1 files changed, 307 insertions, 296 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8c804e24f96f..b10c0d90a6ff 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -60,6 +60,13 @@ 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.
@@ -78,6 +85,10 @@ 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;
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);
+#endif
+
 static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
 {
         struct ftrace_ops *op = ftrace_list;
@@ -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;
                         }
@@ -225,9 +236,13 @@ static void ftrace_update_pid_func(void)
         if (ftrace_trace_function == ftrace_stub)
                 return;
 
+#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
         func = ftrace_trace_function;
+#else
+        func = __ftrace_trace_function;
+#endif
 
-        if (ftrace_pid_trace) {
+        if (!list_empty(&ftrace_pids)) {
                 set_ftrace_pid_function(func);
                 func = ftrace_pid_func;
         } else {
@@ -817,8 +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
@@ -1074,14 +1087,9 @@ static void ftrace_replace_code(int enable)
                 failed = __ftrace_replace_code(rec, enable);
                 if (failed) {
                         rec->flags |= FTRACE_FL_FAILED;
-                        if ((system_state == SYSTEM_BOOTING) ||
-                            !core_kernel_text(rec->ip)) {
-                                ftrace_free_rec(rec);
-                                } else {
-                                ftrace_bug(failed, rec->ip);
-                                        /* Stop processing */
-                                        return;
-                                }
+                        ftrace_bug(failed, rec->ip);
+                        /* Stop processing */
+                        return;
                 }
         } while_for_each_ftrace_rec();
 }
@@ -1262,12 +1270,34 @@ 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());
@@ -1323,11 +1353,10 @@ static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
 
 enum {
         FTRACE_ITER_FILTER      = (1 << 0),
-        FTRACE_ITER_CONT        = (1 << 1),
-        FTRACE_ITER_NOTRACE     = (1 << 2),
-        FTRACE_ITER_FAILURES    = (1 << 3),
-        FTRACE_ITER_PRINTALL    = (1 << 4),
-        FTRACE_ITER_HASH        = (1 << 5),
+        FTRACE_ITER_NOTRACE     = (1 << 1),
+        FTRACE_ITER_FAILURES    = (1 << 2),
+        FTRACE_ITER_PRINTALL    = (1 << 3),
+        FTRACE_ITER_HASH        = (1 << 4),
 };
 
 #define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
@@ -1337,8 +1366,7 @@ struct ftrace_iterator {
         int                     hidx;
         int                     idx;
         unsigned                flags;
-        unsigned char           buffer[FTRACE_BUFF_MAX+1];
-        unsigned                buffer_idx;
+        struct trace_parser     parser;
 };
 
 static void *
@@ -1407,7 +1435,7 @@ static int t_hash_show(struct seq_file *m, void *v)
         if (rec->ops->print)
                 return rec->ops->print(m, rec->ip, rec->ops, rec->data);
 
-        seq_printf(m, "%pf:%pf", (void *)rec->ip, (void *)rec->ops->func);
+        seq_printf(m, "%ps:%ps", (void *)rec->ip, (void *)rec->ops->func);
 
         if (rec->data)
                 seq_printf(m, ":%p", rec->data);
@@ -1517,12 +1545,12 @@ static int t_show(struct seq_file *m, void *v)
         if (!rec)
                 return 0;
 
-        seq_printf(m, "%pf\n", (void *)rec->ip);
+        seq_printf(m, "%ps\n", (void *)rec->ip);
 
         return 0;
 }
 
-static struct seq_operations show_ftrace_seq_ops = {
+static const struct seq_operations show_ftrace_seq_ops = {
         .start = t_start,
         .next = t_next,
         .stop = t_stop,
@@ -1604,6 +1632,11 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
         if (!iter)
                 return -ENOMEM;
 
+        if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) {
+                kfree(iter);
+                return -ENOMEM;
+        }
+
         mutex_lock(&ftrace_regex_lock);
         if ((file->f_mode & FMODE_WRITE) &&
             (file->f_flags & O_TRUNC))
@@ -1618,8 +1651,10 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
                 if (!ret) {
                         struct seq_file *m = file->private_data;
                         m->private = iter;
-                } else
+                } else {
+                        trace_parser_put(&iter->parser);
                         kfree(iter);
+                }
         } else
                 file->private_data = iter;
         mutex_unlock(&ftrace_regex_lock);
@@ -1652,60 +1687,6 @@ 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;
@@ -1754,7 +1735,7 @@ static void ftrace_match_records(char *buff, int len, int enable)
         int not;
 
         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);
 
@@ -1822,7 +1803,7 @@ 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);
         }
 
@@ -1987,7 +1968,7 @@ 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 */
@@ -2059,12 +2040,12 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
         int i, len = 0;
         char *search;
 
