[PATCH v6 14/44] mm: kmsan: maintain KMSAN metadata for page operations

Alexander Potapenko
2022-09-05T12:28:05Z

Insert KMSAN hooks that make the necessary bookkeeping changes:
- poison page shadow and origins in alloc_pages()/free_page();
- clear page shadow and origins in clear_page(), copy_user_highpage();
- copy page metadata in copy_highpage(), wp_page_copy();
- handle vmap()/vunmap()/iounmap();

Signed-off-by: Alexander Potapenko <glider@google.com>
---
v2:
-- move page metadata hooks implementation here
-- remove call to kmsan_memblock_free_pages()

v3:
-- use PAGE_SHIFT in kmsan_ioremap_page_range()

v4:
-- change sizeof(type) to sizeof(*ptr)
-- replace occurrences of |var| with @var
-- swap mm: and kmsan: in the subject
-- drop __no_sanitize_memory from clear_page()

v5:
-- do not export KMSAN hooks that are not called from modules
-- use modern style for-loops
-- simplify clear_page() instrumentation as suggested by Marco Elver
-- move forward declaration of `struct page` in kmsan.h to this patch

v6:
-- <linux/kmsan.h> doesn't exist prior to this patch

Link: https://linux-review.googlesource.com/id/I6d4f53a0e7eab46fa29f0348f3095d9f2e326850
---
arch/x86/include/asm/page_64.h | 7 ++
arch/x86/mm/ioremap.c | 3 +
include/linux/highmem.h | 3 +
include/linux/kmsan.h | 145 +++++++++++++++++++++++++++++++++
mm/internal.h | 6 ++
mm/kmsan/hooks.c | 86 +++++++++++++++++++
mm/kmsan/shadow.c | 113 +++++++++++++++++++++++++
mm/memory.c | 2 +
mm/page_alloc.c | 11 +++
mm/vmalloc.c | 20 ++++-
10 files changed, 394 insertions(+), 2 deletions(-)
create mode 100644 include/linux/kmsan.h

diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index baa70451b8df5..198e03e59ca19 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -8,6 +8,8 @@
#include <asm/cpufeatures.h>
#include <asm/alternative.h>

+#include <linux/kmsan-checks.h>
+
/* duplicated to the one in bootmem.h */
extern unsigned long max_pfn;
extern unsigned long phys_base;
@@ -47,6 +49,11 @@ void clear_page_erms(void *page);

static inline void clear_page(void *page)
{
+ /*
+ * Clean up KMSAN metadata for the page being cleared. The assembly call
+ * below clobbers @page, so we perform unpoisoning before it.
+ */
+ kmsan_unpoison_memory(page, PAGE_SIZE);
alternative_call_2(clear_page_orig,
clear_page_rep, X86_FEATURE_REP_GOOD,
clear_page_erms, X86_FEATURE_ERMS,
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 1ad0228f8ceb9..78c5bc654cff5 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -17,6 +17,7 @@
#include <linux/cc_platform.h>
#include <linux/efi.h>
#include <linux/pgtable.h>
+#include <linux/kmsan.h>

#include <asm/set_memory.h>
#include <asm/e820/api.h>
@@ -479,6 +480,8 @@ void iounmap(volatile void __iomem *addr)
return;
}

+ kmsan_iounmap_page_range((unsigned long)addr,
+ (unsigned long)addr + get_vm_area_size(p));
memtype_free(p->phys_addr, p->phys_addr + get_vm_area_size(p));

