Merge branch 'kmemleak' of git://linux-arm.org/linux-2.6

* 'kmemleak' of git://linux-arm.org/linux-2.6:
  kmemleak: fix kconfig for crc32 build error
  kmemleak: Reduce the false positives by checking for modified objects
  kmemleak: Show the age of an unreferenced object
  kmemleak: Release the object lock before calling put_object()
  kmemleak: Scan the _ftrace_events section in modules
  kmemleak: Simplify the kmemleak_scan_area() function prototype
  kmemleak: Do not use off-slab management with SLAB_NOLEAKTRACE

include/linux/kmemleak.h

@@ -32,8 +32,7 @@ extern void kmemleak_padding(const void *ptr, unsigned long offset,
 			     size_t size) __ref;
 extern void kmemleak_not_leak(const void *ptr) __ref;
 extern void kmemleak_ignore(const void *ptr) __ref;
-extern void kmemleak_scan_area(const void *ptr, unsigned long offset,
-			       size_t length, gfp_t gfp) __ref;
+extern void kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp) __ref;
 extern void kmemleak_no_scan(const void *ptr) __ref;
 
 static inline void kmemleak_alloc_recursive(const void *ptr, size_t size,
@@ -84,8 +83,7 @@ static inline void kmemleak_not_leak(const void *ptr)
 static inline void kmemleak_ignore(const void *ptr)
 {
 }
-static inline void kmemleak_scan_area(const void *ptr, unsigned long offset,
-				      size_t length, gfp_t gfp)
+static inline void kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
 {
 }
 static inline void kmemleak_erase(void **ptr)

kernel/module.c

@@ -1910,9 +1910,7 @@ static void kmemleak_load_module(struct module *mod, Elf_Ehdr *hdr,
 	unsigned int i;
 
 	/* only scan the sections containing data */
-	kmemleak_scan_area(mod->module_core, (unsigned long)mod -
-			   (unsigned long)mod->module_core,
-			   sizeof(struct module), GFP_KERNEL);
+	kmemleak_scan_area(mod, sizeof(struct module), GFP_KERNEL);
 
 	for (i = 1; i < hdr->e_shnum; i++) {
 		if (!(sechdrs[i].sh_flags & SHF_ALLOC))
@@ -1921,8 +1919,7 @@ static void kmemleak_load_module(struct module *mod, Elf_Ehdr *hdr,
 		    && strncmp(secstrings + sechdrs[i].sh_name, ".bss", 4) != 0)
 			continue;
 
-		kmemleak_scan_area(mod->module_core, sechdrs[i].sh_addr -
-				   (unsigned long)mod->module_core,
+		kmemleak_scan_area((void *)sechdrs[i].sh_addr,
 				   sechdrs[i].sh_size, GFP_KERNEL);
 	}
 }
@@ -2250,6 +2247,12 @@ static noinline struct module *load_module(void __user *umod,
 					 "_ftrace_events",
 					 sizeof(*mod->trace_events),
 					 &mod->num_trace_events);
+	/*
+	 * This section contains pointers to allocated objects in the trace
+	 * code and not scanning it leads to false positives.
+	 */
+	kmemleak_scan_area(mod->trace_events, sizeof(*mod->trace_events) *
+			   mod->num_trace_events, GFP_KERNEL);
 #endif
 #ifdef CONFIG_FTRACE_MCOUNT_RECORD
 	/* sechdrs[0].sh_size is always zero */

lib/Kconfig.debug

@@ -360,6 +360,7 @@ config DEBUG_KMEMLEAK
 	select DEBUG_FS if SYSFS
 	select STACKTRACE if STACKTRACE_SUPPORT
 	select KALLSYMS
+	select CRC32
 	help
 	  Say Y here if you want to enable the memory leak
 	  detector. The memory allocation/freeing is traced in a way

mm/kmemleak.c

@@ -93,6 +93,7 @@
 #include <linux/nodemask.h>
 #include <linux/mm.h>
 #include <linux/workqueue.h>
+#include <linux/crc32.h>
 
