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Diffstat (limited to 'mm/kmemleak.c')
| -rw-r--r-- | mm/kmemleak.c | 1498 |
1 files changed, 1498 insertions, 0 deletions
diff --git a/mm/kmemleak.c b/mm/kmemleak.c new file mode 100644 index 000000000000..58ec86c9e58a --- /dev/null +++ b/mm/kmemleak.c @@ -0,0 +1,1498 @@ +/* + * mm/kmemleak.c + * + * Copyright (C) 2008 ARM Limited + * Written by Catalin Marinas <catalin.marinas@arm.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + * + * + * For more information on the algorithm and kmemleak usage, please see + * Documentation/kmemleak.txt. + * + * Notes on locking + * ---------------- + * + * The following locks and mutexes are used by kmemleak: + * + * - kmemleak_lock (rwlock): protects the object_list modifications and + * accesses to the object_tree_root. The object_list is the main list + * holding the metadata (struct kmemleak_object) for the allocated memory + * blocks. The object_tree_root is a priority search tree used to look-up + * metadata based on a pointer to the corresponding memory block. The + * kmemleak_object structures are added to the object_list and + * object_tree_root in the create_object() function called from the + * kmemleak_alloc() callback and removed in delete_object() called from the + * kmemleak_free() callback + * - kmemleak_object.lock (spinlock): protects a kmemleak_object. Accesses to + * the metadata (e.g. count) are protected by this lock. Note that some + * members of this structure may be protected by other means (atomic or + * kmemleak_lock). This lock is also held when scanning the corresponding + * memory block to avoid the kernel freeing it via the kmemleak_free() + * callback. This is less heavyweight than holding a global lock like + * kmemleak_lock during scanning + * - scan_mutex (mutex): ensures that only one thread may scan the memory for + * unreferenced objects at a time. The gray_list contains the objects which + * are already referenced or marked as false positives and need to be + * scanned. This list is only modified during a scanning episode when the + * scan_mutex is held. At the end of a scan, the gray_list is always empty. + * Note that the kmemleak_object.use_count is incremented when an object is + * added to the gray_list and therefore cannot be freed + * - kmemleak_mutex (mutex): prevents multiple users of the "kmemleak" debugfs + * file together with modifications to the memory scanning parameters + * including the scan_thread pointer + * + * The kmemleak_object structures have a use_count incremented or decremented + * using the get_object()/put_object() functions. When the use_count becomes + * 0, this count can no longer be incremented and put_object() schedules the + * kmemleak_object freeing via an RCU callback. All calls to the get_object() + * function must be protected by rcu_read_lock() to avoid accessing a freed + * structure. + */ + +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/list.h> +#include <linux/sched.h> +#include <linux/jiffies.h> +#include <linux/delay.h> +#include <linux/module.h> +#include <linux/kthread.h> +#include <linux/prio_tree.h> +#include <linux/gfp.h> +#include <linux/fs.h> +#include <linux/debugfs.h> +#include <linux/seq_file.h> +#include <linux/cpumask.h> +#include <linux/spinlock.h> +#include <linux/mutex.h> +#include <linux/rcupdate.h> +#include <linux/stacktrace.h> +#include <linux/cache.h> +#include <linux/percpu.h> +#include <linux/hardirq.h> +#include <linux/mmzone.h> +#include <linux/slab.h> +#include <linux/thread_info.h> +#include <linux/err.h> +#include <linux/uaccess.h> +#include <linux/string.h> +#include <linux/nodemask.h> +#include <linux/mm.h> + +#include <asm/sections.h> +#include <asm/processor.h> +#include <asm/atomic.h> + +#include <linux/kmemleak.h> + +/* + * Kmemleak configuration and common defines. + */ +#define MAX_TRACE 16 /* stack trace length */ +#define REPORTS_NR 50 /* maximum number of reported leaks */ +#define MSECS_MIN_AGE 5000 /* minimum object age for reporting */ +#define MSECS_SCAN_YIELD 10 /* CPU yielding period */ +#define SECS_FIRST_SCAN 60 /* delay before the first scan */ +#define SECS_SCAN_WAIT 600 /* subsequent auto scanning delay */ + +#define BYTES_PER_POINTER sizeof(void *) + +/* scanning area inside a memory block */ +struct kmemleak_scan_area { + struct hlist_node node; + unsigned long offset; + size_t length; +}; + +/* + * Structure holding the metadata for each allocated memory block. + * Modifications to such objects should be made while holding the + * object->lock. Insertions or deletions from object_list, gray_list or + * tree_node are already protected by the corresponding locks or mutex (see + * the notes on locking above). These objects are reference-counted + * (use_count) and freed using the RCU mechanism. + */ +struct kmemleak_object { + spinlock_t lock; + unsigned long flags; /* object status flags */ + struct list_head object_list; + struct list_head gray_list; + struct prio_tree_node tree_node; + struct rcu_head rcu; /* object_list lockless traversal */ + /* object usage count; object freed when use_count == 0 */ + atomic_t use_count; + unsigned long pointer; + size_t size; + /* minimum number of a pointers found before it is considered leak */ + int min_count; + /* the total number of pointers found pointing to this object */ + int count; + /* memory ranges to be scanned inside an