/*
* mm/kmemleak.c
*
* Copyright (C) 2008 ARM Limited
* Written by Catalin Marinas <catalin.marinas@arm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*
* For more information on the algorithm and kmemleak usage, please see
* Documentation/kmemleak.txt.
*
* Notes on locking
* ----------------
*
* The following locks and mutexes are used by kmemleak:
*
* - kmemleak_lock (rwlock): protects the object_list modifications and
* accesses to the object_tree_root. The object_list is the main list
* holding the metadata (struct kmemleak_object) for the allocated memory
* blocks. The object_tree_root is a priority search tree used to look-up
* metadata based on a pointer to the corresponding memory block. The
* kmemleak_object structures are added to the object_list and
* object_tree_root in the create_object() function called from the
* kmemleak_alloc() callback and removed in delete_object() called from the
* kmemleak_free() callback
* - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to
* the metadata (e.g. count) are protected by this lock. Note that some
* members of this structure may be protected by other means (atomic or
* kmemleak_lock). This lock is also held when scanning the corresponding
* memory block to avoid the kernel freeing it via the kmemleak_free()
* callback. This is less heavyweight than holding a global lock like
* kmemleak_lock during scanning
* - scan_mutex (mutex): ensures that only one thread may scan the memory for
* unreferenced objects at a time. The gray_list contains the objects which
* are already referenced or marked as false positives and need to be
* scanned. This list is only modified during a scanning episode when the
* scan_mutex is held. At the end of a scan, the gray_list is always empty.
* Note that the kmemleak_object.use_count is incremented when an object is
* added to the gray_list and therefore cannot be freed
* - kmemleak_mutex (mutex): prevents multiple users of the "kmemleak" debugfs
* file together with modifications to the memory scanning parameters
* including the scan_thread pointer
*
* The kmemleak_object structures have a use_count incremented or decremented
* using the get_object()/put_object() functions. When the use_count becomes
* 0, this count can no longer be incremented and put_object() schedules the
* kmemleak_object freeing via an RCU callback. All calls to the get_object()
* function must be protected by rcu_read_lock() to avoid accessing a freed
* structure.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/jiffies.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/prio_tree.h>
#include <linux/gfp.h>
#include <linux/fs.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/stacktrace.h>
#include <linux/cache.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/mmzone.h>
#include <linux/slab.h>
#include <linux/thread_info.h>
#include <linux/err.h>
#include <linux/uaccess.h>
#include <linux/string.h>
#include <linux/nodemask.h>
#include <linux/mm.h>
#include <asm/sections.h>
#include <asm/processor.h>
#include <asm/atomic.h>
#include <linux/kmemleak.h>
/*
* Kmemleak configuration and common defines.
*/
#define MAX_TRACE 16 /* stack trace length */
#define REPORTS_NR 50 /* maximum number of reported leaks */
#define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
#define MSECS_SCAN_YIELD 10 /* CPU yielding period */
#define SECS_FIRST_SCAN 60 /* delay before the first scan */
#define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
#define BYTES_PER_POINTER sizeof(void *)
/* GFP bitmask for kmemleak internal allocations */
#define GFP_KMEMLEAK_MASK (GFP_KERNEL | GFP_ATOMIC)
/* scanning area inside a memory block */
struct kmemleak_scan_area {
struct hlist_node node;
unsigned long offset;
size_t length;
};
/*
* Structure holding the metadata for each allocated memory block.
* Modifications to such objects should be made while holding the
* object->lock. Insertions or deletions from object_list, gray_list or
* tree_node are already protected by the corresponding locks or mutex (see
* the notes on locking above). These objects are reference-counted
* (use_count) and freed using the RCU mechanism.
