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SubjectRe: [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the immovable memory
On 08/07/18 at 02:50pm, Chao Fan wrote:
> If 'CONFIG_MEMORY_HOTREMOVE' specified and the account of immovable
If CONFIG_MEMORY_HOTREMOVE is enabled,
> memory regions is not zero. Calculate the intersection between memory
> regions from e820/efi memory table and immovable memory regions.
> Or go on the old code.
>
> Rename process_mem_region to slots_count to match slots_fetch_random,
> and name new function as process_mem_region.
>
> Signed-off-by: Chao Fan <fanc.fnst@cn.fujitsu.com>
> ---
> arch/x86/boot/compressed/kaslr.c | 66 ++++++++++++++++++++++++++------
> 1 file changed, 55 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 720878f967a3..9c6e24a23a2d 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -635,9 +635,9 @@ 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;
> struct slot_area slot_area;
> @@ -714,6 +714,56 @@ 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)
> +{

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.


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
}

> +#ifdef CONFIG_MEMORY_HOTREMOVE
> + /*
> + * If immovable memory found, filter the intersection between
> + * immovable memory and region to slots_count.
> + * Otherwise, go on old code.
> + */
> + if (num_immovable_mem > 0) {
> + int i;
> +
> + for (i = 0; i < num_immovable_mem; i++) {
> + struct mem_vector entry;
> + unsigned long long start, end, entry_end, region_end;
> +
> + 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);
> +
> + if (entry.start + image_size < entry_end) {
> + entry.size = entry_end - entry.start;
> + slots_count(&entry, 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;
> + }
> +#endif
> + /*
> + * If no immovable memory found, or MEMORY_HOTREMOVE disabled,
> + * walk all the regions, so use region directely.
> + */
> + 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_EFI
> /*
> * Returns true if mirror region found (and must have been processed
> @@ -779,11 +829,8 @@ 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;
> }
> @@ -810,11 +857,8 @@ 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;
> - }
> }
> }
>
> --
> 2.17.1
>
>
>

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