6 files changed, 366 insertions, 39 deletions

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index b8378fad29a3..9cbf7761f498 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -3,6 +3,9 @@
 #  select HAVE_FUNCTION_TRACER:
 #
 
+config USER_STACKTRACE_SUPPORT
+        bool
+
 config NOP_TRACER
         bool
 
@@ -166,14 +169,29 @@ config TRACE_BRANCH_PROFILING
           This tracer profiles all the the likely and unlikely macros
           in the kernel. It will display the results in:
 
-          /debugfs/tracing/profile_likely
-          /debugfs/tracing/profile_unlikely
+          /debugfs/tracing/profile_annotated_branch
 
           Note: this will add a significant overhead, only turn this
           on if you need to profile the system's use of these macros.
 
           Say N if unsure.
 
+config PROFILE_ALL_BRANCHES
+        bool "Profile all if conditionals"
+        depends on TRACE_BRANCH_PROFILING
+        help
+          This tracer profiles all branch conditions. Every if ()
+          taken in the kernel is recorded whether it hit or miss.
+          The results will be displayed in:
+
+          /debugfs/tracing/profile_branch
+
+          This configuration, when enabled, will impose a great overhead
+          on the system. This should only be enabled when the system
+          is to be analyzed
+
+          Say N if unsure.
+
 config TRACING_BRANCHES
         bool
         help
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f212da486689..53042f118f23 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1498,10 +1498,77 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 #ifdef CONFIG_FUNCTION_RET_TRACER
 
+static atomic_t ftrace_retfunc_active;
+
 /* The callback that hooks the return of a function */
 trace_function_return_t ftrace_function_return =
                         (trace_function_return_t)ftrace_stub;
 
+
+/* Try to assign a return stack array on FTRACE_RETSTACK_ALLOC_SIZE tasks. */
+static int alloc_retstack_tasklist(struct ftrace_ret_stack **ret_stack_list)
+{
+        int i;
+        int ret = 0;
+        unsigned long flags;
+        int start = 0, end = FTRACE_RETSTACK_ALLOC_SIZE;
+        struct task_struct *g, *t;
+
+        for (i = 0; i < FTRACE_RETSTACK_ALLOC_SIZE; i++) {
+                ret_stack_list[i] = kmalloc(FTRACE_RETFUNC_DEPTH
+                                        * sizeof(struct ftrace_ret_stack),
+                                        GFP_KERNEL);
+                if (!ret_stack_list[i]) {
+                        start = 0;
+                        end = i;
+                        ret = -ENOMEM;
+                        goto free;
+                }
+        }
+
+        read_lock_irqsave(&tasklist_lock, flags);
+        do_each_thread(g, t) {
+                if (start == end) {
+                        ret = -EAGAIN;
+                        goto unlock;
+                }
+
+                if (t->ret_stack == NULL) {
+                        t->ret_stack = ret_stack_list[start++];
+                        t->curr_ret_stack = -1;
+                        atomic_set(&t->trace_overrun, 0);
+                }
+        } while_each_thread(g, t);
+
+unlock:
+        read_unlock_irqrestore(&tasklist_lock, flags);
+free:
+        for (i = start; i < end; i++)
+                kfree(ret_stack_list[i]);
+        return ret;
+}
+
+/* Allocate a return stack for each task */
+static int start_return_tracing(void)
+{
+        struct ftrace_ret_stack **ret_stack_list;
+        int ret;
+
+        ret_stack_list = kmalloc(FTRACE_RETSTACK_ALLOC_SIZE *
+                                sizeof(struct ftrace_ret_stack *),
+                                GFP_KERNEL);
+
+        if (!ret_stack_list)
+                return -ENOMEM;
+
+        do {
+                ret = alloc_retstack_tasklist(ret_stack_list);
+        } while (ret == -EAGAIN);
+
+        kfree(ret_stack_list);
+        return ret;
+}
+
 int register_ftrace_return(trace_function_return_t func)
 {
         int ret = 0;
@@ -1516,7 +1583,12 @@ int register_ftrace_return(trace_function_return_t func)
                 ret = -EBUSY;
                 goto out;
         }
-
+        atomic_inc(&ftrace_retfunc_active);
+        ret = start_return_tracing();
+        if (ret) {
+                atomic_dec(&ftrace_retfunc_active);
+                goto out;
+        }
         ftrace_tracing_type = FTRACE_TYPE_RETURN;
         ftrace_function_return = func;
         ftrace_startup();
@@ -1530,6 +1602,7 @@ void unregister_ftrace_return(void)
 {
         mutex_lock(&ftrace_sysctl_lock);
 
