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/*
* 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. This mutex also
* 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/export.h>
#include <linux/kthread.h>
#include <linux/prio_tree.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 <linux/workqueue.h>
#include <linux/crc32.h>

#include <asm/sections.h>
#include <asm/processor.h>
#include <linux/atomic.h>

#include <linux/kmemcheck.h>
#include <linux/kmemleak.h>
#include <linux/memory_hotplug.h>

/*
* Kmemleak configuration and common defines.
*/
#define MAX_TRACE 16 /* stack trace length */
#define MSECS_MIN_AGE 5000 /* minimum object age for reporting */
#define SECS_FIRST_SCAN 60 /* delay before the first scan */
#define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */
#define MAX_SCAN_SIZE 4096 /* maximum size of a scanned block */

#define BYTES_PER_POINTER sizeof(void *)

/* GFP bitmask for kmemleak internal allocations */
#define gfp_kmemleak_mask(gfp) (((gfp) & (GFP_KERNEL | GFP_ATOMIC)) | \
__GFP_NORETRY | __GFP_NOMEMALLOC | \
__GFP_NOWARN)

/* scanning area inside a memory block */
struct kmemleak_scan_area {
struct hlist_node node;
unsigned long start;
size_t size;
};

#define KMEMLEAK_GREY 0
#define KMEMLEAK_BLACK -1

/*
* 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;
/* checksum for detecting modified objects */
u32 checksum;
/* memory ranges to be scanned inside an object (empty for all) */
struct hlist_head area_list;
unsigned long trace[MAX_TRACE];
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)

/* number of bytes to print per line; must be 16 or 32 */
#define HEX_ROW_SIZE 16
/* number of bytes to print at a time (1, 2, 4, 8) */
#define HEX_GROUP_SIZE 1
/* include ASCII after the hex output */
#define HEX_ASCII 1
/* max number of lines to be printed */
#define HEX_MAX_LINES 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 kmemleak warning was issued */
static atomic_t kmemleak_warning = ATOMIC_INIT(0);
/* set if a fatal 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;

static struct task_struct *scan_thread;
/* used to avoid reporting of recently allocated objects */
static unsigned long jiffies_min_age;
static unsigned long jiffies_last_scan;
/* delay between automatic memory scannings */
static signed long jiffies_scan_wait;
/* enables or disables the task stacks scanning */
static int kmemleak_stack_scan = 1;
/* protects the memory scanning, parameters and debug/kmemleak file access */
static DEFINE_MUTEX(scan_mutex);
/* setting kmemleak=on, will set this var, skipping the disable */
static int kmemleak_skip_disable;


/*
* 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_ALLOC_PERCPU,
KMEMLEAK_FREE,
KMEMLEAK_FREE_PART,
KMEMLEAK_FREE_PERCPU,
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 trace[MAX_TRACE]; /* stack trace */
unsigned int trace_len; /* stack trace length */
};

/* early logging buffer and current position */
static struct early_log
early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE] __initdata;
static int crt_early_log __initdata;

static void kmemleak_disable(void);

/*
* Print a warning and dump the stack trace.
*/
#define kmemleak_warn(x...) do { \
pr_warning(x); \
dump_stack(); \
atomic_set(&kmemleak_warning, 1); \
} while (0)

/*
* Macro invoked when a serious kmemleak condition occurred 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)

/*
* Printing of the objects hex dump to the seq file. The number of lines to be
* printed is limited to HEX_MAX_LINES to prevent seq file spamming. The
* actual number of printed bytes depends on HEX_ROW_SIZE. It must be called
* with the object->lock held.
*/
static void hex_dump_object(struct seq_file *seq,
struct kmemleak_object *object)
{
const u8 *ptr = (const u8 *)object->pointer;
int i, len, remaining;
unsigned char linebuf[HEX_ROW_SIZE * 5];

/* limit the number of lines to HEX_MAX_LINES */
remaining = len =
min(object->size, (size_t)(HEX_MAX_LINES * HEX_ROW_SIZE));

seq_printf(seq, " hex dump (first %d bytes):\n", len);
for (i = 0; i < len; i += HEX_ROW_SIZE) {
int linelen = min(remaining, HEX_ROW_SIZE);

remaining -= HEX_ROW_SIZE;
hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE,
HEX_GROUP_SIZE, linebuf, sizeof(linebuf),
HEX_ASCII);
seq_printf(seq, " %s\n", linebuf);
}
}