*/
struct kmemleak_object {
spinlock_t lock;
unsigned long flags; /* object status flags */
struct list_head object_list;
struct list_head gray_list;
struct prio_tree_node tree_node;
struct rcu_head rcu; /* object_list lockless traversal */
/* object usage count; object freed when use_count == 0 */
atomic_t use_count;
unsigned long pointer;
size_t size;
/* minimum number of a pointers found before it is considered leak */
int min_count;
/* the total number of pointers found pointing to this object */
int count;
/* memory ranges to be scanned inside an object (empty for all) */
struct hlist_head area_list;
unsigned long trace[MAX_TRACE];
unsigned int trace_len;
unsigned long jiffies; /* creation timestamp */
pid_t pid; /* pid of the current task */
char comm[TASK_COMM_LEN]; /* executable name */
};
/* flag representing the memory block allocation status */
#define OBJECT_ALLOCATED (1 << 0)
/* flag set after the first reporting of an unreference object */
#define OBJECT_REPORTED (1 << 1)
/* flag set to not scan the object */
#define OBJECT_NO_SCAN (1 << 2)
/* the list of all allocated objects */
static LIST_HEAD(object_list);
/* the list of gray-colored objects (see color_gray comment below) */
static LIST_HEAD(gray_list);
/* prio search tree for object boundaries */
static struct prio_tree_root object_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 *scan_area_cache;
/* set if tracing memory operations is enabled */
static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
/* set in the late_initcall if there were no errors */
static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
/* enables or disables early logging of the memory operations */
static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
/* set if a fata kmemleak error has occurred */
static atomic_t kmemleak_error = ATOMIC_INIT(0);
/* minimum and maximum address that may be valid pointers */
static unsigned long min_addr = ULONG_MAX;
static unsigned long max_addr;
/* used for yielding the CPU to other tasks during scanning */
static unsigned long next_scan_yield;
static struct task_struct *scan_thread;
static unsigned long jiffies_scan_yield;
static unsigned long jiffies_min_age;
/* delay between automatic memory scannings */
static signed long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
static int kmemleak_stack_scan;
/* mutex protecting the memory scanning */
static DEFINE_MUTEX(scan_mutex);
/* mutex protecting the access to the /sys/kernel/debug/kmemleak file */
static DEFINE_MUTEX(kmemleak_mutex);
/* number of leaks reported (for limitation purposes) */
static int reported_leaks;
/*
* Early object allocation/freeing logging. Kmemleak is initialized after the
* kernel allocator. However, both the kernel allocator and kmemleak may
* allocate memory blocks which need to be tracked. Kmemleak defines an
* arbitrary buffer to hold the allocation/freeing information before it is
* fully initialized.
*/
/* kmemleak operation type for early logging */
enum {
KMEMLEAK_ALLOC,
KMEMLEAK_FREE,
KMEMLEAK_NOT_LEAK,
KMEMLEAK_IGNORE,
KMEMLEAK_SCAN_AREA,
KMEMLEAK_NO_SCAN
};
/*
* Structure holding the information passed to kmemleak callbacks during the
* early logging.
*/
struct early_log {
int op_type; /* kmemleak operation type */
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 */
};
/* early logging buffer and current position */
static struct early_log early_log[200];
static int crt_early_log;
static void kmemleak_disable(void);
/*
* Print a warning and dump the stack trace.
*/
#define kmemleak_warn(x...) do { \
pr_warning(x); \
dump_stack(); \
} while (0)
/*
* Macro invoked when a serious kmemleak condition occured and cannot be
* recovered from. Kmemleak will be disabled and further allocation/freeing
* tracing no longer available.
*/
#define kmemleak_stop(x...) do { \
kmemleak_warn(x); \
kmemleak_disable(); \
} while (0)
/*
* Object colors, encoded with count and min_count:
* - white - orphan object, not enough references to it (count < min_count)
* - gray - not orphan, not marked as false positive (min_count == 0) or
* sufficient references to it (count >= min_count)
* - black - ignore, it doesn't contain references (e.g. text section)
* (min_count == -1). No function defined for this color.
* Newly created objects don't have any color assigned (object->count == -1)
* before the next memory scan when they become white.
*/
static int color_white(const struct kmemleak_object *object)
{
return object->count != -1 && object->count < object->min_count;
}
static int color_gray(const struct kmemleak_object *object)
{
return object->min_count != -1 && object->count >= object->min_count;
}
/*
* Objects are considered referenced if their color is gray and they have not
* been deleted.
*/
static int referenced_object(struct kmemleak_object *object)
{
return (object->flags & OBJECT_ALLOCATED) && color_gray(object);
}
/*
* 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
* pointers temporarily stored in CPU registers.
*/
static int unreferenced_object(struct kmemleak_object *object)
{
return (object->flags & OBJECT_ALLOCATED) && color_white(object) &&
time_is_before_eq_jiffies(object->jiffies + jiffies_min_age);
}
/*
* Printing of the (un)referenced objects information, either to the seq file
* or to the kernel log. The print_referenced/print_unreferenced functions
* must be called with the object->lock held.
