Root/mm/kmemleak.c

1/*
2 * mm/kmemleak.c
3 *
4 * Copyright (C) 2008 ARM Limited
5 * Written by Catalin Marinas <catalin.marinas@arm.com>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
19 *
20 *
21 * For more information on the algorithm and kmemleak usage, please see
22 * Documentation/kmemleak.txt.
23 *
24 * Notes on locking
25 * ----------------
26 *
27 * The following locks and mutexes are used by kmemleak:
28 *
29 * - kmemleak_lock (rwlock): protects the object_list modifications and
30 * accesses to the object_tree_root. The object_list is the main list
31 * holding the metadata (struct kmemleak_object) for the allocated memory
32 * blocks. The object_tree_root is a red black tree used to look-up
33 * metadata based on a pointer to the corresponding memory block. The
34 * kmemleak_object structures are added to the object_list and
35 * object_tree_root in the create_object() function called from the
36 * kmemleak_alloc() callback and removed in delete_object() called from the
37 * kmemleak_free() callback
38 * - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to
39 * the metadata (e.g. count) are protected by this lock. Note that some
40 * members of this structure may be protected by other means (atomic or
41 * kmemleak_lock). This lock is also held when scanning the corresponding
42 * memory block to avoid the kernel freeing it via the kmemleak_free()
43 * callback. This is less heavyweight than holding a global lock like
44 * kmemleak_lock during scanning
45 * - scan_mutex (mutex): ensures that only one thread may scan the memory for
46 * unreferenced objects at a time. The gray_list contains the objects which
47 * are already referenced or marked as false positives and need to be
48 * scanned. This list is only modified during a scanning episode when the
49 * scan_mutex is held. At the end of a scan, the gray_list is always empty.
50 * Note that the kmemleak_object.use_count is incremented when an object is
51 * added to the gray_list and therefore cannot be freed. This mutex also
52 * prevents multiple users of the "kmemleak" debugfs file together with
53 * modifications to the memory scanning parameters including the scan_thread
54 * pointer
55 *
56 * The kmemleak_object structures have a use_count incremented or decremented
57 * using the get_object()/put_object() functions. When the use_count becomes
58 * 0, this count can no longer be incremented and put_object() schedules the
59 * kmemleak_object freeing via an RCU callback. All calls to the get_object()
60 * function must be protected by rcu_read_lock() to avoid accessing a freed
61 * structure.
62 */
63
64#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
65
66#include <linux/init.h>
67#include <linux/kernel.h>
68#include <linux/list.h>
69#include <linux/sched.h>
70#include <linux/jiffies.h>
71#include <linux/delay.h>
72#include <linux/export.h>
73#include <linux/kthread.h>
74#include <linux/rbtree.h>
75#include <linux/fs.h>
76#include <linux/debugfs.h>
77#include <linux/seq_file.h>
78#include <linux/cpumask.h>
79#include <linux/spinlock.h>
80#include <linux/mutex.h>
81#include <linux/rcupdate.h>
82#include <linux/stacktrace.h>
83#include <linux/cache.h>
84#include <linux/percpu.h>
85#include <linux/hardirq.h>
86#include <linux/mmzone.h>
87#include <linux/slab.h>
88#include <linux/thread_info.h>
89#include <linux/err.h>
90#include <linux/uaccess.h>
91#include <linux/string.h>
92#include <linux/nodemask.h>
93#include <linux/mm.h>
94#include <linux/workqueue.h>
95#include <linux/crc32.h>
96
97#include <asm/sections.h>
98#include <asm/processor.h>
99#include <linux/atomic.h>
100
101#include <linux/kmemcheck.h>
102#include <linux/kmemleak.h>
103#include <linux/memory_hotplug.h>
104
105/*
106 * Kmemleak configuration and common defines.
107 */
108#define MAX_TRACE 16 /* stack trace length */
109#define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
110#define SECS_FIRST_SCAN 60 /* delay before the first scan */
111#define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
112#define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */
113
114#define BYTES_PER_POINTER sizeof(void *)
115
116/* GFP bitmask for kmemleak internal allocations */
117#define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \
118                 __GFP_NORETRY | __GFP_NOMEMALLOC | \
119                 __GFP_NOWARN)
120
121/* scanning area inside a memory block */
122struct kmemleak_scan_area {
123    struct hlist_node node;
124    unsigned long start;
125    size_t size;
126};
127
128#define KMEMLEAK_GREY 0
129#define KMEMLEAK_BLACK -1
130
131/*
132 * Structure holding the metadata for each allocated memory block.
133 * Modifications to such objects should be made while holding the
134 * object->lock. Insertions or deletions from object_list, gray_list or
135 * rb_node are already protected by the corresponding locks or mutex (see
136 * the notes on locking above). These objects are reference-counted
137 * (use_count) and freed using the RCU mechanism.
138 */
139struct kmemleak_object {
140    spinlock_t lock;
141    unsigned long flags; /* object status flags */
142    struct list_head object_list;
143    struct list_head gray_list;
144    struct rb_node rb_node;
145    struct rcu_head rcu; /* object_list lockless traversal */
146    /* object usage count; object freed when use_count == 0 */
147    atomic_t use_count;
148    unsigned long pointer;
149    size_t size;
150    /* minimum number of a pointers found before it is considered leak */
151    int min_count;
152    /* the total number of pointers found pointing to this object */
153    int count;
154    /* checksum for detecting modified objects */
155    u32 checksum;
156    /* memory ranges to be scanned inside an object (empty for all) */
157    struct hlist_head area_list;
158    unsigned long trace[MAX_TRACE];
159    unsigned int trace_len;
160    unsigned long jiffies; /* creation timestamp */
161    pid_t pid; /* pid of the current task */
162    char comm[TASK_COMM_LEN]; /* executable name */
163};
164
165/* flag representing the memory block allocation status */
166#define OBJECT_ALLOCATED (1 << 0)
167/* flag set after the first reporting of an unreference object */
168#define OBJECT_REPORTED (1 << 1)
169/* flag set to not scan the object */
170#define OBJECT_NO_SCAN (1 << 2)
171
172/* number of bytes to print per line; must be 16 or 32 */
173#define HEX_ROW_SIZE 16
174/* number of bytes to print at a time (1, 2, 4, 8) */
175#define HEX_GROUP_SIZE 1
176/* include ASCII after the hex output */
177#define HEX_ASCII 1
178/* max number of lines to be printed */
179#define HEX_MAX_LINES 2
180
181/* the list of all allocated objects */
182static LIST_HEAD(object_list);
183/* the list of gray-colored objects (see color_gray comment below) */
184static LIST_HEAD(gray_list);
185/* search tree for object boundaries */
186static struct rb_root object_tree_root = RB_ROOT;
187/* rw_lock protecting the access to object_list and object_tree_root */
188static DEFINE_RWLOCK(kmemleak_lock);
189
190/* allocation caches for kmemleak internal data */
191static struct kmem_cache *object_cache;
192static struct kmem_cache *scan_area_cache;
193
194/* set if tracing memory operations is enabled */
195static atomic_t kmemleak_enabled = ATOMIC_INIT(0);
196/* set in the late_initcall if there were no errors */
197static atomic_t kmemleak_initialized = ATOMIC_INIT(0);
198/* enables or disables early logging of the memory operations */
199static atomic_t kmemleak_early_log = ATOMIC_INIT(1);
200/* set if a kmemleak warning was issued */
201static atomic_t kmemleak_warning = ATOMIC_INIT(0);
202/* set if a fatal kmemleak error has occurred */
203static atomic_t kmemleak_error = ATOMIC_INIT(0);
204
205/* minimum and maximum address that may be valid pointers */
206static unsigned long min_addr = ULONG_MAX;
207static unsigned long max_addr;
208
209static struct task_struct *scan_thread;
210/* used to avoid reporting of recently allocated objects */
211static unsigned long jiffies_min_age;
212static unsigned long jiffies_last_scan;
213/* delay between automatic memory scannings */
214static signed long jiffies_scan_wait;
215/* enables or disables the task stacks scanning */
216static int kmemleak_stack_scan = 1;
217/* protects the memory scanning, parameters and debug/kmemleak file access */
218static DEFINE_MUTEX(scan_mutex);
219/* setting kmemleak=on, will set this var, skipping the disable */
220static int kmemleak_skip_disable;
221
222
223/*
224 * Early object allocation/freeing logging. Kmemleak is initialized after the
225 * kernel allocator. However, both the kernel allocator and kmemleak may
226 * allocate memory blocks which need to be tracked. Kmemleak defines an
227 * arbitrary buffer to hold the allocation/freeing information before it is
228 * fully initialized.