-        if (glob && (strcmp(glob, "*") || !strlen(glob)))
+        if (glob && (strcmp(glob, "*") == 0 || !strlen(glob)))
                 glob = NULL;
-        else {
+        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 */
@@ -2196,11 +2177,10 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
                    size_t cnt, loff_t *ppos, int enable)
 {
         struct ftrace_iterator *iter;
-        char ch;
-        size_t read = 0;
-        ssize_t ret;
+        struct trace_parser *parser;
+        ssize_t ret, read;
 
-        if (!cnt || cnt < 0)
+        if (!cnt)
                 return 0;
 
         mutex_lock(&ftrace_regex_lock);
@@ -2211,72 +2191,23 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
         } else
                 iter = file->private_data;
 
-        if (!*ppos) {
-                iter->flags &= ~FTRACE_ITER_CONT;
-                iter->buffer_idx = 0;
-        }
-
-        ret = get_user(ch, ubuf++);
-        if (ret)
-                goto out;
-        read++;
-        cnt--;
+        parser = &iter->parser;
+        read = trace_get_user(parser, ubuf, cnt, ppos);
 
-        /*
-         * If the parser haven't finished with the last write,
-         * continue reading the user input without skipping spaces.
-         */
-        if (!(iter->flags & FTRACE_ITER_CONT)) {
-                /* skip white space */
-                while (cnt && isspace(ch)) {
-                        ret = get_user(ch, ubuf++);
-                        if (ret)
-                                goto out;
-                        read++;
-                        cnt--;
-                }
-
-                /* only spaces were written */
-                if (isspace(ch)) {
-                        *ppos += read;
-                        ret = read;
-                        goto out;
-                }
-
-                iter->buffer_idx = 0;
-        }
-
-        while (cnt && !isspace(ch)) {
-                if (iter->buffer_idx < FTRACE_BUFF_MAX)
-                        iter->buffer[iter->buffer_idx++] = ch;
-                else {
-                        ret = -EINVAL;
-                        goto out;
-                }
-                ret = get_user(ch, ubuf++);
+        if (read >= 0 && trace_parser_loaded(parser) &&
+            !trace_parser_cont(parser)) {
+                ret = ftrace_process_regex(parser->buffer,
+                                           parser->idx, enable);
                 if (ret)
                         goto out;
-                read++;
-                cnt--;
-        }
 
-        if (isspace(ch)) {
-                iter->buffer[iter->buffer_idx] = 0;
-                ret = ftrace_process_regex(iter->buffer,
-                                           iter->buffer_idx, enable);
-                if (ret)
-                        goto out;
-                iter->buffer_idx = 0;
-        } else {
-                iter->flags |= FTRACE_ITER_CONT;
-                iter->buffer[iter->buffer_idx++] = ch;
+                trace_parser_clear(parser);
         }
 
-        *ppos += read;
         ret = read;
- out:
-        mutex_unlock(&ftrace_regex_lock);
 
+        mutex_unlock(&ftrace_regex_lock);
+out:
         return ret;
 }
 
@@ -2343,6 +2274,7 @@ void ftrace_set_notrace(unsigned char *buf, int len, int reset)
 #define FTRACE_FILTER_SIZE              COMMAND_LINE_SIZE
 static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
 static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
+static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
 
 static int __init set_ftrace_notrace(char *str)
 {
@@ -2358,6 +2290,31 @@ static int __init set_ftrace_filter(char *str)
 }
 __setup("ftrace_filter=", set_ftrace_filter);
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+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;
@@ -2374,6 +2331,10 @@ 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
@@ -2381,6 +2342,7 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
 {
         struct seq_file *m = (struct seq_file *)file->private_data;
         struct ftrace_iterator *iter;
+        struct trace_parser *parser;
 
         mutex_lock(&ftrace_regex_lock);
         if (file->f_mode & FMODE_READ) {
@@ -2390,9 +2352,10 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
         } else
                 iter = file->private_data;
 
-        if (iter->buffer_idx) {
-                iter->buffer[iter->buffer_idx] = 0;
-                ftrace_match_records(iter->buffer, iter->buffer_idx, enable);
+        parser = &iter->parser;
+        if (trace_parser_loaded(parser)) {
+                parser->buffer[parser->idx] = 0;
+                ftrace_match_records(parser->buffer, parser->idx, enable);
         }
 
         mutex_lock(&ftrace_lock);
@@ -2400,7 +2363,9 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
                 ftrace_run_update_code(FTRACE_ENABLE_CALLS);
         mutex_unlock(&ftrace_lock);
 
+        trace_parser_put(parser);
         kfree(iter);
+
         mutex_unlock(&ftrace_regex_lock);
         return 0;
 }
@@ -2457,11 +2422,9 @@ unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
 static void *
 __g_next(struct seq_file *m, loff_t *pos)
 {
-        unsigned long *array = m->private;
-
         if (*pos >= ftrace_graph_count)
                 return NULL;
-        return &array[*pos];
+        return &ftrace_graph_funcs[*pos];
 }
 
 static void *
@@ -2499,12 +2462,12 @@ static int g_show(struct seq_file *m, void *v)
                 return 0;
         }
 
