On 4 May 2015 at 23:16, Anisse Astier wrote:
> SANITIZE_FREED_PAGES feature relies on having all pages going through
> the free_pages_prepare path in order to be cleared before being used. In
> the hibernate use case, pages will automagically appear in the system
> without being cleared.
is this based on debugging/code reading/discussions with hibernation folks
(i see none of them on CC, added them now) or is it just a brute force attempt
to fix the symptoms? if the former, it'd be nice to share some more details
and have Acks from the code owners.
> This fix will make sure free pages are cleared on resume.
>
> Signed-off-by: Anisse Astier <anisse@xxxxxxxxx>
> ---
> kernel/power/hibernate.c | 7 ++++++-
> kernel/power/power.h | 4 ++++
> kernel/power/snapshot.c | 21 +++++++++++++++++++++
> 3 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 2329daa..3193b9a 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -305,9 +305,14 @@ static int create_image(int platform_mode)
> error);
> /* Restore control flow magically appears here */
> restore_processor_state();
> - if (!in_suspend)
> + if (!in_suspend) {
> events_check_enabled = false;
>
> +#ifdef CONFIG_SANITIZE_FREED_PAGES
> + clear_free_pages();
> + printk(KERN_INFO "PM: free pages cleared after restore\n");
> +#endif
> + }
> platform_leave(platform_mode);
>
> Power_up:
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index ce9b832..26b2101 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -92,6 +92,10 @@ extern int create_basic_memory_bitmaps(void);
> extern void free_basic_memory_bitmaps(void);
> extern int hibernate_preallocate_memory(void);
>
> +#ifdef CONFIG_SANITIZE_FREED_PAGES
> +extern void clear_free_pages(void);
> +#endif
> +
> /**
> * 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 5235dd4..673ade1 100644
> --- a/kernel/power/snapshot.c
> +++ b/kernel/power/snapshot.c
> @@ -1032,6 +1032,27 @@ void free_basic_memory_bitmaps(void)
> pr_debug("PM: Basic memory bitmaps freed\n");
> }
>
> +#ifdef CONFIG_SANITIZE_FREED_PAGES
> +void clear_free_pages(void)
> +{
> + 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);
> +}
> +#endif /* SANITIZE_FREED_PAGES */
> +
> /**
> * snapshot_additional_pages - estimate the number of additional pages
> * be needed for setting up the suspend image data structures for given
> --
> 1.9.3
>
>
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