From a9d9058abab4ac17b79d500506e6c74bd16cecdc Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Thu, 25 Jun 2009 10:16:11 +0100 Subject: kmemleak: Allow the early log buffer to be configurable. (feature suggested by Sergey Senozhatsky) Kmemleak needs to track all the memory allocations but some of these happen before kmemleak is initialised. These are stored in an internal buffer which may be exceeded in some kernel configurations. This patch adds a configuration option with a default value of 400 and also removes the stack dump when the early log buffer is exceeded. Signed-off-by: Catalin Marinas Acked-by: Sergey Senozhatsky diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt index 0112da3..f655308 100644 --- a/Documentation/kmemleak.txt +++ b/Documentation/kmemleak.txt @@ -41,6 +41,10 @@ Memory scanning parameters can be modified at run-time by writing to the Kmemleak can also be disabled at boot-time by passing "kmemleak=off" on the kernel command line. +Memory may be allocated or freed before kmemleak is initialised and +these actions are stored in an early log buffer. The size of this buffer +is configured via the CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE option. + Basic Algorithm --------------- diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 4c32b1a..12327b2 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -359,6 +359,18 @@ config DEBUG_KMEMLEAK In order to access the kmemleak file, debugfs needs to be mounted (usually at /sys/kernel/debug). +config DEBUG_KMEMLEAK_EARLY_LOG_SIZE + int "Maximum kmemleak early log entries" + depends on DEBUG_KMEMLEAK + range 200 2000 + default 400 + help + Kmemleak must track all the memory allocations to avoid + reporting false positives. Since memory may be allocated or + freed before kmemleak is initialised, an early log buffer is + used to store these actions. If kmemleak reports "early log + buffer exceeded", please increase this value. + config DEBUG_KMEMLEAK_TEST tristate "Simple test for the kernel memory leak detector" depends on DEBUG_KMEMLEAK diff --git a/mm/kmemleak.c b/mm/kmemleak.c index c96f2c8..17096d1 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -235,7 +235,7 @@ struct early_log { }; /* early logging buffer and current position */ -static struct early_log early_log[200]; +static struct early_log early_log[CONFIG_DEBUG_KMEMLEAK_EARLY_LOG_SIZE]; static int crt_early_log; static void kmemleak_disable(void); @@ -696,7 +696,8 @@ static void log_early(int op_type, const void *ptr, size_t size, struct early_log *log; if (crt_early_log >= ARRAY_SIZE(early_log)) { - kmemleak_stop("Early log buffer exceeded\n"); + pr_warning("Early log buffer exceeded\n"); + kmemleak_disable(); return; } -- cgit v0.10.2 From e0a2a1601bec01243bcad44414d06f59dae2eedb Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 26 Jun 2009 17:38:25 +0100 Subject: kmemleak: Enable task stacks scanning by default This is to reduce the number of false positives reported. Signed-off-by: Catalin Marinas diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt index f655308..9426e94 100644 --- a/Documentation/kmemleak.txt +++ b/Documentation/kmemleak.txt @@ -31,12 +31,12 @@ Memory scanning parameters can be modified at run-time by writing to the /sys/kernel/debug/kmemleak file. The following parameters are supported: off - disable kmemleak (irreversible) - stack=on - enable the task stacks scanning + stack=on - enable the task stacks scanning (default) stack=off - disable the tasks stacks scanning - scan=on - start the automatic memory scanning thread + scan=on - start the automatic memory scanning thread (default) scan=off - stop the automatic memory scanning thread - scan= - set the automatic memory scanning period in seconds (0 - to disable it) + scan= - set the automatic memory scanning period in seconds + (default 600, 0 to stop the automatic scanning) Kmemleak can also be disabled at boot-time by passing "kmemleak=off" on the kernel command line. diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 17096d1..a38418a 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -194,7 +194,7 @@ static unsigned long jiffies_min_age; /* delay between automatic memory scannings */ static signed long jiffies_scan_wait; /* enables or disables the task stacks scanning */ -static int kmemleak_stack_scan; +static int kmemleak_stack_scan = 1; /* mutex protecting the memory scanning */ static DEFINE_MUTEX(scan_mutex); /* mutex protecting the access to the /sys/kernel/debug/kmemleak file */ -- cgit v0.10.2 From bab4a34afc301fdb81b6ea0e3098d96fc356e03a Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 26 Jun 2009 17:38:26 +0100 Subject: kmemleak: Simplify the reports logged by the scanning thread Because of false positives, the memory scanning thread may print too much information. This patch changes the scanning thread to only print the number of newly suspected leaks. Further information can be read from the /sys/kernel/debug/kmemleak file. Signed-off-by: Catalin Marinas diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt index 9426e94..c06f7ba 100644 --- a/Documentation/kmemleak.txt +++ b/Documentation/kmemleak.txt @@ -16,9 +16,9 @@ Usage ----- CONFIG_DEBUG_KMEMLEAK in "Kernel hacking" has to be enabled. A kernel -thread scans the memory every 10 minutes (by default) and prints any new -unreferenced objects found. To trigger an intermediate scan and display -all the possible memory leaks: +thread scans the memory every 10 minutes (by default) and prints the +number of new unreferenced objects found. To trigger an intermediate +scan and display the details of all the possible memory leaks: # mount -t debugfs nodev /sys/kernel/debug/ # cat /sys/kernel/debug/kmemleak diff --git a/mm/kmemleak.c b/mm/kmemleak.c index a38418a..4130a48 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -279,15 +279,6 @@ static int color_gray(const struct kmemleak_object *object) } /* - * Objects are considered referenced if their color is gray and they have not - * been deleted. - */ -static int referenced_object(struct kmemleak_object *object) -{ - return (object->flags & OBJECT_ALLOCATED) && color_gray(object); -} - -/* * Objects are considered unreferenced only if their color is white, they have * not be deleted and have a minimum age to avoid false positives caused by * pointers temporarily stored in CPU registers. @@ -299,38 +290,23 @@ static int unreferenced_object(struct kmemleak_object *object) } /* - * Printing of the (un)referenced objects information, either to the seq file - * or to the kernel log. The print_referenced/print_unreferenced functions - * must be called with the object->lock held. + * Printing of the unreferenced objects information to the seq file. The + * print_unreferenced function must be called with the object->lock held. */ -#define print_helper(seq, x...) do { \ - struct seq_file *s = (seq); \ - if (s) \ - seq_printf(s, x); \ - else \ - pr_info(x); \ -} while (0) - -static void print_referenced(struct kmemleak_object *object) -{ - pr_info("referenced object 0x%08lx (size %zu)\n", - object->pointer, object->size); -} - static void print_unreferenced(struct seq_file *seq, struct kmemleak_object *object) { int i; - print_helper(seq, "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"); + seq_printf(seq, "unreferenced object 0x%08lx (size %zu):\n", + object->pointer, object->size); + seq_printf(seq, " comm \"%s\", pid %d, jiffies %lu\n", + object->comm, object->pid, object->jiffies); + seq_printf(seq, " backtrace:\n"); for (i = 0; i < object->trace_len; i++) { void *ptr = (void *)object->trace[i]; - print_helper(seq, " [<%p>] %pS\n", ptr, ptr); + seq_printf(seq, " [<%p>] %pS\n", ptr, ptr); } } @@ -571,8 +547,6 @@ static void delete_object(unsigned long ptr) * cannot be freed when it is being scanned. */ spin_lock_irqsave(&object->lock, flags); - if (object->flags & OBJECT_REPORTED) - print_referenced(object); object->flags &= ~OBJECT_ALLOCATED; spin_unlock_irqrestore(&object->lock, flags); put_object(object); @@ -1073,33 +1047,30 @@ static int kmemleak_scan_thread(void *arg) while (!kthread_should_stop()) { struct kmemleak_object *object; signed long timeout = jiffies_scan_wait; + int new_leaks = 0; mutex_lock(&scan_mutex); kmemleak_scan(); - reported_leaks = 0; rcu_read_lock(); list_for_each_entry_rcu(object, &object_list, object_list) { unsigned long flags; - if (reported_leaks >= REPORTS_NR) - break; spin_lock_irqsave(&object->lock, flags); - if (!