/*
* 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 bool color_white(const struct kmemleak_object *object)
{
return object->count != KMEMLEAK_BLACK &&
object->count < object->min_count;
}

static bool color_gray(const struct kmemleak_object *object)
{
return object->min_count != KMEMLEAK_BLACK &&
object->count >= object->min_count;
}

/*
* 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 bool unreferenced_object(struct kmemleak_object *object)
{
return (color_white(object) && object->flags & OBJECT_ALLOCATED) &&
time_before_eq(object->jiffies + jiffies_min_age,
jiffies_last_scan);
}

/*
* Printing of the unreferenced objects information to the seq file. The
* print_unreferenced function must be called with the object->lock held.
*/
static void print_unreferenced(struct seq_file *seq,
struct kmemleak_object *object)
{
int i;
unsigned int msecs_age = jiffies_to_msecs(jiffies - object->jiffies);

seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n",
object->pointer, object->size);
seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu (age %d.%03ds)\n",
object->comm, object->pid, object->jiffies,
msecs_age / 1000, msecs_age % 1000);
hex_dump_object(seq, object);
seq_printf(seq, " backtrace:\n");

for (i = 0; i < object->trace_len; i++) {
void *ptr = (void *)object->trace[i];
seq_printf(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(" flags = 0x%lx\n", object->flags);
pr_notice(" checksum = %d\n", object->checksum);
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 at 0x%08lx\n",
ptr);
dump_object_info(object);
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;
}

/*
* Save stack trace to the given array of MAX_TRACE size.
*/
static int __save_stack_trace(unsigned long *trace)
{
struct stack_trace stack_trace;

stack_trace.max_entries = MAX_TRACE;
stack_trace.nr_entries = 0;
stack_trace.entries = trace;
stack_trace.skip = 2;
save_stack_trace(&stack_trace);

return stack_trace.nr_entries;
}

/*
* Create the metadata (struct kmemleak_object) corresponding to an allocated
* memory block and add it to the object_list and object_tree_root.
*/
static struct kmemleak_object *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;

object = kmem_cache_alloc(object_cache, gfp_kmemleak_mask(gfp));
if (!object) {
pr_warning("Cannot allocate a kmemleak_object structure\n");
kmemleak_disable();
return NULL;
}

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 = 0; /* white color initially */
object->jiffies = jiffies;
object->checksum = 0;

/* 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 */
object->trace_len = __save_stack_trace(object->trace);

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) {
kmemleak_stop("Cannot insert 0x%lx into the object search tree "
"(already existing)\n", ptr);
object = lookup_object(ptr, 1);
spin_lock(&object->lock);
dump_object_info(object);
spin_unlock(&object->lock);

goto out;
}
list_add_tail_rcu(&object->object_list, &object_list);
out:
write_unlock_irqrestore(&kmemleak_lock, flags);
return object;
}

/*
* 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(struct kmemleak_object *object)
{
unsigned long flags;

write_lock_irqsave(&kmemleak_lock, flags);
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) < 2);

/*
* Locking here also ensures that the corresponding memory block
* cannot be freed when it is being scanned.
*/
spin_lock_irqsave(&object->lock, flags);
object->flags &= ~OBJECT_ALLOCATED;
spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}

/*
* Look up the metadata (struct kmemleak_object) corresponding to ptr and
* delete it.
*/
static void delete_object_full(unsigned long ptr)
{
struct kmemleak_object *object;

object = find_and_get_object(ptr, 0);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Freeing unknown object at 0x%08lx\n",
ptr);
#endif
return;
}
__delete_object(object);
put_object(object);
}

/*
* Look up the metadata (struct kmemleak_object) corresponding to ptr and
* delete it. If the memory block is partially freed, the function may create
* additional metadata for the remaining parts of the block.
*/
static void delete_object_part(unsigned long ptr, size_t size)
{
struct kmemleak_object *object;
unsigned long start, end;

object = find_and_get_object(ptr, 1);
if (!object) {
#ifdef DEBUG
kmemleak_warn("Partially freeing unknown object at 0x%08lx "
"(size %zu)\n", ptr, size);
#endif
return;
}
__delete_object(object);

