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Subject[PATCH v1 1/2] x86/mm/kasan: don't use vmemmap_populate() to initialize shadow
Date
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.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
arch/x86/Kconfig | 2 +-
arch/x86/mm/kasan_init_64.c | 143 +++++++++++++++++++++++++++++++++++++++++---
2 files changed, 137 insertions(+), 8 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2fdb23313dd5..2896c14da4c1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -108,7 +108,7 @@ config X86
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE
select HAVE_ARCH_JUMP_LABEL
- select HAVE_ARCH_KASAN if X86_64 && SPARSEMEM_VMEMMAP
+ select HAVE_ARCH_KASAN if X86_64
select HAVE_ARCH_KGDB
select HAVE_ARCH_KMEMCHECK
select HAVE_ARCH_MMAP_RND_BITS if MMU
diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c
index 8f5be3eb40dd..31c779b2c3a0 100644
--- a/arch/x86/mm/kasan_init_64.c
+++ b/arch/x86/mm/kasan_init_64.c
@@ -4,19 +4,148 @@
#include <linux/bootmem.h>
#include <linux/kasan.h>
#include <linux/kdebug.h>
+#include <linux/memblock.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/sched/task.h>
#include <linux/vmalloc.h>

#include <asm/e820/types.h>
+#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/pgtable.h>

extern struct range pfn_mapped[E820_MAX_ENTRIES];

-static int __init map_range(struct range *range)
+static __init void *early_alloc(size_t size, int nid)
+{
+ return memblock_virt_alloc_try_nid_nopanic(size, size,
+ __pa(MAX_DMA_ADDRESS), BOOTMEM_ALLOC_ACCESSIBLE, nid);
+}
+
+static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr,
+ unsigned long end, int nid)
+{
+ pte_t *pte;
+
+ if (pmd_none(*pmd)) {
+ void *p;
+
+ if (boot_cpu_has(X86_FEATURE_PSE) &&
+ ((end - addr) == PMD_SIZE) &&
+ IS_ALIGNED(addr, PMD_SIZE)) {
+ p = early_alloc(PMD_SIZE, nid);
+ if (p && pmd_set_huge(pmd, __pa(p), PAGE_KERNEL))
+ return;
+ else if (p)
+ memblock_free(__pa(p), PMD_SIZE);
+ }
+
+ p = early_alloc(PAGE_SIZE, nid);
+ pmd_populate_kernel(&init_mm, pmd, p);
+ }
+
+ pte = pte_offset_kernel(pmd, addr);
+ do {
+ pte_t entry;
+ void *p;
+
+ if (!pte_none(*pte))
+ continue;
+
+ p = early_alloc(PAGE_SIZE, nid);
+ entry = pfn_pte(PFN_DOWN(__pa(p)), PAGE_KERNEL);
+ set_pte_at(&init_mm, addr, pte, entry);
+ } while (pte++, addr += PAGE_SIZE, addr != end);
+}
+
+static void __init kasan_populate_pud(pud_t *pud, unsigned long addr,
+ unsigned long end, int nid)
+{
+ pmd_t *pmd;
+ unsigned long next;
+
+ if (pud_none(*pud)) {
+ void *p;
+
+ if (boot_cpu_has(X86_FEATURE_GBPAGES) &&
+ ((end - addr) == PUD_SIZE) &&
+ IS_ALIGNED(addr, PUD_SIZE)) {
+ p = early_alloc(PUD_SIZE, nid);
+ if (p && pud_set_huge(pud, __pa(p), PAGE_KERNEL))
+ return;
+ else if (p)
+ memblock_free(__pa(p), PUD_SIZE);
+ }
+
+ p = early_alloc(PAGE_SIZE, nid);
+ pud_populate(&init_mm, pud, p);
+ }
+
+ pmd = pmd_offset(pud, addr);
+ do {
+ next = pmd_addr_end(addr, end);
+ if (!pmd_large(*pmd))
+ kasan_populate_pmd(pmd, addr, next, nid);
+ } while (pmd++, addr = next, addr != end);
+}
+
+static void __init kasan_populate_p4d(p4d_t *p4d, unsigned long addr,
+ unsigned long end, int nid)
+{
+ pud_t *pud;
+ unsigned long next;
+
+ if (p4d_none(*p4d)) {
+ void *p = early_alloc(PAGE_SIZE, nid);
+
+ p4d_populate(&init_mm, p4d, p);
+ }
+
+ pud = pud_offset(p4d, addr);
+ do {
+ next = pud_addr_end(addr, end);
+ if (!pud_large(*pud))
+ kasan_populate_pud(pud, addr, next, nid);
+ } while (pud++, addr = next, addr != end);
+}
+
+static void __init kasan_populate_pgd(pgd_t *pgd, unsigned long addr,
+ unsigned long end, int nid)
+{
+ void *p;
+ p4d_t *p4d;
+ unsigned long next;
+
+ if (pgd_none(*pgd)) {
+ p = early_alloc(PAGE_SIZE, nid);
+ pgd_populate(&init_mm, pgd, p);
+ }
+
+ p4d = p4d_offset(pgd, addr);
+ do {
+ next = p4d_addr_end(addr, end);
+ kasan_populate_p4d(p4d, addr, next, nid);
+ } while (p4d++, addr = next, addr != end);
+}
+
+static void __init kasan_populate_shadow(unsigned long addr, unsigned long end,
+ int nid)
+{
+ pgd_t *pgd;
+ unsigned long next;
+
+ addr = addr & PAGE_MASK;
+ end = round_up(end, PAGE_SIZE);
+ pgd = pgd_offset_k(addr);
+ do {
+ next = pgd_addr_end(addr, end);
+ kasan_populate_pgd(pgd, addr, next, nid);
+ } while (pgd++, addr = next, addr != end);
+}
+
+static void __init map_range(struct range *range)
{
unsigned long start;
unsigned long end;
@@ -24,7 +153,7 @@ static int __init map_range(struct range *range)
start = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->start));
end = (unsigned long)kasan_mem_to_shadow(pfn_to_kaddr(range->end));

- return vmemmap_populate(start, end, NUMA_NO_NODE);
+ kasan_populate_shadow(start, end, early_pfn_to_nid(range->start));
}

static void __init clear_pgds(unsigned long start,
@@ -130,16 +259,16 @@ void __init kasan_init(void)
if (pfn_mapped[i].end == 0)
break;

- if (map_range(&pfn_mapped[i]))
- panic("kasan: unable to allocate shadow!");
+ map_range(&pfn_mapped[i]);
}
+
kasan_populate_zero_shadow(
kasan_mem_to_shadow((void *)PAGE_OFFSET + MAXMEM),
kasan_mem_to_shadow((void *)__START_KERNEL_map));

- vmemmap_populate((unsigned long)kasan_mem_to_shadow(_stext),
- (unsigned long)kasan_mem_to_shadow(_end),
- NUMA_NO_NODE);
+ kasan_populate_shadow((unsigned long)kasan_mem_to_shadow(_stext),
+ (unsigned long)kasan_mem_to_shadow(_end),
+ early_pfn_to_nid(__pa(_stext)));

kasan_populate_zero_shadow(kasan_mem_to_shadow((void *)MODULES_END),
(void *)KASAN_SHADOW_END);
--
2.15.0
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