From bf457be1548eee6d106daf9604e029b36fed2b11 Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Tue, 28 Jul 2020 18:57:10 -0400 Subject: [PATCH] x86/kaslr: Drop some redundant checks from __process_mem_region() Clip the start and end of the region to minimum and mem_limit prior to the loop. region.start can only increase during the loop, so raising it to minimum before the loop is enough. A region that becomes empty due to this will get checked in the first iteration of the loop. Drop the check for overlap extending beyond the end of the region. This will get checked in the next loop iteration anyway. Rename end to region_end for symmetry with region.start. Signed-off-by: Arvind Sankar Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20200728225722.67457-10-nivedita@alum.mit.edu --- arch/x86/boot/compressed/kaslr.c | 27 ++++++--------------------- 1 file changed, 6 insertions(+), 21 deletions(-) diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c index 8cc47fa..d074986 100644 --- a/arch/x86/boot/compressed/kaslr.c +++ b/arch/x86/boot/compressed/kaslr.c @@ -623,34 +623,23 @@ static void __process_mem_region(struct mem_vector *entry, unsigned long image_size) { struct mem_vector region, overlap; - unsigned long end; + unsigned long region_end; - /* Ignore entries entirely below our minimum. */ - if (entry->start + entry->size < minimum) - return; - - /* Ignore entries above memory limit */ - end = min(entry->size + entry->start, mem_limit); - if (entry->start >= end) - return; - - region.start = entry->start; + /* Enforce minimum and memory limit. */ + region.start = max_t(unsigned long long, entry->start, minimum); + region_end = min(entry->start + entry->size, mem_limit); /* Give up if slot area array is full. */ while (slot_area_index < MAX_SLOT_AREA) { - /* Potentially raise address to minimum location. */ - if (region.start < minimum) - region.start = minimum; - /* Potentially raise address to meet alignment needs. */ region.start = ALIGN(region.start, CONFIG_PHYSICAL_ALIGN); /* Did we raise the address above the passed in memory entry? */ - if (region.start > end) + if (region.start > region_end) return; /* Reduce size by any delta from the original address. */ - region.size = end - region.start; + region.size = region_end - region.start; /* Return if region can't contain decompressed kernel */ if (region.size < image_size) @@ -668,10 +657,6 @@ static void __process_mem_region(struct mem_vector *entry, process_gb_huge_pages(®ion, image_size); } - /* Return if overlap extends to or past end of region. */ - if (overlap.start + overlap.size >= region.start + region.size) - return; - /* Clip off the overlapping region and start over. */ region.start = overlap.start + overlap.size; } -- 2.7.4