There is a false positive case that a pointer is calculated by other
methods than the usual container_of macro. "kmemleak_ignore" can cover
such a false positive, but it would loose the advantage of memory leak
detection. This patch allows kmemleak to work with such false
positives by aliasing of address. A client module can register an
alias address to an original pointer.
A typical use case could be the IOMMU pagetable allocation which
stores pointers to the second level of page tables with some
conversion, for example, a physical address with attribute bits. Right
now I don't have other use cases but I hope that there could be some
that this special scan works with.
Signed-off-by: Hiroshi DOYU <Hiroshi.DOYU@xxxxxxxxx>
Cc: Phil Carmody <ext-phil.2.carmody@xxxxxxxxx>
---
include/linux/kmemleak.h | 4 +
mm/kmemleak.c | 198 ++++++++++++++++++++++++++++++++++++++--------
2 files changed, 168 insertions(+), 34 deletions(-)
diff --git a/include/linux/kmemleak.h b/include/linux/kmemleak.h
index 99d9a67..0a4ccee 100644
--- a/include/linux/kmemleak.h
+++ b/include/linux/kmemleak.h
@@ -34,6 +34,7 @@ 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, size_t size, gfp_t gfp) __ref;
extern void kmemleak_no_scan(const void *ptr) __ref;
+extern void kmemleak_add_alias(const void *ptr, const void *new) __ref;
static inline void kmemleak_alloc_recursive(const void *ptr, size_t size,
int min_count, unsigned long flags,
@@ -92,6 +93,9 @@ static inline void kmemleak_erase(void **ptr)
static inline void kmemleak_no_scan(const void *ptr)
{
}
+static inline void kmemleak_add_alias(const void *ptr, const void *new)
+{
+}
#endif /* CONFIG_DEBUG_KMEMLEAK */
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index 2c0d032..fa20304 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -157,6 +157,13 @@ struct kmemleak_object {
unsigned long jiffies; /* creation timestamp */
pid_t pid; /* pid of the current task */
char comm[TASK_COMM_LEN]; /* executable name */
+ struct kmemleak_alias *alias; /* if a pointer is modified */
+};
+
+struct kmemleak_alias {
+ struct list_head alias_list;
+ struct prio_tree_node tree_node;
+ struct kmemleak_object *object;
};
/* flag representing the memory block allocation status */
@@ -179,13 +186,18 @@ struct kmemleak_object {
static LIST_HEAD(object_list);
/* the list of gray-colored objects (see color_gray comment below) */
static LIST_HEAD(gray_list);
+/* the list of objects with alias (see alias comment below) */
+static LIST_HEAD(alias_list);
/* prio search tree for object boundaries */
static struct prio_tree_root object_tree_root;
+/* prio search tree for alias object boundaries */
+static struct prio_tree_root alias_tree_root;
/* rw_lock protecting the access to object_list and prio_tree_root */
static DEFINE_RWLOCK(kmemleak_lock);
/* allocation caches for kmemleak internal data */
static struct kmem_cache *object_cache;
+static struct kmem_cache *alias_cache;
static struct kmem_cache *scan_area_cache;
/* set if tracing memory operations is enabled */
@@ -269,6 +281,8 @@ static void kmemleak_disable(void);
kmemleak_disable(); \
} while (0)
+#define to_address(obj) ((obj)->tree_node.start)
+
/*
* Printing of the objects hex dump to the seq file. The number of lines to be
* printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
@@ -369,7 +383,7 @@ static void dump_object_info(struct kmemleak_object *object)
trace.entries = object->trace;
pr_notice("Object 0x%08lx (size %zu):\n",
- object->tree_node.start, object->size);
+ to_address(object), object->size);
pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
object->comm, object->pid, object->jiffies);
pr_notice(" min_count = %d\n", object->min_count);
@@ -436,6 +450,8 @@ static void free_object_rcu(struct rcu_head *rcu)
hlist_del(elem);
kmem_cache_free(scan_area_cache, area);
}
+ if (object->alias)
+ kmem_cache_free(alias_cache, object->alias);
kmem_cache_free(object_cache, object);
}
@@ -479,6 +495,41 @@ static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
return object;
}
+static struct kmemleak_object *find_and_get_object_by_alias(unsigned long ptr,
+ int alias)
+{
+ struct kmemleak_object *object = NULL;
+ struct kmemleak_alias *ao = NULL;
+ struct prio_tree_node *node;
+ struct prio_tree_iter iter;
+ unsigned long flags;
+
+ if (likely(prio_tree_empty(&alias_tree_root)))
+ return NULL;
+
+ rcu_read_lock();
+ read_lock_irqsave(&kmemleak_lock, flags);
+
+ prio_tree_iter_init(&iter, &alias_tree_root, ptr, ptr);
+ node = prio_tree_next(&iter);
+ if (node) {
+ ao = prio_tree_entry(node, struct kmemleak_alias, tree_node);
+ if (!alias && to_address(ao) != ptr) {
+ kmemleak_warn("Found object by alias");
+ ao = NULL;
+ }
+ }
+
+ read_unlock_irqrestore(&kmemleak_lock, flags);
+
+ if (ao && get_object(ao->object))
+ object = ao->object;
+
+ rcu_read_unlock();
+
+ return object;
+}
+
/*
* Save stack trace to the given array of MAX_TRACE size.