 #include <asm/sections.h>
 #include <asm/processor.h>
@@ -108,7 +109,6 @@
 #define MSECS_MIN_AGE		5000	/* minimum object age for reporting */
 #define SECS_FIRST_SCAN		60	/* delay before the first scan */
 #define SECS_SCAN_WAIT		600	/* subsequent auto scanning delay */
-#define GRAY_LIST_PASSES	25	/* maximum number of gray list scans */
 #define MAX_SCAN_SIZE		4096	/* maximum size of a scanned block */
 
 #define BYTES_PER_POINTER	sizeof(void *)
@@ -119,8 +119,8 @@
 /* scanning area inside a memory block */
 struct kmemleak_scan_area {
 	struct hlist_node node;
-	unsigned long offset;
-	size_t length;
+	unsigned long start;
+	size_t size;
 };
 
 #define KMEMLEAK_GREY	0
@@ -149,6 +149,8 @@ struct kmemleak_object {
 	int min_count;
 	/* the total number of pointers found pointing to this object */
 	int count;
+	/* checksum for detecting modified objects */
+	u32 checksum;
 	/* memory ranges to be scanned inside an object (empty for all) */
 	struct hlist_head area_list;
 	unsigned long trace[MAX_TRACE];
@@ -164,8 +166,6 @@ struct kmemleak_object {
 #define OBJECT_REPORTED		(1 << 1)
 /* flag set to not scan the object */
 #define OBJECT_NO_SCAN		(1 << 2)
-/* flag set on newly allocated objects */
-#define OBJECT_NEW		(1 << 3)
 
 /* number of bytes to print per line; must be 16 or 32 */
 #define HEX_ROW_SIZE		16
@@ -241,8 +241,6 @@ struct early_log {
 	const void *ptr;		/* allocated/freed memory block */
 	size_t size;			/* memory block size */
 	int min_count;			/* minimum reference count */
-	unsigned long offset;		/* scan area offset */
-	size_t length;			/* scan area length */
 	unsigned long trace[MAX_TRACE];	/* stack trace */
 	unsigned int trace_len;		/* stack trace length */
 };
@@ -323,11 +321,6 @@ static bool color_gray(const struct kmemleak_object *object)
 		object->count >= object->min_count;
 }
 
-static bool color_black(const struct kmemleak_object *object)
-{
-	return object->min_count == KMEMLEAK_BLACK;
-}
-
 /*
  * Objects are considered unreferenced only if their color is white, they have
  * not be deleted and have a minimum age to avoid false positives caused by
@@ -335,7 +328,7 @@ static bool color_black(const struct kmemleak_object *object)
  */
 static bool unreferenced_object(struct kmemleak_object *object)
 {
-	return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
+	return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&
 		time_before_eq(object->jiffies + jiffies_min_age,
 			       jiffies_last_scan);
 }
@@ -348,11 +341,13 @@ static void print_unreferenced(struct seq_file *seq,
 			       struct kmemleak_object *object)
 {
 	int i;
+	unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
 
 	seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
 		   object->pointer, object->size);
-	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu\n",
-		   object->comm, object->pid, object->jiffies);
+	seq_printf(seq, "  comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
+		   object->comm, object->pid, object->jiffies,
+		   msecs_age / 1000, msecs_age % 1000);
 	hex_dump_object(seq, object);
 	seq_printf(seq, "  backtrace:\n");
 
@@ -381,6 +376,7 @@ static void dump_object_info(struct kmemleak_object *object)
 	pr_notice("  min_count = %d\n", object->min_count);
 	pr_notice("  count = %d\n", object->count);
 	pr_notice("  flags = 0x%lx\n", object->flags);
+	pr_notice("  checksum = %d\n", object->checksum);
 	pr_notice("  backtrace:\n");
 	print_stack_trace(&trace, 4);
 }
@@ -522,12 +518,13 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
 	INIT_HLIST_HEAD(&object->area_list);
 	spin_lock_init(&object->lock);
 	atomic_set(&object->use_count, 1);
-	object->flags = OBJECT_ALLOCATED | OBJECT_NEW;
+	object->flags = OBJECT_ALLOCATED;
 	object->pointer = ptr;
 	object->size = size;
 	object->min_count = min_count;
-	object->count = -1;			/* no color initially */
+	object->count = 0;			/* white color initially */
 	object->jiffies = jiffies;
+	object->checksum = 0;
 