229 */
230
231/* kmemleak operation type for early logging */
232enum {
233    KMEMLEAK_ALLOC,
234    KMEMLEAK_ALLOC_PERCPU,
235    KMEMLEAK_FREE,
236    KMEMLEAK_FREE_PART,
237    KMEMLEAK_FREE_PERCPU,
238    KMEMLEAK_NOT_LEAK,
239    KMEMLEAK_IGNORE,
240    KMEMLEAK_SCAN_AREA,
241    KMEMLEAK_NO_SCAN
242};
243
244/*
245 * Structure holding the information passed to kmemleak callbacks during the
246 * early logging.
247 */
248struct early_log {
249    int op_type; /* kmemleak operation type */
250    const void *ptr; /* allocated/freed memory block */
251    size_t size; /* memory block size */
252    int min_count; /* minimum reference count */
253    unsigned long trace[MAX_TRACE]; /* stack trace */
254    unsigned int trace_len; /* stack trace length */
255};
256
257/* early logging buffer and current position */
258static struct early_log
259    early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
260static int crt_early_log __initdata;
261
262static void kmemleak_disable(void);
263
264/*
265 * Print a warning and dump the stack trace.
266 */
267#define kmemleak_warn(x...) do { \
268    pr_warning(x); \
269    dump_stack(); \
270    atomic_set(&kmemleak_warning, 1); \
271} while (0)
272
273/*
274 * Macro invoked when a serious kmemleak condition occurred and cannot be
275 * recovered from. Kmemleak will be disabled and further allocation/freeing
276 * tracing no longer available.
277 */
278#define kmemleak_stop(x...) do { \
279    kmemleak_warn(x); \
280    kmemleak_disable(); \
281} while (0)
282
283/*
284 * Printing of the objects hex dump to the seq file. The number of lines to be
285 * printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
286 * actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
287 * with the object->lock held.
288 */
289static void hex_dump_object(struct seq_file *seq,
290                struct kmemleak_object *object)
291{
292    const u8 *ptr = (const u8 *)object->pointer;
293    int i, len, remaining;
294    unsigned char linebuf[HEX_ROW_SIZE * 5];
295
296    /* limit the number of lines to HEX_MAX_LINES */
297    remaining = len =
298        min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));
299
300    seq_printf(seq, " hex dump (first %d bytes):\n", len);
301    for (i = 0; i < len; i += HEX_ROW_SIZE) {
302        int linelen = min(remaining, HEX_ROW_SIZE);
303
304        remaining -= HEX_ROW_SIZE;
305        hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
306                   HEX_GROUP_SIZE, linebuf, sizeof(linebuf),
307                   HEX_ASCII);
308        seq_printf(seq, " %s\n", linebuf);
309    }
310}
311
312/*
313 * Object colors, encoded with count and min_count:
314 * - white - orphan object, not enough references to it (count < min_count)
315 * - gray - not orphan, not marked as false positive (min_count == 0) or
316 * sufficient references to it (count >= min_count)
317 * - black - ignore, it doesn't contain references (e.g. text section)
318 * (min_count == -1). No function defined for this color.
319 * Newly created objects don't have any color assigned (object->count == -1)
320 * before the next memory scan when they become white.
321 */
322static bool color_white(const struct kmemleak_object *object)
323{
324    return object->count != KMEMLEAK_BLACK &&
325        object->count < object->min_count;
326}
327
328static bool color_gray(const struct kmemleak_object *object)
329{
330    return object->min_count != KMEMLEAK_BLACK &&
331        object->count >= object->min_count;
332}
333
334/*
335 * Objects are considered unreferenced only if their color is white, they have
336 * not be deleted and have a minimum age to avoid false positives caused by
337 * pointers temporarily stored in CPU registers.
338 */
339static bool unreferenced_object(struct kmemleak_object *object)
340{
341    return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&
342        time_before_eq(object->jiffies + jiffies_min_age,
343                   jiffies_last_scan);
344}
345
346/*
347 * Printing of the unreferenced objects information to the seq file. The
348 * print_unreferenced function must be called with the object->lock held.
349 */
350static void print_unreferenced(struct seq_file *seq,
351                   struct kmemleak_object *object)
352{
353    int i;
354    unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);
355
356    seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
357           object->pointer, object->size);
358    seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
359           object->comm, object->pid, object->jiffies,
360           msecs_age / 1000, msecs_age % 1000);
361    hex_dump_object(seq, object);
362    seq_printf(seq, " backtrace:\n");
363
364    for (i = 0; i < object->trace_len; i++) {
365        void *ptr = (void *)object->trace[i];
366        seq_printf(seq, " [<%p>] %pS\n", ptr, ptr);
367    }
368}
369
370/*
371 * Print the kmemleak_object information. This function is used mainly for
372 * debugging special cases when kmemleak operations. It must be called with
373 * the object->lock held.
374 */
375static void dump_object_info(struct kmemleak_object *object)
376{
377    struct stack_trace trace;
378
379    trace.nr_entries = object->trace_len;
380    trace.entries = object->trace;
381
382    pr_notice("Object 0x%08lx (size %zu):\n",
383          object->pointer, object->size);
384    pr_notice(" comm \"%s\", pid %d, jiffies %lu\n",
385          object->comm, object->pid, object->jiffies);
386    pr_notice(" min_count = %d\n", object->min_count);
387    pr_notice(" count = %d\n", object->count);
388    pr_notice(" flags = 0x%lx\n", object->flags);
389    pr_notice(" checksum = %d\n", object->checksum);
390    pr_notice(" backtrace:\n");
391    print_stack_trace(&trace, 4);
392}
393
394/*
395 * Look-up a memory block metadata (kmemleak_object) in the object search
396 * tree based on a pointer value. If alias is 0, only values pointing to the
397 * beginning of the memory block are allowed. The kmemleak_lock must be held
398 * when calling this function.
399 */
400static struct kmemleak_object *lookup_object(unsigned long ptr, int alias)
401{
402    struct rb_node *rb = object_tree_root.rb_node;
403
404    while (rb) {
405        struct kmemleak_object *object =
406            rb_entry(rb, struct kmemleak_object, rb_node);
407        if (ptr < object->pointer)
408            rb = object->rb_node.rb_left;
409        else if (object->pointer + object->size <= ptr)
410            rb = object->rb_node.rb_right;
411        else if (object->pointer == ptr || alias)
412            return object;
413        else {
414            kmemleak_warn("Found object by alias at 0x%08lx\n",
415                      ptr);
416            dump_object_info(object);
417            break;
418        }
419    }
420    return NULL;
421}
422
423/*
424 * Increment the object use_count. Return 1 if successful or 0 otherwise. Note
425 * that once an object's use_count reached 0, the RCU freeing was already
426 * registered and the object should no longer be used. This function must be
427 * called under the protection of rcu_read_lock().
428 */
429static int get_object(struct kmemleak_object *object)
430{
431    return atomic_inc_not_zero(&object->use_count);
432}
433
434/*
435 * RCU callback to free a kmemleak_object.
