The following commit has been merged into the x86/kaslr branch of tip:
Commit-ID: eb38be6db516fb72ccf7282628b545a185b3bc7a
Gitweb: https://git.kernel.org/tip/eb38be6db516fb72ccf7282628b545a185b3bc7a
Author: Arvind Sankar <nivedita@xxxxxxxxxxxx>
AuthorDate: Tue, 28 Jul 2020 18:57:17 -04:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Fri, 31 Jul 2020 11:08:17 +02:00
x86/kaslr: Drop unnecessary alignment in find_random_virt_addr()
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 <nivedita@xxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200728225722.67457-17-nivedita@xxxxxxxxxxxx
---
arch/x86/boot/compressed/kaslr.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 0c64026..ce34a05 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -825,16 +825,12 @@ static unsigned long find_random_virt_addr(unsigned long minimum,
{
unsigned long slots, random_addr;
- /* Align image_size for easy slot calculations. */
- image_size = ALIGN(image_size, CONFIG_PHYSICAL_ALIGN);
-
/*
* 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;
|