-        seq_printf(m, "%pf\n", v);
+        seq_printf(m, "%ps\n", (void *)*ptr);
 
         return 0;
 }
 
-static struct seq_operations ftrace_graph_seq_ops = {
+static const struct seq_operations ftrace_graph_seq_ops = {
         .start = g_start,
         .next = g_next,
         .stop = g_stop,
@@ -2525,16 +2488,10 @@ ftrace_graph_open(struct inode *inode, struct file *file)
                 ftrace_graph_count = 0;
                 memset(ftrace_graph_funcs, 0, sizeof(ftrace_graph_funcs));
         }
+        mutex_unlock(&graph_lock);
 
-        if (file->f_mode & FMODE_READ) {
+        if (file->f_mode & FMODE_READ)
                 ret = seq_open(file, &ftrace_graph_seq_ops);
-                if (!ret) {
-                        struct seq_file *m = file->private_data;
-                        m->private = ftrace_graph_funcs;
-                }
-        } else
-                file->private_data = ftrace_graph_funcs;
-        mutex_unlock(&graph_lock);
 
         return ret;
 }
@@ -2563,7 +2520,7 @@ ftrace_set_func(unsigned long *array, int *idx, char *buffer)
                 return -ENODEV;
 
         /* decode regex */
-        type = ftrace_setup_glob(buffer, strlen(buffer), &search, &not);
+        type = filter_parse_regex(buffer, strlen(buffer), &search, &not);
         if (not)
                 return -EINVAL;
 
@@ -2602,12 +2559,8 @@ static ssize_t
 ftrace_graph_write(struct file *file, const char __user *ubuf,
                    size_t cnt, loff_t *ppos)
 {
-        unsigned char buffer[FTRACE_BUFF_MAX+1];
-        unsigned long *array;
-        size_t read = 0;
-        ssize_t ret;
-        int index = 0;
-        char ch;
+        struct trace_parser parser;
+        ssize_t read, ret;
 
         if (!cnt || cnt < 0)
                 return 0;
@@ -2616,60 +2569,31 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
 
         if (ftrace_graph_count >= FTRACE_GRAPH_MAX_FUNCS) {
                 ret = -EBUSY;
-                goto out;
+                goto out_unlock;
         }
 
-        if (file->f_mode & FMODE_READ) {
-                struct seq_file *m = file->private_data;
-                array = m->private;
-        } else
-                array = file->private_data;
-
-        ret = get_user(ch, ubuf++);
-        if (ret)
-                goto out;
-        read++;
-        cnt--;
-
-        /* skip white space */
-        while (cnt && isspace(ch)) {
-                ret = get_user(ch, ubuf++);
-                if (ret)
-                        goto out;
-                read++;
-                cnt--;
+        if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
+                ret = -ENOMEM;
+                goto out_unlock;
         }
 
-        if (isspace(ch)) {
-                *ppos += read;
-                ret = read;
-                goto out;
-        }
+        read = trace_get_user(&parser, ubuf, cnt, ppos);
 
-        while (cnt && !isspace(ch)) {
-                if (index < FTRACE_BUFF_MAX)
-                        buffer[index++] = ch;
-                else {
-                        ret = -EINVAL;
-                        goto out;
-                }
-                ret = get_user(ch, ubuf++);
+        if (read >= 0 && trace_parser_loaded((&parser))) {
+                parser.buffer[parser.idx] = 0;
+
+                /* we allow only one expression at a time */
+                ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
+                                        parser.buffer);
                 if (ret)
-                        goto out;
-                read++;
-                cnt--;
+                        goto out_free;
         }
-        buffer[index] = 0;
-
-        /* we allow only one expression at a time */
-        ret = ftrace_set_func(array, &ftrace_graph_count, buffer);
-        if (ret)
-                goto out;
-
-        file->f_pos += read;
 
         ret = read;
- out:
+
+out_free:
+        trace_parser_put(&parser);
+out_unlock:
         mutex_unlock(&graph_lock);
 
         return ret;
@@ -2707,7 +2631,7 @@ 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)
 {
@@ -2740,19 +2664,17 @@ static int ftrace_convert_nops(struct module *mod,
 }
 
 #ifdef CONFIG_MODULES
-void ftrace_release(void *start, void *end)
+void ftrace_release_mod(struct module *mod)
 {
         struct dyn_ftrace *rec;
         struct ftrace_page *pg;
-        unsigned long s = (unsigned long)start;
-        unsigned long e = (unsigned long)end;
 