/*
* Create one or two objects that may result from the memory block
* split. Note that partial freeing is only done by free_bootmem() and
* this happens before kmemleak_init() is called. The path below is
* only executed during early log recording in kmemleak_init(), so
* GFP_KERNEL is enough.
*/
start = object->pointer;
end = object->pointer + object->size;
if (ptr > start)
create_object(start, ptr - start, object->min_count,
GFP_KERNEL);
if (ptr + size < end)
create_object(ptr + size, end - ptr - size, object->min_count,
GFP_KERNEL);

put_object(object);
}

static void __paint_it(struct kmemleak_object *object, int color)
{
object->min_count = color;
if (color == KMEMLEAK_BLACK)
object->flags |= OBJECT_NO_SCAN;
}

static void paint_it(struct kmemleak_object *object, int color)
{
unsigned long flags;

spin_lock_irqsave(&object->lock, flags);
__paint_it(object, color);
spin_unlock_irqrestore(&object->lock, flags);
}

static void paint_ptr(unsigned long ptr, int color)
{
struct kmemleak_object *object;

object = find_and_get_object(ptr, 0);
if (!object) {
kmemleak_warn("Trying to color unknown object "
"at 0x%08lx as %s\n", ptr,
(color == KMEMLEAK_GREY) ? "Grey" :
(color == KMEMLEAK_BLACK) ? "Black" : "Unknown");
return;
}
paint_it(object, color);
put_object(object);
}

/*
* Mark an 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)
{
paint_ptr(ptr, KMEMLEAK_GREY);
}

/*
* Mark the object as black-colored so that it is ignored from scans and
* reporting.
*/
static void make_black_object(unsigned long ptr)
{
paint_ptr(ptr, KMEMLEAK_BLACK);
}

/*
* 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, size_t size, gfp_t gfp)
{
unsigned long flags;
struct kmemleak_object *object;
struct kmemleak_scan_area *area;

object = find_and_get_object(ptr, 1);
if (!object) {
kmemleak_warn("Adding scan area to unknown object at 0x%08lx\n",
ptr);
return;
}

area = kmem_cache_alloc(scan_area_cache, gfp_kmemleak_mask(gfp));
if (!area) {
pr_warning("Cannot allocate a scan area\n");
goto out;
}

spin_lock_irqsave(&object->lock, flags);
if (ptr + size > object->pointer + object->size) {
kmemleak_warn("Scan area larger than object 0x%08lx\n", ptr);
dump_object_info(object);
kmem_cache_free(scan_area_cache, area);
goto out_unlock;
}

INIT_HLIST_NODE(&area->node);
area->start = ptr;
area->size = size;

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 __init log_early(int op_type, const void *ptr, size_t size,
int min_count)
{
unsigned long flags;
struct early_log *log;

if (atomic_read(&kmemleak_error)) {
/* kmemleak stopped recording, just count the requests */
crt_early_log++;
return;
}

if (crt_early_log >= ARRAY_SIZE(early_log)) {
kmemleak_disable();
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->trace_len = __save_stack_trace(log->trace);
crt_early_log++;
local_irq_restore(flags);
}

/*
* Log an early allocated block and populate the stack trace.
*/
static void early_alloc(struct early_log *log)
{
struct kmemleak_object *object;
unsigned long flags;
int i;

if (!atomic_read(&kmemleak_enabled) || !log->ptr || IS_ERR(log->ptr))
return;

/*
* RCU locking needed to ensure object is not freed via put_object().
*/
rcu_read_lock();
object = create_object((unsigned long)log->ptr, log->size,
log->min_count, GFP_ATOMIC);
if (!object)
goto out;
spin_lock_irqsave(&object->lock, flags);
for (i = 0; i < log->trace_len; i++)
object->trace[i] = log->trace[i];
object->trace_len = log->trace_len;
spin_unlock_irqrestore(&object->lock, flags);
out:
rcu_read_unlock();
}