*/
#define print_helper(seq, x...) do { \
struct seq_file *s = (seq); \
if (s) \
seq_printf(s, x); \
else \
pr_info(x); \
} while (0)
static void print_referenced(struct kmemleak_object *object)
{
pr_info("referenced object 0x%08lx (size %zu)\n",
object->pointer, object->size);
}
static void print_unreferenced(struct seq_file *seq,
struct kmemleak_object *object)
{
int i;
print_helper(seq, "unreferenced object 0x%08lx (size %zu):\n",
object->pointer, object->size);
print_helper(seq, " comm \"%s\", pid %d, jiffies %lu\n",
object->comm, object->pid, object->jiffies);
print_helper(seq, " backtrace:\n");
for (i = 0; i < object->trace_len; i++) {
void *ptr = (void *)object->trace[i];
print_helper(seq, " [<%p>] %pS\n", ptr, ptr);
}
}
/*
* Print the kmemleak_object information. This function is used mainly for
* debugging special cases when kmemleak operations. It must be called with
* the object->lock held.
*/
static void dump_object_info(struct kmemleak_object *object)
{
struct stack_trace trace;
trace.nr_entries = object->trace_len;
trace.entries = object->trace;
pr_notice("Object 0x%08lx (size %zu):\n",
object->tree_node.start, 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);
pr_notice(" count = %d\n", object->count);
pr_notice(" backtrace:\n");
print_stack_trace(&trace, 4);
}
/*
* Look-up a memory block metadata (kmemleak_object) in the priority search
* tree based on a pointer value. If alias is 0, only values pointing to the
* beginning of the memory block are allowed. The kmemleak_lock must be held
* when calling this function.
*/
static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
{
struct prio_tree_node *node;
struct prio_tree_iter iter;
struct kmemleak_object *object;
prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr);
node = prio_tree_next(&iter);
if (node) {
object = prio_tree_entry(node, struct kmemleak_object,
tree_node);
if (!alias && object->pointer != ptr) {
kmemleak_warn("Found object by alias");
object = NULL;
}
} else
object = NULL;
return object;
}
/*
* Increment the object use_count. Return 1 if successful or 0 otherwise. Note
* that once an object's use_count reached 0, the RCU freeing was already
* registered and the object should no longer be used. This function must be
* called under the protection of rcu_read_lock().
*/
static int get_object(struct kmemleak_object *object)
{
return atomic_inc_not_zero(&object->use_count);
}
/*
* RCU callback to free a kmemleak_object.
*/
static void free_object_rcu(struct rcu_head *rcu)
{
struct hlist_node *elem, *tmp;
struct kmemleak_scan_area *area;
struct kmemleak_object *object =
container_of(rcu, struct kmemleak_object, rcu);
/*
* Once use_count is 0 (guaranteed by put_object), there is no other
* code accessing this object, hence no need for locking.
*/
hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) {
hlist_del(elem);
kmem_cache_free(scan_area_cache, area);
}
kmem_cache_free(object_cache, object);
}
/*
* Decrement the object use_count. Once the count is 0, free the object using
* an RCU callback. Since put_object() may be called via the kmemleak_free() ->
* delete_object() path, the delayed RCU freeing ensures that there is no
* recursive call to the kernel allocator. Lock-less RCU object_list traversal
* is also possible.
*/
static void put_object(struct kmemleak_object *object)
{
if (!atomic_dec_and_test(&object->use_count))
return;
/* should only get here after delete_object was called */
WARN_ON(object->flags & OBJECT_ALLOCATED);
call_rcu(&object->rcu, free_object_rcu);
}
/*
* Look up an object in the prio search tree and increase its use_count.
*/
static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
{
unsigned long flags;
struct kmemleak_object *object = NULL;
rcu_read_lock();
read_lock_irqsave(&kmemleak_lock, flags);
if (ptr >= min_addr && ptr < max_addr)
object = lookup_object(ptr, alias);
read_unlock_irqrestore(&kmemleak_lock, flags);
/* check whether the object is still available */
if (object && !get_object(object))
object = NULL;
rcu_read_unlock();
return object;
}
/*
* Create the metadata (struct kmemleak_object) corresponding to an allocated
* memory block and add it to the object_list and object_tree_root.
*/
static void create_object(unsigned long ptr, size_t size, int min_count,
gfp_t gfp)
{
unsigned long flags;
struct kmemleak_object *object;
struct prio_tree_node *node;
struct stack_trace trace;
object = kmem_cache_alloc(object_cache, gfp & GFP_KMEMLEAK_MASK);
if (!object) {
kmemleak_stop("Cannot allocate a kmemleak_object structure\n");
return;
}
INIT_LIST_HEAD(&object->object_list);
INIT_LIST_HEAD(&object->gray_list);
INIT_HLIST_HEAD(&object->area_list);
spin_lock_init(&object->lock);
atomic_set(&object->use_count, 1);
object->flags = OBJECT_ALLOCATED;
object->pointer = ptr;
object->size = size;
object->min_count = min_count;
object->count = -1; /* no color initially */
object->jiffies = jiffies;
/* task information */
if (in_irq()) {
object->pid = 0;
strncpy(object->comm, "hardirq", sizeof(object->comm));
} else if (in_softirq()) {
object->pid = 0;
strncpy(object->comm, "softirq", sizeof(object->comm));
} else {
object->pid = current->pid;
/*
* There is a small chance of a race with set_task_comm(),
* however using get_task_comm() here may cause locking
* dependency issues with current->alloc_lock. In the worst
* case, the command line is not correct.