436 */
437static void free_object_rcu(struct rcu_head *rcu)
438{
439    struct hlist_node *tmp;
440    struct kmemleak_scan_area *area;
441    struct kmemleak_object *object =
442        container_of(rcu, struct kmemleak_object, rcu);
443
444    /*
445     * Once use_count is 0 (guaranteed by put_object), there is no other
446     * code accessing this object, hence no need for locking.
447     */
448    hlist_for_each_entry_safe(area, tmp, &object->area_list, node) {
449        hlist_del(&area->node);
450        kmem_cache_free(scan_area_cache, area);
451    }
452    kmem_cache_free(object_cache, object);
453}
454
455/*
456 * Decrement the object use_count. Once the count is 0, free the object using
457 * an RCU callback. Since put_object() may be called via the kmemleak_free() ->
458 * delete_object() path, the delayed RCU freeing ensures that there is no
459 * recursive call to the kernel allocator. Lock-less RCU object_list traversal
460 * is also possible.
461 */
462static void put_object(struct kmemleak_object *object)
463{
464    if (!atomic_dec_and_test(&object->use_count))
465        return;
466
467    /* should only get here after delete_object was called */
468    WARN_ON(object->flags & OBJECT_ALLOCATED);
469
470    call_rcu(&object->rcu, free_object_rcu);
471}
472
473/*
474 * Look up an object in the object search tree and increase its use_count.
475 */
476static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias)
477{
478    unsigned long flags;
479    struct kmemleak_object *object = NULL;
480
481    rcu_read_lock();
482    read_lock_irqsave(&kmemleak_lock, flags);
483    if (ptr >= min_addr && ptr < max_addr)
484        object = lookup_object(ptr, alias);
485    read_unlock_irqrestore(&kmemleak_lock, flags);
486
487    /* check whether the object is still available */
488    if (object && !get_object(object))
489        object = NULL;
490    rcu_read_unlock();
491
492    return object;
493}
494
495/*
496 * Save stack trace to the given array of MAX_TRACE size.
497 */
498static int __save_stack_trace(unsigned long *trace)
499{
500    struct stack_trace stack_trace;
501
502    stack_trace.max_entries = MAX_TRACE;
503    stack_trace.nr_entries = 0;
504    stack_trace.entries = trace;
505    stack_trace.skip = 2;
506    save_stack_trace(&stack_trace);
507
508    return stack_trace.nr_entries;
509}
510
511/*
512 * Create the metadata (struct kmemleak_object) corresponding to an allocated
513 * memory block and add it to the object_list and object_tree_root.
514 */
515static struct kmemleak_object *create_object(unsigned long ptr, size_t size,
516                         int min_count, gfp_t gfp)
517{
518    unsigned long flags;
519    struct kmemleak_object *object, *parent;
520    struct rb_node **link, *rb_parent;
521
522    object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
523    if (!object) {
524        pr_warning("Cannot allocate a kmemleak_object structure\n");
525        kmemleak_disable();
526        return NULL;
527    }
528
529    INIT_LIST_HEAD(&object->object_list);
530    INIT_LIST_HEAD(&object->gray_list);
531    INIT_HLIST_HEAD(&object->area_list);
532    spin_lock_init(&object->lock);
533    atomic_set(&object->use_count, 1);
534    object->flags = OBJECT_ALLOCATED;
535    object->pointer = ptr;
536    object->size = size;
537    object->min_count = min_count;
538    object->count = 0; /* white color initially */
539    object->jiffies = jiffies;
540    object->checksum = 0;
541
542    /* task information */
543    if (in_irq()) {
544        object->pid = 0;
545        strncpy(object->comm, "hardirq", sizeof(object->comm));
546    } else if (in_softirq()) {
547        object->pid = 0;
548        strncpy(object->comm, "softirq", sizeof(object->comm));
549    } else {
550        object->pid = current->pid;
551        /*
552         * There is a small chance of a race with set_task_comm(),
553         * however using get_task_comm() here may cause locking
554         * dependency issues with current->alloc_lock. In the worst
555         * case, the command line is not correct.
556         */
557        strncpy(object->comm, current->comm, sizeof(object->comm));
558    }
559
560    /* kernel backtrace */
561    object->trace_len = __save_stack_trace(object->trace);
562
563    write_lock_irqsave(&kmemleak_lock, flags);
564
565    min_addr = min(min_addr, ptr);
566    max_addr = max(max_addr, ptr + size);
567    link = &object_tree_root.rb_node;
568    rb_parent = NULL;
569    while (*link) {
570        rb_parent = *link;
571        parent = rb_entry(rb_parent, struct kmemleak_object, rb_node);
572        if (ptr + size <= parent->pointer)
573            link = &parent->rb_node.rb_left;
574        else if (parent->pointer + parent->size <= ptr)
575            link = &parent->rb_node.rb_right;
576        else {
577            kmemleak_stop("Cannot insert 0x%lx into the object "
578                      "search tree (overlaps existing)\n",
579                      ptr);
580            kmem_cache_free(object_cache, object);
581            object = parent;
582            spin_lock(&object->lock);
583            dump_object_info(object);
584            spin_unlock(&object->lock);
585            goto out;
586        }
587    }
588    rb_link_node(&object->rb_node, rb_parent, link);
589    rb_insert_color(&object->rb_node, &object_tree_root);
590
591    list_add_tail_rcu(&object->object_list, &object_list);
592out:
593    write_unlock_irqrestore(&kmemleak_lock, flags);
594    return object;
595}
596
597/*
598 * Remove the metadata (struct kmemleak_object) for a memory block from the
599 * object_list and object_tree_root and decrement its use_count.
600 */
601static void __delete_object(struct kmemleak_object *object)
602{
603    unsigned long flags;
604
605    write_lock_irqsave(&kmemleak_lock, flags);
606    rb_erase(&object->rb_node, &object_tree_root);
607    list_del_rcu(&object->object_list);
608    write_unlock_irqrestore(&kmemleak_lock, flags);
609
610    WARN_ON(!(object->flags & OBJECT_ALLOCATED));
611    WARN_ON(atomic_read(&object->use_count) < 2);
612
613    /*
614     * Locking here also ensures that the corresponding memory block
615     * cannot be freed when it is being scanned.
616     */
617    spin_lock_irqsave(&object->lock, flags);
618    object->flags &= ~OBJECT_ALLOCATED;
619    spin_unlock_irqrestore(&object->lock, flags);
620    put_object(object);
621}
622
623/*
624 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
625 * delete it.
626 */
627static void delete_object_full(unsigned long ptr)
628{
629    struct kmemleak_object *object;
630
631    object = find_and_get_object(ptr, 0);
632    if (!object) {
633#ifdef DEBUG
634        kmemleak_warn("Freeing unknown object at 0x%08lx\n",
635                  ptr);
636#endif
637        return;
638    }
639    __delete_object(object);
640    put_object(object);
641}
642
643/*
644 * Look up the metadata (struct kmemleak_object) corresponding to ptr and
645 * delete it. If the memory block is partially freed, the function may create
646 * additional metadata for the remaining parts of the block.
647 */
648static void delete_object_part(unsigned long ptr, size_t size)
649{
650    struct kmemleak_object *object;
651    unsigned long start, end;
652
653    object = find_and_get_object(ptr, 1);
654    if (!object) {
655#ifdef DEBUG
656        kmemleak_warn("Partially freeing unknown object at 0x%08lx "
657                  "(size %zu)\n", ptr, size);
658#endif
659        return;
660    }
661    __delete_object(object);
662
663    /*
664     * Create one or two objects that may result from the memory block
665     * split. Note that partial freeing is only done by free_bootmem() and
666     * this happens before kmemleak_init() is called. The path below is
667     * only executed during early log recording in kmemleak_init(), so
668     * GFP_KERNEL is enough.