/*
* Log an early allocated block and populate the stack trace.
*/
static void early_alloc_percpu(struct early_log *log)
{
unsigned int cpu;
const void __percpu *ptr = log->ptr;

for_each_possible_cpu(cpu) {
log->ptr = per_cpu_ptr(ptr, cpu);
early_alloc(log);
}
}

/**
* kmemleak_alloc - register a newly allocated object
* @ptr: pointer to beginning of the object
* @size: size of the object
* @min_count: minimum number of references to this object. If during memory
* scanning a number of references less than @min_count is found,
* the object is reported as a memory leak. If @min_count is 0,
* the object is never reported as a leak. If @min_count is -1,
* the object is ignored (not scanned and not reported as a leak)
* @gfp: kmalloc() flags used for kmemleak internal memory allocations
*
* This function is called from the kernel allocators when a new object
* (memory block) is allocated (kmem_cache_alloc, kmalloc, vmalloc etc.).
*/
void __ref 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);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc);

/**
* kmemleak_alloc_percpu - register a newly allocated __percpu object
* @ptr: __percpu pointer to beginning of the object
* @size: size of the object
*
* This function is called from the kernel percpu allocator when a new object
* (memory block) is allocated (alloc_percpu). It assumes GFP_KERNEL
* allocation.
*/
void __ref kmemleak_alloc_percpu(const void __percpu *ptr, size_t size)
{
unsigned int cpu;

pr_debug("%s(0x%p, %zu)\n", __func__, ptr, size);

/*
* Percpu allocations are only scanned and not reported as leaks
* (min_count is set to 0).
*/
if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
create_object((unsigned long)per_cpu_ptr(ptr, cpu),
size, 0, GFP_KERNEL);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_ALLOC_PERCPU, ptr, size, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_alloc_percpu);

/**
* kmemleak_free - unregister a previously registered object
* @ptr: pointer to beginning of the object
*
* This function is called from the kernel allocators when an object (memory
* block) is freed (kmem_cache_free, kfree, vfree etc.).
*/
void __ref kmemleak_free(const void *ptr)
{
pr_debug("%s(0x%p)\n", __func__, ptr);

if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
delete_object_full((unsigned long)ptr);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_FREE, ptr, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free);

/**
* kmemleak_free_part - partially unregister a previously registered object
* @ptr: pointer to the beginning or inside the object. This also
* represents the start of the range to be freed
* @size: size to be unregistered
*
* This function is called when only a part of a memory block is freed
* (usually from the bootmem allocator).
*/
void __ref kmemleak_free_part(const void *ptr, size_t size)
{
pr_debug("%s(0x%p)\n", __func__, ptr);

if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
delete_object_part((unsigned long)ptr, size);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_FREE_PART, ptr, size, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free_part);

/**
* kmemleak_free_percpu - unregister a previously registered __percpu object
* @ptr: __percpu pointer to beginning of the object
*
* This function is called from the kernel percpu allocator when an object
* (memory block) is freed (free_percpu).
*/
void __ref kmemleak_free_percpu(const void __percpu *ptr)
{
unsigned int cpu;

pr_debug("%s(0x%p)\n", __func__, ptr);

if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr))
for_each_possible_cpu(cpu)
delete_object_full((unsigned long)per_cpu_ptr(ptr,
cpu));
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_FREE_PERCPU, ptr, 0, 0);
}
EXPORT_SYMBOL_GPL(kmemleak_free_percpu);

/**
* kmemleak_not_leak - mark an allocated object as false positive
* @ptr: pointer to beginning of the object
*
* Calling this function on an object will cause the memory block to no longer
* be reported as leak and always be scanned.
*/
void __ref 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);
}
EXPORT_SYMBOL(kmemleak_not_leak);

/**
* kmemleak_ignore - ignore an allocated object
* @ptr: pointer to beginning of the object
*
* Calling this function on an object will cause the memory block to be
* ignored (not scanned and not reported as a leak). 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 __ref 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);
}
EXPORT_SYMBOL(kmemleak_ignore);

