lkml.org 
[lkml]   [2018]   [Feb]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v28 3/4] mm/page_poison: add a function to expose page poison val to kernel modules
Date
Move the PAGE_POISON value to page_poison.c and add a function to enable
callers from a kernel module to get the poison value if the page poisoning
feature is in use. This also avoids callers directly checking PAGE_POISON
regardless of whether the feature is enabled.

Signed-off-by: Wei Wang <wei.w.wang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
---
include/linux/mm.h | 2 ++
include/linux/poison.h | 7 -------
mm/page_poison.c | 24 ++++++++++++++++++++++++
3 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 1c77d88..d95e5d3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2469,11 +2469,13 @@ extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
extern bool page_poisoning_enabled(void);
extern void kernel_poison_pages(struct page *page, int numpages, int enable);
extern bool page_is_poisoned(struct page *page);
+extern bool page_poison_val_get(u8 *val);
#else
static inline bool page_poisoning_enabled(void) { return false; }
static inline void kernel_poison_pages(struct page *page, int numpages,
int enable) { }
static inline bool page_is_poisoned(struct page *page) { return false; }
+static inline bool page_poison_val_get(u8 *val) { return false; };
#endif

#ifdef CONFIG_DEBUG_PAGEALLOC
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 15927eb..348bf67 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -30,13 +30,6 @@
*/
#define TIMER_ENTRY_STATIC ((void *) 0x300 + POISON_POINTER_DELTA)

-/********** mm/debug-pagealloc.c **********/
-#ifdef CONFIG_PAGE_POISONING_ZERO
-#define PAGE_POISON 0x00
-#else
-#define PAGE_POISON 0xaa
-#endif
-
/********** mm/page_alloc.c ************/

#define TAIL_MAPPING ((void *) 0x400 + POISON_POINTER_DELTA)
diff --git a/mm/page_poison.c b/mm/page_poison.c
index e83fd44..9a07973 100644
--- a/mm/page_poison.c
+++ b/mm/page_poison.c
@@ -7,6 +7,13 @@
#include <linux/poison.h>
#include <linux/ratelimit.h>

+/********** mm/debug-pagealloc.c **********/
+#ifdef CONFIG_PAGE_POISONING_ZERO
+#define PAGE_POISON 0x00
+#else
+#define PAGE_POISON 0xaa
+#endif
+
static bool want_page_poisoning __read_mostly;

static int early_page_poison_param(char *buf)
@@ -30,6 +37,23 @@ bool page_poisoning_enabled(void)
debug_pagealloc_enabled()));
}

+/**
+ * page_poison_val_get - get the page poison value if page poisoning is enabled
+ * @val: the caller's memory to get the page poison value
+ *
+ * Return true with @val stores the poison value if page poisoning is enabled.
+ * Otherwise, return false with @val unchanged.
+ */
+bool page_poison_val_get(u8 *val)
+{
+ if (!page_poisoning_enabled())
+ return false;
+
+ *val = PAGE_POISON;
+ return true;
+}
+EXPORT_SYMBOL_GPL(page_poison_val_get);
+
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
--
2.7.4
\
 
 \ /
  Last update: 2018-02-08 11:10    [W:0.060 / U:3.424 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site