object (empty for all) */ + struct hlist_head area_list; + unsigned long trace[MAX_TRACE]; + unsigned int trace_len; + unsigned long jiffies; /* creation timestamp */ + pid_t pid; /* pid of the current task */ + char comm[TASK_COMM_LEN]; /* executable name */ +}; + +/* flag representing the memory block allocation status */ +#define OBJECT_ALLOCATED (1 << 0) +/* flag set after the first reporting of an unreference object */ +#define OBJECT_REPORTED (1 << 1) +/* flag set to not scan the object */ +#define OBJECT_NO_SCAN (1 << 2) + +/* the list of all allocated objects */ +static LIST_HEAD(object_list); +/* the list of gray-colored objects (see color_gray comment below) */ +static LIST_HEAD(gray_list); +/* prio search tree for object boundaries */ +static struct prio_tree_root object_tree_root; +/* rw_lock protecting the access to object_list and prio_tree_root */ +static DEFINE_RWLOCK(kmemleak_lock); + +/* allocation caches for kmemleak internal data */ +static struct kmem_cache *object_cache; +static struct kmem_cache *scan_area_cache; + +/* set if tracing memory operations is enabled */ +static atomic_t kmemleak_enabled = ATOMIC_INIT(0); +/* set in the late_initcall if there were no errors */ +static atomic_t kmemleak_initialized = ATOMIC_INIT(0); +/* enables or disables early logging of the memory operations */ +static atomic_t kmemleak_early_log = ATOMIC_INIT(1); +/* set if a fata kmemleak error has occurred */ +static atomic_t kmemleak_error = ATOMIC_INIT(0); + +/* minimum and maximum address that may be valid pointers */ +static unsigned long min_addr = ULONG_MAX; +static unsigned long max_addr; + +/* used for yielding the CPU to other tasks during scanning */ +static unsigned long next_scan_yield; +static struct task_struct *scan_thread; +static unsigned long jiffies_scan_yield; +static unsigned long jiffies_min_age; +/* delay between automatic memory scannings */ +static signed long jiffies_scan_wait; +/* enables or disables the task stacks scanning */ +static int kmemleak_stack_scan; +/* mutex protecting the memory scanning */ +static DEFINE_MUTEX(scan_mutex); +/* mutex protecting the access to the /sys/kernel/debug/kmemleak file */ +static DEFINE_MUTEX(kmemleak_mutex); + +/* number of leaks reported (for limitation purposes) */ +static int reported_leaks; + +/* + * Early object allocation/freeing logging. Kkmemleak is initialized after the + * kernel allocator. However, both the kernel allocator and kmemleak may + * allocate memory blocks which need to be tracked. Kkmemleak defines an + * arbitrary buffer to hold the allocation/freeing information before it is + * fully initialized. + */ + +/* kmemleak operation type for early logging */ +enum { + KMEMLEAK_ALLOC, + KMEMLEAK_FREE, + KMEMLEAK_NOT_LEAK, + KMEMLEAK_IGNORE, + KMEMLEAK_SCAN_AREA, + KMEMLEAK_NO_SCAN +}; + +/* + * Structure holding the information passed to kmemleak callbacks during the + * early logging. + */ +struct early_log { + int op_type; /* kmemleak operation type */ + const void *ptr; /* allocated/freed memory block */ + size_t size; /* memory block size */ + int min_count; /* minimum reference count */ + unsigned long offset; /* scan area offset */ + size_t length; /* scan area length */ +}; + +/* early logging buffer and current position */ +static struct early_log early_log[200]; +static int crt_early_log; + +static void kmemleak_disable(void); + +/* + * Print a warning and dump the stack trace. + */ +#define kmemleak_warn(x...) do { \ + pr_warning(x); \ + dump_stack(); \ +} while (0) + +/* + * Macro invoked when a serious kmemleak condition occured and cannot be + * recovered from. Kkmemleak will be disabled and further allocation/freeing + * tracing no longer available. + */ +#define kmemleak_panic(x...) do { \ + kmemleak_warn(x); \ + kmemleak_disable(); \ +} while (0) + +/* + * Object colors, encoded with count and min_count: + * - white - orphan object, not enough references to it (count < min_count) + * - gray - not orphan, not marked as false positive (min_count == 0) or + * sufficient references to it (count >= min_count) + * - black - ignore, it doesn't contain references (e.g. text section) + * (min_count == -1). No function defined for this color. + * Newly created objects don't have any color assigned (object->count == -1) + * before the next memory scan when they become white. + */ +static int color_white(const struct kmemleak_object *object) +{ + return object->count != -1 && object->count < object->min_count; +} + +static int color_gray(const struct kmemleak_object *object) +{ + return object->min_count != -1 && object->count >= object->min_count; +} + +/* + * Objects are considered referenced if their color is gray and they have not + * been deleted. + */ +static int referenced_object(struct kmemleak_object *object) +{ + return (object->flags & OBJECT_ALLOCATED) && color_gray(object); +} + +/* + * Objects are considered unreferenced only if their color is white, they have + * not be deleted and have a minimum age to avoid false positives caused by + * pointers temporarily stored in CPU registers. + */ +static int unreferenced_object(struct kmemleak_object *object) +{ + return (object->flags & OBJECT_ALLOCATED) && color_white(object) && + time_is_before_eq_jiffies(object->jiffies + jiffies_min_age); +} + +/* + * Printing of the (un)referenced objects information, either to the seq file + * or to the kernel log. The