PM / Hibernate: allow hibernation with PAGE_POISONING_ZERO

PAGE_POISONING_ZERO disables zeroing new pages on alloc, they are
poisoned (zeroed) as they become available.
In the hibernate use case, free pages will appear in the system without
being cleared, left there by the loading kernel.

This patch will make sure free pages are cleared on resume when
PAGE_POISONING_ZERO is enabled. We free the pages just after resume
because we can't do it later: going through any device resume code might
allocate some memory and invalidate the free pages bitmap.

Thus we don't need to disable hibernation when PAGE_POISONING_ZERO is
enabled.

Signed-off-by: Anisse Astier <anisse@astier.eu>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 33c79b6105c55fdc4f228bb0348fbc2b92d68f0f..b26dbc48c75b9fa9045fafeccde8b23e69b9ab2e 100644 (file)
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -306,8 +306,10 @@ static int create_image(int platform_mode)
        if (error)
                printk(KERN_ERR "PM: Error %d creating hibernation image\n",
                        error);
-       if (!in_suspend)
+       if (!in_suspend) {
                events_check_enabled = false;
+               clear_free_pages();
+       }
 
        platform_leave(platform_mode);
 
@@ -1189,22 +1191,6 @@ static int __init nohibernate_setup(char *str)
        return 1;
 }
 
-static int __init page_poison_nohibernate_setup(char *str)
-{
-#ifdef CONFIG_PAGE_POISONING_ZERO
-       /*
-        * The zeroing option for page poison skips the checks on alloc.
-        * since hibernation doesn't save free pages there's no way to
-        * guarantee the pages will still be zeroed.
-        */
-       if (!strcmp(str, "on")) {
-               pr_info("Disabling hibernation due to page poisoning\n");
-               return nohibernate_setup(str);
-       }
-#endif
-       return 1;
-}
-
 __setup("noresume", noresume_setup);
 __setup("resume_offset=", resume_offset_setup);
 __setup("resume=", resume_setup);
@@ -1212,4 +1198,3 @@ __setup("hibernate=", hibernate_setup);
 __setup("resumewait", resumewait_setup);
 __setup("resumedelay=", resumedelay_setup);
 __setup("nohibernate", nohibernate_setup);
-__setup("page_poison=", page_poison_nohibernate_setup);

diff --git a/kernel/power/power.h b/kernel/power/power.h
index 242d8b827dd5f5c6724481bb96b50a7e04553eab..56d1d0dedf76c60fb225163bebcaa47f21d62e6b 100644 (file)
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -110,6 +110,8 @@ extern int create_basic_memory_bitmaps(void);
 extern void free_basic_memory_bitmaps(void);
 extern int hibernate_preallocate_memory(void);
 
+extern void clear_free_pages(void);
+
 /**
  *     Auxiliary structure used for reading the snapshot image data and
  *     metadata from and writing them to the list of page backup entries

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index b02228411d575b87ddc62db9f92b3fadf4765a5a..4f0f0604f1c4f581f635284f65665adc34fccf3e 100644 (file)
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -1132,6 +1132,28 @@ void free_basic_memory_bitmaps(void)
        pr_debug("PM: Basic memory bitmaps freed\n");
 }
 
+void clear_free_pages(void)
+{
+#ifdef CONFIG_PAGE_POISONING_ZERO
+       struct memory_bitmap *bm = free_pages_map;
+       unsigned long pfn;
+
+       if (WARN_ON(!(free_pages_map)))
+               return;
+
+       memory_bm_position_reset(bm);
+       pfn = memory_bm_next_pfn(bm);
+       while (pfn != BM_END_OF_MAP) {
+               if (pfn_valid(pfn))
+                       clear_highpage(pfn_to_page(pfn));
+
+               pfn = memory_bm_next_pfn(bm);
+       }
+       memory_bm_position_reset(bm);
+       pr_info("PM: free pages cleared after restore\n");
+#endif /* PAGE_POISONING_ZERO */
+}
+
 /**
  * snapshot_additional_pages - Estimate the number of extra pages needed.
  * @zone: Memory zone to carry out the computation for.

diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index 22f4cd96acb0d3a320c9a6440d63585f0dfd6057..afcc550877fff9d81ef68b10fc28b1a21108f2c5 100644 (file)
--- a/mm/Kconfig.debug
+++ b/mm/Kconfig.debug
@@ -76,8 +76,6 @@ config PAGE_POISONING_ZERO
           no longer necessary to write zeros when GFP_ZERO is used on
           allocation.
 
-          Enabling page poisoning with this option will disable hibernation
-
           If unsure, say N
        bool