/**
* kmemleak_scan_area - limit the range to be scanned in an allocated object
* @ptr: pointer to beginning or inside the object. This also
* represents the start of the scan area
* @size: size of the scan area
* @gfp: kmalloc() flags used for kmemleak internal memory allocations
*
* This function is used when it is known that only certain parts of an object
* contain references to other objects. Kmemleak will only scan these areas
* reducing the number false negatives.
*/
void __ref kmemleak_scan_area(const void *ptr, size_t size, gfp_t gfp)
{
pr_debug("%s(0x%p)\n", __func__, ptr);

if (atomic_read(&kmemleak_enabled) && ptr && size && !IS_ERR(ptr))
add_scan_area((unsigned long)ptr, size, gfp);
else if (atomic_read(&kmemleak_early_log))
log_early(KMEMLEAK_SCAN_AREA, ptr, size, 0);
}
EXPORT_SYMBOL(kmemleak_scan_area);

/**
* kmemleak_no_scan - do not scan an allocated object
* @ptr: pointer to beginning of the object
*
* This function notifies kmemleak not to scan the given memory block. Useful
* in situations where it is known that the given object does not contain any
* references to other objects. Kmemleak will not scan such objects reducing
* the number of false negatives.
*/
void __ref 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);
}
EXPORT_SYMBOL(kmemleak_no_scan);

/*
* Update an object's checksum and return true if it was modified.
*/
static bool update_checksum(struct kmemleak_object *object)
{
u32 old_csum = object->checksum;

if (!kmemcheck_is_obj_initialized(object->pointer, object->size))
return false;

object->checksum = crc32(0, (void *)object->pointer, object->size);
return object->checksum != old_csum;
}

/*
* Memory scanning is a long process and it needs to be interruptable. This
* function checks whether such interrupt condition occurred.
*/
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, int allow_resched)
{
unsigned long *ptr;
unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER);
unsigned long *end = _end - (BYTES_PER_POINTER - 1);

for (ptr = start; ptr < end; ptr++) {
struct kmemleak_object *object;
unsigned long flags;
unsigned long pointer;

if (allow_resched)
cond_resched();
if (scan_should_stop())
break;

/* don't scan uninitialized memory */
if (!kmemcheck_is_obj_initialized((unsigned long)ptr,
BYTES_PER_POINTER))
continue;

pointer = *ptr;

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);
spin_unlock_irqrestore(&object->lock, flags);
continue;
}

spin_unlock_irqrestore(&object->lock, flags);
put_object(object);
}
}

/*
* 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 acquired, the corresponding memory block
* cannot be freed (the same lock is acquired 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)) {
void *start = (void *)object->pointer;
void *end = (void *)(object->pointer + object->size);

while (start < end && (object->flags & OBJECT_ALLOCATED) &&
!(object->flags & OBJECT_NO_SCAN)) {
scan_block(start, min(start + MAX_SCAN_SIZE, end),
object, 0);
start += MAX_SCAN_SIZE;

spin_unlock_irqrestore(&object->lock, flags);
cond_resched();
spin_lock_irqsave(&object->lock, flags);
}
} else
hlist_for_each_entry(area, elem, &object->area_list, node)
scan_block((void *)area->start,
(void *)(area->start + area->size),
object, 0);
out:
spin_unlock_irqrestore(&object->lock, flags);
}

/*
* Scan the objects already referenced (gray objects). More objects will be
* referenced and, if there are no memory leaks, all the objects are scanned.
*/
static void scan_gray_list(void)
{
struct kmemleak_object *object, *tmp;

/*
* The list traversal is safe for both tail additions and removals
* from inside the loop. The kmemleak objects cannot be freed from
* outside the loop because their use_count was incremented.
*/
object = list_entry(gray_list.next, typeof(*object), gray_list);
while (&object->gray_list != &gray_list) {
cond_resched();

/* may add new objects to the list */
if (!scan_should_stop())
scan_object(object);

tmp = list_entry(object->gray_list.next, typeof(*object),
gray_list);

/* remove the object from the list and release it */
list_del(&object->gray_list);
put_object(object);

object = tmp;
}
WARN_ON(!list_empty(&gray_list));
}

/*
* Scan data sections and all the referenced memory blocks allocated via the
* kernel's standard allocators. This function must be called with the
* scan_mutex held.
*/
static void kmemleak_scan(void)
{
unsigned long flags;
struct kmemleak_object *object;
int i;
int new_leaks = 0;

jiffies_last_scan = jiffies;