*/
strncpy(object->comm, current->comm, sizeof(object->comm));
}
/* kernel backtrace */
trace.max_entries = MAX_TRACE;
trace.nr_entries = 0;
trace.entries = object->trace;
trace.skip = 1;
save_stack_trace(&trace);
object->trace_len = trace.nr_entries;
INIT_PRIO_TREE_NODE(&object->tree_node);
object->tree_node.start = ptr;
object->tree_node.last = ptr + size - 1;
write_lock_irqsave(&kmemleak_lock, flags);
min_addr = min(min_addr, ptr);
max_addr = max(max_addr, ptr + size);
node = prio_tree_insert(&object_tree_root, &object->tree_node);
/*
* The code calling the kernel does not yet have the pointer to the
* memory block to be able to free it. However, we still hold the
* kmemleak_lock here in case parts of the kernel started freeing
* random memory blocks.
*/
if (node != &object->tree_node) {
unsigned long flags;
kmemleak_stop("Cannot insert 0x%lx into the object search tree "
"(already existing)\n", ptr);
object = lookup_object(ptr, 1);
spin_lock_irqsave(&object->lock, flags);
dump_object_info(object);
spin_unlock_irqrestore(&object->lock, flags);
goto out;
}
list_add_tail_rcu(&object->object_list, &object_list);
out:
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.
*/
static void delete_object(unsigned long ptr)
{
unsigned long flags;
struct kmemleak_object *object;
write_lock_irqsave(&kmemleak_lock, flags);
object = lookup_object(ptr, 0);
if (!object) {
kmemleak_warn("Freeing unknown object at 0x%08lx\n",
ptr);
write_unlock_irqrestore(&kmemleak_lock, flags);
return;
}
prio_tree_remove(&object_tree_root, &object->tree_node);
list_del_rcu(&object->object_list);
write_unlock_irqrestore(&kmemleak_lock, flags);
WARN_ON(!(object->flags & OBJECT_ALLOCATED));
WARN_ON(atomic_read(&object->use_count) < 1);
/*
* Locking here also ensures that the corresponding memory block
* cannot be freed when it is being scanned.
*/
spin_lock_irqsave(&object->lock, flags);
if (object->flags & OBJECT_REPORTED)
print_referenced(object);
object->flags &= ~OBJECT_ALLOCATED;
spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* Make a object permanently as gray-colored so that it can no longer be
* reported as a leak. This is used in general to mark a false positive.
*/
static void make_gray_object(unsigned long ptr)
{
unsigned long flags;
struct kmemleak_object *object;
object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Graying unknown object at 0x%08lx\n", ptr);
return;
}
spin_lock_irqsave(&object->lock, flags);
object->min_count = 0;
spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* Mark the object as black-colored so that it is ignored from scans and
* reporting.
*/
static void make_black_object(unsigned long ptr)
{
unsigned long flags;
struct kmemleak_object *object;
object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Blacking unknown object at 0x%08lx\n", ptr);
return;
}
spin_lock_irqsave(&object->lock, flags);
object->min_count = -1;
spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* 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)
{
unsigned long flags;
struct kmemleak_object *object;
struct kmemleak_scan_area *area;
object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
ptr);
return;
}
area = kmem_cache_alloc(scan_area_cache, gfp & GFP_KMEMLEAK_MASK);
if (!area) {
kmemleak_warn("Cannot allocate a scan area\n");
goto out;
}
spin_lock_irqsave(&object->lock, flags);
if (offset + length > object->size) {
kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
dump_object_info(object);
kmem_cache_free(scan_area_cache, area);
goto out_unlock;
}
INIT_HLIST_NODE(&area->node);
area->offset = offset;
area->length = length;
hlist_add_head(&area->node, &object->area_list);
out_unlock:
spin_unlock_irqrestore(&object->lock, flags);
out:
put_object(object);
}
/*
* Set the OBJECT_NO_SCAN flag for the object corresponding to the give
* pointer. Such object will not be scanned by kmemleak but references to it
* are searched.
*/
static void object_no_scan(unsigned long ptr)
{
unsigned long flags;
struct kmemleak_object *object;
object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
return;
}
spin_lock_irqsave(&object->lock, flags);
object->flags |= OBJECT_NO_SCAN;
spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
/*
* Log an early kmemleak_* call to the early_log buffer. These calls will be
* processed later once kmemleak is fully initialized.