print_referenced/print_unreferenced functions + * must be called with the object->lock held. + */ +#define print_helper(seq, x...) do { \ + struct seq_file *s = (seq); \ + if (s) \ + seq_printf(s, x); \ + else \ + pr_info(x); \ +} while (0) + +static void print_referenced(struct kmemleak_object *object) +{ + pr_info("kmemleak: referenced object 0x%08lx (size %zu)\n", + object->pointer, object->size); +} + +static void print_unreferenced(struct seq_file *seq, + struct kmemleak_object *object) +{ + int i; + + print_helper(seq, "kmemleak: unreferenced object 0x%08lx (size %zu):\n", + object->pointer, object->size); + print_helper(seq, " comm \"%s\", pid %d, jiffies %lu\n", + object->comm, object->pid, object->jiffies); + print_helper(seq, " backtrace:\n"); + + for (i = 0; i < object->trace_len; i++) { + void *ptr = (void *)object->trace[i]; + print_helper(seq, " [<%p>] %pS\n", ptr, ptr); + } +} + +/* + * Print the kmemleak_object information. This function is used mainly for + * debugging special cases when kmemleak operations. It must be called with + * the object->lock held. + */ +static void dump_object_info(struct kmemleak_object *object) +{ + struct stack_trace trace; + + trace.nr_entries = object->trace_len; + trace.entries = object->trace; + + pr_notice("kmemleak: Object 0x%08lx (size %zu):\n", + object->tree_node.start, object->size); + pr_notice(" comm \"%s\", pid %d, jiffies %lu\n", + object->comm, object->pid, object->jiffies); + pr_notice(" min_count = %d\n", object->min_count); + pr_notice(" count = %d\n", object->count); + pr_notice(" backtrace:\n"); + print_stack_trace(&trace, 4); +} + +/* + * Look-up a memory block metadata (kmemleak_object) in the priority search + * tree based on a pointer value. If alias is 0, only values pointing to the + * beginning of the memory block are allowed. The kmemleak_lock must be held + * when calling this function. + */ +static struct kmemleak_object *lookup_object(unsigned long ptr, int alias) +{ + struct prio_tree_node *node; + struct prio_tree_iter iter; + struct kmemleak_object *object; + + prio_tree_iter_init(&iter, &object_tree_root, ptr, ptr); + node = prio_tree_next(&iter); + if (node) { + object = prio_tree_entry(node, struct kmemleak_object, + tree_node); + if (!alias && object->pointer != ptr) { + kmemleak_warn("kmemleak: Found object by alias"); + object = NULL; + } + } else + object = NULL; + + return object; +} + +/* + * Increment the object use_count. Return 1 if successful or 0 otherwise. Note + * that once an object's use_count reached 0, the RCU freeing was already + * registered and the object should no longer be used. This function must be + * called under the protection of rcu_read_lock(). + */ +static int get_object(struct kmemleak_object *object) +{ + return atomic_inc_not_zero(&object->use_count); +} + +/* + * RCU callback to free a kmemleak_object. + */ +static void free_object_rcu(struct rcu_head *rcu) +{ + struct hlist_node *elem, *tmp; + struct kmemleak_scan_area *area; + struct kmemleak_object *object = + container_of(rcu, struct kmemleak_object, rcu); + + /* + * Once use_count is 0 (guaranteed by put_object), there is no other + * code accessing this object, hence no need for locking. + */ + hlist_for_each_entry_safe(area, elem, tmp, &object->area_list, node) { + hlist_del(elem); + kmem_cache_free(scan_area_cache, area); + } + kmem_cache_free(object_cache, object); +} + +/* + * Decrement the object use_count. Once the count is 0, free the object using + * an RCU callback. Since put_object() may be called via the kmemleak_free() -> + * delete_object() path, the delayed RCU freeing ensures that there is no + * recursive call to the kernel allocator. Lock-less RCU object_list traversal + * is also possible. + */ +static void put_object(struct kmemleak_object *object) +{ + if (!atomic_dec_and_test(&object->use_count)) + return; + + /* should only get here after delete_object was called */ + WARN_ON(object->flags & OBJECT_ALLOCATED); + + call_rcu(&object->rcu, free_object_rcu); +} + +/* + * Look up an object in the prio search tree and increase its use_count. + */ +static struct kmemleak_object *find_and_get_object(unsigned long ptr, int alias) +{ + unsigned long flags; + struct kmemleak_object *object = NULL; + + rcu_read_lock(); + read_lock_irqsave(&kmemleak_lock, flags); + if (ptr >= min_addr && ptr < max_addr) + object = lookup_object(ptr, alias); + read_unlock_irqrestore(&kmemleak_lock, flags); + + /* check whether the object is still available */ + if (object && !get_object(object)) + object = NULL; + rcu_read_unlock(); + + return object; +} + +/* + * Create the metadata (struct kmemleak_object) corresponding to an allocated + * memory block and add it to the object_list and object_tree_root. + */ +static void create_object(unsigned long ptr, size_t size, int min_count, + gfp_t gfp) +{ + unsigned long flags; + struct kmemleak_object *object; + struct prio_tree_node *node; + struct stack_trace trace; + + object = kmem_cache_alloc(object_cache, gfp & ~GFP_SLAB_BUG_MASK); + if (!object) { + kmemleak_panic("kmemleak: Cannot allocate a kmemleak_object " + "structure\n"); + return; + } + + INIT_LIST_HEAD(&object->object_list); + INIT_LIST_HEAD(&object->gray_list); + INIT_HLIST_HEAD(&object->area_list); + spin_lock_init(&object->lock); + atomic_set(&object->use_count, 1); + object->flags = OBJECT_ALLOCATED; + object->pointer = ptr; + object->size = size; + object->min_count = min_count; + object->count = -1; /* no color initially */ + object->jiffies = jiffies; + + /* task information */ + if (in_irq()) { + object->pid = 0; + strncpy(object->comm, "hardirq", sizeof(object->comm)); + } else if (in_softirq()) { + object->pid = 0; + strncpy(object->comm, "softirq", sizeof(object->comm)); + } else { + object->pid = current->pid; + /* + * There is a small chance of a race with set_task_comm(), + * however using get_task_comm() here may cause locking + * dependency issues with current->alloc_lock. In the worst + * case, the command line is not correct. + */ + strncpy(object->comm, current->comm, sizeof(object->comm)); + } + + /* kernel backtrace */ + trace.max_entries = MAX_TRACE; + trace.nr_entries = 0; + trace.entries = object->trace; + trace.skip = 1; + save_stack_trace(&trace); + object->trace_len = trace.nr_entries; + + INIT_PRIO_TREE_NODE(&object->tree_node); + object->tree_node.start = ptr; + object->tree_node.last = ptr + size - 1; + + write_lock_irqsave(&kmemleak_lock, flags); + min_addr = min(min_addr, ptr); + max_addr = max(max_addr, ptr + size); + node = prio_tree_insert(&object_tree_root, &object->tree_node); + /* + * The code calling the kernel does not yet have the pointer to the + * memory block to be able to free it. However, we still hold the + * kmemleak_lock here in case parts of the kernel started freeing + * random memory blocks. + */ + if (node != &object->tree_node) { + unsigned long flags; + + kmemleak_panic("kmemleak: Cannot insert 0x%lx into the object " + "search tree (already existing)\n", ptr); + object = lookup_object(ptr, 1); + spin_lock_irqsave(&object->lock, flags); + dump_object_info(object); + spin_unlock_irqrestore(&object->lock, flags); + + goto out; + } + list_add_tail_rcu(&object->object_list, &object_list); +out: + write_unlock_irqrestore(&kmemleak_lock, flags); +} + +/* + * Remove the metadata (struct kmemleak_object) for a memory block from the + * object_list and object_tree_root and decrement its use_count. + */ +static void delete_object(unsigned long ptr) +{ + unsigned long flags; + struct kmemleak_object *object; + + write_lock_irqsave(&kmemleak_lock, flags); + object = lookup_object(ptr, 0); + if (!object) { + kmemleak_warn("kmemleak: Freeing unknown object at 0x%08lx\n", + ptr); + write_unlock_irqrestore(&kmemleak_lock, flags); + return; + } + prio_tree_remove(&object_tree_root, &object->tree_node); + list_del_rcu(&object->object_list); + write_unlock_irqrestore(&kmemleak_lock, flags); + + WARN_ON(!(object->flags & OBJECT_ALLOCATED)); + WARN_ON(atomic_read(&object->use_count) < 1); + + /* + * Locking here also ensures that the corresponding memory block + * cannot be freed when it is being scanned. + */ + spin_lock_irqsave(&object->lock, flags); + if (object->flags & OBJECT_REPORTED) + print_referenced(object); + object->flags &= ~OBJECT_ALLOCATED; + spin_unlock_irqrestore(&object->lock, flags); + put_object(object); +} + +/* + * Make a object permanently as gray-colored so that it can no longer be + * reported as a leak. This is used in general to mark a false positive. + */ +static void make_gray_object(unsigned long ptr) +{ + unsigned long flags; + struct kmemleak_object *object; + + object = find_and_get_object(ptr, 0); + if (!object) { + kmemleak_warn("kmemleak: Graying unknown object at 0x%08lx\n", + ptr); + return; + } + + spin_lock_irqsave(&object->lock, flags); + object->min_count = 0; + spin_unlock_irqrestore(&object->lock, flags); + put_object(object); +} + +/* + * Mark the object as black-colored so that it is ignored from scans and + * reporting. + */ +static void make_black_object(unsigned long ptr) +{ + unsigned long flags; + struct kmemleak_object *object; + + object = find_and_get_object(ptr, 0); + if (!object) { + kmemleak_warn("kmemleak: Blacking unknown object at 0x%08lx\n", + ptr); + return; + } + + spin_lock_irqsave(&object->lock, flags); + object->min_count = -1; + spin_unlock_irqrestore(&object->lock, flags); + put_object(object); +} + +/* + * Add a scanning area to the object. If at least one such area is added, + * kmemleak will only scan these ranges rather than the whole memory block. + */ +static void add_scan_area(unsigned long ptr, unsigned long offset, + size_t length, gfp_t gfp) +{ + unsigned long flags; + struct kmemleak_object *object; + struct kmemleak_scan_area *area; + + object = find_and_get_object(ptr, 0); + if (!object) { + kmemleak_warn("kmemleak: Adding scan area to unknown " + "object at 0x%08lx\n", ptr); + return; + } + + area = kmem_cache_alloc(scan_area_cache, gfp & ~GFP_SLAB_BUG_MASK); + if (!area) { + kmemleak_warn("kmemleak: Cannot allocate a scan area\n"); + goto out; + } + + spin_lock_irqsave(&object->lock, flags); + if (offset + length > object->size) { + kmemleak_warn("kmemleak: Scan area larger than object " + "0x%08lx\n", ptr); + dump_object_info(object); + kmem_cache_free(scan_area_cache, area); + goto out_unlock; + } + + INIT_HLIST_NODE(&area->node); + area->offset = offset; + area->length = length; + + hlist_add_head(&area->node, &object->area_list); +out_unlock: + spin_unlock_irqrestore(&object->lock, flags); +out: + put_object(object); +} + +/* + * Set the OBJECT_NO_SCAN flag for the object corresponding to the give + * pointer. Such object will not be scanned by kmemleak but references to it + * are searched. + */ +static void object_no_scan(unsigned