+        atomic_dec(&ftrace_retfunc_active);
         ftrace_function_return = (trace_function_return_t)ftrace_stub;
         ftrace_shutdown();
         /* Restore normal tracing type */
@@ -1537,6 +1610,32 @@ void unregister_ftrace_return(void)
 
         mutex_unlock(&ftrace_sysctl_lock);
 }
+
+/* Allocate a return stack for newly created task */
+void ftrace_retfunc_init_task(struct task_struct *t)
+{
+        if (atomic_read(&ftrace_retfunc_active)) {
+                t->ret_stack = kmalloc(FTRACE_RETFUNC_DEPTH
+                                * sizeof(struct ftrace_ret_stack),
+                                GFP_KERNEL);
+                if (!t->ret_stack)
+                        return;
+                t->curr_ret_stack = -1;
+                atomic_set(&t->trace_overrun, 0);
+        } else
+                t->ret_stack = NULL;
+}
+
+void ftrace_retfunc_exit_task(struct task_struct *t)
+{
+        struct ftrace_ret_stack *ret_stack = t->ret_stack;
+
+        t->ret_stack = NULL;
+        /* NULL must become visible to IRQs before we free it: */
+        barrier();
+
+        kfree(ret_stack);
+}
 #endif
 
 
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4ee6f0375222..a45b59e53fbc 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -30,6 +30,7 @@
 #include <linux/gfp.h>
 #include <linux/fs.h>
 #include <linux/kprobes.h>
+#include <linux/seq_file.h>
 #include <linux/writeback.h>
 
 #include <linux/stacktrace.h>
@@ -275,6 +276,8 @@ static const char *trace_options[] = {
         "ftrace_preempt",
         "branch",
         "annotate",
+        "userstacktrace",
+        "sym-userobj",
         NULL
 };
 
@@ -421,6 +424,28 @@ trace_seq_putmem_hex(struct trace_seq *s, void *mem, size_t len)
         return trace_seq_putmem(s, hex, j);
 }
 
+static int
+trace_seq_path(struct trace_seq *s, struct path *path)
+{
+        unsigned char *p;
+
+        if (s->len >= (PAGE_SIZE - 1))
+                return 0;
+        p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len);
+        if (!IS_ERR(p)) {
+                p = mangle_path(s->buffer + s->len, p, "\n");
+                if (p) {
+                        s->len = p - s->buffer;
+                        return 1;
+                }
+        } else {
+                s->buffer[s->len++] = '?';
+                return 1;
+        }
+
+        return 0;
+}
+
 static void
 trace_seq_reset(struct trace_seq *s)
 {
@@ -661,6 +686,21 @@ static int trace_stop_count;
 static DEFINE_SPINLOCK(tracing_start_lock);
 
 /**
+ * ftrace_off_permanent - disable all ftrace code permanently
+ *
+ * This should only be called when a serious anomally has
+ * been detected.  This will turn off the function tracing,
+ * ring buffers, and other tracing utilites. It takes no
+ * locks and can be called from any context.
+ */
+void ftrace_off_permanent(void)
+{
+        tracing_disabled = 1;
+        ftrace_stop();
+        tracing_off_permanent();
+}
+
+/**
  * tracing_start - quick start of the tracer
  *
  * If tracing is enabled but was stopped by tracing_stop,
@@ -801,6 +841,7 @@ tracing_generic_entry_update(struct trace_entry *entry, unsigned long flags,
 
         entry->preempt_count            = pc & 0xff;
         entry->pid                      = (tsk) ? tsk->pid : 0;
+        entry->tgid                     = (tsk) ? tsk->tgid : 0;
         entry->flags =
 #ifdef CONFIG_TRACE_IRQFLAGS_SUPPORT
                 (irqs_disabled_flags(flags) ? TRACE_FLAG_IRQS_OFF : 0) |
@@ -918,6 +959,44 @@ void __trace_stack(struct trace_array *tr,
         ftrace_trace_stack(tr, data, flags, skip, preempt_count());
 }
 
