s390/mm,ptdump: sort markers

Kasan configuration options and size of physical memory present could
affect kernel memory layout. In particular vmemmap, vmalloc and modules
might come before kasan shadow or after it. To make ptdump correctly
output markers in the right order markers have to be sorted.

To preserve the original order of markers with the same start address
avoid using sort() from lib/sort.c (which is not stable sorting algorithm)
and sort markers in place.
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/mm/dump_pagetables.c

@@ -228,6 +228,24 @@ static int ptdump_show(struct seq_file *m, void *v)
 DEFINE_SHOW_ATTRIBUTE(ptdump);
 #endif /* CONFIG_PTDUMP_DEBUGFS */
 
+/*
+ * Heapsort from lib/sort.c is not a stable sorting algorithm, do a simple
+ * insertion sort to preserve the original order of markers with the same
+ * start address.
+ */
+static void sort_address_markers(void)
+{
+	struct addr_marker tmp;
+	int i, j;
+
+	for (i = 1; i < ARRAY_SIZE(address_markers) - 1; i++) {
+		tmp = address_markers[i];
+		for (j = i - 1; j >= 0 && address_markers[j].start_address > tmp.start_address; j--)
+			address_markers[j + 1] = address_markers[j];
+		address_markers[j + 1] = tmp;
+	}
+}
+
 static int pt_dump_init(void)
 {
 	/*
@@ -244,6 +262,7 @@ static int pt_dump_init(void)
 	address_markers[VMEMMAP_END_NR].start_address = (unsigned long)vmemmap + vmemmap_size;
 	address_markers[VMALLOC_NR].start_address = VMALLOC_START;
 	address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
+	sort_address_markers();
 #ifdef CONFIG_PTDUMP_DEBUGFS
 	debugfs_create_file("kernel_page_tables", 0400, NULL, NULL, &ptdump_fops);
 #endif /* CONFIG_PTDUMP_DEBUGFS */