-        if (ftrace_disabled || !start || start == end)
+        if (ftrace_disabled)
                 return;
 
         mutex_lock(&ftrace_lock);
         do_for_each_ftrace_rec(pg, rec) {
-                if ((rec->ip >= s) && (rec->ip < e)) {
+                if (within_module_core(rec->ip, mod)) {
                         /*
                          * rec->ip is changed in ftrace_free_rec()
                          * It should not between s and e if record was freed.
@@ -2769,7 +2691,7 @@ 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,
@@ -2784,9 +2706,7 @@ static int ftrace_module_notify(struct notifier_block *self,
                                    mod->num_ftrace_callsites);
                 break;
         case MODULE_STATE_GOING:
-                ftrace_release(mod->ftrace_callsites,
-                               mod->ftrace_callsites +
-                               mod->num_ftrace_callsites);
+                ftrace_release_mod(mod);
                 break;
         }
 
@@ -2832,7 +2752,7 @@ 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);
 
@@ -2865,23 +2785,6 @@ 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;
@@ -2932,14 +2835,12 @@ 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)
@@ -2950,11 +2851,140 @@ static void set_ftrace_pid_task(struct pid *pid)
                 set_ftrace_pid(pid);
 }
 
+static int ftrace_pid_add(int p)
+{
+        struct pid *pid;
+        struct ftrace_pid *fpid;
+        int ret = -EINVAL;
+
+        mutex_lock(&ftrace_lock);
+
+        if (!p)
+                pid = ftrace_swapper_pid;
+        else
+                pid = find_get_pid(p);
+
+        if (!pid)
+                goto out;
+
+        ret = 0;
+
+        list_for_each_entry(fpid, &ftrace_pids, list)
+                if (fpid->pid == pid)
+                        goto out_put;
+
+        ret = -ENOMEM;
+
+        fpid = kmalloc(sizeof(*fpid), GFP_KERNEL);
+        if (!fpid)
+                goto out_put;
+
+        list_add(&fpid->list, &ftrace_pids);
+        fpid->pid = pid;
+
+        set_ftrace_pid_task(pid);
+
+        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;
+
+                clear_ftrace_pid_task(pid);
+
+                list_del(&fpid->list);
+                kfree(fpid);
+        }
+
+        ftrace_update_pid_func();
+        ftrace_startup_enable(0);
+
+        mutex_unlock(&ftrace_lock);
+}
+
+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)
 {
-        struct pid *pid;
         char buf[64];
         long val;
         int ret;
@@ -2967,57 +2997,38 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
 
         buf[cnt] = 0;
 
+        /*
+         * Allow "echo > set_ftrace_pid" or "echo -n '' > set_ftrace_pid"
+         * to clean the filter quietly.
+         */
+        strstrip(buf);
+        if (strlen(buf) == 0)
+                return 1;
+
         ret = strict_strtol(buf, 10, &val);
         if (ret < 0)
                 return ret;
 
-        mutex_lock(&ftrace_lock);
-        if (val < 0) {
-                /* disable pid tracing */
-                if (!ftrace_pid_trace)
-                        goto out;
-
-                clear_ftrace_pid_task(&ftrace_pid_trace);
-
-        } else {
-                /* swapper task is special */
-                if (!val) {
-                        pid = ftrace_swapper_pid;
-                        if (pid == ftrace_pid_trace)
-                                goto out;
-                } else {
-                        pid = find_get_pid(val);
-
-                        if (pid == ftrace_pid_trace) {
-                                put_pid(pid);
-                                goto out;
-                        }
-                }
-
-                if (ftrace_pid_trace)
-                        clear_ftrace_pid_task(&ftrace_pid_trace);
-
-                if (!pid)
-                        goto out;
+        ret = ftrace_pid_add(val);
 
-                ftrace_pid_trace = pid;
-
-                set_ftrace_pid_task(ftrace_pid_trace);
-        }
-
-        /* update the function call */
-        ftrace_update_pid_func();
-        ftrace_startup_enable(0);
+        return ret ? ret : cnt;
+}
 
- out:
-        mutex_unlock(&ftrace_lock);
+static int
+ftrace_pid_release(struct inode *inode, struct file *file)
+{
+        if (file->f_mode & FMODE_READ)
+                seq_release(inode, file);
 
-        return cnt;
+        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)
@@ -3100,7 +3111,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
 
 int
 ftrace_enable_sysctl(struct ctl_table *table, int write,
-                     struct file *file, void __user *buffer, size_t *lenp,
+                     void __user *buffer, size_t *lenp,
                      loff_t *ppos)
 {
         int ret;
@@ -3110,7 +3121,7 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
         mutex_lock(&ftrace_lock);
 
-        ret  = proc_dointvec(table, write, file, buffer, lenp, ppos);
+        ret  = proc_dointvec(table, write, buffer, lenp, ppos);
 
         if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled))
                 goto out;