*/
static void log_early(int op_type, const void *ptr, size_t size,
int min_count, unsigned long offset, size_t length)
{
unsigned long flags;
struct early_log *log;
if (crt_early_log >= ARRAY_SIZE(early_log)) {
kmemleak_stop("Early log buffer exceeded\n");
return;
}
/*
* There is no need for locking since the kernel is still in UP mode
* at this stage. Disabling the IRQs is enough.
*/
local_irq_save(flags);
log = &early_log[crt_early_log];
log->op_type = op_type;
log->ptr = ptr;
log->size = size;
log->min_count = min_count;
log->offset = offset;
log->length = length;
crt_early_log++;
local_irq_restore(flags);
}
/*
* Memory allocation function callback. This function is called from the
* kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc,
* vmalloc etc.).
*/
void kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp)
{
pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, 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);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc);
/*
* Memory freeing function callback. This function is called from the kernel
* allocators when a block is freed (kmem_cache_free, kfree, vfree etc.).
*/
void kmemleak_free(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, ptr);
if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
delete_object((unsigned long)ptr);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free);
/*
* Mark an already allocated memory block as a false positive. This will cause
* the block to no longer be reported as leak and always be scanned.
*/
void kmemleak_not_leak(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, 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);
}
EXPORT_SYMBOL(kmemleak_not_leak);
/*
* Ignore a memory block. This is usually done when it is known that the
* corresponding block is not a leak and does not contain any references to
* other allocated memory blocks.
*/
void kmemleak_ignore(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, 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);
}
EXPORT_SYMBOL(kmemleak_ignore);
/*
* Limit the range to be scanned in an allocated memory block.
*/
void kmemleak_scan_area(const void *ptr, unsigned long offset, size_t length,
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);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
}
EXPORT_SYMBOL(kmemleak_scan_area);
/*
* Inform kmemleak not to scan the given memory block.
*/
void kmemleak_no_scan(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, 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);
}
EXPORT_SYMBOL(kmemleak_no_scan);
/*
* Yield the CPU so that other tasks get a chance to run. The yielding is
* rate-limited to avoid excessive number of calls to the schedule() function
* during memory scanning.
*/
static void scan_yield(void)
{
might_sleep();
if (time_is_before_eq_jiffies(next_scan_yield)) {
schedule();
next_scan_yield = jiffies + jiffies_scan_yield;
}
}
/*
* Memory scanning is a long process and it needs to be interruptable. This
* function checks whether such interrupt condition occured.
*/
static int scan_should_stop(void)
{
if (!atomic_read(&kmemleak_enabled))
return 1;
/*
* This function may be called from either process or kthread context,
* hence the need to check for both stop conditions.
*/
if (current->mm)
return signal_pending(current);
else
return kthread_should_stop();
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)
{
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++) {
unsigned long flags;
unsigned long pointer = *ptr;
struct kmemleak_object *object;
if (scan_should_stop())
break;
/*
* When scanning a memory block with a corresponding
* kmemleak_object, the CPU yielding is handled in the calling
* code since it holds the object->lock to avoid the block
* freeing.
*/
if (!scanned)
scan_yield();
object = find_and_get_object(pointer, 1);
if (!object)
continue;
if (object == scanned) {
/* self referenced, ignore */
put_object(object);
continue;
}
/*
* Avoid the lockdep recursive warning on object->lock being
* previously acquired in scan_object(). These locks are
* enclosed by scan_mutex.
*/
spin_lock_irqsave_nested(&object->lock, flags,
SINGLE_DEPTH_NESTING);
if (!color_white(object)) {
/* non-orphan, ignored or new */
spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
continue;
}
/*
* Increase the object's reference count (number of pointers
* to the memory block). If this count reaches the required
* minimum, the object's color will become gray and it will be
* added to the gray_list.
*/
object->count++;
if (color_gray(object))
list_add_tail(&object->gray_list, &gray_list);
else
put_object(object);
spin_unlock_irqrestore(&object->lock, flags);
}
}
/*
* Scan a memory block corresponding to a kmemleak_object. A condition is
* that object->use_count >= 1.
*/
static void scan_object(struct kmemleak_object *object)
{
struct kmemleak_scan_area *area;
struct hlist_node *elem;
unsigned long flags;
/*
* Once the object->lock is aquired, the corresponding memory block
* cannot be freed (the same lock is aquired in delete_object).
