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Message-ID: <20081210182659.30323.43898.stgit@pc1117.cambridge.arm.com>
Date: Wed, 10 Dec 2008 18:26:59 +0000
From: Catalin Marinas <catalin.marinas@....com>
To: linux-kernel@...r.kernel.org
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Ingo Molnar <mingo@...e.hu>,
Pekka Enberg <penberg@...helsinki.fi>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 01/15] kmemleak: Add the base support
This patch adds the base support for the kernel memory leak
detector. It traces the memory allocation/freeing in a way similar to
the Boehm's conservative garbage collector, the difference being that
the unreferenced objects are not freed but only shown in
/sys/kernel/debug/memleak. Enabling this feature introduces an
overhead to memory allocations.
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Pekka Enberg <penberg@...helsinki.fi>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
include/linux/memleak.h | 93 +++
init/main.c | 4
mm/memleak.c | 1263 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 1359 insertions(+), 1 deletions(-)
create mode 100644 include/linux/memleak.h
create mode 100644 mm/memleak.c
diff --git a/include/linux/memleak.h b/include/linux/memleak.h
new file mode 100644
index 0000000..340b9fc
--- /dev/null
+++ b/include/linux/memleak.h
@@ -0,0 +1,93 @@
+/*
+ * include/linux/memleak.h
+ *
+ * Copyright (C) 2008 ARM Limited
+ * Written by Catalin Marinas <catalin.marinas@....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
+ */
+
+#ifndef __MEMLEAK_H
+#define __MEMLEAK_H
+
+#ifdef CONFIG_DEBUG_MEMLEAK
+
+extern void memleak_init(void);
+extern void memleak_alloc(const void *ptr, size_t size, int min_count,
+ gfp_t gfp);
+extern void memleak_free(const void *ptr);
+extern void memleak_padding(const void *ptr, unsigned long offset, size_t size);
+extern void memleak_not_leak(const void *ptr);
+extern void memleak_ignore(const void *ptr);
+extern void memleak_scan_area(const void *ptr, unsigned long offset,
+ size_t length, gfp_t gfp);
+
+static inline void memleak_alloc_recursive(const void *ptr, size_t size,
+ int min_count, unsigned long flags,
+ gfp_t gfp)
+{
+ if (!(flags & SLAB_NOLEAKTRACE))
+ memleak_alloc(ptr, size, min_count, gfp);
+}
+
+static inline void memleak_free_recursive(const void *ptr, unsigned long flags)
+{
+ if (!(flags & SLAB_NOLEAKTRACE))
+ memleak_free(ptr);
+}
+
+static inline void memleak_erase(void **ptr)
+{
+ *ptr = NULL;
+}
+
+#else
+
+#define DECLARE_MEMLEAK_OFFSET(name, type, member)
+
+static inline void memleak_init(void)
+{
+}
+static inline void memleak_alloc(const void *ptr, size_t size, int min_count,
+ gfp_t gfp)
+{
+}
+static inline void memleak_alloc_recursive(const void *ptr, size_t size,
+ int min_count, unsigned long flags,
+ gfp_t gfp)
+{
+}
+static inline void memleak_free(const void *ptr)
+{
+}
+static inline void memleak_free_recursive(const void *ptr, unsigned long flags)
+{
+}
+static inline void memleak_not_leak(const void *ptr)
+{
+}
+static inline void memleak_ignore(const void *ptr)
+{
+}
+static inline void memleak_scan_area(const void *ptr, unsigned long offset,
+ size_t length, gfp_t gfp)
+{
+}
+static inline void memleak_erase(void **ptr)
+{
+}
+
+#endif /* CONFIG_DEBUG_MEMLEAK */
+
+#endif /* __MEMLEAK_H */
diff --git a/init/main.c b/init/main.c
index 7e117a2..81cbbb7 100644
--- a/init/main.c
+++ b/init/main.c
@@ -56,6 +56,7 @@
#include <linux/debug_locks.h>
#include <linux/debugobjects.h>
#include <linux/lockdep.h>
+#include <linux/memleak.h>
#include <linux/pid_namespace.h>
#include <linux/device.h>
#include <linux/kthread.h>
@@ -653,6 +654,8 @@ asmlinkage void __init start_kernel(void)