669     */
670    start = object->pointer;
671    end = object->pointer + object->size;
672    if (ptr > start)
673        create_object(start, ptr - start, object->min_count,
674                  GFP_KERNEL);
675    if (ptr + size < end)
676        create_object(ptr + size, end - ptr - size, object->min_count,
677                  GFP_KERNEL);
678
679    put_object(object);
680}
681
682static void __paint_it(struct kmemleak_object *object, int color)
683{
684    object->min_count = color;
685    if (color == KMEMLEAK_BLACK)
686        object->flags |= OBJECT_NO_SCAN;
687}
688
689static void paint_it(struct kmemleak_object *object, int color)
690{
691    unsigned long flags;
692
693    spin_lock_irqsave(&object->lock, flags);
694    __paint_it(object, color);
695    spin_unlock_irqrestore(&object->lock, flags);
696}
697
698static void paint_ptr(unsigned long ptr, int color)
699{
700    struct kmemleak_object *object;
701
702    object = find_and_get_object(ptr, 0);
703    if (!object) {
704        kmemleak_warn("Trying to color unknown object "
705                  "at 0x%08lx as %s\n", ptr,
706                  (color == KMEMLEAK_GREY) ? "Grey" :
707                  (color == KMEMLEAK_BLACK) ? "Black" : "Unknown");
708        return;
709    }
710    paint_it(object, color);
711    put_object(object);
712}
713
714/*
715 * Mark an object permanently as gray-colored so that it can no longer be
716 * reported as a leak. This is used in general to mark a false positive.
717 */
718static void make_gray_object(unsigned long ptr)
719{
720    paint_ptr(ptr, KMEMLEAK_GREY);
721}
722
723/*
724 * Mark the object as black-colored so that it is ignored from scans and
725 * reporting.
726 */
727static void make_black_object(unsigned long ptr)
728{
729    paint_ptr(ptr, KMEMLEAK_BLACK);
730}
731
732/*
733 * Add a scanning area to the object. If at least one such area is added,
734 * kmemleak will only scan these ranges rather than the whole memory block.
735 */
736static void add_scan_area(unsigned long ptr, size_t size, gfp_t gfp)
737{
738    unsigned long flags;
739    struct kmemleak_object *object;
740    struct kmemleak_scan_area *area;
741
742    object = find_and_get_object(ptr, 1);
743    if (!object) {
744        kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
745                  ptr);
746        return;
747    }
748
749    area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
750    if (!area) {
751        pr_warning("Cannot allocate a scan area\n");
752        goto out;
753    }
754
755    spin_lock_irqsave(&object->lock, flags);
756    if (ptr + size > object->pointer + object->size) {
757        kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
758        dump_object_info(object);
759        kmem_cache_free(scan_area_cache, area);
760        goto out_unlock;
761    }
762
763    INIT_HLIST_NODE(&area->node);
764    area->start = ptr;
765    area->size = size;
766
767    hlist_add_head(&area->node, &object->area_list);
768out_unlock:
769    spin_unlock_irqrestore(&object->lock, flags);
770out:
771    put_object(object);
772}
773
774/*
775 * Set the OBJECT_NO_SCAN flag for the object corresponding to the give
776 * pointer. Such object will not be scanned by kmemleak but references to it
777 * are searched.
778 */
779static void object_no_scan(unsigned long ptr)
780{
781    unsigned long flags;
782    struct kmemleak_object *object;
783
784    object = find_and_get_object(ptr, 0);
785    if (!object) {
786        kmemleak_warn("Not scanning unknown object at 0x%08lx\n", ptr);
787        return;
788    }
789
790    spin_lock_irqsave(&object->lock, flags);
791    object->flags |= OBJECT_NO_SCAN;
792    spin_unlock_irqrestore(&object->lock, flags);
793    put_object(object);
794}
795
796/*
797 * Log an early kmemleak_* call to the early_log buffer. These calls will be
798 * processed later once kmemleak is fully initialized.
799 */
800static void __init log_early(int op_type, const void *ptr, size_t size,
801                 int min_count)
802{
803    unsigned long flags;
804    struct early_log *log;
805
806    if (atomic_read(&kmemleak_error)) {
807        /* kmemleak stopped recording, just count the requests */
808        crt_early_log++;
809        return;
810    }
811
812    if (crt_early_log >= ARRAY_SIZE(early_log)) {
813        kmemleak_disable();
814        return;
815    }
816
817    /*
818     * There is no need for locking since the kernel is still in UP mode
819     * at this stage. Disabling the IRQs is enough.
820     */
821    local_irq_save(flags);
822    log = &early_log[crt_early_log];
823    log->op_type = op_type;
824    log->ptr = ptr;
825    log->size = size;
826    log->min_count = min_count;
827    log->trace_len = __save_stack_trace(log->trace);
828    crt_early_log++;
829    local_irq_restore(flags);
830}
831
832/*
833 * Log an early allocated block and populate the stack trace.
834 */
835static void early_alloc(struct early_log *log)
836{
837    struct kmemleak_object *object;
838    unsigned long flags;
839    int i;
840
841    if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr))
842        return;
843
844    /*
845     * RCU locking needed to ensure object is not freed via put_object().
846     */
847    rcu_read_lock();
848    object = create_object((unsigned long)log->ptr, log->size,
849                   log->min_count, GFP_ATOMIC);
850    if (!object)
851        goto out;
852    spin_lock_irqsave(&object->lock, flags);
853    for (i = 0; i < log->trace_len; i++)
854        object->trace[i] = log->trace[i];
855    object->trace_len = log->trace_len;
856    spin_unlock_irqrestore(&object->lock, flags);
857out:
858    rcu_read_unlock();
859}
860
861/*
862 * Log an early allocated block and populate the stack trace.
863 */
864static void early_alloc_percpu(struct early_log *log)
865{
866    unsigned int cpu;
867    const void __percpu *ptr = log->ptr;
868
869    for_each_possible_cpu(cpu) {
870        log->ptr = per_cpu_ptr(ptr, cpu);
871        early_alloc(log);
872    }
873}
874
875/**
876 * kmemleak_alloc - register a newly allocated object
877 * @ptr: pointer to beginning of the object
878 * @size: size of the object
879 * @min_count: minimum number of references to this object. If during memory
880 * scanning a number of references less than @min_count is found,
881 * the object is reported as a memory leak. If @min_count is 0,
882 * the object is never reported as a leak. If @min_count is -1,
883 * the object is ignored (not scanned and not reported as a leak)
884 * @gfp: kmalloc() flags used for kmemleak internal memory allocations
885 *
886 * This function is called from the kernel allocators when a new object
887 * (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.).
888 */
889void __ref kmemleak_alloc(const void *ptr, size_t size, int min_count,
890              gfp_t gfp)
891{
892    pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count);
893
894    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
895        create_object((unsigned long)ptr, size, min_count, gfp);
896    else if (atomic_read(&kmemleak_early_log))
897        log_early(KMEMLEAK_ALLOC, ptr, size, min_count);
898}
899EXPORT_SYMBOL_GPL(kmemleak_alloc);
900
901/**
902 * kmemleak_alloc_percpu - register a newly allocated __percpu object
903 * @ptr: __percpu pointer to beginning of the object
904 * @size: size of the object
905 *
906 * This function is called from the kernel percpu allocator when a new object
907 * (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL
908 * allocation.
909 */
910void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
911{
912    unsigned int cpu;
913
914    pr_debug("%s(0x%p, %zu)\n", __func__, ptr, size);
915
916    /*
917     * Percpu allocations are only scanned and not reported as leaks
918     * (min_count is set to 0).
919     */
920    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
921        for_each_possible_cpu(cpu)
922            create_object((unsigned long)per_cpu_ptr(ptr, cpu),
923                      size, 0, GFP_KERNEL);
924    else if (atomic_read(&kmemleak_early_log))
925        log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
926}
927EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);
928
929/**
930 * kmemleak_free - unregister a previously registered object
931 * @ptr: pointer to beginning of the object
932 *
933 * This function is called from the kernel allocators when an object (memory
934 * block) is freed (kmem_cache_free, kfree, vfree etc.).
