Hi Rafael,
Thanks for taking the time to review this.
On Sat, May 16, 2015 at 2:28 AM, Rafael J. Wysocki <r...@rjwysocki.net> wrote:
> On Thursday, May 14, 2015 04:19:46 PM 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, free pages will automagically 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 we'll
>> enable SANITIZE_FREED_PAGES. 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.
>>
>> Signed-off-by: Anisse Astier <ani...@astier.eu>
>> ---
>> kernel/power/hibernate.c | 4 +++-
>> kernel/power/power.h | 2 ++
>> kernel/power/snapshot.c | 22 ++++++++++++++++++++++
>> 3 files changed, 27 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
>> index 2329daa..0a73126 100644
>> --- a/kernel/power/hibernate.c
>> +++ b/kernel/power/hibernate.c
>> @@ -305,9 +305,11 @@ 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;
>>
>> + clear_free_pages();
>
> Again, why don't you do that at the swsusp_free() time?
Because it's too late, the kernel has already been through device
resume code, and the free pages bitmap isn't valid anymore; device
resume code might allocate memory, and we'd be clearing those pages as
well.
>> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
>> index 5235dd4..2335130 100644
>> --- a/kernel/power/snapshot.c
>> +++ b/kernel/power/snapshot.c
>> @@ -1032,6 +1032,28 @@ void free_basic_memory_bitmaps(void)
>> pr_debug("PM: Basic memory bitmaps freed\n");
>> }
>>
>> +void clear_free_pages(void)
>> +{
>> +#ifdef CONFIG_SANITIZE_FREED_PAGES
>> + struct memory_bitmap *bm = free_pages_map;
>> + unsigned long pfn;
>> +
>> + if (WARN_ON(!(free_pages_map)))
>
> One paren too many.
Thanks, will be fixed.
>
>> + 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));
>
> Is clear_highpage() also fine for non-highmem pages?
>
Yes, it works fine for low memory too because kmap_atomic will just
return the page address if it's already mapped.
Regards,
Anisse
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