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Message-ID: <a7b485cb7b82f808846938e0670d73bb439b6846.1372582756.git.vdavydov@parallels.com>
Date: Mon, 1 Jul 2013 15:57:43 +0400
From: Vladimir Davydov <vdavydov@...allels.com>
To: <linux-kernel@...r.kernel.org>
CC: <linux-mm@...ck.org>, <criu@...nvz.org>, <devel@...nvz.org>,
<xemul@...allels.com>, <khorenko@...allels.com>
Subject: [PATCH RFC 08/13] mm: PRAM: checksum saved data
Checksum PRAM pages with crc32 to ensure persistent memory is not
corrupted during reboot.
---
mm/Kconfig | 4 ++
mm/pram.c | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 130 insertions(+), 2 deletions(-)
diff --git a/mm/Kconfig b/mm/Kconfig
index f1e11a0..0a4d4c6 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -475,6 +475,10 @@ config FRONTSWAP
config PRAM
bool "Persistent over-kexec memory storage"
depends on X86
+ select CRC32
+ select LIBCRC32C
+ select CRYPTO_CRC32C
+ select CRYPTO_CRC32C_INTEL
default n
help
This option adds the kernel API that enables saving memory pages of
diff --git a/mm/pram.c b/mm/pram.c
index 380735f..8a66a86 100644
--- a/mm/pram.c
+++ b/mm/pram.c
@@ -1,4 +1,6 @@
#include <linux/bootmem.h>
+#include <linux/crc32.h>
+#include <linux/crc32c.h>
#include <linux/err.h>
#include <linux/gfp.h>
#include <linux/highmem.h>
@@ -19,11 +21,14 @@
#include <linux/sysfs.h>
#include <linux/types.h>
+#define PRAM_MAGIC 0x7072616D
+
/*
* Represents a reference to a data page saved to PRAM.
*/
struct pram_entry {
__u32 flags; /* see PRAM_PAGE_* flags */
+ __u32 csum; /* the page csum */
__u64 pfn; /* the page frame number */
};
@@ -32,6 +37,9 @@ struct pram_entry {
* The structure occupies a memory page.
*/
struct pram_link {
+ __u32 magic;
+ __u32 csum;
+
__u64 link_pfn; /* points to the next link of the node */
/* the array occupies the rest of the link page; if the link is not
@@ -57,6 +65,9 @@ struct pram_link {
* The structure occupies a memory page.
*/
struct pram_node {
+ __u32 magic;
+ __u32 csum;
+
__u32 flags; /* see PRAM_* flags below */
__u32 type; /* data type, see enum pram_stream_type */
__u64 data_len; /* data size, only for byte streams */
@@ -81,6 +92,9 @@ struct pram_node {
* The structure occupies a memory page.
*/
struct pram_super_block {
+ __u32 magic;
+ __u32 csum;
+
__u64 node_pfn; /* points to the first element of
* the node list */
};
@@ -106,11 +120,34 @@ static int __init parse_pram_sb_pfn(char *arg)
}
early_param("pram", parse_pram_sb_pfn);
+static u32 pram_data_csum(struct page *page)
+{
+ u32 ret;
+ void *addr;
+
+ addr = kmap_atomic(page);
+ ret = crc32c(0, addr, PAGE_SIZE);
+ kunmap_atomic(addr);
+ return ret;
+}
+
+/* SSE-4.2 crc32c faster than crc32, but not available at early boot */
+static inline u32 pram_meta_csum(void *addr)
+{
+ /* skip magic and csum fields */
+ return crc32(0, addr + 8, PAGE_SIZE - 8);
+}
+
static void * __init pram_map_meta(unsigned long pfn)
{
+ __u32 *p;
+
if (pfn >= max_low_pfn)
return ERR_PTR(-EINVAL);
- return pfn_to_kaddr(pfn);
+ p = pfn_to_kaddr(pfn);
+ if (p[0] != PRAM_MAGIC || p[1] != pram_meta_csum(p))
+ return ERR_PTR(-EINVAL);
+ return p;
}
