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Subject[PATCH v1 03/10] kasan: prepare for online/offline of different start/size
Date
The memory notifier has an important restriction right now: it only
works if offline_pages() is called with the same parameters as
online_pages().

To overcome this restriction, let's handle it per section. We could do
it in smaller granularity, but then we get more vm_area overhead and
cannot check that cleanly for actual online parts.

A section is marked online as soon as at least one page is online.
Similarly, a section is marked offline as soon as all pages are offline.

So handling it on a per-section basis allows us to be more flexible. We
asssume here, that a section is not split between boot and hotplug
memory.

Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: kasan-dev@googlegroups.com
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/kasan/kasan.c | 107 ++++++++++++++++++++++++++++++-----------------
1 file changed, 69 insertions(+), 38 deletions(-)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index a8b85706e2d6..901601a562a9 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -827,62 +827,93 @@ static bool shadow_mapped(unsigned long addr)
return !pte_none(*pte);
}

-static int __meminit kasan_mem_notifier(struct notifier_block *nb,
- unsigned long action, void *data)
+static void kasan_offline_pages(unsigned long start_pfn, unsigned long nr_pages)
{
- struct memory_notify *mem_data = data;
- unsigned long nr_shadow_pages, start_kaddr, shadow_start;
- unsigned long shadow_end, shadow_size;
+ unsigned long start = SECTION_ALIGN_DOWN(start_pfn);
+ unsigned long end = SECTION_ALIGN_UP(start_pfn + nr_pages);
+ unsigned long pfn;

- nr_shadow_pages = mem_data->nr_pages >> KASAN_SHADOW_SCALE_SHIFT;
- start_kaddr = (unsigned long)pfn_to_kaddr(mem_data->start_pfn);
- shadow_start = (unsigned long)kasan_mem_to_shadow((void *)start_kaddr);
- shadow_size = nr_shadow_pages << PAGE_SHIFT;
- shadow_end = shadow_start + shadow_size;
+ for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
+ void *addr, *shadow_start;
+ struct vm_struct *vm;

- if (WARN_ON(mem_data->nr_pages % KASAN_SHADOW_SCALE_SIZE) ||
- WARN_ON(start_kaddr % (KASAN_SHADOW_SCALE_SIZE << PAGE_SHIFT)))
- return NOTIFY_BAD;
+ /* still online? nothing to do then */
+ if (online_section_nr(pfn_to_section_nr(pfn)))
+ continue;

- switch (action) {
- case MEM_GOING_ONLINE: {
- void *ret;
+ addr = pfn_to_kaddr(pfn);
+ shadow_start = kasan_mem_to_shadow(addr);
+
+ /*
+ * Only hot-added memory has a vm_area. Freeing shadow mapped
+ * during boot would be tricky, so we'll just have to keep it.
+ */
+ vm = find_vm_area(shadow_start);
+ if (vm)
+ vfree(shadow_start);
+ }
+}
+
+static int kasan_online_pages(unsigned long start_pfn, unsigned long nr_pages)
+{
+ unsigned long start = SECTION_ALIGN_DOWN(start_pfn);
+ unsigned long end = SECTION_ALIGN_UP(start_pfn + nr_pages);
+ unsigned long pfn;
+
+ for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
+ unsigned long shadow_start, shadow_size;
+ void *addr, *ret;
+
+ /* already online? nothing to do then */
+ if (online_section_nr(pfn_to_section_nr(pfn)))
+ continue;
+
+ addr = pfn_to_kaddr(pfn);
+ shadow_size = (PAGES_PER_SECTION << PAGE_SHIFT) >>
+ KASAN_SHADOW_SCALE_SHIFT;
+ shadow_start = (unsigned long)kasan_mem_to_shadow(addr);

/*
* If shadow is mapped already than it must have been mapped
- * during the boot. This could happen if we onlining previously
+ * during boot. This could happen if we're onlining previously
* offlined memory.
*/
if (shadow_mapped(shadow_start))
- return NOTIFY_OK;
+ continue;

ret = __vmalloc_node_range(shadow_size, PAGE_SIZE, shadow_start,
- shadow_end, GFP_KERNEL,
- PAGE_KERNEL, VM_NO_GUARD,
- pfn_to_nid(mem_data->start_pfn),
- __builtin_return_address(0));
+ shadow_start + shadow_size,
+ GFP_KERNEL, PAGE_KERNEL, VM_NO_GUARD,
+ pfn_to_nid(pfn),
+ __builtin_return_address(0));
if (!ret)
- return NOTIFY_BAD;
-
+ goto out_free;
kmemleak_ignore(ret);
- return NOTIFY_OK;
}
- case MEM_CANCEL_ONLINE:
- case MEM_OFFLINE: {
- struct vm_struct *vm;
+ return 0;
+out_free:
+ kasan_offline_pages(start_pfn, nr_pages);
+ return -ENOMEM;
+}

- /*
- * Only hot-added memory have vm_area. Freeing shadow
- * mapped during boot would be tricky, so we'll just
- * have to keep it.
- */
- vm = find_vm_area((void *)shadow_start);
- if (vm)
- vfree((void *)shadow_start);
- }
+static int __meminit kasan_mem_notifier(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct memory_notify *mem_data = data;
+ int ret = 0;
+
+ switch (action) {
+ case MEM_GOING_ONLINE:
+ ret = kasan_online_pages(mem_data->start_pfn,
+ mem_data->nr_pages);
+ break;
+ case MEM_CANCEL_ONLINE:
+ case MEM_OFFLINE:
+ kasan_offline_pages(mem_data->start_pfn, mem_data->nr_pages);
+ break;
}

- return NOTIFY_OK;
+ return notifier_from_errno(ret);
}

static int __init kasan_memhotplug_init(void)
--
2.17.0
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