long ptr) +{ + unsigned long flags; + struct kmemleak_object *object; + + object = find_and_get_object(ptr, 0); + if (!object) { + kmemleak_warn("kmemleak: Not scanning unknown object at " + "0x%08lx\n", ptr); + return; + } + + spin_lock_irqsave(&object->lock, flags); + object->flags |= OBJECT_NO_SCAN; + spin_unlock_irqrestore(&object->lock, flags); + put_object(object); +} + +/* + * Log an early kmemleak_* call to the early_log buffer. These calls will be + * processed later once kmemleak is fully initialized. + */ +static void log_early(int op_type, const void *ptr, size_t size, + int min_count, unsigned long offset, size_t length) +{ + unsigned long flags; + struct early_log *log; + + if (crt_early_log >= ARRAY_SIZE(early_log)) { + kmemleak_panic("kmemleak: Early log buffer exceeded\n"); + return; + } + + /* + * There is no need for locking since the kernel is still in UP mode + * at this stage. Disabling the IRQs is enough. + */ + local_irq_save(flags); + log = &early_log[crt_early_log]; + log->op_type = op_type; + log->ptr = ptr; + log->size = size; + log->min_count = min_count; + log->offset = offset; + log->length = length; + crt_early_log++; + local_irq_restore(flags); +} + +/* + * Memory allocation function callback. This function is called from the + * kernel allocators when a new block is allocated (kmem_cache_alloc, kmalloc, + * vmalloc etc.). + */ +void kmemleak_alloc(const void *ptr, size_t size, int min_count, gfp_t gfp) +{ + pr_debug("%s(0x%p, %zu, %d)\n", __func__, ptr, size, min_count); + + if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) + create_object((unsigned long)ptr, size, min_count, gfp); + else if (atomic_read(&kmemleak_early_log)) + log_early(KMEMLEAK_ALLOC, ptr, size, min_count, 0, 0); +} +EXPORT_SYMBOL_GPL(kmemleak_alloc); + +/* + * Memory freeing function callback. This function is called from the kernel + * allocators when a block is freed (kmem_cache_free, kfree, vfree etc.). + */ +void kmemleak_free(const void *ptr) +{ + pr_debug("%s(0x%p)\n", __func__, ptr); + + if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) + delete_object((unsigned long)ptr); + else if (atomic_read(&kmemleak_early_log)) + log_early(KMEMLEAK_FREE, ptr, 0, 0, 0, 0); +} +EXPORT_SYMBOL_GPL(kmemleak_free); + +/* + * Mark an already allocated memory block as a false positive. This will cause + * the block to no longer be reported as leak and always be scanned. + */ +void kmemleak_not_leak(const void *ptr) +{ + pr_debug("%s(0x%p)\n", __func__, ptr); + + if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) + make_gray_object((unsigned long)ptr); + else if (atomic_read(&kmemleak_early_log)) + log_early(KMEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0); +} +EXPORT_SYMBOL(kmemleak_not_leak); + +/* + * Ignore a memory block. This is usually done when it is known that the + * corresponding block is not a leak and does not contain any references to + * other allocated memory blocks. + */ +void kmemleak_ignore(const void *ptr) +{ + pr_debug("%s(0x%p)\n", __func__, ptr); + + if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) + make_black_object((unsigned long)ptr); + else if (atomic_read(&kmemleak_early_log)) + log_early(KMEMLEAK_IGNORE, ptr, 0, 0, 0, 0); +} +EXPORT_SYMBOL(kmemleak_ignore); + +/* + * Limit the range to be scanned in an allocated memory block. + */ +void kmemleak_scan_area(const void *ptr, unsigned long offset, size_t length, + gfp_t gfp) +{ + pr_debug("%s(0x%p)\n", __func__, ptr); + + if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) + add_scan_area((unsigned long)ptr, offset, length, gfp); + else if (atomic_read(&kmemleak_early_log)) + log_early(KMEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length); +} +EXPORT_SYMBOL(kmemleak_scan_area); + +/* + * Inform kmemleak not to scan the given memory block. + */ +void kmemleak_no_scan(const void *ptr) +{ + pr_debug("%s(0x%p)\n", __func__, ptr); + + if (atomic_read(&kmemleak_enabled) && ptr && !IS_ERR(ptr)) + object_no_scan((unsigned long)ptr); + else if (atomic_read(&kmemleak_early_log)) + log_early(KMEMLEAK_NO_SCAN, ptr, 0, 0, 0, 0); +} +EXPORT_SYMBOL(kmemleak_no_scan); + +/* + * Yield the CPU so that other tasks get a chance to run. The yielding is + * rate-limited to avoid excessive number of calls to the schedule() function + * during memory scanning. + */ +static void scan_yield(void) +{ + might_sleep(); + + if (time_is_before_eq_jiffies(next_scan_yield)) { + schedule(); + next_scan_yield = jiffies + jiffies_scan_yield; + } +} + +/* + * Memory scanning is a long process and it needs to be interruptable. This + * function checks whether such interrupt condition occured. + */ +static int scan_should_stop(void) +{ + if (!atomic_read(&kmemleak_enabled)) + return 1; + + /* + * This function may be called from either process or kthread context, + * hence the need to check for both stop conditions. + */ + if (current->mm) + return signal_pending(current); + else + return kthread_should_stop(); + + return 0; +} + +/* + * Scan a memory block (exclusive range) for valid pointers and add those + * found to the gray list. + */ +static void scan_block(void *_start, void *_end, + struct kmemleak_object *scanned) +{ + unsigned long *ptr; + unsigned long *start = PTR_ALIGN(_start, BYTES_PER_POINTER); + unsigned long *end = _end - (BYTES_PER_POINTER - 1); + + for (ptr = start; ptr < end; ptr++) { + unsigned long