1 files changed, 314 insertions, 219 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 6dc4e5ef7a01..2404b59b3097 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -22,12 +22,13 @@
 #include <linux/hardirq.h>
 #include <linux/kthread.h>
 #include <linux/uaccess.h>
-#include <linux/kprobes.h>
 #include <linux/ftrace.h>
 #include <linux/sysctl.h>
+#include <linux/slab.h>
 #include <linux/ctype.h>
 #include <linux/list.h>
 #include <linux/hash.h>
+#include <linux/rcupdate.h>
 
 #include <trace/events/sched.h>
 
@@ -60,6 +61,13 @@ static int last_ftrace_enabled;
 /* Quick disabling of function tracer. */
 int function_trace_stop;
 
+/* List for set_ftrace_pid's pids. */
+LIST_HEAD(ftrace_pids);
+struct ftrace_pid {
+        struct list_head list;
+        struct pid *pid;
+};
+
 /*
  * ftrace_disabled is set when an anomaly is discovered.
  * ftrace_disabled is much stronger than ftrace_enabled.
@@ -78,18 +86,22 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
 
+/*
+ * Traverse the ftrace_list, invoking all entries.  The reason that we
+ * can use rcu_dereference_raw() is that elements removed from this list
+ * are simply leaked, so there is no need to interact with a grace-period
+ * mechanism.  The rcu_dereference_raw() calls are needed to handle
+ * concurrent insertions into the ftrace_list.
+ *
+ * Silly Alpha and silly pointer-speculation compiler optimizations!
+ */
 static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
 {
-        struct ftrace_ops *op = ftrace_list;
-
-        /* in case someone actually ports this to alpha! */
-        read_barrier_depends();
+        struct ftrace_ops *op = rcu_dereference_raw(ftrace_list); /*see above*/
 
         while (op != &ftrace_list_end) {
-                /* silly alpha */
-                read_barrier_depends();
                 op->func(ip, parent_ip);
-                op = op->next;
+                op = rcu_dereference_raw(op->next); /*see above*/
         };
 }
 
@@ -144,8 +156,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
          * the ops->next pointer is valid before another CPU sees
          * the ops pointer included into the ftrace_list.
          */
-        smp_wmb();
-        ftrace_list = ops;
+        rcu_assign_pointer(ftrace_list, ops);
 
         if (ftrace_enabled) {
                 ftrace_func_t func;
@@ -155,7 +166,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
                 else
                         func = ftrace_list_func;
 
-                if (ftrace_pid_trace) {
+                if (!list_empty(&ftrace_pids)) {
                         set_ftrace_pid_function(func);
                         func = ftrace_pid_func;
                 }
@@ -203,7 +214,7 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
                 if (ftrace_list->next == &ftrace_list_end) {
                         ftrace_func_t func = ftrace_list->func;
 
-                        if (ftrace_pid_trace) {
+                        if (!list_empty(&ftrace_pids)) {
                                 set_ftrace_pid_function(func);
                                 func = ftrace_pid_func;
                         }
@@ -231,7 +242,7 @@ static void ftrace_update_pid_func(void)
         func = __ftrace_trace_function;
 #endif
 
-        if (ftrace_pid_trace) {
+        if (!list_empty(&ftrace_pids)) {
                 set_ftrace_pid_function(func);
                 func = ftrace_pid_func;
         } else {
@@ -821,8 +832,6 @@ static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
 }
 #endif /* CONFIG_FUNCTION_PROFILER */
 
-/* set when tracing only a pid */
-struct pid *ftrace_pid_trace;
 static struct pid * const ftrace_swapper_pid = &init_struct_pid;
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -889,36 +898,6 @@ static struct dyn_ftrace *ftrace_free_records;
                 }                               \
         }
 
