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

Baoquan He
2018-10-18T04:21:23Z

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?

> + */
> + 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.

> +
> + 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
>
>
>