Re: [PATCH v3 2/4] kaslr: calculate the memory region in immovable node

[Kees Cook]

On Tue, Dec 5, 2017 at 12:51 AM, Chao Fan <fanc.fnst@xxxxxxxxxxxxxx> wrote:
> If there is no immovable memory region specified, go on the old code.
> There are several conditons:
> 1. CONFIG_MEMORY_HOTPLUG is not specified to y.
> 2. immovable_mem= is not specified.
>
> Otherwise, calculate the intersecting between memmap entry and
> immovable memory.

Instead of copy/pasting code between process_efi_entries() and
process_e820_entries(), I'd rather that process_mem_region() is
modified to deal with immovable regions.

-Kees

>
> Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
> ---
>  arch/x86/boot/compressed/kaslr.c | 59 ++++++++++++++++++++++++++++++++++------
>  1 file changed, 51 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
> index 0bbbaf5f6370..e3a3b6132da0 100644
> --- a/arch/x86/boot/compressed/kaslr.c
> +++ b/arch/x86/boot/compressed/kaslr.c
> @@ -635,6 +635,39 @@ static void process_mem_region(struct mem_vector *entry,
>         }
>  }
>
> +static bool process_immovable_mem(struct mem_vector region,
> +                                 unsigned long long minimum,
> +                                 unsigned long long image_size)
> +{
> +       int i;
> +
> +       /*
> +        * Walk all immovable regions, and filter the intersection
> +        * to process_mem_region.
> +        */
> +       for (i = 0; i < num_immovable_region; i++) {
> +               struct mem_vector entry;
> +               unsigned long long start, end, entry_end;
> +
> +               start = immovable_mem[i].start;
> +               end = start + immovable_mem[i].size;
> +
> +               entry.start = clamp(region.start, start, end);
> +               entry_end = clamp(region.start + region.size, start, end);
> +
> +               if (entry.start < entry_end) {
> +                       entry.size = entry_end - entry.start;
> +                       process_mem_region(&entry, minimum, image_size);
> +               }
> +
> +               if (slot_area_index == MAX_SLOT_AREA) {
> +                       debug_putstr("Aborted memmap scan (slot_areas full)!\n");
> +                       return 1;
> +               }
> +       }
> +       return 0;
> +}
> +
>  #ifdef CONFIG_EFI
>  /*
>   * Returns true if mirror region found (and must have been processed
> @@ -700,11 +733,16 @@ 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 no immovable_mem stored, use region directly */
> +               if (num_immovable_region == 0) {
> +                       process_mem_region(&region, minimum, image_size);
> +                       if (slot_area_index == MAX_SLOT_AREA) {
> +                               debug_putstr("Aborted memmap scan (slot_areas full)!\n");
> +                               break;
> +                       }
> +               } else if (process_immovable_mem(region, minimum, image_size))
>                         break;
> -               }
>         }
>         return true;
>  }
> @@ -731,11 +769,16 @@ 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 no immovable_mem stored, use region directly */
> +               if (num_immovable_region == 0) {
> +                       process_mem_region(&region, minimum, image_size);
> +                       if (slot_area_index == MAX_SLOT_AREA) {
> +                               debug_putstr("Aborted memmap scan (slot_areas full)!\n");
> +                               break;
> +                       }
> +               } else if (process_immovable_mem(region, minimum, image_size))
>                         break;
> -               }
>         }
>  }
>
> --
> 2.14.3
>
>
>



-- 
Kees Cook
Pixel Security