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SubjectRe: [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the immovable memory
On Mon, Aug 27, 2018 at 02:28:54PM +0800, Chao Fan wrote:
>On Mon, Aug 27, 2018 at 01:56:07PM +0800, Baoquan He wrote:
>>On 08/07/18 at 02:50pm, Chao Fan wrote:
[...]
>>
>>Is it possible to take num_immovable_mem definition out from #ifdef
>>CONFIG_MEMORY_HOTREMOVE block and check it here like below? This way,
>>one level of indentation can be reduced in the for loop, and code is
>>more readable.
>>
>
>I think there is a mistake.
>
>The logical is:
>if (#ifdef CONFIG_MEMORY_HOTREMOVE) && (num_immovable_mem > 0)
> then A;
>else
> then B;
>
>But below is:

Sorry for that, here the 'below' means the code in your mail.

Thanks,
Chao Fan

>if (num_immovable_mem > 0)
> then B;
>else if (#ifdef CONFIG_MEMORY_HOTREMOVE)
> then A;
>else
> nothing;
>
>The precondition of the loop is (num_immovable_mem > 0), because
>there is only one condition that we need go the A code:
>CONFIG_MEMORY_HOTREMOVE is defined, and memory information in srat
>found.
>
>But there is many conditions we go the B code:
>1. CONFIG_MEMORY_HOTREMOVE is not defined.
>2. CONFIG_MEMORY_HOTREMOVE defined, but we didn't get the right acpi tables
>3. CONFIG_MEMORY_HOTREMOVE defined, or there is only one node in this machine.
>
>Yes, the code is hard to read, but you have changed the logical, there
>is a compromise method, I don't know whether is better:
>
>#ifdef CONFIG_MEMORY_HOTREMOVE
> if (num_immovable_mem == 0)
> goto B;
>
> for (i = 0; i < num_immovable_mem; i++) {
> ...
> }
>#endif
>
>B:
> 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;
>
>
>>
>>static bool process_mem_region(struct mem_vector *region,
>> unsigned long long minimum,
>> unsigned long long image_size)
>>{
>>
>> /*
>> * 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
>> for (i = 0; i < num_immovable_mem; i++) {
>> ...
>> }
>>#endif
>>}
>>


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