[RFC PATCH 4/4] x86/boot/KASLR: Limit kaslr to choosing the immovable memory

[Chao Fan]

If 'CONFIG_MEMORY_HOTREMOVE' specified and the account of immovable
memory regions is not zero. Calculate the intersection between memory
regions from e820/efi memory table and immovable memory regions.

Rename process_mem_region to slots_count to match slots_fetch_random,
and name new function as process_mem_region.

Signed-off-by: Chao Fan <fanc.fnst@xxxxxxxxxxxxxx>
---
 arch/x86/boot/compressed/kaslr.c | 65 ++++++++++++++++++++++++++------
 1 file changed, 54 insertions(+), 11 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 4edff0501540..a0a07e549ef8 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -545,9 +545,9 @@ static unsigned long slots_fetch_random(void)
 	return 0;
 }
 
-static void process_mem_region(struct mem_vector *entry,
-			       unsigned long minimum,
-			       unsigned long image_size)
+static void slots_count(struct mem_vector *entry,
+			unsigned long minimum,
+			unsigned long image_size)
 {
 	struct mem_vector region, overlap;
 	struct slot_area slot_area;
@@ -624,6 +624,55 @@ static void process_mem_region(struct mem_vector *entry,
 	}
 }
 
+static bool process_mem_region(struct mem_vector *region,
+			       unsigned long long minimum,
+			       unsigned long long image_size)
+{
+#ifdef CONFIG_MEMORY_HOTREMOVE
+	/*
+	 * If hotplug memory found, filter the intersection between
+	 * immovable memory and region to slots_count.
+	 */
+	if (num_immovable_mem > 0) {
+		int i;
+
+		for (i = 0; i < num_immovable_mem; i++) {
+			struct mem_vector entry;
+			unsigned long long start, end, entry_end, region_end;
+
+			start = immovable_mem[i].start;
+			end = start + immovable_mem[i].size;
+			region_end = region->start + region->size;
+
+			entry.start = clamp(region->start, start, end);
+			entry_end = clamp(region_end, start, end);
+
+			if (entry.start + image_size < entry_end) {
+				entry.size = entry_end - entry.start;
+				slots_count(&entry, minimum, image_size);
+
+				if (slot_area_index == MAX_SLOT_AREA) {
+					debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
+					return 1;
+				}
+			}
+		}
+		return 0;
+	}
+#endif
+	/*
+	 * If no hotplug memory found, walk all the regions,
+	 * so use region directely.
+	 */
+	slots_count(region, minimum, image_size);
+
+	if (slot_area_index == MAX_SLOT_AREA) {
+		debug_putstr("Aborted e820/efi memmap scan (slot_areas full)!\n");
+		return 1;
+	}
+	return 0;
+}
+
 #ifdef CONFIG_EFI
 /*
  * Returns true if mirror region found (and must have been processed
@@ -689,11 +738,8 @@ 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 (process_mem_region(&region, minimum, image_size))
 			break;
-		}
 	}
 	return true;
 }
@@ -720,11 +766,8 @@ 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 (process_mem_region(&region, minimum, image_size))
 			break;
-		}
 	}
 }
 
-- 
2.17.0