enable_debug_pagealloc();
cpu_hotplug_init();
kmem_cache_init();
+ prio_tree_init();
+ memleak_init();
debug_objects_mem_init();
idr_init_cache();
setup_per_cpu_pageset();
@@ -662,7 +665,6 @@ asmlinkage void __init start_kernel(void)
calibrate_delay();
pidmap_init();
pgtable_cache_init();
- prio_tree_init();
anon_vma_init();
#ifdef CONFIG_X86
if (efi_enabled)
diff --git a/mm/memleak.c b/mm/memleak.c
new file mode 100644
index 0000000..bd84ee0
--- /dev/null
+++ b/mm/memleak.c
@@ -0,0 +1,1263 @@
+/*
+ * mm/memleak.c
+ *
+ * Copyright (C) 2008 ARM Limited
+ * Written by Catalin Marinas <catalin.marinas@....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 are used by kmemleak:
+ *
+ * - memleak_lock (rw_lock): protects the object_list modifications and
+ * accesses to the object_tree_root. The object_list is the main
+ * list holding the metadata (struct memleak_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 memleak_object structures are added to the object_list and
+ * object_tree_root in the create_object() function called from the
+ * memleak_alloc() callback and removed in delete_object() called from the
+ * memleak_free() callback
+ * - memleak_object.lock (spinlock): protects a memleak_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
+ * memleak_lock). This lock is also held when scanning the corresponding
+ * memory block to avoid the kernel freeing it via the memleak_free()
+ * callback. This is less heavyweight than holding a global lock like
+ * memleak_lock during scanning
+ *
+ * The memleak_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
+ * memleak_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.
+ *
+ * The only mutex used is scan_mutex. This 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 memleak_object.use_count is incremented when an object
+ * is added to the gray_list and therefore cannot be freed.
+ */
+
+#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/kallsyms.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 <asm/sections.h>
+#include <asm/processor.h>
+#include <asm/atomic.h>
+
+#include <linux/memleak.h>
+
+/*
+ * Kmemleak configuration and common defines.
+ */
+#define MAX_TRACE 16 /* stack trace length */
+#define REPORTS_NR 100 /* 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_PERIOD 600 /* auto scanning period */
+#undef SCAN_TASK_STACKS /* scan the task kernel stacks */
+#undef REPORT_ORPHAN_FREEING /* notify when freeing orphan objects */
+
+#define BYTES_PER_POINTER sizeof(void *)
+
+/* scanning area inside a memory block */
+struct memleak_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 memleak_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)
+
+/* 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(memleak_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 memleak_enabled = ATOMIC_INIT(0);
+/* set in the late_initcall if there were no errors */
+static atomic_t memleak_initialized = ATOMIC_INIT(0);
+/* enables or disables early logging of the memory operations */
+static atomic_t memleak_early_log = ATOMIC_INIT(1);
+/* set if a fata kmemleak error has occurred */
+static atomic_t memleak_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;
+static DEFINE_MUTEX(scan_mutex);
+
+/* number of leaks reported (for limitation purposes) */
+static int reported_leaks;
+
+/*
+ * Early object allocation/freeing logging. Kmemleak is initialized after the
+ * kernel allocator. However, both the kernel allocator and kmemleak may
+ * allocate memory blocks which need to be tracked. Kmemleak defines an
+ * arbitrary buffer to hold the allocation/freeing information before it is
+ * fully initialized.