*/
@@ -524,6 +575,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
object->count = 0; /* white color initially */
object->jiffies = jiffies;
object->checksum = 0;
+ object->alias = NULL;
/* task information */
if (in_irq()) {
@@ -547,7 +599,7 @@ static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
object->trace_len = __save_stack_trace(object->trace);
INIT_PRIO_TREE_NODE(&object->tree_node);
- object->tree_node.start = ptr;
+ to_address(object) = ptr;
object->tree_node.last = ptr + size - 1;
write_lock_irqsave(&kmemleak_lock, flags);
@@ -577,6 +629,40 @@ out:
return object;
}
+static void create_alias_object(struct kmemleak_object *object,
+ unsigned long ptr)
+{
+ struct kmemleak_alias *alias;
+ struct prio_tree_node *node;
+ unsigned long flags;
+
+ alias = kmem_cache_alloc(alias_cache, GFP_KERNEL);
+ if (!alias) {
+ kmemleak_stop("Cannot allocate a kmemleak_alias structure\n");
+ return;
+ }
+ INIT_LIST_HEAD(&alias->alias_list);
+ INIT_PRIO_TREE_NODE(&alias->tree_node);
+ to_address(alias) = ptr;
+
+ spin_lock_irqsave(&object->lock, flags);
+ alias->tree_node.last = ptr + object->size - 1;
+ alias->object = object;
+ object->alias = alias;
+ spin_unlock_irqrestore(&object->lock, flags);
+
+ write_lock_irqsave(&kmemleak_lock, flags);
+
+ node = prio_tree_insert(&alias_tree_root, &alias->tree_node);
+ if (!node) {
+ kmemleak_warn("Cannot allocate a kmemleak_alias structure\n");
+ kmem_cache_free(alias_cache, alias);
+ }
+ list_add_tail_rcu(&alias->alias_list, &alias_list);
+
+ write_unlock_irqrestore(&kmemleak_lock, flags);
+}
+
/*
* Remove the metadata (struct kmemleak_object) for a memory block from the
* object_list and object_tree_root and decrement its use_count.
