/* * 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/module.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 <asm/atomic.h> #include <linux/kmemcheck.h> #include <linux/kmemleak.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_KERNEL | GFP_ATOMIC) /* 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 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; 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); /* * Early object allocation/freeing logging. Kmemleak is initialized after the * kernel allocator. However, both the kernel allocator and kmemleak may * allocate memory blocks which need to be tracked. Kmemleak defines an * arbitrary buffer to hold the allocation/freeing information before it is * fully initialized. */ /* kmemleak operation type for early logging */ enum { KMEMLEAK_ALLOC, KMEMLEAK_FREE, KMEMLEAK_FREE_PART, 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(); \ } while (0) /* * Macro invoked when a serious kmemleak condition occured and cannot be * recovered from. Kmemleak will be disabled and further allocation/freeing * tracing no longer available. */ #define kmemleak_stop(x...) do { \ kmemleak_warn(x); \ kmemleak_disable(); \ } while (0) /* * 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"); 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 & GFP_KMEMLEAK_MASK); if (!object) { kmemleak_stop("Cannot allocate a kmemleak_object structure\n"); 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); } /* * 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) { 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 & GFP_KMEMLEAK_MASK); if (!area) { kmemleak_warn("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 (crt_early_log >= ARRAY_SIZE(early_log)) { pr_warning("Early log buffer exceeded, " "please increase DEBUG_KMEMLEAK_EARLY_LOG_SIZE\n"); 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; if (op_type == KMEMLEAK_ALLOC) 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(); } /* * 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 __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); /* * Memory freeing function callback. This function is called from the kernel * allocators when a 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); /* * Partial memory freeing function callback. This function is usually called * from bootmem allocator when (part of) a memory block is freed. */ 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); /* * 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 __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); /* * 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 __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); /* * Limit the range to be scanned in an allocated memory block. */ 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 && !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); /* * Inform kmemleak not to scan the given memory block. */ 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 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, 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. 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, 1); } } /* * 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) { next_obj = list_entry(n, struct kmemleak_object, object_list); if (get_object(next_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) { if (!atomic_read(&kmemleak_enabled)) return -EBUSY; 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; 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, }; /* * Perform the freeing of the kmemleak internal objects after waiting for any * current memory scan to complete. */ static void kmemleak_do_cleanup(struct work_struct *work) { struct kmemleak_object *object; mutex_lock(&scan_mutex); stop_scan_thread(); 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_early_log, 0); 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) return -EINVAL; return 0; } early_param("kmemleak", kmemleak_boot_config); /* * Kmemleak initialization. */ void __init kmemleak_init(void) { int i; unsigned long flags; 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: early_alloc(log); break; case KMEMLEAK_FREE: kmemleak_free(log->ptr); break; case KMEMLEAK_FREE_PART: kmemleak_free_part(log->ptr, log->size); 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: 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. */ 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);