+static void ftrace_trace_userstack(struct trace_array *tr,
+                   struct trace_array_cpu *data,
+                   unsigned long flags, int pc)
+{
+        struct ring_buffer_event *event;
+        struct userstack_entry *entry;
+        struct stack_trace trace;
+        unsigned long irq_flags;
+
+        if (!(trace_flags & TRACE_ITER_USERSTACKTRACE))
+                return;
+
+        event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
+                                         &irq_flags);
+        if (!event)
+                return;
+        entry   = ring_buffer_event_data(event);
+        tracing_generic_entry_update(&entry->ent, flags, pc);
+        entry->ent.type         = TRACE_USER_STACK;
+
+        memset(&entry->caller, 0, sizeof(entry->caller));
+
+        trace.nr_entries        = 0;
+        trace.max_entries       = FTRACE_STACK_ENTRIES;
+        trace.skip              = 0;
+        trace.entries           = entry->caller;
+
+        save_stack_trace_user(&trace);
+        ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
+}
+
+void __trace_userstack(struct trace_array *tr,
+                   struct trace_array_cpu *data,
+                   unsigned long flags)
+{
+        ftrace_trace_userstack(tr, data, flags, preempt_count());
+}
+
 static void
 ftrace_trace_special(void *__tr, void *__data,
                      unsigned long arg1, unsigned long arg2, unsigned long arg3,
@@ -941,6 +1020,7 @@ ftrace_trace_special(void *__tr, void *__data,
         entry->arg3                     = arg3;
         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
         ftrace_trace_stack(tr, data, irq_flags, 4, pc);
+        ftrace_trace_userstack(tr, data, irq_flags, pc);
 
         trace_wake_up();
 }
@@ -979,6 +1059,7 @@ tracing_sched_switch_trace(struct trace_array *tr,
         entry->next_cpu = task_cpu(next);
         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
         ftrace_trace_stack(tr, data, flags, 5, pc);
+        ftrace_trace_userstack(tr, data, flags, pc);
 }
 
 void
@@ -1008,6 +1089,7 @@ tracing_sched_wakeup_trace(struct trace_array *tr,
         entry->next_cpu                 = task_cpu(wakee);
         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
         ftrace_trace_stack(tr, data, flags, 6, pc);
+        ftrace_trace_userstack(tr, data, flags, pc);
 
         trace_wake_up();
 }
@@ -1387,6 +1469,78 @@ seq_print_ip_sym(struct trace_seq *s, unsigned long ip, unsigned long sym_flags)
         return ret;
 }
 