/* 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, 1);
scan_block(__bss_start, __bss_stop, NULL, 1);

#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, 1);
#endif

/*
* Struct page scanning for each node.
*/
lock_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, 1);
}
}
unlock_memory_hotplug();

/*
* Scanning the task stacks (may introduce false negatives).
*/
if (kmemleak_stack_scan) {
struct task_struct *p, *g;

read_lock(&tasklist_lock);
do_each_thread(g, p) {
scan_block(task_stack_page(p), task_stack_page(p) +
THREAD_SIZE, NULL, 0);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}

/*
* Scan the objects already referenced from the sections scanned
* above.
*/
scan_gray_list();

/*
* Check for new or unreferenced objects modified since the previous
* scan and color them gray until the next scan.
*/
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
spin_lock_irqsave(&object->lock, flags);
if (color_white(object) && (object->flags & OBJECT_ALLOCATED)
&& update_checksum(object) && get_object(object)) {
/* color it gray temporarily */
object->count = object->min_count;
list_add_tail(&object->gray_list, &gray_list);
}
spin_unlock_irqrestore(&object->lock, flags);
}
rcu_read_unlock();

/*
* Re-scan the gray list for modified unreferenced objects.
*/
scan_gray_list();

/*
* If scanning was stopped do not report any new unreferenced objects.
*/
if (scan_should_stop())
return;

/*
* Scanning result reporting.
*/
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
spin_lock_irqsave(&object->lock, flags);
if (unreferenced_object(object) &&
!(object->flags & OBJECT_REPORTED)) {
object->flags |= OBJECT_REPORTED;
new_leaks++;
}
spin_unlock_irqrestore(&object->lock, flags);
}
rcu_read_unlock();

if (new_leaks)
pr_info("%d new suspected memory leaks (see "
"/sys/kernel/debug/kmemleak)\n", new_leaks);

}

/*
* 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");
set_user_nice(current, 10);

/*
* 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()) {
signed long timeout = jiffies_scan_wait;

mutex_lock(&scan_mutex);
kmemleak_scan();
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 scan_mutex held.
*/
static 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 scan_mutex held.
*/
static 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;
int err;

err = mutex_lock_interruptible(&scan_mutex);
if (err < 0)
return ERR_PTR(err);

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:
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);

list_for_each_continue_rcu(n, &object_list) {
struct kmemleak_object *obj =
list_entry(n, struct kmemleak_object, object_list);
if (get_object(obj)) {
next_obj = obj;
break;
}
}

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 (!IS_ERR(v)) {
/*
* kmemleak_seq_start may return ERR_PTR if the scan_mutex
* waiting was interrupted, so only release it if !IS_ERR.
*/
rcu_read_unlock();
mutex_unlock(&scan_mutex);
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 ((object->flags & OBJECT_REPORTED) && unreferenced_object(object))
print_unreferenced(seq, object);
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)
{
return seq_open(file, &kmemleak_seq_ops);
}

static int kmemleak_release(struct inode *inode, struct file *file)
{
return seq_release(inode, file);
}

static int dump_str_object_info(const char *str)
{
unsigned long flags;
struct kmemleak_object *object;
unsigned long addr;

addr= simple_strtoul(str, NULL, 0);
object = find_and_get_object(addr, 0);
if (!object) {
pr_info("Unknown object at 0x%08lx\n", addr);
return -EINVAL;
}

spin_lock_irqsave(&object->lock, flags);
dump_object_info(object);
spin_unlock_irqrestore(&object->lock, flags);

put_object(object);
return 0;
}

/*
* We use grey instead of black to ensure we can do future scans on the same
* objects. If we did not do future scans these black objects could
* potentially contain references to newly allocated objects in the future and
* we'd end up with false positives.
*/
static void kmemleak_clear(void)
{
struct kmemleak_object *object;
unsigned long flags;

rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list) {
spin_lock_irqsave(&object->lock, flags);
if ((object->flags & OBJECT_REPORTED) &&
unreferenced_object(object))
__paint_it(object, KMEMLEAK_GREY);
spin_unlock_irqrestore(&object->lock, flags);
}
rcu_read_unlock();
}