static int __init pram_reserve_page(unsigned long pfn)
@@ -332,6 +369,65 @@ static struct pram_node *pram_find_node(const char *name)
return NULL;
}
+static void pram_csum_link(struct pram_link *link)
+{
+ int i;
+ struct pram_entry *entry;
+
+ for (i = 0; i < PRAM_LINK_ENTRIES_MAX; i++) {
+ entry = &link->entry[i];
+ if (entry->pfn)
+ entry->csum = pram_data_csum(pfn_to_page(entry->pfn));
+ }
+}
+
+static void pram_csum_node(struct pram_node *node)
+{
+ unsigned long link_pfn;
+ struct pram_link *link;
+
+ link_pfn = node->link_pfn;
+ while (link_pfn) {
+ link = pfn_to_kaddr(link_pfn);
+ pram_csum_link(link);
+ link_pfn = link->link_pfn;
+ cond_resched();
+ }
+}
+
+static int pram_check_link(struct pram_link *link)
+{
+ int i;
+ struct pram_entry *entry;
+
+ for (i = 0; i < PRAM_LINK_ENTRIES_MAX; i++) {
+ entry = &link->entry[i];
+ if (!entry->pfn)
+ break;
+ if (entry->csum != pram_data_csum(pfn_to_page(entry->pfn)))
+ return -EFAULT;
+ }
+ return 0;
+}
+
+static int pram_check_node(struct pram_node *node)
+{
+ unsigned long link_pfn;
+ struct pram_link *link;
+ int ret = 0;
+
+ link_pfn = node->link_pfn;
+ while (link_pfn) {
+ link = pfn_to_kaddr(link_pfn);
+ ret = pram_check_link(link);
+ if (ret)
+ break;
+ link_pfn = link->link_pfn;
+ cond_resched();
+ }
+ return ret;
+}
+
static void pram_truncate_link(struct pram_link *link)
{
int i;
@@ -449,6 +545,7 @@ void pram_finish_save(struct pram_stream *ps)
BUG_ON((node->flags & PRAM_ACCMODE_MASK) != PRAM_SAVE);
+ pram_csum_node(node);
smp_wmb();
node->flags &= ~PRAM_ACCMODE_MASK;
}
@@ -488,6 +585,7 @@ void pram_discard_save(struct pram_stream *ps)
* %ENOENT: node with specified name does not exist
* %EBUSY: save to required node has not finished yet
* %EPERM: specified type conflicts with type of required node
+ * %EFAULT: node corrupted
*
* After the load has finished, pram_finish_load() is to be called.
*/
@@ -520,6 +618,13 @@ out_unlock:
if (err)
return err;
+ err = pram_check_node(node);
+ if (err) {
+ pram_truncate_node(node);
+ pram_free_page(node);
+ return err;
+ }
+
node->flags |= PRAM_LOAD;
pram_stream_init(ps, node, 0);
return 0;
@@ -775,8 +880,24 @@ size_t pram_read(struct pram_stream *ps, void *buf, size_t count)
return read_count;
}
+static void pram_csum_node_meta(struct pram_node *node)
+{
+ unsigned long link_pfn;
+ struct pram_link *link;
+
+ link_pfn = node->link_pfn;
+ while (link_pfn) {
+ link = pfn_to_kaddr(link_pfn);
+ link->magic = PRAM_MAGIC;
+ link->csum = pram_meta_csum(link);
+ link_pfn = link->link_pfn;
+ }
+ node->magic = PRAM_MAGIC;
+ node->csum = pram_meta_csum(node);
+}
+
/*
- * Build the list of PRAM nodes.
+ * Build the list of PRAM nodes and update metadata csums.
*/
static void __pram_reboot(void)
{
@@ -789,9 +910,12 @@ static void __pram_reboot(void)
if (WARN_ON(node->flags & PRAM_ACCMODE_MASK))
continue;
node->node_pfn = node_pfn;
+ pram_csum_node_meta(node);
node_pfn = page_to_pfn(page);
}
pram_sb->node_pfn = node_pfn;
+ pram_sb->magic = PRAM_MAGIC;
+ pram_sb->csum = pram_meta_csum(pram_sb);
}
static int pram_reboot(struct notifier_block *notifier,
--
1.7.10.4
--
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