flags; + unsigned long pointer = *ptr; + struct kmemleak_object *object; + + if (scan_should_stop()) + break; + + /* + * When scanning a memory block with a corresponding + * kmemleak_object, the CPU yielding is handled in the calling + * code since it holds the object->lock to avoid the block + * freeing. + */ + if (!scanned) + scan_yield(); + + object = find_and_get_object(pointer, 1); + if (!object) + continue; + if (object == scanned) { + /* self referenced, ignore */ + put_object(object); + continue; + } + + /* + * Avoid the lockdep recursive warning on object->lock being + * previously acquired in scan_object(). These locks are + * enclosed by scan_mutex. + */ + spin_lock_irqsave_nested(&object->lock, flags, + SINGLE_DEPTH_NESTING); + if (!color_white(object)) { + /* non-orphan, ignored or new */ + spin_unlock_irqrestore(&object->lock, flags); + put_object(object); + continue; + } + + /* + * Increase the object's reference count (number of pointers + * to the memory block). If this count reaches the required + * minimum, the object's color will become gray and it will be + * added to the gray_list. + */ + object->count++; + if (color_gray(object)) + list_add_tail(&object->gray_list, &gray_list); + else + put_object(object); + spin_unlock_irqrestore(&object->lock, flags); + } +} + +/* + * Scan a memory block corresponding to a kmemleak_object. A condition is + * that object->use_count >= 1. + */ +static void scan_object(struct kmemleak_object *object) +{ + struct kmemleak_scan_area *area; + struct hlist_node *elem; + unsigned long flags; + + /* + * Once the object->lock is aquired, the corresponding memory block + * cannot be freed (the same lock is aquired in delete_object). + */ + spin_lock_irqsave(&object->lock, flags); + if (object->flags & OBJECT_NO_SCAN) + goto out; + if (!(object->flags & OBJECT_ALLOCATED)) + /* already freed object */ + goto out; + if (hlist_empty(&object->area_list)) + scan_block((void *)object->pointer, + (void *)(object->pointer + object->size), object); + else + hlist_for_each_entry(area, elem, &object->area_list, node) + scan_block((void *)(object->pointer + area->offset), + (void *)(object->pointer + area->offset + + area->length), object); +out: + spin_unlock_irqrestore(&object->lock, flags); +} + +/* + * Scan data sections and all the referenced memory blocks allocated via the + * kernel's standard allocators. This function must be called with the + * scan_mutex held. + */ +static void kmemleak_scan(void) +{ + unsigned long flags; + struct kmemleak_object *object, *tmp; + struct task_struct *task; + int i; + + /* prepare the kmemleak_object's */ + rcu_read_lock(); + list_for_each_entry_rcu(object, &object_list, object_list) { + spin_lock_irqsave(&object->lock, flags); +#ifdef DEBUG + /* + * With a few exceptions there should be a maximum of + * 1 reference to any object at this point. + */ + if (atomic_read(&object->use_count) > 1) { + pr_debug("kmemleak: object->use_count = %d\n", + atomic_read(&object->use_count)); + dump_object_info(object); + } +#endif + /* reset the reference count (whiten the object) */ + object->count = 0; + if (color_gray(object) && get_object(object)) + list_add_tail(&object->gray_list, &gray_list); + + spin_unlock_irqrestore(&object->lock, flags); + } + rcu_read_unlock(); + + /* data/bss scanning */ + scan_block(_sdata, _edata, NULL); + scan_block(__bss_start, __bss_stop, NULL); + +#ifdef CONFIG_SMP + /* per-cpu sections scanning */ + for_each_possible_cpu(i) + scan_block(__per_cpu_start + per_cpu_offset(i), + __per_cpu_end + per_cpu_offset(i), NULL); +#endif + + /* + * Struct page scanning for each node. The code below is not yet safe + * with MEMORY_HOTPLUG. + */ + for_each_online_node(i) { + pg_data_t *pgdat = NODE_DATA(i); + unsigned long start_pfn = pgdat->node_start_pfn; + unsigned long end_pfn = start_pfn + pgdat->node_spanned_pages; + unsigned long pfn; + + for (pfn = start_pfn; pfn < end_pfn; pfn++) { + struct page *page; + + if (!pfn_valid(pfn)) + continue; + page = pfn_to_page(pfn); + /* only scan if page is in use */ + if (page_count(page) == 0) + continue; + scan_block(page, page + 1, NULL); + } + } + + /* + * Scanning the task stacks may introduce false negatives and it is + * not enabled by default. + */ + if (kmemleak_stack_scan) { + read_lock(&tasklist_lock); + for_each_process(task) + scan_block(task_stack_page(task), + task_stack_page(task) + THREAD_SIZE, NULL); + read_unlock(&tasklist_lock); + } + + /* + * Scan the objects already referenced from the sections scanned + * above. More objects will be referenced and, if there are no memory + * leaks, all the objects will be scanned. The list traversal is safe + * for both tail additions and removals from inside the loop. The + * kmemleak objects cannot be freed from outside the loop because their + * use_count was increased. + */ + object = list_entry(gray_list.next, typeof(*object), gray_list); + while (&object->gray_list != &gray_list) { + scan_yield(); + + /* may add new objects to the list */ + if (!scan_should_stop()) + scan_object(object); + + tmp = list_entry(object->gray_list.next, typeof(*object), + gray_list); + + /* remove the object from the list and release it */ + list_del(&object->gray_list); + put_object(object); + + object = tmp; + } + WARN_ON(!list_empty(&gray_list)); +} + +/* + * Thread function performing automatic memory scanning. Unreferenced objects + * at the end of a memory scan are reported but only the first time. + */ +static int kmemleak_scan_thread(void *arg) +{ + static int first_run = 1; + + pr_info("kmemleak: Automatic memory scanning thread started\n"); + + /* + * Wait before the first scan to allow the system to fully initialize. + */ + if (first_run) { + first_run = 0; + ssleep(SECS_FIRST_SCAN); + } + + while (!kthread_should_stop()) { + struct kmemleak_object *object; + signed long timeout = jiffies_scan_wait; + + mutex_lock(&scan_mutex); + + kmemleak_scan(); + reported_leaks = 0; + + rcu_read_lock(); + list_for_each_entry_rcu(object, &object_list, object_list) { + unsigned long flags; + + if (reported_leaks >= REPORTS_NR) + break; + spin_lock_irqsave(&object->lock, flags); + if (!