s390/kasan: dynamic shadow mem allocation for modules

Move from modules area entire shadow memory preallocation to dynamic
allocation per module load.

This behaivior has been introduced for x86 with bebf56a1b: "This patch
also forces module_alloc() to return 8*PAGE_SIZE aligned address making
shadow memory handling ( kasan_module_alloc()/kasan_module_free() )
more simple. Such alignment guarantees that each shadow page backing
modules address space correspond to only one module_alloc() allocation"

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/module.c

@@ -16,6 +16,7 @@
 #include <linux/fs.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
+#include <linux/kasan.h>
 #include <linux/moduleloader.h>
 #include <linux/bug.h>
 #include <asm/alternative.h>
@@ -32,12 +33,18 @@
 
 void *module_alloc(unsigned long size)
 {
+	void *p;
+
 	if (PAGE_ALIGN(size) > MODULES_LEN)
 		return NULL;
-	return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END,
-				    GFP_KERNEL, PAGE_KERNEL_EXEC,
-				    0, NUMA_NO_NODE,
-				    __builtin_return_address(0));
+	p = __vmalloc_node_range(size, MODULE_ALIGN, MODULES_VADDR, MODULES_END,
+				 GFP_KERNEL, PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
+				 __builtin_return_address(0));
+	if (p && (kasan_module_alloc(p, size) < 0)) {
+		vfree(p);
+		return NULL;
+	}
+	return p;
 }
 
 void module_arch_freeing_init(struct module *mod)

arch/s390/mm/kasan_init.c

@@ -214,8 +214,6 @@ void __init kasan_early_init(void)
 
 	memsize = min(max_physmem_end, KASAN_SHADOW_START);
 	shadow_alloc_size = memsize >> KASAN_SHADOW_SCALE_SHIFT;
-	if (IS_ENABLED(CONFIG_MODULES))
-		shadow_alloc_size += MODULES_LEN >> KASAN_SHADOW_SCALE_SHIFT;
 	pgalloc_low = round_up((unsigned long)_end, _SEGMENT_SIZE);
 	if (IS_ENABLED(CONFIG_BLK_DEV_INITRD)) {
 		initrd_end =
@@ -239,18 +237,15 @@ void __init kasan_early_init(void)
 	 * +- shadow end    -+	 |	mapping	  |
 	 * | ... gap ...     |\  |    (untracked) |
 	 * +- modules vaddr -+ \ +----------------+
-	 * | 2Gb	     |	\| 256Mb	  |
+	 * | 2Gb	     |	\|	unmapped  | allocated per module
 	 * +-----------------+	 +- shadow end ---+
 	 */
 	/* populate identity mapping */
 	kasan_early_vmemmap_populate(0, memsize, POPULATE_ONE2ONE);
-	/* populate kasan shadow (for identity mapping / modules / zero page) */
+	/* populate kasan shadow (for identity mapping and zero page mapping) */
 	kasan_early_vmemmap_populate(__sha(0), __sha(memsize), POPULATE_MAP);
-	if (IS_ENABLED(CONFIG_MODULES)) {
+	if (IS_ENABLED(CONFIG_MODULES))
 		untracked_mem_end = vmax - MODULES_LEN;
-		kasan_early_vmemmap_populate(__sha(untracked_mem_end),
-					     __sha(vmax), POPULATE_MAP);
-	}
 	kasan_early_vmemmap_populate(__sha(memsize), __sha(untracked_mem_end),
 				     POPULATE_ZERO_SHADOW);
 	kasan_set_pgd(early_pg_dir, asce_type);