The number of slots and slot areas can be unsigned int, since on 64-bit,
the maximum amount of memory is 2^52, the minimum alignment is 2^21, so
the slot number cannot be greater than 2^31. The slot areas are limited
by MAX_SLOT_AREA, currently 100. Replace the type used for slot number,
which is currently a mix of int and unsigned long, with unsigned int
consistently.
Drop unnecessary check that number of slots is not zero in
store_slot_info, it's guaranteed to be at least 1 by the calculation.
Drop unnecessary alignment of image_size to CONFIG_PHYSICAL_ALIGN in
find_random_virt_addr, it cannot change the result: the largest valid
slot is the largest n that satisfies
minimum + n * CONFIG_PHYSICAL_ALIGN + image_size <= KERNEL_IMAGE_SIZE
(since minimum is already aligned) and so n is equal to
(KERNEL_IMAGE_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN
even if image_size is not aligned to CONFIG_PHYSICAL_ALIGN.
Signed-off-by: Arvind Sankar <[email protected]>
---
arch/x86/boot/compressed/kaslr.c | 36 ++++++++++++--------------------
1 file changed, 13 insertions(+), 23 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 29ec964b1330..ffbcc0444f70 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -511,16 +511,14 @@ static bool mem_avoid_overlap(struct mem_vector *img,
struct slot_area {
unsigned long addr;
- int num;
+ unsigned int num;
};
#define MAX_SLOT_AREA 100
static struct slot_area slot_areas[MAX_SLOT_AREA];
-
-static unsigned long slot_max;
-
-static unsigned long slot_area_index;
+static unsigned int slot_area_index;
+static unsigned int slot_max;
static void store_slot_info(struct mem_vector *region, unsigned long image_size)
{
@@ -530,13 +528,10 @@ static void store_slot_info(struct mem_vector *region, unsigned long image_size)
return;
slot_area.addr = region->start;
- slot_area.num = (region->size - image_size) /
- CONFIG_PHYSICAL_ALIGN + 1;
+ slot_area.num = 1 + (region->size - image_size) / CONFIG_PHYSICAL_ALIGN;
- if (slot_area.num > 0) {
- slot_areas[slot_area_index++] = slot_area;
- slot_max += slot_area.num;
- }
+ slot_areas[slot_area_index++] = slot_area;
+ slot_max += slot_area.num;
}
/*
@@ -589,8 +584,7 @@ process_gb_huge_pages(struct mem_vector *region, unsigned long image_size)
static unsigned long slots_fetch_random(void)
{
- unsigned long slot;
- int i;
+ unsigned int slot, i;
/* Handle case of no slots stored. */
if (slot_max == 0)
@@ -603,7 +597,7 @@ static unsigned long slots_fetch_random(void)
slot -= slot_areas[i].num;
continue;
}
- return slot_areas[i].addr + slot * CONFIG_PHYSICAL_ALIGN;
+ return slot_areas[i].addr + (unsigned long)slot * CONFIG_PHYSICAL_ALIGN;
}
if (i == slot_area_index)
@@ -819,28 +813,24 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
return 0;
}
- if (process_efi_entries(minimum, image_size))
- return slots_fetch_random();
+ if (!process_efi_entries(minimum, image_size))
+ process_e820_entries(minimum, image_size);
- process_e820_entries(minimum, image_size);
return slots_fetch_random();
}
static unsigned long find_random_virt_addr(unsigned long minimum,
unsigned long image_size)
{
- unsigned long slots, random_addr;
-
- /* Align image_size for easy slot calculations. */
- image_size = ALIGN(image_size, CONFIG_PHYSICAL_ALIGN);
+ unsigned int slots;
+ unsigned long random_addr;
/*
* There are how many CONFIG_PHYSICAL_ALIGN-sized slots
* that can hold image_size within the range of minimum to
* KERNEL_IMAGE_SIZE?
*/
- slots = (KERNEL_IMAGE_SIZE - minimum - image_size) /
- CONFIG_PHYSICAL_ALIGN + 1;
+ slots = 1 + (KERNEL_IMAGE_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN;
random_addr = kaslr_get_random_long("Virtual") % slots;
--
2.26.2
* Arvind Sankar <[email protected]> wrote:
> The number of slots and slot areas can be unsigned int, since on 64-bit,
> the maximum amount of memory is 2^52, the minimum alignment is 2^21, so
> the slot number cannot be greater than 2^31. The slot areas are limited
> by MAX_SLOT_AREA, currently 100. Replace the type used for slot number,
> which is currently a mix of int and unsigned long, with unsigned int
> consistently.
>
> Drop unnecessary check that number of slots is not zero in
> store_slot_info, it's guaranteed to be at least 1 by the calculation.
>
> Drop unnecessary alignment of image_size to CONFIG_PHYSICAL_ALIGN in
> find_random_virt_addr, it cannot change the result: the largest valid
> slot is the largest n that satisfies
>
> minimum + n * CONFIG_PHYSICAL_ALIGN + image_size <= KERNEL_IMAGE_SIZE
>
> (since minimum is already aligned) and so n is equal to
>
> (KERNEL_IMAGE_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN
>
> even if image_size is not aligned to CONFIG_PHYSICAL_ALIGN.
Please split this up into a couple of easily bisectable patches as
well:
- first one harmonizes the integer types used
- patch that drops the unnecessary check
- patch that drops the unnecessary alignment operation
Thanks,
Ingo