+ */
+
+/* kmemleak operation type for early logging */
+enum {
+ MEMLEAK_ALLOC,
+ MEMLEAK_FREE,
+ MEMLEAK_NOT_LEAK,
+ MEMLEAK_IGNORE,
+ MEMLEAK_SCAN_AREA,
+};
+
+/*
+ * 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 __initdata early_log[200];
+static int __initdata crt_early_log;
+
+static void memleak_disable(void);
+
+/*
+ * 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 memleak_panic(x...) { \
+ pr_warning(x); \
+ memleak_disable(); \
+}
+
+/*
+ * Object colors, encoded with count and min_count:
+ * - white - orphan object, not enough references to it (count < min_count)
+ * - gray - not orphan, 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 memleak_object *object)
+{
+ return object->count != -1 && object->count < object->min_count;
+}
+
+static int color_gray(const struct memleak_object *object)
+{
+ return object->min_count != -1 && 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 int unreferenced_object(struct memleak_object *object)
+{
+ if (color_white(object) &&
+ (object->flags & OBJECT_ALLOCATED) &&
+ time_is_before_eq_jiffies(object->jiffies + jiffies_min_age))
+ return 1;
+ else
+ return 0;
+}
+
+/*
+ * Printing of the unreferenced objects information, either to the seq file
+ * or to the kernel log. The print_unreferenced() function must be called with
+ * the object->lock held.
+ */
+#define print_helper(seq, x...) \
+do { \
+ if (seq) \
+ seq_printf(seq, x); \
+ else \
+ pr_info(x); \
+} while (0)
+
+static void print_unreferenced(struct seq_file *seq,
+ struct memleak_object *object)
+{
+ char namebuf[KSYM_NAME_LEN + 1] = "";
+ char *modname;
+ unsigned long symsize;
+ int i;
+
+ print_helper(seq, "unreferenced object 0x%08lx (size %zu):\n",
+ object->pointer, object->size);
+ print_helper(seq, " comm \"%s\", pid %d, jiffies %lu\n",
+ object->comm, object->pid, object->jiffies);
+ print_helper(seq, " backtrace:\n");
+
+ for (i = 0; i < object->trace_len; i++) {
+ unsigned long trace = object->trace[i];
+ unsigned long offset = 0;
+
+ kallsyms_lookup(trace, &symsize, &offset, &modname, namebuf);
+ print_helper(seq, " [<%08lx>] %s\n", trace, namebuf);
+ }
+}
+
+/*
+ * Print the memleak_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 memleak_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 (memleak_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 memleak_lock must be held
+ * when calling this function.
+ */
+static struct memleak_object *lookup_object(unsigned long ptr, int alias)
+{
+ struct prio_tree_node *node;
+ struct prio_tree_iter iter;
+ struct memleak_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 memleak_object,
+ tree_node);
+ if (!alias && object->pointer != ptr) {
+ pr_warning("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 memleak_object *object)
+{
+ return atomic_inc_not_zero(&object->use_count);
+}
+
+/*
+ * RCU callback to free a memleak_object.
+ */
+static void free_object_rcu(struct rcu_head *rcu)
+{
+ struct hlist_node *elem, *tmp;
+ struct memleak_scan_area *area;
+ struct memleak_object *object =
+ container_of(rcu, struct memleak_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 memleak_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 memleak_object *object)
+{
+ if (!atomic_dec_and_test(&object->use_count))
+ return;
+
+ /* should only get here after delete_object was called */
+ BUG_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 memleak_object *find_and_get_object(unsigned long ptr, int alias)
+{
+ unsigned long flags;
+ struct memleak_object *object = NULL;
+
+ rcu_read_lock();
+ read_lock_irqsave(&memleak_lock, flags);
+ if (ptr >= min_addr && ptr < max_addr)
+ object = lookup_object(ptr, alias);
+ read_unlock_irqrestore(&memleak_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 memleak_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 memleak_object *object;
+ struct prio_tree_node *node;
+ struct stack_trace trace;
+
+ object = kmem_cache_alloc(object_cache, gfp);
+ if (!object)
+ memleak_panic("kmemleak: Cannot allocate a memleak_object "
+ "structure\n");
+
+ 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", TASK_COMM_LEN);
+ } else if (in_softirq()) {
+ object->pid = 0;
+ strncpy(object->comm, "softirq", TASK_COMM_LEN);
+ } else {
+ object->pid = current->pid;
+ get_task_comm(object->comm, current);
+ }
+
+ /* 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(&memleak_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
+ * memleak_lock here in case parts of the kernel started freeing
+ * random memory blocks.