-#ifdef CONFIG_KPROBES
-
-static int frozen_record_count;
-
-static inline void freeze_record(struct dyn_ftrace *rec)
-{
-        if (!(rec->flags & FTRACE_FL_FROZEN)) {
-                rec->flags |= FTRACE_FL_FROZEN;
-                frozen_record_count++;
-        }
-}
-
-static inline void unfreeze_record(struct dyn_ftrace *rec)
-{
-        if (rec->flags & FTRACE_FL_FROZEN) {
-                rec->flags &= ~FTRACE_FL_FROZEN;
-                frozen_record_count--;
-        }
-}
-
-static inline int record_frozen(struct dyn_ftrace *rec)
-{
-        return rec->flags & FTRACE_FL_FROZEN;
-}
-#else
-# define freeze_record(rec)                     ({ 0; })
-# define unfreeze_record(rec)                   ({ 0; })
-# define record_frozen(rec)                     ({ 0; })
-#endif /* CONFIG_KPROBES */
-
 static void ftrace_free_rec(struct dyn_ftrace *rec)
 {
         rec->freelist = ftrace_free_records;
@@ -1016,6 +995,21 @@ static void ftrace_bug(int failed, unsigned long ip)
 }
 
 
+/* Return 1 if the address range is reserved for ftrace */
+int ftrace_text_reserved(void *start, void *end)
+{
+        struct dyn_ftrace *rec;
+        struct ftrace_page *pg;
+
+        do_for_each_ftrace_rec(pg, rec) {
+                if (rec->ip <= (unsigned long)end &&
+                    rec->ip + MCOUNT_INSN_SIZE > (unsigned long)start)
+                        return 1;
+        } while_for_each_ftrace_rec();
+        return 0;
+}
+
+
 static int
 __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
 {
@@ -1067,14 +1061,6 @@ static void ftrace_replace_code(int enable)
                     !(rec->flags & FTRACE_FL_CONVERTED))
                         continue;
 
-                /* ignore updates to this record's mcount site */
-                if (get_kprobe((void *)rec->ip)) {
-                        freeze_record(rec);
-                        continue;
-                } else {
-                        unfreeze_record(rec);
-                }
-
                 failed = __ftrace_replace_code(rec, enable);
                 if (failed) {
                         rec->flags |= FTRACE_FL_FAILED;
@@ -1261,12 +1247,34 @@ static int ftrace_update_code(struct module *mod)
                 ftrace_new_addrs = p->newlist;
                 p->flags = 0L;
 
-                /* convert record (i.e, patch mcount-call with NOP) */
-                if (ftrace_code_disable(mod, p)) {
-                        p->flags |= FTRACE_FL_CONVERTED;
-                        ftrace_update_cnt++;
-                } else
+                /*
+                 * Do the initial record convertion from mcount jump
+                 * to the NOP instructions.
+                 */
+                if (!ftrace_code_disable(mod, p)) {
                         ftrace_free_rec(p);
+                        continue;
+                }
+
+                p->flags |= FTRACE_FL_CONVERTED;
+                ftrace_update_cnt++;
+
+                /*
+                 * If the tracing is enabled, go ahead and enable the record.
+                 *
+                 * The reason not to enable the record immediatelly is the
+                 * inherent check of ftrace_make_nop/ftrace_make_call for
+                 * correct previous instructions.  Making first the NOP
+                 * conversion puts the module to the correct state, thus
+                 * passing the ftrace_make_call check.
+                 */
+                if (ftrace_start_up) {
+                        int failed = __ftrace_replace_code(p, 1);
+                        if (failed) {
+                                ftrace_bug(failed, p->ip);
+                                ftrace_free_rec(p);
+                        }
+                }
         }
 
         stop = ftrace_now(raw_smp_processor_id());
@@ -1656,64 +1664,10 @@ ftrace_regex_lseek(struct file *file, loff_t offset, int origin)
         return ret;
 }
 