+static inline int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm,
+                                    unsigned long ip, unsigned long sym_flags)
+{
+        struct file *file = NULL;
+        unsigned long vmstart = 0;
+        int ret = 1;
+
+        if (mm) {
+                const struct vm_area_struct *vma;
+
+                down_read(&mm->mmap_sem);
+                vma = find_vma(mm, ip);
+                if (vma) {
+                        file = vma->vm_file;
+                        vmstart = vma->vm_start;
+                }
+                if (file) {
+                        ret = trace_seq_path(s, &file->f_path);
+                        if (ret)
+                                ret = trace_seq_printf(s, "[+0x%lx]", ip - vmstart);
+                }
+                up_read(&mm->mmap_sem);
+        }
+        if (ret && ((sym_flags & TRACE_ITER_SYM_ADDR) || !file))
+                ret = trace_seq_printf(s, " <" IP_FMT ">", ip);
+        return ret;
+}
+
+static int
+seq_print_userip_objs(const struct userstack_entry *entry, struct trace_seq *s,
+                      unsigned long sym_flags)
+{
+        struct mm_struct *mm = NULL;
+        int ret = 1;
+        unsigned int i;
+
+        if (trace_flags & TRACE_ITER_SYM_USEROBJ) {
+                struct task_struct *task;
+                /*
+                 * we do the lookup on the thread group leader,
+                 * since individual threads might have already quit!
+                 */
+                rcu_read_lock();
+                task = find_task_by_vpid(entry->ent.tgid);
+                if (task)
+                        mm = get_task_mm(task);
+                rcu_read_unlock();
+        }
+
+        for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
+                unsigned long ip = entry->caller[i];
+
+                if (ip == ULONG_MAX || !ret)
+                        break;
+                if (i && ret)
+                        ret = trace_seq_puts(s, " <- ");
+                if (!ip) {
+                        if (ret)
+                                ret = trace_seq_puts(s, "??");
+                        continue;
+                }
+                if (!ret)
+                        break;
+                if (ret)
+                        ret = seq_print_user_ip(s, mm, ip, sym_flags);
+        }
+
+        if (mm)
+                mmput(mm);
+        return ret;
+}
+
 static void print_lat_help_header(struct seq_file *m)
 {
         seq_puts(m, "#                  _------=> CPU#            \n");
@@ -1702,6 +1856,15 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
                                  field->line);
                 break;
         }
+        case TRACE_USER_STACK: {
+                struct userstack_entry *field;
+
+                trace_assign_type(field, entry);
+
+                seq_print_userip_objs(field, s, sym_flags);
+                trace_seq_putc(s, '\n');
+                break;
+        }
         default:
                 trace_seq_printf(s, "Unknown type %d\n", entry->type);
         }
@@ -1853,6 +2016,19 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
                                  field->line);
                 break;
         }
+        case TRACE_USER_STACK: {
+                struct userstack_entry *field;
+
+                trace_assign_type(field, entry);
+
+                ret = seq_print_userip_objs(field, s, sym_flags);
+                if (!ret)
+                        return TRACE_TYPE_PARTIAL_LINE;
+                ret = trace_seq_putc(s, '\n');
+                if (!ret)
+                        return TRACE_TYPE_PARTIAL_LINE;
+                break;
+        }
         }
         return TRACE_TYPE_HANDLED;
 }
@@ -1912,6 +2088,7 @@ static enum print_line_t print_raw_fmt(struct trace_iterator *iter)
                 break;
         }
         case TRACE_SPECIAL:
+        case TRACE_USER_STACK:
         case TRACE_STACK: {
                 struct special_entry *field;
 
@@ -2000,6 +2177,7 @@ static enum print_line_t print_hex_fmt(struct trace_iterator *iter)
                 break;
         }
         case TRACE_SPECIAL:
+        case TRACE_USER_STACK:
         case TRACE_STACK: {
                 struct special_entry *field;
 
@@ -2054,6 +2232,7 @@ static enum print_line_t print_bin_fmt(struct trace_iterator *iter)
                 break;
         }
         case TRACE_SPECIAL:
+        case TRACE_USER_STACK:
         case TRACE_STACK: {
                 struct special_entry *field;
 
@@ -3488,6 +3667,9 @@ void ftrace_dump(void)
                 atomic_inc(&global_trace.data[cpu]->disabled);
         }
 
+        /* don't look at user memory in panic mode */
+        trace_flags &= ~TRACE_ITER_SYM_USEROBJ;
+
         printk(KERN_TRACE "Dumping ftrace buffer:\n");
 
         iter.tr = &global_trace;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 2cb12fd98f6b..28c15c2ebc22 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -26,6 +26,7 @@ enum trace_type {
         TRACE_BOOT_CALL,
         TRACE_BOOT_RET,
         TRACE_FN_RET,
+        TRACE_USER_STACK,
 
         __TRACE_LAST_TYPE
 };
@@ -42,6 +43,7 @@ struct trace_entry {
         unsigned char           flags;
         unsigned char           preempt_count;
         int                     pid;
+        int                     tgid;
 };
 