+ */
+ if (node != &object->tree_node) {
+ unsigned long flags;
+
+ pr_warning("kmemleak: Existing pointer\n");
+ dump_stack();
+
+ object = lookup_object(ptr, 1);
+ spin_lock_irqsave(&object->lock, flags);
+ dump_object_info(object);
+ spin_unlock_irqrestore(&object->lock, flags);
+
+ memleak_panic("kmemleak: Cannot insert 0x%lx into the object "
+ "search tree\n", ptr);
+ }
+ list_add_tail_rcu(&object->object_list, &object_list);
+ write_unlock_irqrestore(&memleak_lock, flags);
+}
+
+/*
+ * Remove the metadata (struct memleak_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 memleak_object *object;
+
+ write_lock_irqsave(&memleak_lock, flags);
+ object = lookup_object(ptr, 0);
+ if (!object) {
+ pr_warning("kmemleak: Freeing unknown object at 0x%08lx\n",
+ ptr);
+ dump_stack();
+ write_unlock_irqrestore(&memleak_lock, flags);
+ return;
+ }
+ prio_tree_remove(&object_tree_root, &object->tree_node);
+ list_del_rcu(&object->object_list);
+ write_unlock_irqrestore(&memleak_lock, flags);
+
+ BUG_ON(!(object->flags & OBJECT_ALLOCATED));
+ BUG_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);
+ object->flags &= ~OBJECT_ALLOCATED;
+#ifdef REPORT_ORPHAN_FREEING
+ if (color_white(object)) {
+ pr_warning("kmemleak: Freeing orphan object 0x%08lx\n", ptr);
+ dump_stack();
+ dump_object_info(object);
+ }
+#endif
+ 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 memleak_object *object;
+
+ object = find_and_get_object(ptr, 0);
+ if (!object) {
+ dump_stack();
+ memleak_panic("kmemleak: Graying unknown object at 0x%08lx\n",
+ ptr);
+ }
+
+ 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 memleak_object *object;
+
+ object = find_and_get_object(ptr, 0);
+ if (!object) {
+ dump_stack();
+ memleak_panic("kmemleak: Blacking unknown object at 0x%08lx\n",
+ ptr);
+ }
+
+ 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 memleak_object *object;
+ struct memleak_scan_area *area;
+
+ object = find_and_get_object(ptr, 0);
+ if (!object) {
+ dump_stack();
+ memleak_panic("kmemleak: Adding scan area to unknown "
+ "object at 0x%08lx\n", ptr);
+ }
+
+ area = kmem_cache_alloc(scan_area_cache, gfp);
+ if (!area)
+ memleak_panic("kmemleak: Cannot allocate a scan area\n");
+
+ spin_lock_irqsave(&object->lock, flags);
+ if (offset + length > object->size) {
+ dump_stack();
+ dump_object_info(object);
+ memleak_panic("kmemleak: Scan area larger than object "
+ "0x%08lx\n", ptr);
+ }
+
+ INIT_HLIST_NODE(&area->node);
+ area->offset = offset;
+ area->length = length;
+
+ hlist_add_head(&area->node, &object->area_list);
+ spin_unlock_irqrestore(&object->lock, flags);
+ put_object(object);
+}
+
+/*
+ * Log an early memleak_* 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 offset, size_t length)
+{
+ unsigned long flags;
+ struct early_log *log;
+
+ if (crt_early_log >= ARRAY_SIZE(early_log))
+ memleak_panic("kmemleak: Early log buffer exceeded\n");
+
+ /*
+ * 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 memleak_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(&memleak_enabled) && ptr)
+ create_object((unsigned long)ptr, size, min_count, gfp);
+ else if (atomic_read(&memleak_early_log))
+ log_early(MEMLEAK_ALLOC, ptr, size, min_count, 0, 0);
+}
+EXPORT_SYMBOL_GPL(memleak_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 memleak_free(const void *ptr)
+{
+ pr_debug("%s(0x%p)\n", __func__, ptr);
+
+ if (atomic_read(&memleak_enabled) && ptr)
+ delete_object((unsigned long)ptr);
+ else if (atomic_read(&memleak_early_log))
+ log_early(MEMLEAK_FREE, ptr, 0, 0, 0, 0);
+}
+EXPORT_SYMBOL_GPL(memleak_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 memleak_not_leak(const void *ptr)
+{
+ pr_debug("%s(0x%p)\n", __func__, ptr);
+
+ if (atomic_read(&memleak_enabled) && ptr)
+ make_gray_object((unsigned long)ptr);
+ else if (atomic_read(&memleak_early_log))
+ log_early(MEMLEAK_NOT_LEAK, ptr, 0, 0, 0, 0);
+}
+EXPORT_SYMBOL(memleak_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 memleak_ignore(const void *ptr)
+{
+ pr_debug("%s(0x%p)\n", __func__, ptr);
+
+ if (atomic_read(&memleak_enabled) && ptr)
+ make_black_object((unsigned long)ptr);
+ else if (atomic_read(&memleak_early_log))
+ log_early(MEMLEAK_IGNORE, ptr, 0, 0, 0, 0);
+}
+EXPORT_SYMBOL(memleak_ignore);
+
+/*
+ * Limit the range to be scanned in an allocated memory block.