-enum {
-        MATCH_FULL,
-        MATCH_FRONT_ONLY,
-        MATCH_MIDDLE_ONLY,
-        MATCH_END_ONLY,
-};
-
-/*
- * (static function - no need for kernel doc)
- *
- * Pass in a buffer containing a glob and this function will
- * set search to point to the search part of the buffer and
- * return the type of search it is (see enum above).
- * This does modify buff.
- *
- * Returns enum type.
- *  search returns the pointer to use for comparison.
- *  not returns 1 if buff started with a '!'
- *     0 otherwise.
- */
-static int
-ftrace_setup_glob(char *buff, int len, char **search, int *not)
-{
-        int type = MATCH_FULL;
-        int i;
-
-        if (buff[0] == '!') {
-                *not = 1;
-                buff++;
-                len--;
-        } else
-                *not = 0;
-
-        *search = buff;
-
-        for (i = 0; i < len; i++) {
-                if (buff[i] == '*') {
-                        if (!i) {
-                                *search = buff + 1;
-                                type = MATCH_END_ONLY;
-                        } else {
-                                if (type == MATCH_END_ONLY)
-                                        type = MATCH_MIDDLE_ONLY;
-                                else
-                                        type = MATCH_FRONT_ONLY;
-                                buff[i] = 0;
-                                break;
-                        }
-                }
-        }
-
-        return type;
-}
-
 static int ftrace_match(char *str, char *regex, int len, int type)
 {
         int matched = 0;
-        char *ptr;
+        int slen;
 
         switch (type) {
         case MATCH_FULL:
@@ -1729,8 +1683,8 @@ static int ftrace_match(char *str, char *regex, int len, int type)
                         matched = 1;
                 break;
         case MATCH_END_ONLY:
-                ptr = strstr(str, regex);
-                if (ptr && (ptr[len] == 0))
+                slen = strlen(str);
+                if (slen >= len && memcmp(str + slen - len, regex, len) == 0)
                         matched = 1;
                 break;
         }
@@ -1747,7 +1701,7 @@ ftrace_match_record(struct dyn_ftrace *rec, char *regex, int len, int type)
         return ftrace_match(str, regex, len, type);
 }
 
-static void ftrace_match_records(char *buff, int len, int enable)
+static int ftrace_match_records(char *buff, int len, int enable)
 {
         unsigned int search_len;
         struct ftrace_page *pg;
@@ -1756,9 +1710,10 @@ static void ftrace_match_records(char *buff, int len, int enable)
         char *search;
         int type;
         int not;
+        int found = 0;
 
         flag = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
-        type = ftrace_setup_glob(buff, len, &search, &not);
+        type = filter_parse_regex(buff, len, &search, &not);
 
         search_len = strlen(search);
 
@@ -1773,6 +1728,7 @@ static void ftrace_match_records(char *buff, int len, int enable)
                                 rec->flags &= ~flag;
                         else
                                 rec->flags |= flag;
+                        found = 1;
                 }
                 /*
                  * Only enable filtering if we have a function that
@@ -1782,6 +1738,8 @@ static void ftrace_match_records(char *buff, int len, int enable)
                         ftrace_filtered = 1;
         } while_for_each_ftrace_rec();
         mutex_unlock(&ftrace_lock);
+
+        return found;
 }
 
 static int
@@ -1803,7 +1761,7 @@ ftrace_match_module_record(struct dyn_ftrace *rec, char *mod,
                 return 1;
 }
 
-static void ftrace_match_module_records(char *buff, char *mod, int enable)
+static int ftrace_match_module_records(char *buff, char *mod, int enable)
 {
         unsigned search_len = 0;
         struct ftrace_page *pg;
@@ -1812,6 +1770,7 @@ static void ftrace_match_module_records(char *buff, char *mod, int enable)
         char *search = buff;
         unsigned long flag;
         int not = 0;
+        int found = 0;
 
         flag = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
 
@@ -1826,7 +1785,7 @@ static void ftrace_match_module_records(char *buff, char *mod, int enable)
         }
 
         if (strlen(buff)) {
-                type = ftrace_setup_glob(buff, strlen(buff), &search, &not);
+                type = filter_parse_regex(buff, strlen(buff), &search, &not);
                 search_len = strlen(search);
         }
 
@@ -1842,12 +1801,15 @@ static void ftrace_match_module_records(char *buff, char *mod, int enable)
                                 rec->flags &= ~flag;
                         else
                                 rec->flags |= flag;
+                        found = 1;
                 }
                 if (enable && (rec->flags & FTRACE_FL_FILTER))
                         ftrace_filtered = 1;
 
         } while_for_each_ftrace_rec();
         mutex_unlock(&ftrace_lock);
+
+        return found;
 }
 
