*pmd));
+
+	if (pmd_large(*pmd))
+		return PMD_SIZE;
+	return PAGE_SIZE;
+}
+
+/*
+ * Memory that was allocated by vmemmap_populate is not zeroed, so we must
+ * zero it here explicitly.
+ */
+static void
+zero_vmemmap_populated_memory(void)
+{
+	u64 i, start, end;
+
+	for (i = 0; i < E820_MAX_ENTRIES && pfn_mapped[i].end; i++) {
+		void *kaddr_start = pfn_to_kaddr(pfn_mapped[i].start);
+		void *kaddr_end = pfn_to_kaddr(pfn_mapped[i].end);
+
+		start = (u64)kasan_mem_to_shadow(kaddr_start);
+		end = (u64)kasan_mem_to_shadow(kaddr_end);
+
+		/* Round to the start end of the mapped pages */
+		start = rounddown(start, get_vmemmap_pgsz(start));
+		end = roundup(end, get_vmemmap_pgsz(start));
+		memset((void *)start, 0, end - start);
+	}
+
+	start = (u64)kasan_mem_to_shadow(_stext);
+	end = (u64)kasan_mem_to_shadow(_end);
+
+	/* Round to the start end of the mapped pages */
+	start = rounddown(start, get_vmemmap_pgsz(start));
+	end = roundup(end, get_vmemmap_pgsz(start));
+	memset((void *)start, 0, end - start);
+}
+
 void __init kasan_early_init(void)
 {
 	int i;
@@ -146,6 +206,12 @@ void __init kasan_init(void)
 	load_cr3(init_top_pgt);
 	__flush_tlb_all();
 
+	/*
+	 * vmemmap_populate does not zero the memory, so we need to zero it
+	 * explicitly
+	 */
+	zero_vmemmap_populated_memory();
+
 	/*
 	 * kasan_zero_page has been used as early shadow memory, thus it may
 	 * contain some garbage. Now we can clear and write protect it, since
-- 
2.14.1

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[PATCH v7 00/11] complete deferred page initialization Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 03/11] mm: deferred_init_memmap improvements Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 02/11] sparc64/mm: setting fields in deferred pages Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 11/11] mm: stop zeroing memory during allocation in vmemmap Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 05/11] mm: defining memblock_virt_alloc_try_nid_raw Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 09/11] x86/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 08/11] mm: zero reserved and unavailable struct pages Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 07/11] sparc64: optimized struct page zeroing Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 06/11] mm: zero struct pages during initialization Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 04/11] sparc64: simplify vmemmap_populate Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 01/11] x86/mm: setting fields in deferred pages Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
  [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:40 +0200
    Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Mark Rutland <mark.rutland@arm.com> - 2017-09-15 03:20 +0200
      Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 03:40 +0200
        Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Mark Rutland <mark.rutland@arm.com> - 2017-09-15 22:40 +0200
          Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 23:30 +0200
            Re: [PATCH v8 10/11] arm64/kasan: explicitly zero kasan shadow memory Mark Rutland <mark.rutland@arm.com> - 2017-09-16 00:20 +0200
  [PATCH v8 00/11] complete deferred page initialization Pavel Tatashin <pasha.tatashin@oracle.com> - 2017-09-15 00:50 +0200

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