 /*
@@ -99,6 +101,11 @@ struct stack_entry {
         unsigned long           caller[FTRACE_STACK_ENTRIES];
 };
 
+struct userstack_entry {
+        struct trace_entry      ent;
+        unsigned long           caller[FTRACE_STACK_ENTRIES];
+};
+
 /*
  * ftrace_printk entry:
  */
@@ -240,6 +247,7 @@ extern void __ftrace_bad_type(void);
                 IF_ASSIGN(var, ent, struct ctx_switch_entry, 0);        \
                 IF_ASSIGN(var, ent, struct trace_field_cont, TRACE_CONT); \
                 IF_ASSIGN(var, ent, struct stack_entry, TRACE_STACK);   \
+                IF_ASSIGN(var, ent, struct userstack_entry, TRACE_USER_STACK);\
                 IF_ASSIGN(var, ent, struct print_entry, TRACE_PRINT);   \
                 IF_ASSIGN(var, ent, struct special_entry, 0);           \
                 IF_ASSIGN(var, ent, struct trace_mmiotrace_rw,          \
@@ -500,6 +508,8 @@ enum trace_iterator_flags {
         TRACE_ITER_PREEMPTONLY          = 0x800,
         TRACE_ITER_BRANCH               = 0x1000,
         TRACE_ITER_ANNOTATE             = 0x2000,
+        TRACE_ITER_USERSTACKTRACE       = 0x4000,
+        TRACE_ITER_SYM_USEROBJ          = 0x8000
 };
 
 /*
diff --git a/kernel/trace/trace_branch.c b/kernel/trace/trace_branch.c
index 23f9b02ce967..877ee88e6a74 100644
--- a/kernel/trace/trace_branch.c
+++ b/kernel/trace/trace_branch.c
@@ -185,12 +185,13 @@ EXPORT_SYMBOL(ftrace_likely_update);
 struct ftrace_pointer {
         void            *start;
         void            *stop;
+        int             hit;
 };
 
 static void *
 t_next(struct seq_file *m, void *v, loff_t *pos)
 {
-        struct ftrace_pointer *f = m->private;
+        const struct ftrace_pointer *f = m->private;
         struct ftrace_branch_data *p = v;
 
         (*pos)++;
@@ -223,13 +224,17 @@ static void t_stop(struct seq_file *m, void *p)
 
 static int t_show(struct seq_file *m, void *v)
 {
+        const struct ftrace_pointer *fp = m->private;
         struct ftrace_branch_data *p = v;
         const char *f;
-        unsigned long percent;
+        long percent;
 
         if (v == (void *)1) {
-                seq_printf(m, " correct incorrect  %% "
-                              "       Function                "
+                if (fp->hit)
+                        seq_printf(m, "   miss      hit    %% ");
+                else
+                        seq_printf(m, " correct incorrect  %% ");
+                seq_printf(m, "       Function                "
                               "  File              Line\n"
                               " ------- ---------  - "
                               "       --------                "
@@ -243,13 +248,20 @@ static int t_show(struct seq_file *m, void *v)
                 f--;
         f++;
 
+        /*
+         * The miss is overlayed on correct, and hit on incorrect.
+         */
         if (p->correct) {
                 percent = p->incorrect * 100;
                 percent /= p->correct + p->incorrect;
         } else
-                percent = p->incorrect ? 100 : 0;
+                percent = p->incorrect ? 100 : -1;
 
-        seq_printf(m, "%8lu %8lu %3lu ", p->correct, p->incorrect, percent);
+        seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
+        if (percent < 0)
+                seq_printf(m, "  X ");
+        else
+                seq_printf(m, "%3ld ", percent);
         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
         return 0;
 }
@@ -261,7 +273,7 @@ static struct seq_operations tracing_likely_seq_ops = {
         .show           = t_show,
 };
 
-static int tracing_likely_open(struct inode *inode, struct file *file)
+static int tracing_branch_open(struct inode *inode, struct file *file)
 {
         int ret;
 
@@ -274,25 +286,30 @@ static int tracing_likely_open(struct inode *inode, struct file *file)
         return ret;
 }
 
