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 <nived...@alum.mit.edu> AuthorDate: Tue, 28 Jul 2020 18:57:17 -04:00 Committer: Ingo Molnar <mi...@kernel.org> 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 <nived...@alum.mit.edu> Signed-off-by: Ingo Molnar <mi...@kernel.org> Link: https://lore.kernel.org/r/20200728225722.67457-17-nived...@alum.mit.edu --- 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;