/* Finally remove it */
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 25679035ca283..e9912da5441b4 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -6,6 +6,7 @@
#include <linux/kernel.h>
#include <linux/bug.h>
#include <linux/cacheflush.h>
+#include <linux/kmsan.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
@@ -311,6 +312,7 @@ static inline void copy_user_highpage(struct page *to, struct page *from,
vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
copy_user_page(vto, vfrom, vaddr, to);
+ kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
kunmap_local(vto);
kunmap_local(vfrom);
}
@@ -326,6 +328,7 @@ static inline void copy_highpage(struct page *to, struct page *from)
vfrom = kmap_local_page(from);
vto = kmap_local_page(to);
copy_page(vto, vfrom);
+ kmsan_copy_page_meta(to, from);
kunmap_local(vto);
kunmap_local(vfrom);
}
diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
new file mode 100644
index 0000000000000..b36bf3db835ee
--- /dev/null
+++ b/include/linux/kmsan.h
@@ -0,0 +1,145 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * KMSAN API for subsystems.
+ *
+ * Copyright (C) 2017-2022 Google LLC
+ * Author: Alexander Potapenko <glider@google.com>
+ *
+ */
+#ifndef _LINUX_KMSAN_H
+#define _LINUX_KMSAN_H
+
+#include <linux/gfp.h>
+#include <linux/kmsan-checks.h>
+#include <linux/types.h>
+
+struct page;
+
+#ifdef CONFIG_KMSAN
+
+/**
+ * kmsan_alloc_page() - Notify KMSAN about an alloc_pages() call.
+ * @page: struct page pointer returned by alloc_pages().
+ * @order: order of allocated struct page.
+ * @flags: GFP flags used by alloc_pages()
+ *
+ * KMSAN marks 1<<@order pages starting at @page as uninitialized, unless
+ * @flags contain __GFP_ZERO.
+ */
+void kmsan_alloc_page(struct page *page, unsigned int order, gfp_t flags);
+
+/**
+ * kmsan_free_page() - Notify KMSAN about a free_pages() call.
+ * @page: struct page pointer passed to free_pages().
+ * @order: order of deallocated struct page.
+ *
+ * KMSAN marks freed memory as uninitialized.
+ */
+void kmsan_free_page(struct page *page, unsigned int order);
+
+/**
+ * kmsan_copy_page_meta() - Copy KMSAN metadata between two pages.
+ * @dst: destination page.
+ * @src: source page.
+ *
+ * KMSAN copies the contents of metadata pages for @src into the metadata pages
+ * for @dst. If @dst has no associated metadata pages, nothing happens.
+ * If @src has no associated metadata pages, @dst metadata pages are unpoisoned.
+ */
+void kmsan_copy_page_meta(struct page *dst, struct page *src);
+
+/**
+ * kmsan_map_kernel_range_noflush() - Notify KMSAN about a vmap.
+ * @start: start of vmapped range.
+ * @end: end of vmapped range.
+ * @prot: page protection flags used for vmap.
+ * @pages: array of pages.
+ * @page_shift: page_shift passed to vmap_range_noflush().
+ *
+ * KMSAN maps shadow and origin pages of @pages into contiguous ranges in
+ * vmalloc metadata address range.
+ */
+void kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
+ pgprot_t prot, struct page **pages,
+ unsigned int page_shift);
+
+/**
+ * kmsan_vunmap_kernel_range_noflush() - Notify KMSAN about a vunmap.
+ * @start: start of vunmapped range.
+ * @end: end of vunmapped range.
+ *
+ * KMSAN unmaps the contiguous metadata ranges created by
+ * kmsan_map_kernel_range_noflush().
+ */
+void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end);
+
+/**
+ * kmsan_ioremap_page_range() - Notify KMSAN about a ioremap_page_range() call.
+ * @addr: range start.
+ * @end: range end.
+ * @phys_addr: physical range start.
+ * @prot: page protection flags used for ioremap_page_range().
+ * @page_shift: page_shift argument passed to vmap_range_noflush().
+ *
+ * KMSAN creates new metadata pages for the physical pages mapped into the
+ * virtual memory.
+ */
+void kmsan_ioremap_page_range(unsigned long addr, unsigned long end,
+ phys_addr_t phys_addr, pgprot_t prot,
+ unsigned int page_shift);
+
+/**
+ * kmsan_iounmap_page_range() - Notify KMSAN about a iounmap_page_range() call.
+ * @start: range start.
+ * @end: range end.
+ *
+ * KMSAN unmaps the metadata pages for the given range and, unlike for
+ * vunmap_page_range(), also deallocates them.
+ */
+void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
+
+#else
+
+static inline int kmsan_alloc_page(struct page *page, unsigned int order,
+ gfp_t flags)
+{
+ return 0;
+}
+
+static inline void kmsan_free_page(struct page *page, unsigned int order)
+{
+}
+
+static inline void kmsan_copy_page_meta(struct page *dst, struct page *src)
+{
+}
+
+static inline void kmsan_vmap_pages_range_noflush(unsigned long start,
+ unsigned long end,
+ pgprot_t prot,
+ struct page **pages,
+ unsigned int page_shift)
+{
+}
+
+static inline void kmsan_vunmap_range_noflush(unsigned long start,
+ unsigned long end)
+{
+}
+
+static inline void kmsan_ioremap_page_range(unsigned long start,
+ unsigned long end,
+ phys_addr_t phys_addr,
+ pgprot_t prot,
+ unsigned int page_shift)
+{
+}
+
+static inline void kmsan_iounmap_page_range(unsigned long start,
+ unsigned long end)
+{
+}
+
+#endif
+
+#endif /* _LINUX_KMSAN_H */
diff --git a/mm/internal.h b/mm/internal.h
index 785409805ed79..fd7247a2367ed 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -847,8 +847,14 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
}
#endif