(object->flags & OBJECT_REPORTED) && - unreferenced_object(object)) { - print_unreferenced(NULL, object); + if (unreferenced_object(object) && + !(object->flags & OBJECT_REPORTED)) { object->flags |= OBJECT_REPORTED; - reported_leaks++; - } else if ((object->flags & OBJECT_REPORTED) && - referenced_object(object)) { - print_referenced(object); - 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); + mutex_unlock(&scan_mutex); /* wait before the next scan */ while (timeout && !kthread_should_stop()) -- cgit v0.10.2 From 4698c1f2bbe44ce852ef1a6716973c1f5401a4c4 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 26 Jun 2009 17:38:27 +0100 Subject: kmemleak: Do not trigger a scan when reading the debug/kmemleak file Since there is a kernel thread for automatically scanning the memory, it makes sense for the debug/kmemleak file to only show its findings. This patch also adds support for "echo scan > debug/kmemleak" to trigger an intermediate memory scan and eliminates the kmemleak_mutex (scan_mutex covers all the cases now). Signed-off-by: Catalin Marinas diff --git a/Documentation/kmemleak.txt b/Documentation/kmemleak.txt index c06f7ba..8906803 100644 --- a/Documentation/kmemleak.txt +++ b/Documentation/kmemleak.txt @@ -17,12 +17,16 @@ Usage CONFIG_DEBUG_KMEMLEAK in "Kernel hacking" has to be enabled. A kernel thread scans the memory every 10 minutes (by default) and prints the -number of new unreferenced objects found. To trigger an intermediate -scan and display the details of all the possible memory leaks: +number of new unreferenced objects found. To display the details of all +the possible memory leaks: # mount -t debugfs nodev /sys/kernel/debug/ # cat /sys/kernel/debug/kmemleak +To trigger an intermediate memory scan: + + # echo scan > /sys/kernel/debug/kmemleak + Note that the orphan objects are listed in the order they were allocated and one object at the beginning of the list may cause other subsequent objects to be reported as orphan. @@ -37,6 +41,7 @@ Memory scanning parameters can be modified at run-time by writing to the scan=off - stop the automatic memory scanning thread scan= - set the automatic memory scanning period in seconds (default 600, 0 to stop the automatic scanning) + scan - trigger a memory scan Kmemleak can also be disabled at boot-time by passing "kmemleak=off" on the kernel command line. diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 4130a48..e96e0ec 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -48,10 +48,10 @@ * scanned. This list is only modified during a scanning episode when the * scan_mutex is held. At the end of a scan, the gray_list is always empty. * Note that the kmemleak_object.use_count is incremented when an object is - * added to the gray_list and therefore cannot be freed - * - kmemleak_mutex (mutex): prevents multiple users of the "kmemleak" debugfs - * file together with modifications to the memory scanning parameters - * including the scan_thread pointer + * 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 @@ -195,10 +195,8 @@ static unsigned long jiffies_min_age; static signed long jiffies_scan_wait; /* enables or disables the task stacks scanning */ static int kmemleak_stack_scan = 1; -/* mutex protecting the memory scanning */ +/* protects the memory scanning, parameters and debug/kmemleak file access */ static DEFINE_MUTEX(scan_mutex); -/* mutex protecting the access to the /sys/kernel/debug/kmemleak file */ -static DEFINE_MUTEX(kmemleak_mutex); /* number of leaks reported (for limitation purposes) */ static int reported_leaks; @@ -927,6 +925,7 @@ static void kmemleak_scan(void) struct kmemleak_object *object, *tmp; struct task_struct *task; int i; + int new_leaks = 0; /* prepare the kmemleak_object's */ rcu_read_lock(); @@ -1024,6 +1023,26 @@ static void kmemleak_scan(void) object = tmp; } WARN_ON(!list_empty(&gray_list)); + + /* + * 