935 */
936void __ref kmemleak_free(const void *ptr)
937{
938    pr_debug("%s(0x%p)\n", __func__, ptr);
939
940    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
941        delete_object_full((unsigned long)ptr);
942    else if (atomic_read(&kmemleak_early_log))
943        log_early(KMEMLEAK_FREE, ptr, 0, 0);
944}
945EXPORT_SYMBOL_GPL(kmemleak_free);
946
947/**
948 * kmemleak_free_part - partially unregister a previously registered object
949 * @ptr: pointer to the beginning or inside the object. This also
950 * represents the start of the range to be freed
951 * @size: size to be unregistered
952 *
953 * This function is called when only a part of a memory block is freed
954 * (usually from the bootmem allocator).
955 */
956void __ref kmemleak_free_part(const void *ptr, size_t size)
957{
958    pr_debug("%s(0x%p)\n", __func__, ptr);
959
960    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
961        delete_object_part((unsigned long)ptr, size);
962    else if (atomic_read(&kmemleak_early_log))
963        log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
964}
965EXPORT_SYMBOL_GPL(kmemleak_free_part);
966
967/**
968 * kmemleak_free_percpu - unregister a previously registered __percpu object
969 * @ptr: __percpu pointer to beginning of the object
970 *
971 * This function is called from the kernel percpu allocator when an object
972 * (memory block) is freed (free_percpu).
973 */
974void __ref kmemleak_free_percpu(const void __percpu *ptr)
975{
976    unsigned int cpu;
977
978    pr_debug("%s(0x%p)\n", __func__, ptr);
979
980    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
981        for_each_possible_cpu(cpu)
982            delete_object_full((unsigned long)per_cpu_ptr(ptr,
983                                      cpu));
984    else if (atomic_read(&kmemleak_early_log))
985        log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
986}
987EXPORT_SYMBOL_GPL(kmemleak_free_percpu);
988
989/**
990 * kmemleak_not_leak - mark an allocated object as false positive
991 * @ptr: pointer to beginning of the object
992 *
993 * Calling this function on an object will cause the memory block to no longer
994 * be reported as leak and always be scanned.
995 */
996void __ref kmemleak_not_leak(const void *ptr)
997{
998    pr_debug("%s(0x%p)\n", __func__, ptr);
999
1000    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
1001        make_gray_object((unsigned long)ptr);
1002    else if (atomic_read(&kmemleak_early_log))
1003        log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0);
1004}
1005EXPORT_SYMBOL(kmemleak_not_leak);
1006
1007/**
1008 * kmemleak_ignore - ignore an allocated object
1009 * @ptr: pointer to beginning of the object
1010 *
1011 * Calling this function on an object will cause the memory block to be
1012 * ignored (not scanned and not reported as a leak). This is usually done when
1013 * it is known that the corresponding block is not a leak and does not contain
1014 * any references to other allocated memory blocks.
1015 */
1016void __ref kmemleak_ignore(const void *ptr)
1017{
1018    pr_debug("%s(0x%p)\n", __func__, ptr);
1019
1020    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
1021        make_black_object((unsigned long)ptr);
1022    else if (atomic_read(&kmemleak_early_log))
1023        log_early(KMEMLEAK_IGNORE, ptr, 0, 0);
1024}
1025EXPORT_SYMBOL(kmemleak_ignore);
1026
1027/**
1028 * kmemleak_scan_area - limit the range to be scanned in an allocated object
1029 * @ptr: pointer to beginning or inside the object. This also
1030 * represents the start of the scan area
1031 * @size: size of the scan area
1032 * @gfp: kmalloc() flags used for kmemleak internal memory allocations
1033 *
1034 * This function is used when it is known that only certain parts of an object
1035 * contain references to other objects. Kmemleak will only scan these areas
1036 * reducing the number false negatives.
1037 */
1038void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
1039{
1040    pr_debug("%s(0x%p)\n", __func__, ptr);
1041
1042    if (atomic_read(&kmemleak_enabled) && ptr && size && !IS_ERR(ptr))
1043        add_scan_area((unsigned long)ptr, size, gfp);
1044    else if (atomic_read(&kmemleak_early_log))
1045        log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
1046}
1047EXPORT_SYMBOL(kmemleak_scan_area);
1048
1049/**
1050 * kmemleak_no_scan - do not scan an allocated object
1051 * @ptr: pointer to beginning of the object
1052 *
1053 * This function notifies kmemleak not to scan the given memory block. Useful
1054 * in situations where it is known that the given object does not contain any
1055 * references to other objects. Kmemleak will not scan such objects reducing
1056 * the number of false negatives.
1057 */
1058void __ref kmemleak_no_scan(const void *ptr)
1059{
1060    pr_debug("%s(0x%p)\n", __func__, ptr);
1061
1062    if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
1063        object_no_scan((unsigned long)ptr);
1064    else if (atomic_read(&kmemleak_early_log))
1065        log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0);
1066}
1067EXPORT_SYMBOL(kmemleak_no_scan);
1068
1069/*
1070 * Update an object's checksum and return true if it was modified.
1071 */
1072static bool update_checksum(struct kmemleak_object *object)
1073{
1074    u32 old_csum = object->checksum;
1075
1076    if (!kmemcheck_is_obj_initialized(object->pointer, object->size))
1077        return false;
1078
1079    object->checksum = crc32(0, (void *)object->pointer, object->size);
1080    return object->checksum != old_csum;
1081}
1082
1083/*
1084 * Memory scanning is a long process and it needs to be interruptable. This
1085 * function checks whether such interrupt condition occurred.
1086 */
1087static int scan_should_stop(void)
1088{
1089    if (!atomic_read(&kmemleak_enabled))
1090        return 1;
1091
1092    /*
1093     * This function may be called from either process or kthread context,
1094     * hence the need to check for both stop conditions.
1095     */
1096    if (current->mm)
1097        return signal_pending(current);
1098    else
1099        return kthread_should_stop();
1100
1101    return 0;
1102}
1103
1104/*
1105 * Scan a memory block (exclusive range) for valid pointers and add those
1106 * found to the gray list.
1107 */
1108static void scan_block(void *_start, void *_end,
1109               struct kmemleak_object *scanned, int allow_resched)
1110{
1111    unsigned long *ptr;
1112    unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
1113    unsigned long *end = _end - (BYTES_PER_POINTER - 1);
1114
1115    for (ptr = start; ptr < end; ptr++) {
1116        struct kmemleak_object *object;
1117        unsigned long flags;
1118        unsigned long pointer;
1119
1120        if (allow_resched)
1121            cond_resched();
1122        if (scan_should_stop())
1123            break;
1124
1125        /* don't scan uninitialized memory */
1126        if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
1127                          BYTES_PER_POINTER))
1128            continue;
1129
1130        pointer = *ptr;
1131
1132        object = find_and_get_object(pointer, 1);
1133        if (!object)
1134            continue;
1135        if (object == scanned) {
1136            /* self referenced, ignore */
1137            put_object(object);
1138            continue;
1139        }
1140
1141        /*
1142         * Avoid the lockdep recursive warning on object->lock being
1143         * previously acquired in scan_object(). These locks are
1144         * enclosed by scan_mutex.
1145         */
1146        spin_lock_irqsave_nested(&object->lock, flags,
1147                     SINGLE_DEPTH_NESTING);
1148        if (!color_white(object)) {
1149            /* non-orphan, ignored or new */
1150            spin_unlock_irqrestore(&object->lock, flags);
1151            put_object(object);
1152            continue;
1153        }
1154
1155        /*
1156         * Increase the object's reference count (number of pointers
1157         * to the memory block). If this count reaches the required
1158         * minimum, the object's color will become gray and it will be
1159         * added to the gray_list.