+int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages,
+ unsigned int page_shift);
+
void vunmap_range_noflush(unsigned long start, unsigned long end);

+void __vunmap_range_noflush(unsigned long start, unsigned long end);
+
int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
unsigned long addr, int page_nid, int *flags);

diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 4ac62fa67a02a..040111bb9f6a3 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -11,6 +11,7 @@

#include <linux/cacheflush.h>
#include <linux/gfp.h>
+#include <linux/kmsan.h>
#include <linux/mm.h>
#include <linux/mm_types.h>
#include <linux/slab.h>
@@ -26,6 +27,91 @@
* skipping effects of functions like memset() inside instrumented code.
*/

+static unsigned long vmalloc_shadow(unsigned long addr)
+{
+ return (unsigned long)kmsan_get_metadata((void *)addr,
+ KMSAN_META_SHADOW);
+}
+
+static unsigned long vmalloc_origin(unsigned long addr)
+{
+ return (unsigned long)kmsan_get_metadata((void *)addr,
+ KMSAN_META_ORIGIN);
+}
+
+void kmsan_vunmap_range_noflush(unsigned long start, unsigned long end)
+{
+ __vunmap_range_noflush(vmalloc_shadow(start), vmalloc_shadow(end));
+ __vunmap_range_noflush(vmalloc_origin(start), vmalloc_origin(end));
+ flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
+ flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
+}
+
+/*
+ * This function creates new shadow/origin pages for the physical pages mapped
+ * into the virtual memory. If those physical pages already had shadow/origin,
+ * those are ignored.
+ */
+void kmsan_ioremap_page_range(unsigned long start, unsigned long end,
+ phys_addr_t phys_addr, pgprot_t prot,
+ unsigned int page_shift)
+{
+ gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
+ struct page *shadow, *origin;
+ unsigned long off = 0;
+ int nr;
+
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+
+ nr = (end - start) / PAGE_SIZE;
+ kmsan_enter_runtime();
+ for (int i = 0; i < nr; i++, off += PAGE_SIZE) {
+ shadow = alloc_pages(gfp_mask, 1);
+ origin = alloc_pages(gfp_mask, 1);
+ __vmap_pages_range_noflush(
+ vmalloc_shadow(start + off),
+ vmalloc_shadow(start + off + PAGE_SIZE), prot, &shadow,
+ PAGE_SHIFT);
+ __vmap_pages_range_noflush(
+ vmalloc_origin(start + off),
+ vmalloc_origin(start + off + PAGE_SIZE), prot, &origin,
+ PAGE_SHIFT);
+ }
+ flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
+ flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
+ kmsan_leave_runtime();
+}
+
+void kmsan_iounmap_page_range(unsigned long start, unsigned long end)
+{
+ unsigned long v_shadow, v_origin;
+ struct page *shadow, *origin;
+ int nr;
+
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+
+ nr = (end - start) / PAGE_SIZE;
+ kmsan_enter_runtime();
+ v_shadow = (unsigned long)vmalloc_shadow(start);
+ v_origin = (unsigned long)vmalloc_origin(start);
+ for (int i = 0; i < nr;
+ i++, v_shadow += PAGE_SIZE, v_origin += PAGE_SIZE) {
+ shadow = kmsan_vmalloc_to_page_or_null((void *)v_shadow);
+ origin = kmsan_vmalloc_to_page_or_null((void *)v_origin);
+ __vunmap_range_noflush(v_shadow, vmalloc_shadow(end));
+ __vunmap_range_noflush(v_origin, vmalloc_origin(end));
+ if (shadow)
+ __free_pages(shadow, 1);
+ if (origin)
+ __free_pages(origin, 1);
+ }
+ flush_cache_vmap(vmalloc_shadow(start), vmalloc_shadow(end));
+ flush_cache_vmap(vmalloc_origin(start), vmalloc_origin(end));
+ kmsan_leave_runtime();
+}
+
/* Functions from kmsan-checks.h follow. */
void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)
{
diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
index acc5279acc3be..8c81a059beea6 100644
--- a/mm/kmsan/shadow.c
+++ b/mm/kmsan/shadow.c
@@ -145,3 +145,116 @@ void *kmsan_get_metadata(void *address, bool is_origin)