*/
spin_lock_irqsave(&object->lock, flags);
if (object->flags & OBJECT_NO_SCAN)
goto out;
if (!(object->flags & OBJECT_ALLOCATED))
/* already freed object */
goto out;
if (hlist_empty(&object->area_list))
scan_block((void *)object->pointer,
(void *)(object->pointer + object->size), 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);
out:
spin_unlock_irqrestore(&object->lock, flags);
}
/*
* Scan data sections and all the referenced memory blocks allocated via the
* kernel's standard allocators. This function must be called with the
* scan_mutex held.
*/
static void kmemleak_scan(void)
{
unsigned long flags;
struct kmemleak_object *object, *tmp;
struct task_struct *task;
int i;
/* prepare the kmemleak_object's */
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
spin_lock_irqsave(&object->lock, flags);
#ifdef DEBUG
/*
* With a few exceptions there should be a maximum of
* 1 reference to any object at this point.
*/
if (atomic_read(&object->use_count) > 1) {
pr_debug("object->use_count = %d\n",
atomic_read(&object->use_count));
dump_object_info(object);
}
#endif
/* reset the reference count (whiten the object) */
object->count = 0;
if (color_gray(object) && get_object(object))
list_add_tail(&object->gray_list, &gray_list);
spin_unlock_irqrestore(&object->lock, flags);
}
rcu_read_unlock();
/* data/bss scanning */
scan_block(_sdata, _edata, NULL);
scan_block(__bss_start, __bss_stop, NULL);
#ifdef CONFIG_SMP
/* per-cpu sections scanning */
for_each_possible_cpu(i)
scan_block(__per_cpu_start + per_cpu_offset(i),
__per_cpu_end + per_cpu_offset(i), NULL);
#endif
/*
* Struct page scanning for each node. The code below is not yet safe
* with MEMORY_HOTPLUG.
*/
for_each_online_node(i) {
pg_data_t *pgdat = NODE_DATA(i);
unsigned long start_pfn = pgdat->node_start_pfn;
unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages;
unsigned long pfn;
for (pfn = start_pfn; pfn < end_pfn; pfn++) {
struct page *page;
if (!pfn_valid(pfn))
continue;
page = pfn_to_page(pfn);
/* only scan if page is in use */
if (page_count(page) == 0)
continue;
scan_block(page, page + 1, NULL);
}
}
/*
* Scanning the task stacks may introduce false negatives and it is
* not enabled by default.
*/
if (kmemleak_stack_scan) {
read_lock(&tasklist_lock);
for_each_process(task)
scan_block(task_stack_page(task),
task_stack_page(task) + THREAD_SIZE, NULL);
read_unlock(&tasklist_lock);
}
/*
* 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.
*/
object = list_entry(gray_list.next, typeof(*object), gray_list);
while (&object->gray_list != &gray_list) {
scan_yield();
/* 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));
}
/*
* Thread function performing automatic memory scanning. Unreferenced objects
* at the end of a memory scan are reported but only the first time.
*/
static int kmemleak_scan_thread(void *arg)
{
static int first_run = 1;
pr_info("Automatic memory scanning thread started\n");
/*
* Wait before the first scan to allow the system to fully initialize.
*/
if (first_run) {
first_run = 0;
ssleep(SECS_FIRST_SCAN);
}
while (!kthread_should_stop()) {
struct kmemleak_object *object;
signed long timeout = jiffies_scan_wait;
mutex_lock(&scan_mutex);
kmemleak_scan();
reported_leaks = 0;
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
unsigned long flags;
if (reported_leaks >= REPORTS_NR)
break;
spin_lock_irqsave(&object->lock, flags);
if (!(object->flags & OBJECT_REPORTED) &&
unreferenced_object(object)) {
print_unreferenced(NULL, object);
object->flags |= OBJECT_REPORTED;
reported_leaks++;
} else if ((object->flags & OBJECT_REPORTED) &&
referenced_object(object)) {
print_referenced(object);
object->flags &= ~OBJECT_REPORTED;
}
spin_unlock_irqrestore(&object->lock, flags);
}
rcu_read_unlock();
mutex_unlock(&scan_mutex);
/* wait before the next scan */
while (timeout && !kthread_should_stop())
timeout = schedule_timeout_interruptible(timeout);
}
pr_info("Automatic memory scanning thread ended\n");
return 0;
}
/*
* Start the automatic memory scanning thread. This function must be called
* with the kmemleak_mutex held.
*/
void start_scan_thread(void)
{
if (scan_thread)
return;
scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
if (IS_ERR(scan_thread)) {
pr_warning("Failed to create the scan thread\n");
scan_thread = NULL;
}
}
/*
* Stop the automatic memory scanning thread. This function must be called
* with the kmemleak_mutex held.