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); + } /* @@ -1045,33 +1064,12 @@ static int kmemleak_scan_thread(void *arg) } while (!kthread_should_stop()) { - struct kmemleak_object *object; signed long timeout = jiffies_scan_wait; - int new_leaks = 0; mutex_lock(&scan_mutex); - kmemleak_scan(); - - rcu_read_lock(); - list_for_each_entry_rcu(object, &object_list, object_list) { - unsigned long flags; - - 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); - mutex_unlock(&scan_mutex); + /* wait before the next scan */ while (timeout && !kthread_should_stop()) timeout = schedule_timeout_interruptible(timeout); @@ -1084,7 +1082,7 @@ static int kmemleak_scan_thread(void *arg) /* * Start the automatic memory scanning thread. This function must be called - * with the kmemleak_mutex held. + * with the scan_mutex held. */ void start_scan_thread(void) { @@ -1099,7 +1097,7 @@ void start_scan_thread(void) /* * Stop the automatic memory scanning thread. This function must be called - * with the kmemleak_mutex held. + * with the scan_mutex held. */ void stop_scan_thread(void) { @@ -1119,10 +1117,8 @@ static void *kmemleak_seq_start(struct seq_file *seq, loff_t *pos) struct kmemleak_object *object; loff_t n = *pos; - if (!n) { - kmemleak_scan(); + if (!n) reported_leaks = 0; - } if (reported_leaks >= REPORTS_NR) return NULL; @@ -1206,13 +1202,10 @@ static int kmemleak_open(struct inode *inode, struct file *file) if (!atomic_read(&kmemleak_enabled)) return -EBUSY; - ret = mutex_lock_interruptible(&kmemleak_mutex); + ret = mutex_lock_interruptible(&scan_mutex); if (ret < 0) goto out; if (file->f_mode & FMODE_READ) { - ret = mutex_lock_interruptible(&scan_mutex); - if (ret < 0) - goto kmemleak_unlock; ret = seq_open(file, &kmemleak_seq_ops); if (ret < 0) goto scan_unlock; @@ -1221,8 +1214,6 @@ static int kmemleak_open(struct inode *inode, struct file *file) scan_unlock: mutex_unlock(&scan_mutex); -kmemleak_unlock: - mutex_unlock(&kmemleak_mutex); out: return ret; } @@ -1231,11 +1222,9 @@ static int kmemleak_release(struct inode *inode, struct file *file) { int ret = 0; - if (file->f_mode & FMODE_READ) { + if (file->f_mode & FMODE_READ) seq_release(inode, file); - mutex_unlock(&scan_mutex); - } - mutex_unlock(&kmemleak_mutex); + mutex_unlock(&scan_mutex); return ret; } @@ -1250,6 +1239,7 @@ static int kmemleak_release(struct inode *inode, struct file *file) * 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 */ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, size_t size, loff_t *ppos) @@ -1287,7 +1277,9 @@ static ssize_t kmemleak_write(struct file *file, const char __user *user_buf, jiffies_scan_wait = msecs_to_jiffies(secs * 1000); start_scan_thread(); } - } else + } else if (strncmp(buf, "scan", 4) == 0) + kmemleak_scan(); + else return -EINVAL; /* ignore the rest of the buffer, only one command at a time */ @@ -1312,11 +1304,9 @@ static int kmemleak_cleanup_thread(void *arg) { struct kmemleak_object *object; - mutex_lock(&kmemleak_mutex); + mutex_lock(&scan_mutex); stop_scan_thread(); - mutex_unlock(&kmemleak_mutex); - mutex_lock(&scan_mutex); rcu_read_lock(); list_for_each_entry_rcu(object, &object_list, object_list) delete_object(object->pointer); @@ -1458,9 +1448,9 @@ static int __init kmemleak_late_init(void) &kmemleak_fops); if (!dentry) pr_warning("Failed to create the debugfs kmemleak file\n"); - mutex_lock(&kmemleak_mutex); + mutex_lock(&scan_mutex); start_scan_thread(); - mutex_unlock(&kmemleak_mutex); + mutex_unlock(&scan_mutex); pr_info("Kernel memory leak detector initialized\n"); -- cgit v0.10.2 From acf4968ec9dea49387ca8b3d36dfaa0850bdb2d5 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Fri, 26 Jun 2009 17:38:29 +0100 Subject: kmemleak: Slightly change the policy on newly allocated objects Newly allocated objects are more likely to be reported as false positives. Kmemleak ignores the reporting of objects younger than 5 seconds. However, this age was calculated after the memory scanning completed which usually takes longer than 5 seconds. This patch make the minimum object age calculation in relation to the