return (is_origin ? origin_ptr_for(page) : shadow_ptr_for(page)) + off;
}
+
+void kmsan_copy_page_meta(struct page *dst, struct page *src)
+{
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+ if (!dst || !page_has_metadata(dst))
+ return;
+ if (!src || !page_has_metadata(src)) {
+ kmsan_internal_unpoison_memory(page_address(dst), PAGE_SIZE,
+ /*checked*/ false);
+ return;
+ }
+
+ kmsan_enter_runtime();
+ __memcpy(shadow_ptr_for(dst), shadow_ptr_for(src), PAGE_SIZE);
+ __memcpy(origin_ptr_for(dst), origin_ptr_for(src), PAGE_SIZE);
+ kmsan_leave_runtime();
+}
+
+void kmsan_alloc_page(struct page *page, unsigned int order, gfp_t flags)
+{
+ bool initialized = (flags & __GFP_ZERO) || !kmsan_enabled;
+ struct page *shadow, *origin;
+ depot_stack_handle_t handle;
+ int pages = 1 << order;
+
+ if (!page)
+ return;
+
+ shadow = shadow_page_for(page);
+ origin = origin_page_for(page);
+
+ if (initialized) {
+ __memset(page_address(shadow), 0, PAGE_SIZE * pages);
+ __memset(page_address(origin), 0, PAGE_SIZE * pages);
+ return;
+ }
+
+ /* Zero pages allocated by the runtime should also be initialized. */
+ if (kmsan_in_runtime())
+ return;
+
+ __memset(page_address(shadow), -1, PAGE_SIZE * pages);
+ kmsan_enter_runtime();
+ handle = kmsan_save_stack_with_flags(flags, /*extra_bits*/ 0);
+ kmsan_leave_runtime();
+ /*
+ * Addresses are page-aligned, pages are contiguous, so it's ok
+ * to just fill the origin pages with @handle.
+ */
+ for (int i = 0; i < PAGE_SIZE * pages / sizeof(handle); i++)
+ ((depot_stack_handle_t *)page_address(origin))[i] = handle;
+}
+
+void kmsan_free_page(struct page *page, unsigned int order)
+{
+ if (!kmsan_enabled || kmsan_in_runtime())
+ return;
+ kmsan_enter_runtime();
+ kmsan_internal_poison_memory(page_address(page),
+ PAGE_SIZE << compound_order(page),
+ GFP_KERNEL,
+ KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
+ kmsan_leave_runtime();
+}
+
+void kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
+ pgprot_t prot, struct page **pages,
+ unsigned int page_shift)
+{
+ unsigned long shadow_start, origin_start, shadow_end, origin_end;
+ struct page **s_pages, **o_pages;
+ int nr, mapped;
+
+ if (!kmsan_enabled)
+ return;
+
+ shadow_start = vmalloc_meta((void *)start, KMSAN_META_SHADOW);
+ shadow_end = vmalloc_meta((void *)end, KMSAN_META_SHADOW);
+ if (!shadow_start)
+ return;
+
+ nr = (end - start) / PAGE_SIZE;
+ s_pages = kcalloc(nr, sizeof(*s_pages), GFP_KERNEL);
+ o_pages = kcalloc(nr, sizeof(*o_pages), GFP_KERNEL);
+ if (!s_pages || !o_pages)
+ goto ret;
+ for (int i = 0; i < nr; i++) {
+ s_pages[i] = shadow_page_for(pages[i]);
+ o_pages[i] = origin_page_for(pages[i]);
+ }
+ prot = __pgprot(pgprot_val(prot) | _PAGE_NX);
+ prot = PAGE_KERNEL;
+
+ origin_start = vmalloc_meta((void *)start, KMSAN_META_ORIGIN);
+ origin_end = vmalloc_meta((void *)end, KMSAN_META_ORIGIN);
+ kmsan_enter_runtime();
+ mapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,
+ s_pages, page_shift);
+ KMSAN_WARN_ON(mapped);
+ mapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,
+ o_pages, page_shift);
+ KMSAN_WARN_ON(mapped);
+ kmsan_leave_runtime();
+ flush_tlb_kernel_range(shadow_start, shadow_end);
+ flush_tlb_kernel_range(origin_start, origin_end);
+ flush_cache_vmap(shadow_start, shadow_end);
+ flush_cache_vmap(origin_start, origin_end);
+
+ret:
+ kfree(s_pages);
+ kfree(o_pages);
+}
diff --git a/mm/memory.c b/mm/memory.c
index 4ba73f5aa8bb7..6cc35d2cae8fd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -52,6 +52,7 @@
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/memremap.h>
+#include <linux/kmsan.h>
#include <linux/ksm.h>
#include <linux/rmap.h>
#include <linux/export.h>
@@ -3128,6 +3129,7 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
delayacct_wpcopy_end();
return 0;
}
+ kmsan_copy_page_meta(new_page, old_page);
}