 /*
@@ -1876,8 +1838,9 @@ ftrace_mod_callback(char *func, char *cmd, char *param, int enable)
         if (!strlen(mod))
                 return -EINVAL;
 
-        ftrace_match_module_records(func, mod, enable);
-        return 0;
+        if (ftrace_match_module_records(func, mod, enable))
+                return 0;
+        return -EINVAL;
 }
 
 static struct ftrace_func_command ftrace_mod_cmd = {
@@ -1991,7 +1954,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         int count = 0;
         char *search;
 
-        type = ftrace_setup_glob(glob, strlen(glob), &search, &not);
+        type = filter_parse_regex(glob, strlen(glob), &search, &not);
         len = strlen(search);
 
         /* we do not support '!' for function probes */
@@ -2068,7 +2031,7 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         else if (glob) {
                 int not;
 
-                type = ftrace_setup_glob(glob, strlen(glob), &search, &not);
+                type = filter_parse_regex(glob, strlen(glob), &search, &not);
                 len = strlen(search);
 
                 /* we do not support '!' for function probes */
@@ -2174,8 +2137,9 @@ static int ftrace_process_regex(char *buff, int len, int enable)
         func = strsep(&next, ":");
 
         if (!next) {
-                ftrace_match_records(func, len, enable);
-                return 0;
+                if (ftrace_match_records(func, len, enable))
+                        return 0;
+                return ret;
         }
 
         /* command found */
@@ -2221,10 +2185,9 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
             !trace_parser_cont(parser)) {
                 ret = ftrace_process_regex(parser->buffer,
                                            parser->idx, enable);
+                trace_parser_clear(parser);
                 if (ret)
                         goto out_unlock;
-
-                trace_parser_clear(parser);
         }
 
         ret = read;
@@ -2312,6 +2275,34 @@ static int __init set_ftrace_filter(char *str)
 }
 __setup("ftrace_filter=", set_ftrace_filter);
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
+static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);
+
+static int __init set_graph_function(char *str)
+{
+        strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
+        return 1;
+}
+__setup("ftrace_graph_filter=", set_graph_function);
+
+static void __init set_ftrace_early_graph(char *buf)
+{
+        int ret;
+        char *func;
+
+        while (buf) {
+                func = strsep(&buf, ",");
+                /* we allow only one expression at a time */
+                ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
+                                      func);
+                if (ret)
+                        printk(KERN_DEBUG "ftrace: function %s not "
+                                          "traceable\n", func);
+        }
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
 static void __init set_ftrace_early_filter(char *buf, int enable)
 {
         char *func;
@@ -2328,6 +2319,10 @@ static void __init set_ftrace_early_filters(void)
                 set_ftrace_early_filter(ftrace_filter_buf, 1);
         if (ftrace_notrace_buf[0])
                 set_ftrace_early_filter(ftrace_notrace_buf, 0);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+        if (ftrace_graph_buf[0])
+                set_ftrace_early_graph(ftrace_graph_buf);
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 }
 
 static int
@@ -2410,6 +2405,7 @@ static const struct file_operations ftrace_notrace_fops = {
 static DEFINE_MUTEX(graph_lock);
 
 int ftrace_graph_count;
+int ftrace_graph_filter_enabled;
 unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
 
 static void *
@@ -2432,7 +2428,7 @@ static void *g_start(struct seq_file *m, loff_t *pos)
         mutex_lock(&graph_lock);
 
         /* Nothing, tell g_show to print all functions are enabled */
-        if (!ftrace_graph_count && !*pos)
+        if (!ftrace_graph_filter_enabled && !*pos)
                 return (void *)1;
 
         return __g_next(m, pos);
@@ -2478,6 +2474,7 @@ ftrace_graph_open(struct inode *inode, struct file *file)
         mutex_lock(&graph_lock);
         if ((file->f_mode & FMODE_WRITE) &&
             (file->f_flags & O_TRUNC)) {
+                ftrace_graph_filter_enabled = 0;
                 ftrace_graph_count = 0;
                 memset(ftrace_graph_funcs, 0, sizeof(ftrace_graph_funcs));
         }
@@ -2503,7 +2500,7 @@ ftrace_set_func(unsigned long *array, int *idx, char *buffer)
         struct dyn_ftrace *rec;
         struct ftrace_page *pg;
         int search_len;
-        int found = 0;
+        int fail = 1;
         int type, not;
         char *search;
         bool exists;
@@ -2513,39 +2510,52 @@ ftrace_set_func(unsigned long *array, int *idx, char *buffer)
                 return -ENODEV;
 
