Re: [PATCH v9 8/8] x86/boot/KASLR: Limit kaslr to choosing the immovable memory

Chao Fan
2018-10-22T10:13:30Z

On Thu, Oct 18, 2018 at 12:21:23PM +0800, Baoquan He wrote:
>On 10/17/18 at 06:20pm, Chao Fan wrote:
>> If CONFIG_MEMORY_HOTREMOVE enabled and the amount of immovable
>> memory regions is not zero. Calculate the intersection between memory
>
>This if conditional adverbial clauses is not an complete sentence.
>
>> regions from e820/efi memory table and immovable memory regions.
> ^ get?
>>
>> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
>> ---
>> arch/x86/boot/compressed/kaslr.c | 72 +++++++++++++++++++++++++++-----
>> 1 file changed, 61 insertions(+), 11 deletions(-)
>>
>> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
>> index 0c3567bc231c..3ebb150f61eb 100644
>> --- a/arch/x86/boot/compressed/kaslr.c
>> +++ b/arch/x86/boot/compressed/kaslr.c
>> @@ -101,6 +101,11 @@ static bool memmap_too_large;
>> /* Store memory limit specified by "mem=nn[KMG]" or "memmap=nn[KMG]" */
>> static unsigned long long mem_limit = ULLONG_MAX;
>>
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +/* Store the immovable memory regions */
>> +extern struct mem_vector immovable_mem[MAX_NUMNODES*2];
>
>Sorry, Chao. I may not follow your old patch change, why the length of
>immovable_mem is MAX_NUMNODES*2, is there any reason or basis?
>
>> +#endif
>> +
>>
>> enum mem_avoid_index {
>> MEM_AVOID_ZO_RANGE = 0,
>> @@ -577,9 +582,9 @@ static unsigned long slots_fetch_random(void)
>> return 0;
>> }
>>
>> -static void process_mem_region(struct mem_vector *entry,
>> - unsigned long minimum,
>> - unsigned long image_size)
>> +static void slots_count(struct mem_vector *entry,
>> + unsigned long minimum,
>> + unsigned long image_size)
>> {
>> struct mem_vector region, overlap;
>> unsigned long start_orig, end;
>> @@ -655,6 +660,57 @@ static void process_mem_region(struct mem_vector *entry,
>> }
>> }
>>
>> +static bool process_mem_region(struct mem_vector *region,
>> + unsigned long long minimum,
>> + unsigned long long image_size)
>> +{
>> + int i;
>> + /*
>> + * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
>> + * walk all the regions, so use region directely.
>> + */
>> + if (num_immovable_mem == 0) {
>> + slots_count(region, minimum, image_size);
>> +
>> + if (slot_area_index == MAX_SLOT_AREA) {
>> + debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
>> + return 1;
>> + }
>> + return 0;
>> + }
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> + /*
>> + * If immovable memory found, filter the intersection between
>> + * immovable memory and region to slots_count.
>> + * Otherwise, go on old code.
>
>Could you explain more about what is the old code in otherwise case you
>want to go on?

Sure,
1. 'movable_node' not specified in cmdline.
2. CONFIG_HOT_REMOVE not difned.
3. Just one node in this machine.
>
>> + */
>> + for (i = 0; i < num_immovable_mem; i++) {
>> + struct mem_vector entry;
>> + unsigned long long start, end, entry_end, region_end;
>> +
>> + if (!mem_overlaps(region, &immovable_mem[i]))
>> + continue;
>> +
>> + start = immovable_mem[i].start;
>> + end = start + immovable_mem[i].size;
>> + region_end = region->start + region->size;
>> +
>> + entry.start = clamp(region->start, start, end);
>> + entry_end = clamp(region_end, start, end);
>> + entry.size = entry_end - entry.start;
>> +
>> + slots_count(&entry, minimum, image_size);
>
>Obviously, your patch log only covers this place of code. About renaming
>process_mem_region() to slot_count(), and add another level of wrapper
>process_mem_region(), may also need be mentioned in patch log.
>
Sorry for missing the comment.
Rename process_mem_region to slots_count to match slots_fetch_random,
and name new function as process_mem_region.

Thanks,
Chao Fan

>> +
>> + if (slot_area_index == MAX_SLOT_AREA) {
>> + debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
>> + return 1;
>> + }
>> + }
>> + return 0;
>> +#endif
>> +}
>> +
>> #ifdef CONFIG_EFI
>> /*
>> * Returns true if mirror region found (and must have been processed
>> @@ -720,11 +776,8 @@ process_efi_entries(unsigned long minimum, unsigned long image_size)
>>
>> region.start = md->phys_addr;
>> region.size = md->num_pages << EFI_PAGE_SHIFT;
>> - process_mem_region(&region, minimum, image_size);
>> - if (slot_area_index == MAX_SLOT_AREA) {
>> - debug_putstr("Aborted EFI scan (slot_areas full)!\n");
>> + if (process_mem_region(&region, minimum, image_size))
>> break;
>> - }
>> }
>> return true;
>> }
>> @@ -751,11 +804,8 @@ static void process_e820_entries(unsigned long minimum,
>> continue;
>> region.start = entry->addr;
>> region.size = entry->size;
>> - process_mem_region(&region, minimum, image_size);
>> - if (slot_area_index == MAX_SLOT_AREA) {
>> - debug_putstr("Aborted e820 scan (slot_areas full)!\n");
>> + if (process_mem_region(&region, minimum, image_size))
>> break;
>> - }
>> }
>> }
>>
>> --
>> 2.17.2
>>
>>
>>
>
>