+ */
+void memleak_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(&memleak_enabled) && ptr)
+ add_scan_area((unsigned long)ptr, offset, length, gfp);
+ else if (atomic_read(&memleak_early_log))
+ log_early(MEMLEAK_SCAN_AREA, ptr, 0, 0, offset, length);
+}
+EXPORT_SYMBOL(memleak_scan_area);
+
+/*
+ * 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(&memleak_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 && signal_pending(current)) ||
+ (!current->mm && kthread_should_stop()))
+ return 1;
+ 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 memleak_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 memleak_object *object;
+
+ if (scan_should_stop())
+ break;
+
+ /*
+ * When scanning a memory block with a corresponding
+ * memleak_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 memleak_object. A condition is
+ * that object->use_count >= 1.
+ */
+static void scan_object(struct memleak_object *object)
+{
+ struct memleak_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_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 memleak_scan(void)
+{
+ unsigned long flags;
+ struct memleak_object *object, *tmp;
+#ifdef CONFIG_SMP
+ int i;
+#endif
+#ifdef SCAN_TASK_STACKS
+ struct task_struct *task;
+#endif
+
+ /* prepare the memleak_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
+
+#ifdef SCAN_TASK_STACKS
+ /*
+ * Scanning the task stacks may introduce false negatives and it is
+ * not enabled by default.
+ */
+ 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);
+#endif
+
+ /*
+ * 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
+ * memleak 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;
+ }
+ BUG_ON(!list_empty(&gray_list));
+}
+
+/*
+ * 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 *memleak_seq_start(struct seq_file *seq, loff_t *pos)
+{
+ struct memleak_object *object;
+ loff_t n = *pos;
+
+ if (!atomic_read(&memleak_enabled)) {
+ seq_printf(seq, "Kernel memory leak detector disabled\n");
+ return ERR_PTR(-EBUSY);
+ }
+ if (!n) {
+ memleak_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 *memleak_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+ struct memleak_object *prev_obj = v;
+ struct memleak_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 memleak_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 memleak_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 memleak_seq_show(struct seq_file *seq, void *v)
+{
+ struct memleak_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 memleak_seq_ops = {
+ .start = memleak_seq_start,
+ .next = memleak_seq_next,
+ .stop = memleak_seq_stop,
+ .show = memleak_seq_show,
+};
+
+static int memleak_seq_open(struct inode *inode, struct file *file)
+{
+ int ret = mutex_lock_interruptible(&scan_mutex);
+ if (ret < 0)
+ return ret;
+ ret = seq_open(file, &memleak_seq_ops);
+ if (ret < 0)
+ mutex_unlock(&scan_mutex);
+ return ret;
+}
+
+static int memleak_seq_release(struct inode *inode, struct file *file)
+{
+ int ret = seq_release(inode, file);
+ mutex_unlock(&scan_mutex);
+ return ret;
+}
+
+static const struct file_operations memleak_fops = {
+ .owner = THIS_MODULE,
+ .open = memleak_seq_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = memleak_seq_release,
+};
+
+/*
+ * Thread function performing automatic memory scanning. Unreferenced objects
+ * at the end of a memory scan are reported but only the first time.