 	/* task information */
 	if (in_irq()) {
@@ -720,14 +717,13 @@ static void make_black_object(unsigned long ptr)
  * Add a scanning area to the object. If at least one such area is added,
  * kmemleak will only scan these ranges rather than the whole memory block.
  */
-static void add_scan_area(unsigned long ptr, unsigned long offset,
-			  size_t length, gfp_t gfp)
+static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
 {
 	unsigned long flags;
 	struct kmemleak_object *object;
 	struct kmemleak_scan_area *area;
 
-	object = find_and_get_object(ptr, 0);
+	object = find_and_get_object(ptr, 1);
 	if (!object) {
 		kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
 			      ptr);
@@ -741,7 +737,7 @@ static void add_scan_area(unsigned long ptr, unsigned long offset,
 	}
 
 	spin_lock_irqsave(&object->lock, flags);
-	if (offset + length > object->size) {
+	if (ptr + size > object->pointer + object->size) {
 		kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
 		dump_object_info(object);
 		kmem_cache_free(scan_area_cache, area);
@@ -749,8 +745,8 @@ static void add_scan_area(unsigned long ptr, unsigned long offset,
 	}
 
 	INIT_HLIST_NODE(&area->node);
-	area->offset = offset;
-	area->length = length;
+	area->start = ptr;
+	area->size = size;
 
 	hlist_add_head(&area->node, &object->area_list);
 out_unlock:
@@ -786,7 +782,7 @@ static void object_no_scan(unsigned long ptr)
  * processed later once kmemleak is fully initialized.
  */
 static void __init log_early(int op_type, const void *ptr, size_t size,
-			     int min_count, unsigned long offset, size_t length)
+			     int min_count)
 {
 	unsigned long flags;
 	struct early_log *log;
@@ -808,8 +804,6 @@ static void __init log_early(int op_type, const void *ptr, size_t size,
 	log->ptr = ptr;
 	log->size = size;
 	log->min_count = min_count;
-	log->offset = offset;
-	log->length = length;
 	if (op_type == KMEMLEAK_ALLOC)
 		log->trace_len = __save_stack_trace(log->trace);
 	crt_early_log++;
@@ -858,7 +852,7 @@ void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
 		create_object((unsigned long)ptr, size, min_count, gfp);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
+		log_early(KMEMLEAK_ALLOC, ptr, size, min_count);
 }
 EXPORT_SYMBOL_GPL(kmemleak_alloc);
 
@@ -873,7 +867,7 @@ void __ref kmemleak_free(const void *ptr)
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
 		delete_object_full((unsigned long)ptr);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
+		log_early(KMEMLEAK_FREE, ptr, 0, 0);
 }
 EXPORT_SYMBOL_GPL(kmemleak_free);
 
@@ -888,7 +882,7 @@ void __ref kmemleak_free_part(const void *ptr, size_t size)
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
 		delete_object_part((unsigned long)ptr, size);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_FREE_PART, ptr, size, 0, 0, 0);
+		log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
 }
 EXPORT_SYMBOL_GPL(kmemleak_free_part);
 
@@ -903,7 +897,7 @@ void __ref kmemleak_not_leak(const void *ptr)
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
 		make_gray_object((unsigned long)ptr);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
+		log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);
 }
 EXPORT_SYMBOL(kmemleak_not_leak);
 
@@ -919,22 +913,21 @@ void __ref kmemleak_ignore(const void *ptr)
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
 		make_black_object((unsigned long)ptr);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
+		log_early(KMEMLEAK_IGNORE, ptr, 0, 0);
 }
 EXPORT_SYMBOL(kmemleak_ignore);
 
 /*
  * Limit the range to be scanned in an allocated memory block.
  */
-void __ref kmemleak_scan_area(const void *ptr, unsigned long offset,
-			      size_t length, gfp_t gfp)
+void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
 {
 	pr_debug("%s(0x%p)\n", __func__, ptr);
 
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
-		add_scan_area((unsigned long)ptr, offset, length, gfp);
+		add_scan_area((unsigned long)ptr, size, gfp);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
+		log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
 }
 EXPORT_SYMBOL(kmemleak_scan_area);
 