/*
* 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)
* scan - trigger a memory scan
* clear - mark all current reported unreferenced kmemleak objects as
* grey to ignore printing them
* dump=... - dump information about the object found at the given address
*/
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;
int ret;

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;

ret = mutex_lock_interruptible(&scan_mutex);
if (ret < 0)
return ret;

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;

ret = strict_strtoul(buf + 5, 0, &secs);
if (ret < 0)
goto out;
stop_scan_thread();
if (secs) {
jiffies_scan_wait = msecs_to_jiffies(secs * 1000);
start_scan_thread();
}
} else if (strncmp(buf, "scan", 4) == 0)
kmemleak_scan();
else if (strncmp(buf, "clear", 5) == 0)
kmemleak_clear();
else if (strncmp(buf, "dump=", 5) == 0)
ret = dump_str_object_info(buf + 5);
else
ret = -EINVAL;

out:
mutex_unlock(&scan_mutex);
if (ret < 0)
return ret;

/* 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,
};

/*
* Stop the memory scanning thread and free the kmemleak internal objects if
* no previous scan thread (otherwise, kmemleak may still have some useful
* information on memory leaks).
*/
static void kmemleak_do_cleanup(struct work_struct *work)
{
struct kmemleak_object *object;
bool cleanup = scan_thread == NULL;

mutex_lock(&scan_mutex);
stop_scan_thread();

if (cleanup) {
rcu_read_lock();
list_for_each_entry_rcu(object, &object_list, object_list)
delete_object_full(object->pointer);
rcu_read_unlock();
}
mutex_unlock(&scan_mutex);
}

static DECLARE_WORK(cleanup_work, kmemleak_do_cleanup);

/*
* 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_enabled, 0);

/* check whether it is too early for a kernel thread */
if (atomic_read(&kmemleak_initialized))
schedule_work(&cleanup_work);

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)
kmemleak_skip_disable = 1;
else
return -EINVAL;
return 0;
}
early_param("kmemleak", kmemleak_boot_config);

static void __init print_log_trace(struct early_log *log)
{
struct stack_trace trace;

trace.nr_entries = log->trace_len;
trace.entries = log->trace;

pr_notice("Early log backtrace:\n");
print_stack_trace(&trace, 2);
}

/*
* Kmemleak initialization.
*/
void __init kmemleak_init(void)
{
int i;
unsigned long flags;

#ifdef CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF
if (!kmemleak_skip_disable) {
atomic_set(&kmemleak_early_log, 0);
kmemleak_disable();
return;
}
#endif

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);

if (crt_early_log >= ARRAY_SIZE(early_log))
pr_warning("Early log buffer exceeded (%d), please increase "
"DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n", crt_early_log);

/* the kernel is still in UP mode, so disabling the IRQs is enough */
local_irq_save(flags);
atomic_set(&kmemleak_early_log, 0);
if (atomic_read(&kmemleak_error)) {
local_irq_restore(flags);
return;
} else
atomic_set(&kmemleak_enabled, 1);
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:
early_alloc(log);
break;
case KMEMLEAK_ALLOC_PERCPU:
early_alloc_percpu(log);
break;
case KMEMLEAK_FREE:
kmemleak_free(log->ptr);
break;
case KMEMLEAK_FREE_PART:
kmemleak_free_part(log->ptr, log->size);
break;
case KMEMLEAK_FREE_PERCPU:
kmemleak_free_percpu(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->size, GFP_KERNEL);
break;
case KMEMLEAK_NO_SCAN:
kmemleak_no_scan(log->ptr);
break;
default:
kmemleak_warn("Unknown early log operation: %d\n",
log->op_type);
}

if (atomic_read(&kmemleak_warning)) {
print_log_trace(log);
atomic_set(&kmemleak_warning, 0);
}
}
}

/*
* 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 occurred 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.
*/
schedule_work(&cleanup_work);
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(&scan_mutex);
start_scan_thread();
mutex_unlock(&scan_mutex);

pr_info("Kernel memory leak detector initialized\n");

return 0;
}
late_initcall(kmemleak_late_init);
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