         /* decode regex */
-        type = ftrace_setup_glob(buffer, strlen(buffer), &search, &not);
-        if (not)
-                return -EINVAL;
+        type = filter_parse_regex(buffer, strlen(buffer), &search, &not);
+        if (!not && *idx >= FTRACE_GRAPH_MAX_FUNCS)
+                return -EBUSY;
 
         search_len = strlen(search);
 
         mutex_lock(&ftrace_lock);
         do_for_each_ftrace_rec(pg, rec) {
 
-                if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
-                        break;
-
                 if (rec->flags & (FTRACE_FL_FAILED | FTRACE_FL_FREE))
                         continue;
 
                 if (ftrace_match_record(rec, search, search_len, type)) {
-                        /* ensure it is not already in the array */
+                        /* if it is in the array */
                         exists = false;
-                        for (i = 0; i < *idx; i++)
+                        for (i = 0; i < *idx; i++) {
                                 if (array[i] == rec->ip) {
                                         exists = true;
                                         break;
                                 }
-                        if (!exists) {
-                                array[(*idx)++] = rec->ip;
-                                found = 1;
+                        }
+
+                        if (!not) {
+                                fail = 0;
+                                if (!exists) {
+                                        array[(*idx)++] = rec->ip;
+                                        if (*idx >= FTRACE_GRAPH_MAX_FUNCS)
+                                                goto out;
+                                }
+                        } else {
+                                if (exists) {
+                                        array[i] = array[--(*idx)];
+                                        array[*idx] = 0;
+                                        fail = 0;
+                                }
                         }
                 }
         } while_for_each_ftrace_rec();
-
+out:
         mutex_unlock(&ftrace_lock);
 
-        return found ? 0 : -EINVAL;
+        if (fail)
+                return -EINVAL;
+
+        ftrace_graph_filter_enabled = 1;
+        return 0;
 }
 
 static ssize_t
@@ -2555,16 +2565,11 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
         struct trace_parser parser;
         ssize_t read, ret;
 
-        if (!cnt || cnt < 0)
+        if (!cnt)
                 return 0;
 
         mutex_lock(&graph_lock);
 
-        if (ftrace_graph_count >= FTRACE_GRAPH_MAX_FUNCS) {
-                ret = -EBUSY;
-                goto out_unlock;
-        }
-
         if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
                 ret = -ENOMEM;
                 goto out_unlock;
@@ -2624,7 +2629,7 @@ static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
         return 0;
 }
 
-static int ftrace_convert_nops(struct module *mod,
+static int ftrace_process_locs(struct module *mod,
                                unsigned long *start,
                                unsigned long *end)
 {
@@ -2684,7 +2689,7 @@ static void ftrace_init_module(struct module *mod,
 {
         if (ftrace_disabled || start == end)
                 return;
-        ftrace_convert_nops(mod, start, end);
+        ftrace_process_locs(mod, start, end);
 }
 
 static int ftrace_module_notify(struct notifier_block *self,
@@ -2745,7 +2750,7 @@ void __init ftrace_init(void)
 
         last_ftrace_enabled = ftrace_enabled = 1;
 
-        ret = ftrace_convert_nops(NULL,
+        ret = ftrace_process_locs(NULL,
                                   __start_mcount_loc,
                                   __stop_mcount_loc);
 
