Re: [PATCH v5 4/4] x86/boot/KASLR: Limit kaslr to choosing the immovable memory

[Baoquan He]

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.f...@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
> 
> 
>