@@ -948,10 +941,24 @@ void __ref kmemleak_no_scan(const void *ptr)
 	if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
 		object_no_scan((unsigned long)ptr);
 	else if (atomic_read(&kmemleak_early_log))
-		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0);
+		log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);
 }
 EXPORT_SYMBOL(kmemleak_no_scan);
 
+/*
+ * Update an object's checksum and return true if it was modified.
+ */
+static bool update_checksum(struct kmemleak_object *object)
+{
+	u32 old_csum = object->checksum;
+
+	if (!kmemcheck_is_obj_initialized(object->pointer, object->size))
+		return false;
+
+	object->checksum = crc32(0, (void *)object->pointer, object->size);
+	return object->checksum != old_csum;
+}
+
 /*
  * Memory scanning is a long process and it needs to be interruptable. This
  * function checks whether such interrupt condition occured.
@@ -1031,11 +1038,14 @@ static void scan_block(void *_start, void *_end,
 		 * added to the gray_list.
 		 */
 		object->count++;
-		if (color_gray(object))
+		if (color_gray(object)) {
 			list_add_tail(&object->gray_list, &gray_list);
-		else
-			put_object(object);
 			spin_unlock_irqrestore(&object->lock, flags);
+			continue;
+		}
+
+		spin_unlock_irqrestore(&object->lock, flags);
+		put_object(object);
 	}
 }
 
@@ -1075,13 +1085,46 @@ static void scan_object(struct kmemleak_object *object)
 		}
 	} else
 		hlist_for_each_entry(area, elem, &object->area_list, node)
-			scan_block((void *)(object->pointer + area->offset),
-				   (void *)(object->pointer + area->offset
-					    + area->length), object, 0);
+			scan_block((void *)area->start,
+				   (void *)(area->start + area->size),
+				   object, 0);
 out:
 	spin_unlock_irqrestore(&object->lock, flags);
 }
 
+/*
+ * Scan the objects already referenced (gray objects). More objects will be
+ * referenced and, if there are no memory leaks, all the objects are scanned.
+ */
+static void scan_gray_list(void)
+{
+	struct kmemleak_object *object, *tmp;
+
+	/*
+	 * The list traversal is safe for both tail additions and removals
+	 * from inside the loop. The kmemleak objects cannot be freed from
+	 * outside the loop because their use_count was incremented.
+	 */
+	object = list_entry(gray_list.next, typeof(*object), gray_list);
+	while (&object->gray_list != &gray_list) {
+		cond_resched();
+
+		/* may add new objects to the list */
+		if (!scan_should_stop())
+			scan_object(object);
+
+		tmp = list_entry(object->gray_list.next, typeof(*object),
+				 gray_list);
+
+		/* remove the object from the list and release it */
+		list_del(&object->gray_list);
+		put_object(object);
+
+		object = tmp;
+	}
+	WARN_ON(!list_empty(&gray_list));
+}
+
 /*
  * Scan data sections and all the referenced memory blocks allocated via the
  * kernel's standard allocators. This function must be called with the
@@ -1090,10 +1133,9 @@ static void scan_object(struct kmemleak_object *object)
 static void kmemleak_scan(void)
 {
 	unsigned long flags;
-	struct kmemleak_object *object, *tmp;
+	struct kmemleak_object *object;
 	int i;
 	int new_leaks = 0;
-	int gray_list_pass = 0;
 
 	jiffies_last_scan = jiffies;
 
@@ -1114,7 +1156,6 @@ static void kmemleak_scan(void)
 #endif
 		/* reset the reference count (whiten the object) */
 		object->count = 0;
-		object->flags &= ~OBJECT_NEW;
 		if (color_gray(object) && get_object(object))
 			list_add_tail(&object->gray_list, &gray_list);
 
@@ -1172,62 +1213,36 @@ static void kmemleak_scan(void)
 
