arm64/mm/kasan: don't use vmemmap_populate() to initialize shadow

The kasan shadow is currently mapped using vmemmap_populate() since that
provides a semi-convenient way to map pages into init_top_pgt.  However,
since that no longer zeroes the mapped pages, it is not suitable for
kasan, which requires zeroed shadow memory.

Add kasan_populate_shadow() interface and use it instead of
vmemmap_populate().  Besides, this allows us to take advantage of
gigantic pages and use them to populate the shadow, which should save us
some memory wasted on page tables and reduce TLB pressure.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>
Signed-off-by: Pavel Tatashin <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Steven Sistare <[email protected]>
Cc: Daniel Jordan <[email protected]>
Cc: Bob Picco <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Ard Biesheuvel <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: David S. Miller <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: wildea01

arch/arm64/Kconfig

@@ -85,7 +85,7 @@ config ARM64
 	select HAVE_ARCH_BITREVERSE
 	select HAVE_ARCH_HUGE_VMAP
 	select HAVE_ARCH_JUMP_LABEL
-	select HAVE_ARCH_KASAN if SPARSEMEM_VMEMMAP && !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
+	select HAVE_ARCH_KASAN if !(ARM64_16K_PAGES && ARM64_VA_BITS_48)
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_MMAP_RND_BITS
 	select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT

arch/arm64/mm/kasan_init.c

@@ -11,6 +11,7 @@
  */
 
 #define pr_fmt(fmt) "kasan: " fmt
+#include <linux/bootmem.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/sched/task.h>
@@ -35,77 +36,117 @@ static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
  * with the physical address from __pa_symbol.
  */
 
-static void __init kasan_early_pte_populate(pmd_t *pmd, unsigned long addr,
-					unsigned long end)
+static phys_addr_t __init kasan_alloc_zeroed_page(int node)
 {
-	pte_t *pte;
-	unsigned long next;
+	void *p = memblock_virt_alloc_try_nid(PAGE_SIZE, PAGE_SIZE,
+					      __pa(MAX_DMA_ADDRESS),
+					      MEMBLOCK_ALLOC_ACCESSIBLE, node);
+	return __pa(p);
+}
+
+static pte_t *__init kasan_pte_offset(pmd_t *pmd, unsigned long addr, int node,
+				      bool early)
+{
+	if (pmd_none(*pmd)) {
+		phys_addr_t pte_phys = early ? __pa_symbol(kasan_zero_pte)
+					     : kasan_alloc_zeroed_page(node);
+		__pmd_populate(pmd, pte_phys, PMD_TYPE_TABLE);
+	}
+
+	return early ? pte_offset_kimg(pmd, addr)
+		     : pte_offset_kernel(pmd, addr);
+}
 
-	if (pmd_none(*pmd))
-		__pmd_populate(pmd, __pa_symbol(kasan_zero_pte), PMD_TYPE_TABLE);
+static pmd_t *__init kasan_pmd_offset(pud_t *pud, unsigned long addr, int node,
+				      bool early)
+{
+	if (pud_none(*pud)) {
+		phys_addr_t pmd_phys = early ? __pa_symbol(kasan_zero_pmd)
+					     : kasan_alloc_zeroed_page(node);
+		__pud_populate(pud, pmd_phys, PMD_TYPE_TABLE);
+	}
+
+	return early ? pmd_offset_kimg(pud, addr) : pmd_offset(pud, addr);
+}
+
+static pud_t *__init kasan_pud_offset(pgd_t *pgd, unsigned long addr, int node,
+				      bool early)
+{
+	if (pgd_none(*pgd)) {
+		phys_addr_t pud_phys = early ? __pa_symbol(kasan_zero_pud)
+					     : kasan_alloc_zeroed_page(node);
+		__pgd_populate(pgd, pud_phys, PMD_TYPE_TABLE);
+	}
+
+	return early ? pud_offset_kimg(pgd, addr) : pud_offset(pgd, addr);
+}
+
+static void __init kasan_pte_populate(pmd_t *pmd, unsigned long addr,
+				      unsigned long end, int node, bool early)
+{
+	unsigned long next;
+	pte_t *pte = kasan_pte_offset(pmd, addr, node, early);
 
-	pte = pte_offset_kimg(pmd, addr);
 	do {
+		phys_addr_t page_phys = early ? __pa_symbol(kasan_zero_page)
+					      : kasan_alloc_zeroed_page(node);
 		next = addr + PAGE_SIZE;
-		set_pte(pte, pfn_pte(sym_to_pfn(kasan_zero_page),
-					PAGE_KERNEL));
+		set_pte(pte, pfn_pte(__phys_to_pfn(page_phys), PAGE_KERNEL));
 	} while (pte++, addr = next, addr != end && pte_none(*pte));
 }
 
-static void __init kasan_early_pmd_populate(pud_t *pud,
-					unsigned long addr,
-					unsigned long end)
+static void __init kasan_pmd_populate(pud_t *pud, unsigned long addr,
+				      unsigned long end, int node, bool early)
 {
-	pmd_t *pmd;
 	unsigned long next;
+	pmd_t *pmd = kasan_pmd_offset(pud, addr, node, early);
 