start of the memory scanning. Signed-off-by: Catalin Marinas diff --git a/mm/kmemleak.c b/mm/kmemleak.c index e96e0ec..c37e8e5 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -190,7 +190,9 @@ static unsigned long max_addr; static unsigned long next_scan_yield; static struct task_struct *scan_thread; static unsigned long jiffies_scan_yield; +/* 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 */ @@ -284,7 +286,8 @@ static int color_gray(const struct kmemleak_object *object) static int unreferenced_object(struct kmemleak_object *object) { return (object->flags & OBJECT_ALLOCATED) && color_white(object) && - time_is_before_eq_jiffies(object->jiffies + jiffies_min_age); + time_before_eq(object->jiffies + jiffies_min_age, + jiffies_last_scan); } /* @@ -927,6 +930,8 @@ static void kmemleak_scan(void) 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) { -- cgit v0.10.2 From 17bb9e0d906b625f86e9d31740bb1c35bc0f63d7 Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 29 Jun 2009 17:13:56 +0100 Subject: kmemleak: Do not report new leaked objects if the scanning was stopped If the scanning was stopped with a signal, it is possible that some objects are left with a white colour (potential leaks) and reported. Add a check to avoid reporting such objects. Signed-off-by: Catalin Marinas diff --git a/mm/kmemleak.c b/mm/kmemleak.c index c37e8e5..e094c4d 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -1030,6 +1030,12 @@ static void kmemleak_scan(void) WARN_ON(!list_empty(&gray_list)); /* + * If scanning was stopped do not report any new unreferenced objects. + */ + if (scan_should_stop()) + return; + + /* * Scanning result reporting. */ rcu_read_lock(); @@ -1184,11 +1190,10 @@ static int kmemleak_seq_show(struct seq_file *seq, void *v) unsigned long flags; spin_lock_irqsave(&object->lock, flags); - if (!unreferenced_object(object)) - goto out; - print_unreferenced(seq, object); - reported_leaks++; -out: + if ((object->flags & OBJECT_REPORTED) && unreferenced_object(object)) { + print_unreferenced(seq, object); + reported_leaks++; + } spin_unlock_irqrestore(&object->lock, flags); return 0; } -- cgit v0.10.2 From b6e687221eb840bacd4d4a991e5f8e7ed3ae910a Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 29 Jun 2009 17:13:57 +0100 Subject: kmemleak: Do not warn if an unknown object is freed vmap'ed memory blocks are not tracked by kmemleak (yet) but they may be released with vfree() which is tracked. The corresponding kmemleak warning is only enabled in debug mode. Future patch will add support for ioremap and vmap. Signed-off-by: Catalin Marinas diff --git a/mm/kmemleak.c b/mm/kmemleak.c index e094c4d..eeece2d 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -531,8 +531,10 @@ static void delete_object(unsigned long ptr) write_lock_irqsave(&kmemleak_lock, flags); object = lookup_object(ptr, 0); if (!object) { +#ifdef DEBUG kmemleak_warn("Freeing unknown object at 0x%08lx\n", ptr); +#endif write_unlock_irqrestore(&kmemleak_lock, flags); return; } -- cgit v0.10.2 From 12de38b186c2af97bf0b4a1f907f766df46b1def Mon Sep 17 00:00:00 2001 From: Catalin Marinas Date: Mon, 29 Jun 2009 17:13:55 +0100 Subject: kmemleak: Inform kmemleak about pid_hash Kmemleak does not track alloc_bootmem calls but the pid_hash allocated in pidhash_init() would need to be scanned as it contains pointers to struct pid objects. Signed-off-by: Catalin Marinas diff --git a/kernel/pid.c b/kernel/pid.c index 31310b5..5fa1db4 100644 --- a/kernel/pid.c +++ b/kernel/pid.c @@ -36,6 +36,7 @@ #include #include #include +#include #define pid_hashfn(nr, ns) \ hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift) @@ -512,6 +513,12 @@ void __init pidhash_init(void) pid_hash = alloc_bootmem(pidhash_size * sizeof(*(pid_hash))); if (!pid_hash) panic("Could not alloc pidhash!\n"); + /* + * pid_hash contains references to allocated struct pid objects and it + * must be scanned by kmemleak to avoid false positives. + */ + kmemleak_alloc(pid_hash, pidhash_size * sizeof(*(pid_hash)), 0, + GFP_KERNEL); for (i = 0; i < pidhash_size; i++) INIT_HLIST_HEAD(&pid_hash[i]); } -- cgit v0.10.2