-static struct file_operations tracing_likely_fops = {
-        .open           = tracing_likely_open,
+static const struct file_operations tracing_branch_fops = {
+        .open           = tracing_branch_open,
         .read           = seq_read,
         .llseek         = seq_lseek,
 };
 
-extern unsigned long __start_likely_profile[];
-extern unsigned long __stop_likely_profile[];
-extern unsigned long __start_unlikely_profile[];
-extern unsigned long __stop_unlikely_profile[];
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+extern unsigned long __start_branch_profile[];
+extern unsigned long __stop_branch_profile[];
 
-static struct ftrace_pointer ftrace_likely_pos = {
-        .start                  = __start_likely_profile,
-        .stop                   = __stop_likely_profile,
+static const struct ftrace_pointer ftrace_branch_pos = {
+        .start                  = __start_branch_profile,
+        .stop                   = __stop_branch_profile,
+        .hit                    = 1,
 };
 
-static struct ftrace_pointer ftrace_unlikely_pos = {
-        .start                  = __start_unlikely_profile,
-        .stop                   = __stop_unlikely_profile,
+#endif /* CONFIG_PROFILE_ALL_BRANCHES */
+
+extern unsigned long __start_annotated_branch_profile[];
+extern unsigned long __stop_annotated_branch_profile[];
+
+static const struct ftrace_pointer ftrace_annotated_branch_pos = {
+        .start                  = __start_annotated_branch_profile,
+        .stop                   = __stop_annotated_branch_profile,
 };
 
 static __init int ftrace_branch_init(void)
@@ -302,18 +319,21 @@ static __init int ftrace_branch_init(void)
 
         d_tracer = tracing_init_dentry();
 
-        entry = debugfs_create_file("profile_likely", 0444, d_tracer,
-                                    &ftrace_likely_pos,
-                                    &tracing_likely_fops);
+        entry = debugfs_create_file("profile_annotated_branch", 0444, d_tracer,
+                                    (void *)&ftrace_annotated_branch_pos,
+                                    &tracing_branch_fops);
         if (!entry)
-                pr_warning("Could not create debugfs 'profile_likely' entry\n");
+                pr_warning("Could not create debugfs "
+                           "'profile_annotatet_branch' entry\n");
 
-        entry = debugfs_create_file("profile_unlikely", 0444, d_tracer,
-                                    &ftrace_unlikely_pos,
-                                    &tracing_likely_fops);
+#ifdef CONFIG_PROFILE_ALL_BRANCHES
+        entry = debugfs_create_file("profile_branch", 0444, d_tracer,
+                                    (void *)&ftrace_branch_pos,
+                                    &tracing_branch_fops);
         if (!entry)
                 pr_warning("Could not create debugfs"
-                           " 'profile_unlikely' entry\n");
+                           " 'profile_branch' entry\n");
+#endif
 
         return 0;
 }
diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 433d650eda9f..2a98a206acc2 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -18,12 +18,14 @@ struct header_iter {
 
 static struct trace_array *mmio_trace_array;
 static bool overrun_detected;
+static unsigned long prev_overruns;
 
 static void mmio_reset_data(struct trace_array *tr)
 {
         int cpu;
 
         overrun_detected = false;
+        prev_overruns = 0;
         tr->time_start = ftrace_now(tr->cpu);
 
         for_each_online_cpu(cpu)
@@ -123,16 +125,12 @@ static void mmio_close(struct trace_iterator *iter)
 
 static unsigned long count_overruns(struct trace_iterator *iter)
 {
-        int cpu;
         unsigned long cnt = 0;
-/* FIXME: */
-#if 0
-        for_each_online_cpu(cpu) {
-                cnt += iter->overrun[cpu];
-                iter->overrun[cpu] = 0;
-        }
-#endif
-        (void)cpu;
+        unsigned long over = ring_buffer_overruns(iter->tr->buffer);
+
+        if (over > prev_overruns)
+                cnt = over - prev_overruns;
+        prev_overruns = over;
         return cnt;
 }