+ */
+static int memleak_scan_thread(void *arg)
+{
+ /*
+ * Wait before the first scan to allow the system to fully initialize.
+ */
+ ssleep(SECS_FIRST_SCAN);
+
+ while (!kthread_should_stop()) {
+ struct memleak_object *object;
+ int ret;
+
+ ret = mutex_lock_interruptible(&scan_mutex);
+ if (ret < 0)
+ continue;
+
+ memleak_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++;
+ }
+ spin_unlock_irqrestore(&object->lock, flags);
+ }
+ rcu_read_unlock();
+
+ mutex_unlock(&scan_mutex);
+ /* sleep before the next scan */
+ ssleep(SECS_SCAN_PERIOD);
+ }
+
+ return 0;
+}
+
+/*
+ * Perform the freeing of the kmemleak internal objects after waiting for any
+ * current memory scan to complete.
+ */
+static int memleak_cleanup_thread(void *arg)
+{
+ struct memleak_object *object;
+
+ 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 memleak_cleanup(void)
+{
+ struct task_struct *cleanup_thread;
+
+ cleanup_thread = kthread_run(memleak_cleanup_thread, NULL,
+ "kmemleak-cleanup");
+ 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 memleak_disable(void)
+{
+ if (atomic_cmpxchg(&memleak_error, 0, 1))
+ return;
+
+ /* stop any memory operation tracing */
+ atomic_set(&memleak_early_log, 0);
+ atomic_set(&memleak_enabled, 0);
+
+ /* check whether it is too early for a kernel thread */
+ if (atomic_read(&memleak_initialized))
+ memleak_cleanup();
+
+ pr_info("Kernel memory leak detector disabled\n");
+}
+
+/*
+ * Kmemleak initialization.
+ */
+void __init memleak_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);
+
+ object_cache = KMEM_CACHE(memleak_object, SLAB_NOLEAKTRACE);
+ scan_area_cache = KMEM_CACHE(memleak_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(&memleak_error)) {
+ atomic_set(&memleak_enabled, 1);
+ atomic_set(&memleak_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 MEMLEAK_ALLOC:
+ memleak_alloc(log->ptr, log->size, log->min_count,
+ GFP_ATOMIC);
+ break;
+ case MEMLEAK_FREE:
+ memleak_free(log->ptr);
+ break;
+ case MEMLEAK_NOT_LEAK:
+ memleak_not_leak(log->ptr);
+ break;
+ case MEMLEAK_IGNORE:
+ memleak_ignore(log->ptr);
+ break;
+ case MEMLEAK_SCAN_AREA:
+ memleak_scan_area(log->ptr, log->offset, log->length,
+ GFP_ATOMIC);
+ break;
+ default:
+ BUG();
+ }
+ }
+}
+
+/*
+ * Late initialization function.
+ */
+static int __init memleak_late_init(void)
+{
+ struct dentry *dentry;
+
+ atomic_set(&memleak_initialized, 1);
+
+ if (atomic_read(&memleak_error)) {
+ /*
+ * Some error occured and kmemleak was disabled. There is a
+ * small chance that memleak_disable() was called immediately
+ * after setting memleak_initialized and we may end up with
+ * two clean-up threads but serialized by scan_mutex.
+ */
+ memleak_cleanup();
+ return -EBUSY;
+ }
+
+ dentry = debugfs_create_file("memleak", S_IRUGO, NULL, NULL,
+ &memleak_fops);
+ if (!dentry)
+ return -ENOMEM;
+
+ scan_thread = kthread_run(memleak_scan_thread, NULL, "kmemleak");
+ if (IS_ERR(scan_thread))
+ pr_warning("kmemleak: Failed to create the scan thread\n");
+
+ pr_info("Kernel memory leak detector initialized\n");
+
+ return 0;
+}
+late_initcall(memleak_late_init);
--
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