if (mem_cgroup_charge(page_folio(new_page), mm, GFP_KERNEL))
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e5486d47406e8..d488dab76a6e8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -27,6 +27,7 @@
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/kasan.h>
+#include <linux/kmsan.h>
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/pagevec.h>
@@ -1398,6 +1399,7 @@ static __always_inline bool free_pages_prepare(struct page *page,
VM_BUG_ON_PAGE(PageTail(page), page);

trace_mm_page_free(page, order);
+ kmsan_free_page(page, order);

if (unlikely(PageHWPoison(page)) && !order) {
/*
@@ -3817,6 +3819,14 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
/*
* Allocate a page from the given zone. Use pcplists for order-0 allocations.
*/
+
+/*
+ * Do not instrument rmqueue() with KMSAN. This function may call
+ * __msan_poison_alloca() through a call to set_pfnblock_flags_mask().
+ * If __msan_poison_alloca() attempts to allocate pages for the stack depot, it
+ * may call rmqueue() again, which will result in a deadlock.
+ */
+__no_sanitize_memory
static inline
struct page *rmqueue(struct zone *preferred_zone,
struct zone *zone, unsigned int order,
@@ -5535,6 +5545,7 @@ struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
}

trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype);
+ kmsan_alloc_page(page, order, alloc_gfp);

return page;
}
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index dd6cdb2011953..68b656e0125c9 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -320,6 +320,9 @@ int ioremap_page_range(unsigned long addr, unsigned long end,
err = vmap_range_noflush(addr, end, phys_addr, pgprot_nx(prot),
ioremap_max_page_shift);
flush_cache_vmap(addr, end);
+ if (!err)
+ kmsan_ioremap_page_range(addr, end, phys_addr, prot,
+ ioremap_max_page_shift);
return err;
}

@@ -416,7 +419,7 @@ static void vunmap_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
*
* This is an internal function only. Do not use outside mm/.
*/
-void vunmap_range_noflush(unsigned long start, unsigned long end)
+void __vunmap_range_noflush(unsigned long start, unsigned long end)
{
unsigned long next;
pgd_t *pgd;
@@ -438,6 +441,12 @@ void vunmap_range_noflush(unsigned long start, unsigned long end)
arch_sync_kernel_mappings(start, end);
}

+void vunmap_range_noflush(unsigned long start, unsigned long end)
+{
+ kmsan_vunmap_range_noflush(start, end);
+ __vunmap_range_noflush(start, end);
+}
+
/**
* vunmap_range - unmap kernel virtual addresses
* @addr: start of the VM area to unmap
@@ -575,7 +584,7 @@ static int vmap_small_pages_range_noflush(unsigned long addr, unsigned long end,
*
* This is an internal function only. Do not use outside mm/.
*/
-int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
+int __vmap_pages_range_noflush(unsigned long addr, unsigned long end,
pgprot_t prot, struct page **pages, unsigned int page_shift)
{
unsigned int i, nr = (end - addr) >> PAGE_SHIFT;
@@ -601,6 +610,13 @@ int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
return 0;
}

+int vmap_pages_range_noflush(unsigned long addr, unsigned long end,
+ pgprot_t prot, struct page **pages, unsigned int page_shift)
+{
+ kmsan_vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+ return __vmap_pages_range_noflush(addr, end, prot, pages, page_shift);
+}
+
/**
* vmap_pages_range - map pages to a kernel virtual address
* @addr: start of the VM area to map
--
2.37.2.789.g6183377224-goog