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

[Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxx>
>> ---
>>  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
>> 
>> 
>> 
>
>