1160         */
1161        object->count++;
1162        if (color_gray(object)) {
1163            list_add_tail(&object->gray_list, &gray_list);
1164            spin_unlock_irqrestore(&object->lock, flags);
1165            continue;
1166        }
1167
1168        spin_unlock_irqrestore(&object->lock, flags);
1169        put_object(object);
1170    }
1171}
1172
1173/*
1174 * Scan a memory block corresponding to a kmemleak_object. A condition is
1175 * that object->use_count >= 1.
1176 */
1177static void scan_object(struct kmemleak_object *object)
1178{
1179    struct kmemleak_scan_area *area;
1180    unsigned long flags;
1181
1182    /*
1183     * Once the object->lock is acquired, the corresponding memory block
1184     * cannot be freed (the same lock is acquired in delete_object).
1185     */
1186    spin_lock_irqsave(&object->lock, flags);
1187    if (object->flags & OBJECT_NO_SCAN)
1188        goto out;
1189    if (!(object->flags & OBJECT_ALLOCATED))
1190        /* already freed object */
1191        goto out;
1192    if (hlist_empty(&object->area_list)) {
1193        void *start = (void *)object->pointer;
1194        void *end = (void *)(object->pointer + object->size);
1195
1196        while (start < end && (object->flags & OBJECT_ALLOCATED) &&
1197               !(object->flags & OBJECT_NO_SCAN)) {
1198            scan_block(start, min(start + MAX_SCAN_SIZE, end),
1199                   object, 0);
1200            start += MAX_SCAN_SIZE;
1201
1202            spin_unlock_irqrestore(&object->lock, flags);
1203            cond_resched();
1204            spin_lock_irqsave(&object->lock, flags);
1205        }
1206    } else
1207        hlist_for_each_entry(area, &object->area_list, node)
1208            scan_block((void *)area->start,
1209                   (void *)(area->start + area->size),
1210                   object, 0);
1211out:
1212    spin_unlock_irqrestore(&object->lock, flags);
1213}
1214
1215/*
1216 * Scan the objects already referenced (gray objects). More objects will be
1217 * referenced and, if there are no memory leaks, all the objects are scanned.
1218 */
1219static void scan_gray_list(void)
1220{
1221    struct kmemleak_object *object, *tmp;
1222
1223    /*
1224     * The list traversal is safe for both tail additions and removals
1225     * from inside the loop. The kmemleak objects cannot be freed from
1226     * outside the loop because their use_count was incremented.
1227     */
1228    object = list_entry(gray_list.next, typeof(*object), gray_list);
1229    while (&object->gray_list != &gray_list) {
1230        cond_resched();
1231
1232        /* may add new objects to the list */
1233        if (!scan_should_stop())
1234            scan_object(object);
1235
1236        tmp = list_entry(object->gray_list.next, typeof(*object),
1237                 gray_list);
1238
1239        /* remove the object from the list and release it */
1240        list_del(&object->gray_list);
1241        put_object(object);
1242
1243        object = tmp;
1244    }
1245    WARN_ON(!list_empty(&gray_list));
1246}
1247
1248/*
1249 * Scan data sections and all the referenced memory blocks allocated via the
1250 * kernel's standard allocators. This function must be called with the
1251 * scan_mutex held.
1252 */
1253static void kmemleak_scan(void)
1254{
1255    unsigned long flags;
1256    struct kmemleak_object *object;
1257    int i;
1258    int new_leaks = 0;
1259
1260    jiffies_last_scan = jiffies;
1261
1262    /* prepare the kmemleak_object's */
1263    rcu_read_lock();
1264    list_for_each_entry_rcu(object, &object_list, object_list) {
1265        spin_lock_irqsave(&object->lock, flags);
1266#ifdef DEBUG
1267        /*
1268         * With a few exceptions there should be a maximum of
1269         * 1 reference to any object at this point.
1270         */
1271        if (atomic_read(&object->use_count) > 1) {
1272            pr_debug("object->use_count = %d\n",
1273                 atomic_read(&object->use_count));
1274            dump_object_info(object);
1275        }
1276#endif
1277        /* reset the reference count (whiten the object) */
1278        object->count = 0;
1279        if (color_gray(object) && get_object(object))
1280            list_add_tail(&object->gray_list, &gray_list);
1281
1282        spin_unlock_irqrestore(&object->lock, flags);
1283    }
1284    rcu_read_unlock();
1285
1286    /* data/bss scanning */
1287    scan_block(_sdata, _edata, NULL, 1);
1288    scan_block(__bss_start, __bss_stop, NULL, 1);
1289
1290#ifdef CONFIG_SMP
1291    /* per-cpu sections scanning */
1292    for_each_possible_cpu(i)
1293        scan_block(__per_cpu_start + per_cpu_offset(i),
1294               __per_cpu_end + per_cpu_offset(i), NULL, 1);
1295#endif
1296
1297    /*
1298     * Struct page scanning for each node.
1299     */
1300    lock_memory_hotplug();
1301    for_each_online_node(i) {
1302        unsigned long start_pfn = node_start_pfn(i);
1303        unsigned long end_pfn = node_end_pfn(i);
1304        unsigned long pfn;
1305
1306        for (pfn = start_pfn; pfn < end_pfn; pfn++) {
1307            struct page *page;
1308
1309            if (!pfn_valid(pfn))
1310                continue;
1311            page = pfn_to_page(pfn);
1312            /* only scan if page is in use */
1313            if (page_count(page) == 0)
1314                continue;
1315            scan_block(page, page + 1, NULL, 1);
1316        }
1317    }
1318    unlock_memory_hotplug();
1319
1320    /*
1321     * Scanning the task stacks (may introduce false negatives).
1322     */
1323    if (kmemleak_stack_scan) {
1324        struct task_struct *p, *g;
1325
1326        read_lock(&tasklist_lock);
1327        do_each_thread(g, p) {
1328            scan_block(task_stack_page(p), task_stack_page(p) +
1329                   THREAD_SIZE, NULL, 0);
1330        } while_each_thread(g, p);
1331        read_unlock(&tasklist_lock);
1332    }
1333
1334    /*
1335     * Scan the objects already referenced from the sections scanned
1336     * above.
1337     */
1338    scan_gray_list();
1339
1340    /*
1341     * Check for new or unreferenced objects modified since the previous
1342     * scan and color them gray until the next scan.
1343     */
1344    rcu_read_lock();
1345    list_for_each_entry_rcu(object, &object_list, object_list) {
1346        spin_lock_irqsave(&object->lock, flags);
1347        if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
1348            && update_checksum(object) && get_object(object)) {
1349            /* color it gray temporarily */
1350            object->count = object->min_count;
1351            list_add_tail(&object->gray_list, &gray_list);
1352        }
1353        spin_unlock_irqrestore(&object->lock, flags);
1354    }
1355    rcu_read_unlock();
1356
1357    /*
1358     * Re-scan the gray list for modified unreferenced objects.
1359     */
1360    scan_gray_list();
1361
1362    /*
1363     * If scanning was stopped do not report any new unreferenced objects.
1364     */
1365    if (scan_should_stop())
1366        return;
1367
1368    /*
1369     * Scanning result reporting.
1370     */
1371    rcu_read_lock();
1372    list_for_each_entry_rcu(object, &object_list, object_list) {
1373        spin_lock_irqsave(&object->lock, flags);
1374        if (unreferenced_object(object) &&
1375            !(object->flags & OBJECT_REPORTED)) {
1376            object->flags |= OBJECT_REPORTED;
1377            new_leaks++;
1378        }
1379        spin_unlock_irqrestore(&object->lock, flags);
1380    }
1381    rcu_read_unlock();
1382
1383    if (new_leaks)
1384        pr_info("%d new suspected memory leaks (see "
1385            "/sys/kernel/debug/kmemleak)\n", new_leaks);
1386
1387}
1388
1389/*
1390 * Thread function performing automatic memory scanning. Unreferenced objects
1391 * at the end of a memory scan are reported but only the first time.