*/
void stop_scan_thread(void)
{
if (scan_thread) {
kthread_stop(scan_thread);
scan_thread = NULL;
}
}
/*
* Iterate over the object_list and return the first valid object at or after
* the required position with its use_count incremented. The function triggers
* a memory scanning when the pos argument points to the first position.
*/
static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
{
struct kmemleak_object *object;
loff_t n = *pos;
if (!n) {
kmemleak_scan();
reported_leaks = 0;
}
if (reported_leaks >= REPORTS_NR)
return NULL;
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
if (n-- > 0)
continue;
if (get_object(object))
goto out;
}
object = NULL;
out:
rcu_read_unlock();
return object;
}
/*
* Return the next object in the object_list. The function decrements the
* use_count of the previous object and increases that of the next one.
*/
static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct kmemleak_object *prev_obj = v;
struct kmemleak_object *next_obj = NULL;
struct list_head *n = &prev_obj->object_list;
++(*pos);
if (reported_leaks >= REPORTS_NR)
goto out;
rcu_read_lock();
list_for_each_continue_rcu(n, &object_list) {
next_obj = list_entry(n, struct kmemleak_object, object_list);
if (get_object(next_obj))
break;
}
rcu_read_unlock();
out:
put_object(prev_obj);
return next_obj;
}
/*
* Decrement the use_count of the last object required, if any.
*/
static void kmemleak_seq_stop(struct seq_file *seq, void *v)
{
if (v)
put_object(v);
}
/*
* Print the information for an unreferenced object to the seq file.
*/
static int kmemleak_seq_show(struct seq_file *seq, void *v)
{
struct kmemleak_object *object = v;
unsigned long flags;
spin_lock_irqsave(&object->lock, flags);
if (!unreferenced_object(object))
goto out;
print_unreferenced(seq, object);
reported_leaks++;
out:
spin_unlock_irqrestore(&object->lock, flags);
return 0;
}
static const struct seq_operations kmemleak_seq_ops = {
.start = kmemleak_seq_start,
.next = kmemleak_seq_next,
.stop = kmemleak_seq_stop,
.show = kmemleak_seq_show,
};
static int kmemleak_open(struct inode *inode, struct file *file)
{
int ret = 0;
if (!atomic_read(&kmemleak_enabled))
return -EBUSY;
ret = mutex_lock_interruptible(&kmemleak_mutex);
if (ret < 0)
goto out;
if (file->f_mode & FMODE_READ) {
ret = mutex_lock_interruptible(&scan_mutex);
if (ret < 0)
goto kmemleak_unlock;
ret = seq_open(file, &kmemleak_seq_ops);
if (ret < 0)
goto scan_unlock;
}
return ret;
scan_unlock:
mutex_unlock(&scan_mutex);
kmemleak_unlock:
mutex_unlock(&kmemleak_mutex);
out:
return ret;
}
static int kmemleak_release(struct inode *inode, struct file *file)
{
int ret = 0;
if (file->f_mode & FMODE_READ) {
seq_release(inode, file);
mutex_unlock(&scan_mutex);
}
mutex_unlock(&kmemleak_mutex);
return ret;
}
/*
* File write operation to configure kmemleak at run-time. The following
* commands can be written to the /sys/kernel/debug/kmemleak file:
* off - disable kmemleak (irreversible)
* stack=on - enable the task stacks scanning
* stack=off - disable the tasks stacks scanning
* scan=on - start the automatic memory scanning thread
* scan=off - stop the automatic memory scanning thread
* scan=... - set the automatic memory scanning period in seconds (0 to
* disable it)
*/
static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
size_t size, loff_t *ppos)
{
char buf[64];
int buf_size;
if (!atomic_read(&kmemleak_enabled))
return -EBUSY;
buf_size = min(size, (sizeof(buf) - 1));
if (strncpy_from_user(buf, user_buf, buf_size) < 0)
return -EFAULT;
buf[buf_size] = 0;
if (strncmp(buf, "off", 3) == 0)
kmemleak_disable();
else if (strncmp(buf, "stack=on", 8) == 0)
kmemleak_stack_scan = 1;
else if (strncmp(buf, "stack=off", 9) == 0)
kmemleak_stack_scan = 0;
else if (strncmp(buf, "scan=on", 7) == 0)
start_scan_thread();
else if (strncmp(buf, "scan=off", 8) == 0)
stop_scan_thread();
else if (strncmp(buf, "scan=", 5) == 0) {
unsigned long secs;
int err;
err = strict_strtoul(buf + 5, 0, &secs);
if (err < 0)
return err;
stop_scan_thread();
if (secs) {
jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
start_scan_thread();
}
} else
return -EINVAL;
/* ignore the rest of the buffer, only one command at a time */
*ppos += size;
return size;
}
static const struct file_operations kmemleak_fops = {
.owner = THIS_MODULE,
.open = kmemleak_open,
.read = seq_read,
.write = kmemleak_write,
.llseek = seq_lseek,
.release = kmemleak_release,
};
/*
* Perform the freeing of the kmemleak internal objects after waiting for any
* current memory scan to complete.