@@ -588,6 +674,10 @@ static void __delete_object(struct kmemleak_object *object)
write_lock_irqsave(&kmemleak_lock, flags);
prio_tree_remove(&object_tree_root, &object->tree_node);
list_del_rcu(&object->object_list);
+ if (object->alias) {
+ prio_tree_remove(&alias_tree_root, &object->alias->tree_node);
+ list_del_rcu(&object->alias->alias_list);
+ }
write_unlock_irqrestore(&kmemleak_lock, flags);
WARN_ON(!(object->flags & OBJECT_ALLOCATED));
@@ -630,7 +720,7 @@ static void delete_object_full(unsigned long ptr)
*/
static void delete_object_part(unsigned long ptr, size_t size)
{
- struct kmemleak_object *object;
+ struct kmemleak_object *object, *new;
unsigned long start, end;
object = find_and_get_object(ptr, 1);
@@ -652,12 +742,24 @@ static void delete_object_part(unsigned long ptr, size_t size)
*/
start = object->pointer;
end = object->pointer + object->size;
- if (ptr > start)
- create_object(start, ptr - start, object->min_count,
- GFP_KERNEL);
- if (ptr + size < end)
- create_object(ptr + size, end - ptr - size, object->min_count,
- GFP_KERNEL);
+ if (ptr > start) {
+ new = create_object(start, ptr - start, object->min_count,
+ GFP_KERNEL);
+ if (new && unlikely(object->alias))
+ create_alias_object(new, to_address(object->alias));
+ }
+ if (ptr + size < end) {
+ new = create_object(ptr + size, end - ptr - size,
+ object->min_count, GFP_KERNEL);
+ if (new && unlikely(object->alias)) {
+ unsigned long alias_ptr;
+
+ alias_ptr = to_address(object->alias);
+ alias_ptr += ptr - start + size;
+
+ create_alias_object(new, alias_ptr);
+ }
+ }
put_object(object);
}
@@ -944,6 +1046,22 @@ void __ref kmemleak_no_scan(const void *ptr)
}
EXPORT_SYMBOL(kmemleak_no_scan);
+void kmemleak_add_alias(const void *ptr, const void *alias)
+{
+ struct kmemleak_object *object;
+
+ pr_debug("%s(0x%p -> 0x%p)\n", __func__, ptr, alias);
+
+ object = find_and_get_object((unsigned long)ptr, 0);
+ if (!object) {
+ kmemleak_warn("Aliasing unknown object at 0x%p\n", ptr);
+ return;
+ }
+ create_alias_object(object, (unsigned long)alias);
+ put_object(object);
+}
+EXPORT_SYMBOL(kmemleak_add_alias);
+
/*
* Update an object's checksum and return true if it was modified.
*/
@@ -979,37 +1097,21 @@ static int scan_should_stop(void)
return 0;
}
-/*
- * Scan a memory block (exclusive range) for valid pointers and add those
- * found to the gray list.
- */
-static void scan_block(void *_start, void *_end,
- struct kmemleak_object *scanned, int allow_resched)
+static void __scan_block(unsigned long *ptr, struct kmemleak_object *scanned)
{
- unsigned long *ptr;
- unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
- unsigned long *end = _end - (BYTES_PER_POINTER - 1);
+ int i;
+ unsigned long pointer = *ptr;
+ typedef struct kmemleak_object *(*fn_t)(unsigned long, int);
+ fn_t fns[] = { find_and_get_object, find_and_get_object_by_alias, };
- for (ptr = start; ptr < end; ptr++) {
- struct kmemleak_object *object;
+ for (i = 0; i < ARRAY_SIZE(fns); i++) {
unsigned long flags;
- unsigned long pointer;
-
- if (allow_resched)
- cond_resched();
- if (scan_should_stop())
- break;
-
- /* don't scan uninitialized memory */
- if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
- BYTES_PER_POINTER))
- continue;
-
- pointer = *ptr;
+ struct kmemleak_object *object;
- object = find_and_get_object(pointer, 1);
+ object = fns[i](pointer, 1);
if (!object)
continue;
+
if (object == scanned) {
/* self referenced, ignore */
put_object(object);
@@ -1049,6 +1151,32 @@ static void scan_block(void *_start, void *_end,
}
/*
+ * Scan a memory block (exclusive range) for valid pointers and add those
+ * found to the gray list.
+ */
+static void scan_block(void *_start, void *_end,
+ struct kmemleak_object *scanned, int allow_resched)
+{
+ unsigned long *ptr;
+ unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
+ unsigned long *end = _end - (BYTES_PER_POINTER - 1);
+
+ for (ptr = start; ptr < end; ptr++) {
+ if (allow_resched)
+ cond_resched();
+ if (scan_should_stop())
+ break;
+
+ /* don't scan uninitialized memory */
+ if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
+ BYTES_PER_POINTER))
+ continue;
+
+ __scan_block(ptr, scanned);
+ }
+}
+
+/*
* Scan a memory block corresponding to a kmemleak_object. A condition is
* that object->use_count >= 1.
*/
@@ -1620,8 +1748,10 @@ void __init kmemleak_init(void)
jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
+ alias_cache = KMEM_CACHE(kmemleak_alias, SLAB_NOLEAKTRACE);
scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
INIT_PRIO_TREE_ROOT(&object_tree_root);
+ INIT_PRIO_TREE_ROOT(&alias_tree_root);
/* the kernel is still in UP mode, so disabling the IRQs is enough */
local_irq_save(flags);
--
1.7.1.rc2
--
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