1392 */
1393static int kmemleak_scan_thread(void *arg)
1394{
1395    static int first_run = 1;
1396
1397    pr_info("Automatic memory scanning thread started\n");
1398    set_user_nice(current, 10);
1399
1400    /*
1401     * Wait before the first scan to allow the system to fully initialize.
1402     */
1403    if (first_run) {
1404        first_run = 0;
1405        ssleep(SECS_FIRST_SCAN);
1406    }
1407
1408    while (!kthread_should_stop()) {
1409        signed long timeout = jiffies_scan_wait;
1410
1411        mutex_lock(&scan_mutex);
1412        kmemleak_scan();
1413        mutex_unlock(&scan_mutex);
1414
1415        /* wait before the next scan */
1416        while (timeout && !kthread_should_stop())
1417            timeout = schedule_timeout_interruptible(timeout);
1418    }
1419
1420    pr_info("Automatic memory scanning thread ended\n");
1421
1422    return 0;
1423}
1424
1425/*
1426 * Start the automatic memory scanning thread. This function must be called
1427 * with the scan_mutex held.
1428 */
1429static void start_scan_thread(void)
1430{
1431    if (scan_thread)
1432        return;
1433    scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak");
1434    if (IS_ERR(scan_thread)) {
1435        pr_warning("Failed to create the scan thread\n");
1436        scan_thread = NULL;
1437    }
1438}
1439
1440/*
1441 * Stop the automatic memory scanning thread. This function must be called
1442 * with the scan_mutex held.
1443 */
1444static void stop_scan_thread(void)
1445{
1446    if (scan_thread) {
1447        kthread_stop(scan_thread);
1448        scan_thread = NULL;
1449    }
1450}
1451
1452/*
1453 * Iterate over the object_list and return the first valid object at or after
1454 * the required position with its use_count incremented. The function triggers
1455 * a memory scanning when the pos argument points to the first position.
1456 */
1457static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos)
1458{
1459    struct kmemleak_object *object;
1460    loff_t n = *pos;
1461    int err;
1462
1463    err = mutex_lock_interruptible(&scan_mutex);
1464    if (err < 0)
1465        return ERR_PTR(err);
1466
1467    rcu_read_lock();
1468    list_for_each_entry_rcu(object, &object_list, object_list) {
1469        if (n-- > 0)
1470            continue;
1471        if (get_object(object))
1472            goto out;
1473    }
1474    object = NULL;
1475out:
1476    return object;
1477}
1478
1479/*
1480 * Return the next object in the object_list. The function decrements the
1481 * use_count of the previous object and increases that of the next one.
1482 */
1483static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
1484{
1485    struct kmemleak_object *prev_obj = v;
1486    struct kmemleak_object *next_obj = NULL;
1487    struct kmemleak_object *obj = prev_obj;
1488
1489    ++(*pos);
1490
1491    list_for_each_entry_continue_rcu(obj, &object_list, object_list) {
1492        if (get_object(obj)) {
1493            next_obj = obj;
1494            break;
1495        }
1496    }
1497
1498    put_object(prev_obj);
1499    return next_obj;
1500}
1501
1502/*
1503 * Decrement the use_count of the last object required, if any.
1504 */
1505static void kmemleak_seq_stop(struct seq_file *seq, void *v)
1506{
1507    if (!IS_ERR(v)) {
1508        /*
1509         * kmemleak_seq_start may return ERR_PTR if the scan_mutex
1510         * waiting was interrupted, so only release it if !IS_ERR.
1511         */
1512        rcu_read_unlock();
1513        mutex_unlock(&scan_mutex);
1514        if (v)
1515            put_object(v);
1516    }
1517}
1518
1519/*
1520 * Print the information for an unreferenced object to the seq file.
1521 */
1522static int kmemleak_seq_show(struct seq_file *seq, void *v)
1523{
1524    struct kmemleak_object *object = v;
1525    unsigned long flags;
1526
1527    spin_lock_irqsave(&object->lock, flags);
1528    if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
1529        print_unreferenced(seq, object);
1530    spin_unlock_irqrestore(&object->lock, flags);
1531    return 0;
1532}
1533
1534static const struct seq_operations kmemleak_seq_ops = {
1535    .start = kmemleak_seq_start,
1536    .next = kmemleak_seq_next,
1537    .stop = kmemleak_seq_stop,
1538    .show = kmemleak_seq_show,
1539};
1540
1541static int kmemleak_open(struct inode *inode, struct file *file)
1542{
1543    return seq_open(file, &kmemleak_seq_ops);
1544}
1545
1546static int kmemleak_release(struct inode *inode, struct file *file)
1547{
1548    return seq_release(inode, file);
1549}
1550
1551static int dump_str_object_info(const char *str)
1552{
1553    unsigned long flags;
1554    struct kmemleak_object *object;
1555    unsigned long addr;
1556
1557    if (kstrtoul(str, 0, &addr))
1558        return -EINVAL;
1559    object = find_and_get_object(addr, 0);
1560    if (!object) {
1561        pr_info("Unknown object at 0x%08lx\n", addr);
1562        return -EINVAL;
1563    }
1564
1565    spin_lock_irqsave(&object->lock, flags);
1566    dump_object_info(object);
1567    spin_unlock_irqrestore(&object->lock, flags);
1568
1569    put_object(object);
1570    return 0;
1571}
1572
1573/*
1574 * We use grey instead of black to ensure we can do future scans on the same
1575 * objects. If we did not do future scans these black objects could
1576 * potentially contain references to newly allocated objects in the future and
1577 * we'd end up with false positives.
1578 */
1579static void kmemleak_clear(void)
1580{
1581    struct kmemleak_object *object;
1582    unsigned long flags;
1583
1584    rcu_read_lock();
1585    list_for_each_entry_rcu(object, &object_list, object_list) {
1586        spin_lock_irqsave(&object->lock, flags);
1587        if ((object->flags & OBJECT_REPORTED) &&
1588            unreferenced_object(object))
1589            __paint_it(object, KMEMLEAK_GREY);
1590        spin_unlock_irqrestore(&object->lock, flags);
1591    }
1592    rcu_read_unlock();
1593}
1594
1595/*
1596 * File write operation to configure kmemleak at run-time. The following
1597 * commands can be written to the /sys/kernel/debug/kmemleak file:
1598 * off - disable kmemleak (irreversible)
1599 * stack=on - enable the task stacks scanning
1600 * stack=off - disable the tasks stacks scanning
1601 * scan=on - start the automatic memory scanning thread
1602 * scan=off - stop the automatic memory scanning thread
1603 * scan=... - set the automatic memory scanning period in seconds (0 to
1604 * disable it)
1605 * scan - trigger a memory scan
1606 * clear - mark all current reported unreferenced kmemleak objects as
1607 * grey to ignore printing them
1608 * dump=... - dump information about the object found at the given address
1609 */
1610static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
1611                  size_t size, loff_t *ppos)
1612{
1613    char buf[64];
1614    int buf_size;
1615    int ret;
1616
1617    if (!atomic_read(&kmemleak_enabled))
1618        return -EBUSY;
1619
1620    buf_size = min(size, (sizeof(buf) - 1));
1621    if (strncpy_from_user(buf, user_buf, buf_size) < 0)
1622        return -EFAULT;
1623    buf[buf_size] = 0;
1624
1625    ret = mutex_lock_interruptible(&scan_mutex);
1626    if (ret < 0)
1627        return ret;
1628
1629    if (strncmp(buf, "off", 3) == 0)
1630        kmemleak_disable();
1631    else if (strncmp(buf, "stack=on", 8) == 0)
1632        kmemleak_stack_scan = 1;
1633    else if (strncmp(buf, "stack=off", 9) == 0)
1634        kmemleak_stack_scan = 0;
1635    else if (strncmp(buf, "scan=on", 7) == 0)
1636        start_scan_thread();
1637    else if (strncmp(buf, "scan=off", 8) == 0)
1638        stop_scan_thread();
1639    else if (strncmp(buf, "scan=", 5) == 0) {
1640        unsigned long secs;
1641
1642        ret = kstrtoul(buf + 5, 0, &secs);
1643        if (ret < 0)
1644            goto out;
1645        stop_scan_thread();
1646        if (secs) {
1647            jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
1648            start_scan_thread();
1649        }
1650    } else if (strncmp(buf, "scan", 4) == 0)
1651        kmemleak_scan();
1652    else if (strncmp(buf, "clear", 5) == 0)
1653        kmemleak_clear();
1654    else if (strncmp(buf, "dump=", 5) == 0)
1655        ret = dump_str_object_info(buf + 5);
1656    else
1657        ret = -EINVAL;
1658
1659out:
1660    mutex_unlock(&scan_mutex);
1661    if (ret < 0)
1662        return ret;
1663
1664    /* ignore the rest of the buffer, only one command at a time */
1665    *ppos += size;
1666    return size;
1667}
1668
1669static const struct file_operations kmemleak_fops = {
1670    .owner = THIS_MODULE,
1671    .open = kmemleak_open,
1672    .read = seq_read,
1673    .write = kmemleak_write,
1674    .llseek = seq_lseek,
1675    .release = kmemleak_release,
1676};
1677
1678/*
1679 * Stop the memory scanning thread and free the kmemleak internal objects if
1680 * no previous scan thread (otherwise, kmemleak may still have some useful
1681 * information on memory leaks).