-	if (pud_none(*pud))
-		__pud_populate(pud, __pa_symbol(kasan_zero_pmd), PMD_TYPE_TABLE);
-
-	pmd = pmd_offset_kimg(pud, addr);
 	do {
 		next = pmd_addr_end(addr, end);
-		kasan_early_pte_populate(pmd, addr, next);
+		kasan_pte_populate(pmd, addr, next, node, early);
 	} while (pmd++, addr = next, addr != end && pmd_none(*pmd));
 }
 
-static void __init kasan_early_pud_populate(pgd_t *pgd,
-					unsigned long addr,
-					unsigned long end)
+static void __init kasan_pud_populate(pgd_t *pgd, unsigned long addr,
+				      unsigned long end, int node, bool early)
 {
-	pud_t *pud;
 	unsigned long next;
+	pud_t *pud = kasan_pud_offset(pgd, addr, node, early);
 
-	if (pgd_none(*pgd))
-		__pgd_populate(pgd, __pa_symbol(kasan_zero_pud), PUD_TYPE_TABLE);
-
-	pud = pud_offset_kimg(pgd, addr);
 	do {
 		next = pud_addr_end(addr, end);
-		kasan_early_pmd_populate(pud, addr, next);
+		kasan_pmd_populate(pud, addr, next, node, early);
 	} while (pud++, addr = next, addr != end && pud_none(*pud));
 }
 
-static void __init kasan_map_early_shadow(void)
+static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
+				      int node, bool early)
 {
-	unsigned long addr = KASAN_SHADOW_START;
-	unsigned long end = KASAN_SHADOW_END;
 	unsigned long next;
 	pgd_t *pgd;
 
 	pgd = pgd_offset_k(addr);
 	do {
 		next = pgd_addr_end(addr, end);
-		kasan_early_pud_populate(pgd, addr, next);
+		kasan_pud_populate(pgd, addr, next, node, early);
 	} while (pgd++, addr = next, addr != end);
 }
 
+/* The early shadow maps everything to a single page of zeroes */
 asmlinkage void __init kasan_early_init(void)
 {
 	BUILD_BUG_ON(KASAN_SHADOW_OFFSET != KASAN_SHADOW_END - (1UL << 61));
 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_START, PGDIR_SIZE));
 	BUILD_BUG_ON(!IS_ALIGNED(KASAN_SHADOW_END, PGDIR_SIZE));
-	kasan_map_early_shadow();
+	kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, NUMA_NO_NODE,
+			   true);
+}
+
+/* Set up full kasan mappings, ensuring that the mapped pages are zeroed */
+static void __init kasan_map_populate(unsigned long start, unsigned long end,
+				      int node)
+{
+	kasan_pgd_populate(start & PAGE_MASK, PAGE_ALIGN(end), node, false);
 }
 
 /*
@@ -142,8 +183,8 @@ void __init kasan_init(void)
 	struct memblock_region *reg;
 	int i;
 
-	kimg_shadow_start = (u64)kasan_mem_to_shadow(_text);
-	kimg_shadow_end = (u64)kasan_mem_to_shadow(_end);
+	kimg_shadow_start = (u64)kasan_mem_to_shadow(_text) & PAGE_MASK;
+	kimg_shadow_end = PAGE_ALIGN((u64)kasan_mem_to_shadow(_end));
 
 	mod_shadow_start = (u64)kasan_mem_to_shadow((void *)MODULES_VADDR);
 	mod_shadow_end = (u64)kasan_mem_to_shadow((void *)MODULES_END);
@@ -161,19 +202,8 @@ void __init kasan_init(void)
 
 	clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
 
-	vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
-			 pfn_to_nid(virt_to_pfn(lm_alias(_text))));
-
-	/*
-	 * vmemmap_populate() has populated the shadow region that covers the
-	 * kernel image with SWAPPER_BLOCK_SIZE mappings, so we have to round
-	 * the start and end addresses to SWAPPER_BLOCK_SIZE as well, to prevent
-	 * kasan_populate_zero_shadow() from replacing the page table entries
-	 * (PMD or PTE) at the edges of the shadow region for the kernel
-	 * image.
-	 */
-	kimg_shadow_start = round_down(kimg_shadow_start, SWAPPER_BLOCK_SIZE);
-	kimg_shadow_end = round_up(kimg_shadow_end, SWAPPER_BLOCK_SIZE);
+	kasan_map_populate(kimg_shadow_start, kimg_shadow_end,
+			   pfn_to_nid(virt_to_pfn(lm_alias(_text))));
 
 	kasan_populate_zero_shadow((void *)KASAN_SHADOW_START,
 				   (void *)mod_shadow_start);
@@ -191,9 +221,9 @@ void __init kasan_init(void)
 		if (start >= end)
 			break;
 
-		vmemmap_populate((unsigned long)kasan_mem_to_shadow(start),
-				(unsigned long)kasan_mem_to_shadow(end),
-				pfn_to_nid(virt_to_pfn(start)));
+		kasan_map_populate((unsigned long)kasan_mem_to_shadow(start),
+				   (unsigned long)kasan_mem_to_shadow(end),
+				   pfn_to_nid(virt_to_pfn(start)));
 	}
 
 	/*