*/
static int kmemleak_cleanup_thread(void *arg)
{
struct kmemleak_object *object;
mutex_lock(&kmemleak_mutex);
stop_scan_thread();
mutex_unlock(&kmemleak_mutex);
mutex_lock(&scan_mutex);
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list)
delete_object(object->pointer);
rcu_read_unlock();
mutex_unlock(&scan_mutex);
return 0;
}
/*
* Start the clean-up thread.
*/
static void kmemleak_cleanup(void)
{
struct task_struct *cleanup_thread;
cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL,
"kmemleak-clean");
if (IS_ERR(cleanup_thread))
pr_warning("Failed to create the clean-up thread\n");
}
/*
* Disable kmemleak. No memory allocation/freeing will be traced once this
* function is called. Disabling kmemleak is an irreversible operation.
*/
static void kmemleak_disable(void)
{
/* atomically check whether it was already invoked */
if (atomic_cmpxchg(&kmemleak_error, 0, 1))
return;
/* stop any memory operation tracing */
atomic_set(&kmemleak_early_log, 0);
atomic_set(&kmemleak_enabled, 0);
/* check whether it is too early for a kernel thread */
if (atomic_read(&kmemleak_initialized))
kmemleak_cleanup();
pr_info("Kernel memory leak detector disabled\n");
}
/*
* Allow boot-time kmemleak disabling (enabled by default).
*/
static int kmemleak_boot_config(char *str)
{
if (!str)
return -EINVAL;
if (strcmp(str, "off") == 0)
kmemleak_disable();
else if (strcmp(str, "on") != 0)
return -EINVAL;
return 0;
}
early_param("kmemleak", kmemleak_boot_config);
/*
* Kmemleak initialization.
*/
void __init kmemleak_init(void)
{
int i;
unsigned long flags;
jiffies_scan_yield = msecs_to_jiffies(MSECS_SCAN_YIELD);
jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
INIT_PRIO_TREE_ROOT(&object_tree_root);
/* the kernel is still in UP mode, so disabling the IRQs is enough */
local_irq_save(flags);
if (!atomic_read(&kmemleak_error)) {
atomic_set(&kmemleak_enabled, 1);
atomic_set(&kmemleak_early_log, 0);
}
local_irq_restore(flags);
/*
* This is the point where tracking allocations is safe. Automatic
* scanning is started during the late initcall. Add the early logged
* callbacks to the kmemleak infrastructure.
*/
for (i = 0; i < crt_early_log; i++) {
struct early_log *log = &early_log[i];
switch (log->op_type) {
case KMEMLEAK_ALLOC:
kmemleak_alloc(log->ptr, log->size, log->min_count,
GFP_KERNEL);
break;
case KMEMLEAK_FREE:
kmemleak_free(log->ptr);
break;
case KMEMLEAK_NOT_LEAK:
kmemleak_not_leak(log->ptr);
break;
case KMEMLEAK_IGNORE:
kmemleak_ignore(log->ptr);
break;
case KMEMLEAK_SCAN_AREA:
kmemleak_scan_area(log->ptr, log->offset, log->length,
GFP_KERNEL);
break;
case KMEMLEAK_NO_SCAN:
kmemleak_no_scan(log->ptr);
break;
default:
WARN_ON(1);
}
}
}
/*
* Late initialization function.
*/
static int __init kmemleak_late_init(void)
{
struct dentry *dentry;
atomic_set(&kmemleak_initialized, 1);
if (atomic_read(&kmemleak_error)) {
/*
* Some error occured and kmemleak was disabled. There is a
* small chance that kmemleak_disable() was called immediately
* after setting kmemleak_initialized and we may end up with
* two clean-up threads but serialized by scan_mutex.
*/
kmemleak_cleanup();
return -ENOMEM;
}
dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
&kmemleak_fops);
if (!dentry)
pr_warning("Failed to create the debugfs kmemleak file\n");
mutex_lock(&kmemleak_mutex);
start_scan_thread();
mutex_unlock(&kmemleak_mutex);
pr_info("Kernel memory leak detector initialized\n");
return 0;
}
late_initcall(kmemleak_late_init);
