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Date: Tue, 16 Dec 2008 11:36:48 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Pekka Enberg <penberg@...helsinki.fi>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 01/15] kmemleak: Add the base support
On Wed, Dec 10, 2008 at 06:26:59PM +0000, Catalin Marinas wrote:
> 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.
Looks good to me from an RCU viewpoint!
Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 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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