 	/*
 	 * Scan the objects already referenced from the sections scanned
-	 * above. More objects will be referenced and, if there are no memory
-	 * leaks, all the objects will be scanned. The list traversal is safe
-	 * for both tail additions and removals from inside the loop. The
-	 * kmemleak objects cannot be freed from outside the loop because their
-	 * use_count was increased.
+	 * above.
 	 */
-repeat:
-	object = list_entry(gray_list.next, typeof(*object), gray_list);
-	while (&object->gray_list != &gray_list) {
-		cond_resched();
-
-		/* may add new objects to the list */
-		if (!scan_should_stop())
-			scan_object(object);
-
-		tmp = list_entry(object->gray_list.next, typeof(*object),
-				 gray_list);
-
-		/* remove the object from the list and release it */
-		list_del(&object->gray_list);
-		put_object(object);
-
-		object = tmp;
-	}
-
-	if (scan_should_stop() || ++gray_list_pass >= GRAY_LIST_PASSES)
-		goto scan_end;
+	scan_gray_list();
 
 	/*
-	 * Check for new objects allocated during this scanning and add them
-	 * to the gray list.
+	 * Check for new or unreferenced objects modified since the previous
+	 * scan and color them gray until the next scan.
 	 */
 	rcu_read_lock();
 	list_for_each_entry_rcu(object, &object_list, object_list) {
 		spin_lock_irqsave(&object->lock, flags);
-		if ((object->flags & OBJECT_NEW) && !color_black(object) &&
-		    get_object(object)) {
-			object->flags &= ~OBJECT_NEW;
+		if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
+		    && update_checksum(object) && get_object(object)) {
+			/* color it gray temporarily */
+			object->count = object->min_count;
 			list_add_tail(&object->gray_list, &gray_list);
 		}
 		spin_unlock_irqrestore(&object->lock, flags);
 	}
 	rcu_read_unlock();
 
-	if (!list_empty(&gray_list))
-		goto repeat;
-
-scan_end:
-	WARN_ON(!list_empty(&gray_list));
+	/*
+	 * Re-scan the gray list for modified unreferenced objects.
+	 */
+	scan_gray_list();
 
 	/*
-	 * If scanning was stopped or new objects were being allocated at a
-	 * higher rate than gray list scanning, do not report any new
-	 * unreferenced objects.
+	 * If scanning was stopped do not report any new unreferenced objects.
 	 */
-	if (scan_should_stop() || gray_list_pass >= GRAY_LIST_PASSES)
+	if (scan_should_stop())
 		return;
 
 	/*
@@ -1642,8 +1657,7 @@ void __init kmemleak_init(void)
 			kmemleak_ignore(log->ptr);
 			break;
 		case KMEMLEAK_SCAN_AREA:
-			kmemleak_scan_area(log->ptr, log->offset, log->length,
-					   GFP_KERNEL);
+			kmemleak_scan_area(log->ptr, log->size, GFP_KERNEL);
 			break;
 		case KMEMLEAK_NO_SCAN:
 			kmemleak_no_scan(log->ptr);

mm/slab.c

@@ -2275,9 +2275,11 @@ kmem_cache_create (const char *name, size_t size, size_t align,
 	/*
 	 * Determine if the slab management is 'on' or 'off' slab.
 	 * (bootstrapping cannot cope with offslab caches so don't do
-	 * it too early on.)
+	 * it too early on. Always use on-slab management when
+	 * SLAB_NOLEAKTRACE to avoid recursive calls into kmemleak)
 	 */
-	if ((size >= (PAGE_SIZE >> 3)) && !slab_early_init)
+	if ((size >= (PAGE_SIZE >> 3)) && !slab_early_init &&
+	    !(flags & SLAB_NOLEAKTRACE))
 		/*
 		 * Size is large, assume best to place the slab management obj
 		 * off-slab (should allow better packing of objs).
@@ -2596,8 +2598,8 @@ static struct slab *alloc_slabmgmt(struct kmem_cache *cachep, void *objp,
 		 * kmemleak does not treat the ->s_mem pointer as a reference
 		 * to the object. Otherwise we will not report the leak.
 		 */
-		kmemleak_scan_area(slabp, offsetof(struct slab, list),
-				   sizeof(struct list_head), local_flags);
+		kmemleak_scan_area(&slabp->list, sizeof(struct list_head),
+				   local_flags);
 		if (!slabp)
 			return NULL;
 	} else {