@@ -2778,23 +2783,6 @@ static inline void ftrace_startup_enable(int command) { }
 # define ftrace_shutdown_sysctl()       do { } while (0)
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
-static ssize_t
-ftrace_pid_read(struct file *file, char __user *ubuf,
-                       size_t cnt, loff_t *ppos)
-{
-        char buf[64];
-        int r;
-
-        if (ftrace_pid_trace == ftrace_swapper_pid)
-                r = sprintf(buf, "swapper tasks\n");
-        else if (ftrace_pid_trace)
-                r = sprintf(buf, "%u\n", pid_vnr(ftrace_pid_trace));
-        else
-                r = sprintf(buf, "no pid\n");
-
-        return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
-}
-
 static void clear_ftrace_swapper(void)
 {
         struct task_struct *p;
@@ -2845,14 +2833,12 @@ static void set_ftrace_pid(struct pid *pid)
         rcu_read_unlock();
 }
 
-static void clear_ftrace_pid_task(struct pid **pid)
+static void clear_ftrace_pid_task(struct pid *pid)
 {
-        if (*pid == ftrace_swapper_pid)
+        if (pid == ftrace_swapper_pid)
                 clear_ftrace_swapper();
         else
-                clear_ftrace_pid(*pid);
-
-        *pid = NULL;
+                clear_ftrace_pid(pid);
 }
 
 static void set_ftrace_pid_task(struct pid *pid)
@@ -2863,74 +2849,184 @@ static void set_ftrace_pid_task(struct pid *pid)
                 set_ftrace_pid(pid);
 }
 
-static ssize_t
-ftrace_pid_write(struct file *filp, const char __user *ubuf,
-                   size_t cnt, loff_t *ppos)
+static int ftrace_pid_add(int p)
 {
         struct pid *pid;
-        char buf[64];
-        long val;
-        int ret;
+        struct ftrace_pid *fpid;
+        int ret = -EINVAL;
 
-        if (cnt >= sizeof(buf))
-                return -EINVAL;
+        mutex_lock(&ftrace_lock);
 
-        if (copy_from_user(&buf, ubuf, cnt))
-                return -EFAULT;
+        if (!p)
+                pid = ftrace_swapper_pid;
+        else
+                pid = find_get_pid(p);
 
-        buf[cnt] = 0;
+        if (!pid)
+                goto out;
 
-        ret = strict_strtol(buf, 10, &val);
-        if (ret < 0)
-                return ret;
+        ret = 0;
 
-        mutex_lock(&ftrace_lock);
-        if (val < 0) {
-                /* disable pid tracing */
-                if (!ftrace_pid_trace)
-                        goto out;
+        list_for_each_entry(fpid, &ftrace_pids, list)
+                if (fpid->pid == pid)
+                        goto out_put;
 
-                clear_ftrace_pid_task(&ftrace_pid_trace);
+        ret = -ENOMEM;
 
-        } else {
-                /* swapper task is special */
-                if (!val) {
-                        pid = ftrace_swapper_pid;
-                        if (pid == ftrace_pid_trace)
-                                goto out;
-                } else {
-                        pid = find_get_pid(val);
+        fpid = kmalloc(sizeof(*fpid), GFP_KERNEL);
+        if (!fpid)
+                goto out_put;
 
-                        if (pid == ftrace_pid_trace) {
-                                put_pid(pid);
-                                goto out;
-                        }
-                }
+        list_add(&fpid->list, &ftrace_pids);
+        fpid->pid = pid;
 
-                if (ftrace_pid_trace)
-                        clear_ftrace_pid_task(&ftrace_pid_trace);
+        set_ftrace_pid_task(pid);
 
-                if (!pid)
-                        goto out;
+        ftrace_update_pid_func();
+        ftrace_startup_enable(0);
+
+        mutex_unlock(&ftrace_lock);
+        return 0;
+
+out_put:
+        if (pid != ftrace_swapper_pid)
+                put_pid(pid);
+
+out:
+        mutex_unlock(&ftrace_lock);
+        return ret;
+}
+
+static void ftrace_pid_reset(void)
+{
+        struct ftrace_pid *fpid, *safe;
+
+        mutex_lock(&ftrace_lock);
+        list_for_each_entry_safe(fpid, safe, &ftrace_pids, list) {
+                struct pid *pid = fpid->pid;
 
-                ftrace_pid_trace = pid;
+                clear_ftrace_pid_task(pid);
 
-                set_ftrace_pid_task(ftrace_pid_trace);
+                list_del(&fpid->list);
+                kfree(fpid);
         }
 