1682 */
1683static void kmemleak_do_cleanup(struct work_struct *work)
1684{
1685    struct kmemleak_object *object;
1686    bool cleanup = scan_thread == NULL;
1687
1688    mutex_lock(&scan_mutex);
1689    stop_scan_thread();
1690
1691    if (cleanup) {
1692        rcu_read_lock();
1693        list_for_each_entry_rcu(object, &object_list, object_list)
1694            delete_object_full(object->pointer);
1695        rcu_read_unlock();
1696    }
1697    mutex_unlock(&scan_mutex);
1698}
1699
1700static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);
1701
1702/*
1703 * Disable kmemleak. No memory allocation/freeing will be traced once this
1704 * function is called. Disabling kmemleak is an irreversible operation.
1705 */
1706static void kmemleak_disable(void)
1707{
1708    /* atomically check whether it was already invoked */
1709    if (atomic_cmpxchg(&kmemleak_error, 0, 1))
1710        return;
1711
1712    /* stop any memory operation tracing */
1713    atomic_set(&kmemleak_enabled, 0);
1714
1715    /* check whether it is too early for a kernel thread */
1716    if (atomic_read(&kmemleak_initialized))
1717        schedule_work(&cleanup_work);
1718
1719    pr_info("Kernel memory leak detector disabled\n");
1720}
1721
1722/*
1723 * Allow boot-time kmemleak disabling (enabled by default).
1724 */
1725static int kmemleak_boot_config(char *str)
1726{
1727    if (!str)
1728        return -EINVAL;
1729    if (strcmp(str, "off") == 0)
1730        kmemleak_disable();
1731    else if (strcmp(str, "on") == 0)
1732        kmemleak_skip_disable = 1;
1733    else
1734        return -EINVAL;
1735    return 0;
1736}
1737early_param("kmemleak", kmemleak_boot_config);
1738
1739static void __init print_log_trace(struct early_log *log)
1740{
1741    struct stack_trace trace;
1742
1743    trace.nr_entries = log->trace_len;
1744    trace.entries = log->trace;
1745
1746    pr_notice("Early log backtrace:\n");
1747    print_stack_trace(&trace, 2);
1748}
1749
1750/*
1751 * Kmemleak initialization.
1752 */
1753void __init kmemleak_init(void)
1754{
1755    int i;
1756    unsigned long flags;
1757
1758#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
1759    if (!kmemleak_skip_disable) {
1760        atomic_set(&kmemleak_early_log, 0);
1761        kmemleak_disable();
1762        return;
1763    }
1764#endif
1765
1766    jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE);
1767    jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000);
1768
1769    object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE);
1770    scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE);
1771
1772    if (crt_early_log >= ARRAY_SIZE(early_log))
1773        pr_warning("Early log buffer exceeded (%d), please increase "
1774               "DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n", crt_early_log);
1775
1776    /* the kernel is still in UP mode, so disabling the IRQs is enough */
1777    local_irq_save(flags);
1778    atomic_set(&kmemleak_early_log, 0);
1779    if (atomic_read(&kmemleak_error)) {
1780        local_irq_restore(flags);
1781        return;
1782    } else
1783        atomic_set(&kmemleak_enabled, 1);
1784    local_irq_restore(flags);
1785
1786    /*
1787     * This is the point where tracking allocations is safe. Automatic
1788     * scanning is started during the late initcall. Add the early logged
1789     * callbacks to the kmemleak infrastructure.
1790     */
1791    for (i = 0; i < crt_early_log; i++) {
1792        struct early_log *log = &early_log[i];
1793
1794        switch (log->op_type) {
1795        case KMEMLEAK_ALLOC:
1796            early_alloc(log);
1797            break;
1798        case KMEMLEAK_ALLOC_PERCPU:
1799            early_alloc_percpu(log);
1800            break;
1801        case KMEMLEAK_FREE:
1802            kmemleak_free(log->ptr);
1803            break;
1804        case KMEMLEAK_FREE_PART:
1805            kmemleak_free_part(log->ptr, log->size);
1806            break;
1807        case KMEMLEAK_FREE_PERCPU:
1808            kmemleak_free_percpu(log->ptr);
1809            break;
1810        case KMEMLEAK_NOT_LEAK:
1811            kmemleak_not_leak(log->ptr);
1812            break;
1813        case KMEMLEAK_IGNORE:
1814            kmemleak_ignore(log->ptr);
1815            break;
1816        case KMEMLEAK_SCAN_AREA:
1817            kmemleak_scan_area(log->ptr, log->size, GFP_KERNEL);
1818            break;
1819        case KMEMLEAK_NO_SCAN:
1820            kmemleak_no_scan(log->ptr);
1821            break;
1822        default:
1823            kmemleak_warn("Unknown early log operation: %d\n",
1824                      log->op_type);
1825        }
1826
1827        if (atomic_read(&kmemleak_warning)) {
1828            print_log_trace(log);
1829            atomic_set(&kmemleak_warning, 0);
1830        }
1831    }
1832}
1833
1834/*
1835 * Late initialization function.
1836 */
1837static int __init kmemleak_late_init(void)
1838{
1839    struct dentry *dentry;
1840
1841    atomic_set(&kmemleak_initialized, 1);
1842
1843    if (atomic_read(&kmemleak_error)) {
1844        /*
1845         * Some error occurred and kmemleak was disabled. There is a
1846         * small chance that kmemleak_disable() was called immediately
1847         * after setting kmemleak_initialized and we may end up with
1848         * two clean-up threads but serialized by scan_mutex.
1849         */
1850        schedule_work(&cleanup_work);
1851        return -ENOMEM;
1852    }
1853
1854    dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL,
1855                     &kmemleak_fops);
1856    if (!dentry)
1857        pr_warning("Failed to create the debugfs kmemleak file\n");
1858    mutex_lock(&scan_mutex);
1859    start_scan_thread();
1860    mutex_unlock(&scan_mutex);
1861
1862    pr_info("Kernel memory leak detector initialized\n");
1863
1864    return 0;
1865}
1866late_initcall(kmemleak_late_init);
1867

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