(object->flags & OBJECT_REPORTED) && + unreferenced_object(object)) { + print_unreferenced(NULL, object); + object->flags |= OBJECT_REPORTED; + reported_leaks++; + } else if ((object->flags & OBJECT_REPORTED) && + referenced_object(object)) { + print_referenced(object); + object->flags &= ~OBJECT_REPORTED; + } + spin_unlock_irqrestore(&object->lock, flags); + } + rcu_read_unlock(); + + mutex_unlock(&scan_mutex); + /* wait before the next scan */ + while (timeout && !kthread_should_stop()) + timeout = schedule_timeout_interruptible(timeout); + } + + pr_info("kmemleak: Automatic memory scanning thread ended\n"); + + return 0; +} + +/* + * Start the automatic memory scanning thread. This function must be called + * with the kmemleak_mutex held. + */ +void start_scan_thread(void) +{ + if (scan_thread) + return; + scan_thread = kthread_run(kmemleak_scan_thread, NULL, "kmemleak"); + if (IS_ERR(scan_thread)) { + pr_warning("kmemleak: Failed to create the scan thread\n"); + scan_thread = NULL; + } +} + +/* + * Stop the automatic memory scanning thread. This function must be called + * with the kmemleak_mutex held. + */ +void stop_scan_thread(void) +{ + if (scan_thread) { + kthread_stop(scan_thread); + scan_thread = NULL; + } +} + +/* + * Iterate over the object_list and return the first valid object at or after + * the required position with its use_count incremented. The function triggers + * a memory scanning when the pos argument points to the first position. + */ +static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos) +{ + struct kmemleak_object *object; + loff_t n = *pos; + + if (!n) { + kmemleak_scan(); + reported_leaks = 0; + } + if (reported_leaks >= REPORTS_NR) + return NULL; + + rcu_read_lock(); + list_for_each_entry_rcu(object, &object_list, object_list) { + if (n-- > 0) + continue; + if (get_object(object)) + goto out; + } + object = NULL; +out: + rcu_read_unlock(); + return object; +} + +/* + * Return the next object in the object_list. The function decrements the + * use_count of the previous object and increases that of the next one. + */ +static void *kmemleak_seq_next(struct seq_file *seq, void *v, loff_t *pos) +{ + struct kmemleak_object *prev_obj = v; + struct kmemleak_object *next_obj = NULL; + struct list_head *n = &prev_obj->object_list; + + ++(*pos); + if (reported_leaks >= REPORTS_NR) + goto out; + + rcu_read_lock(); + list_for_each_continue_rcu(n, &object_list) { + next_obj = list_entry(n, struct kmemleak_object, object_list); + if (get_object(next_obj)) + break; + } + rcu_read_unlock(); +out: + put_object(prev_obj); + return next_obj; +} + +/* + * Decrement the use_count of the last object required, if any. + */ +static void kmemleak_seq_stop(struct seq_file *seq, void *v) +{ + if (v) + put_object(v); +} + +/* + * Print the information for an unreferenced object to the seq file. + */ +static int kmemleak_seq_show(struct seq_file *seq, void *v) +{ + struct kmemleak_object *object = v; + unsigned long flags; + + spin_lock_irqsave(&object->lock, flags); + if (!unreferenced_object(object)) + goto out; + print_unreferenced(seq, object); + reported_leaks++; +out: + spin_unlock_irqrestore(&object->lock, flags); + return 0; +} + +static const struct seq_operations kmemleak_seq_ops = { + .start = kmemleak_seq_start, + .next = kmemleak_seq_next, + .stop = kmemleak_seq_stop, + .show = kmemleak_seq_show, +}; + +static int kmemleak_open(struct inode *inode, struct file *file) +{ + int ret = 0; + + if (!atomic_read(&kmemleak_enabled)) + return -EBUSY; + + ret = mutex_lock_interruptible(&kmemleak_mutex); + if (ret < 0) + goto out; + if (file->f_mode & FMODE_READ) { + ret = mutex_lock_interruptible(&scan_mutex); + if (ret < 0) + goto kmemleak_unlock; + ret = seq_open(file, &kmemleak_seq_ops); + if (ret < 0) + goto scan_unlock; + } + return ret; + +scan_unlock: + mutex_unlock(&scan_mutex); +kmemleak_unlock: + mutex_unlock(&kmemleak_mutex); +out: + return ret; +} + +static int kmemleak_release(struct inode *inode, struct file *file) +{ + int ret = 0; + + if (file->f_mode & FMODE_READ) { + seq_release(inode, file); + mutex_unlock(&scan_mutex); + } + mutex_unlock(&kmemleak_mutex); + + return ret; +} + +/* + * File write operation to configure kmemleak at run-time. The following + * commands can be written to the /sys/kernel/debug/kmemleak file: + * off - disable kmemleak (irreversible) + * stack=on - enable the task stacks scanning + * stack=off - disable the tasks stacks scanning + * scan=on - start the automatic memory scanning thread + * scan=off - stop the automatic memory scanning thread + * scan=... - set the automatic memory scanning period in seconds (0 to + * disable it) + */ +static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, + size_t size, loff_t *ppos) +{ + char buf[64]; + int buf_size; + + if (!atomic_read(&kmemleak_enabled)) + return -EBUSY; + + buf_size = min(size, (sizeof(buf) - 1)); + if (strncpy_from_user(buf, user_buf, buf_size) < 0) + return -EFAULT; + buf[buf_size] = 0; + + if (strncmp(buf, "off", 3) == 0) + kmemleak_disable(); + else if (strncmp(buf, "stack=on", 8) == 0) + kmemleak_stack_scan = 1; + else if (strncmp(buf, "stack=off", 9) == 0) + kmemleak_stack_scan = 0; + else if (strncmp(buf, "scan=on", 7) == 0) + start_scan_thread(); + else if (strncmp(buf, "scan=off", 8) == 0) + stop_scan_thread(); + else if (strncmp(buf, "scan=", 5) == 0) { + unsigned long secs; + int err; + + err = strict_strtoul(buf + 5, 0, &secs); + if (err < 0) + return err; + stop_scan_thread(); + if (secs) { + jiffies_scan_wait = msecs_to_jiffies(secs * 1000); + start_scan_thread(); + } + } else + return -EINVAL; + + /* ignore the rest of the buffer, only one command at a time */ + *ppos += size; + return size; +} + +static const struct file_operations kmemleak_fops = { + .owner = THIS_MODULE, + .open = kmemleak_open, + .read = seq_read, + .write = kmemleak_write, + .llseek = seq_lseek, + .release = kmemleak_release, +}; + +/* + * Perform the freeing of the kmemleak internal objects after waiting for any + * current memory scan to complete. + */ +static int kmemleak_cleanup_thread(void *arg) +{ + struct kmemleak_object *object; + + mutex_lock(&kmemleak_mutex); + stop_scan_thread(); + mutex_unlock(&kmemleak_mutex); + + mutex_lock(&scan_mutex); + rcu_read_lock(); + list_for_each_entry_rcu(object, &object_list, object_list) + delete_object(object->pointer); + rcu_read_unlock(); + mutex_unlock(&scan_mutex); + + return 0; +} + +/* + * Start the clean-up thread. + */ +static void kmemleak_cleanup(void) +{ + struct task_struct *cleanup_thread; + + cleanup_thread = kthread_run(kmemleak_cleanup_thread, NULL, + "kmemleak-clean"); + if (IS_ERR(cleanup_thread)) + pr_warning("kmemleak: Failed to create the clean-up thread\n"); +} + +/* + * Disable kmemleak. No memory allocation/freeing will be traced once this + * function is called. Disabling kmemleak is an irreversible operation. + */ +static void kmemleak_disable(void) +{ + /* atomically check whether it was already invoked */ + if (atomic_cmpxchg(&kmemleak_error, 0, 1)) + return; + + /* stop any memory operation tracing */ + atomic_set(&kmemleak_early_log, 0); + atomic_set(&kmemleak_enabled, 0); + + /* check whether it is too early for a kernel thread */ + if (atomic_read(&kmemleak_initialized)) + kmemleak_cleanup(); + + pr_info("Kernel memory leak detector disabled\n"); +} + +/* + * Allow boot-time kmemleak disabling (enabled by default). + */ +static int kmemleak_boot_config(char *str) +{ + if (!str) + return -EINVAL; + if (strcmp(str, "off") == 0) + kmemleak_disable(); + else if (strcmp(str, "on") != 0) + return -EINVAL; + return 0; +} +early_param("kmemleak", kmemleak_boot_config); + +/* + * Kkmemleak initialization. + */ +void __init kmemleak_init(void) +{ + int i; + unsigned long flags; + + jiffies_scan_yield = msecs_to_jiffies(MSECS_SCAN_YIELD); + jiffies_min_age = msecs_to_jiffies(MSECS_MIN_AGE); + jiffies_scan_wait = msecs_to_jiffies(SECS_SCAN_WAIT * 1000); + + object_cache = KMEM_CACHE(kmemleak_object, SLAB_NOLEAKTRACE); + scan_area_cache = KMEM_CACHE(kmemleak_scan_area, SLAB_NOLEAKTRACE); + INIT_PRIO_TREE_ROOT(&object_tree_root); + + /* the kernel is still in UP mode, so disabling the IRQs is enough */ + local_irq_save(flags); + if (!atomic_read(&kmemleak_error)) { + atomic_set(&kmemleak_enabled, 1); + atomic_set(&kmemleak_early_log, 0); + } + local_irq_restore(flags); + + /* + * This is the point where tracking allocations is safe. Automatic + * scanning is started during the late initcall. Add the early logged + * callbacks to the kmemleak infrastructure. + */ + for (i = 0; i < crt_early_log; i++) { + struct early_log *log = &early_log[i]; + + switch (log->op_type) { + case KMEMLEAK_ALLOC: + kmemleak_alloc(log->ptr, log->size, log->min_count, + GFP_KERNEL); + break; + case KMEMLEAK_FREE: + kmemleak_free(log->ptr); + break; + case KMEMLEAK_NOT_LEAK: + kmemleak_not_leak(log->ptr); + break; + case KMEMLEAK_IGNORE: + kmemleak_ignore(log->ptr); + break; + case KMEMLEAK_SCAN_AREA: + kmemleak_scan_area(log->ptr, log->offset, log->length, + GFP_KERNEL); + break; + case KMEMLEAK_NO_SCAN: + kmemleak_no_scan(log->ptr); + break; + default: + WARN_ON(1); + } + } +} + +/* + * Late initialization function. + */ +static int __init kmemleak_late_init(void) +{ + struct dentry *dentry; + + atomic_set(&kmemleak_initialized, 1); + + if (atomic_read(&kmemleak_error)) { + /* + * Some error occured and kmemleak was disabled. There is a + * small chance that kmemleak_disable() was called immediately + * after setting kmemleak_initialized and we may end up with + * two clean-up threads but serialized by scan_mutex. + */ + kmemleak_cleanup(); + return -ENOMEM; + } + + dentry = debugfs_create_file("kmemleak", S_IRUGO, NULL, NULL, + &kmemleak_fops); + if (!dentry) + pr_warning("kmemleak: Failed to create the debugfs kmemleak " + "file\n"); + mutex_lock(&kmemleak_mutex); + start_scan_thread(); + mutex_unlock(&kmemleak_mutex); + + pr_info("Kernel memory leak detector initialized\n"); + + return 0; +} +late_initcall(kmemleak_late_init); |