-        /* update the function call */
         ftrace_update_pid_func();
         ftrace_startup_enable(0);
 
- out:
         mutex_unlock(&ftrace_lock);
+}
 
-        return cnt;
+static void *fpid_start(struct seq_file *m, loff_t *pos)
+{
+        mutex_lock(&ftrace_lock);
+
+        if (list_empty(&ftrace_pids) && (!*pos))
+                return (void *) 1;
+
+        return seq_list_start(&ftrace_pids, *pos);
+}
+
+static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
+{
+        if (v == (void *)1)
+                return NULL;
+
+        return seq_list_next(v, &ftrace_pids, pos);
+}
+
+static void fpid_stop(struct seq_file *m, void *p)
+{
+        mutex_unlock(&ftrace_lock);
+}
+
+static int fpid_show(struct seq_file *m, void *v)
+{
+        const struct ftrace_pid *fpid = list_entry(v, struct ftrace_pid, list);
+
+        if (v == (void *)1) {
+                seq_printf(m, "no pid\n");
+                return 0;
+        }
+
+        if (fpid->pid == ftrace_swapper_pid)
+                seq_printf(m, "swapper tasks\n");
+        else
+                seq_printf(m, "%u\n", pid_vnr(fpid->pid));
+
+        return 0;
+}
+
+static const struct seq_operations ftrace_pid_sops = {
+        .start = fpid_start,
+        .next = fpid_next,
+        .stop = fpid_stop,
+        .show = fpid_show,
+};
+
+static int
+ftrace_pid_open(struct inode *inode, struct file *file)
+{
+        int ret = 0;
+
+        if ((file->f_mode & FMODE_WRITE) &&
+            (file->f_flags & O_TRUNC))
+                ftrace_pid_reset();
+
+        if (file->f_mode & FMODE_READ)
+                ret = seq_open(file, &ftrace_pid_sops);
+
+        return ret;
+}
+
+static ssize_t
+ftrace_pid_write(struct file *filp, const char __user *ubuf,
+                   size_t cnt, loff_t *ppos)
+{
+        char buf[64], *tmp;
+        long val;
+        int ret;
+
+        if (cnt >= sizeof(buf))
+                return -EINVAL;
+
+        if (copy_from_user(&buf, ubuf, cnt))
+                return -EFAULT;
+
+        buf[cnt] = 0;
+
+        /*
+         * Allow "echo > set_ftrace_pid" or "echo -n '' > set_ftrace_pid"
+         * to clean the filter quietly.
+         */
+        tmp = strstrip(buf);
+        if (strlen(tmp) == 0)
+                return 1;
+
+        ret = strict_strtol(tmp, 10, &val);
+        if (ret < 0)
+                return ret;
+
+        ret = ftrace_pid_add(val);
+
+        return ret ? ret : cnt;
+}
+
+static int
+ftrace_pid_release(struct inode *inode, struct file *file)
+{
+        if (file->f_mode & FMODE_READ)
+                seq_release(inode, file);
+
+        return 0;
 }
 
 static const struct file_operations ftrace_pid_fops = {
-        .read = ftrace_pid_read,
-        .write = ftrace_pid_write,
+        .open           = ftrace_pid_open,
+        .write          = ftrace_pid_write,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = ftrace_pid_release,
 };
 
 static __init int ftrace_init_debugfs(void)
@@ -3258,6 +3354,7 @@ void ftrace_graph_init_task(struct task_struct *t)
 {
         /* Make sure we do not use the parent ret_stack */
         t->ret_stack = NULL;
+        t->curr_ret_stack = -1;
 
         if (ftrace_graph_active) {
                 struct ftrace_ret_stack *ret_stack;
@@ -3267,7 +3364,6 @@ void ftrace_graph_init_task(struct task_struct *t)
                                 GFP_KERNEL);
                 if (!ret_stack)
                         return;
-                t->curr_ret_stack = -1;
                 atomic_set(&t->tracing_graph_pause, 0);
                 atomic_set(&t->trace_overrun, 0);
                 t->ftrace_timestamp = 0;
@@ -3293,4 +3389,3 @@ void ftrace_graph_stop(void)
         ftrace_stop();
 }
 #endif
-