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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * event tracer
  *
  * Copyright (C) 2008 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
  *
  *  - Added format output of fields of the trace point.
  *    This was based off of work by Tom Zanussi <tzanussi@gmail.com>.
  *
  */
 
 #define pr_fmt(fmt) fmt
 
 #include <linux/workqueue.h>
 #include <linux/security.h>
 #include <linux/spinlock.h>
 #include <linux/kthread.h>
 #include <linux/tracefs.h>
 #include <linux/uaccess.h>
 #include <linux/module.h>
 #include <linux/ctype.h>
 #include <linux/sort.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
 
 #include <trace/events/sched.h>
 #include <trace/syscall.h>
 
 #include <asm/setup.h>
 
 #include "trace_output.h"
 
 #undef TRACE_SYSTEM
 #define TRACE_SYSTEM "TRACE_SYSTEM"
 
 DEFINE_MUTEX(event_mutex);
 
 LIST_HEAD(ftrace_events);
 static LIST_HEAD(ftrace_generic_fields);
 static LIST_HEAD(ftrace_common_fields);
 static bool eventdir_initialized;
 
 static LIST_HEAD(module_strings);
 
 struct module_string {
     struct list_head    next;
     struct module       *module;
     char            *str;
 };
 
 #define GFP_TRACE (GFP_KERNEL | __GFP_ZERO)
 
 static struct kmem_cache *field_cachep;
 static struct kmem_cache *file_cachep;
 
 static inline int system_refcount(struct event_subsystem *system)
 {
     return system->ref_count;
 }
 
 static int system_refcount_inc(struct event_subsystem *system)
 {
     return system->ref_count++;
 }
 
 static int system_refcount_dec(struct event_subsystem *system)
 {
     return --system->ref_count;
 }
 
 /* Double loops, do not use break, only goto's work */
 #define do_for_each_event_file(tr, file)            \
     list_for_each_entry(tr, &ftrace_trace_arrays, list) {   \
         list_for_each_entry(file, &tr->events, list)
 
 #define do_for_each_event_file_safe(tr, file)           \
     list_for_each_entry(tr, &ftrace_trace_arrays, list) {   \
         struct trace_event_file *___n;              \
         list_for_each_entry_safe(file, ___n, &tr->events, list)
 
 #define while_for_each_event_file()     \
     }
 
 static struct ftrace_event_field *
 __find_event_field(struct list_head *head, char *name)
 {
     struct ftrace_event_field *field;
 
     list_for_each_entry(field, head, link) {
         if (!strcmp(field->name, name))
             return field;
     }
 
     return NULL;
 }
 
 struct ftrace_event_field *
 trace_find_event_field(struct trace_event_call *call, char *name)
 {
     struct ftrace_event_field *field;
     struct list_head *head;
 
     head = trace_get_fields(call);
     field = __find_event_field(head, name);
     if (field)
         return field;
 
     field = __find_event_field(&ftrace_generic_fields, name);
     if (field)
         return field;
 
     return __find_event_field(&ftrace_common_fields, name);
 }
 
 static int __trace_define_field(struct list_head *head, const char *type,
                 const char *name, int offset, int size,
                 int is_signed, int filter_type)
 {
     struct ftrace_event_field *field;
 
     field = kmem_cache_alloc(field_cachep, GFP_TRACE);
     if (!field)
         return -ENOMEM;
 
     field->name = name;
     field->type = type;
 
     if (filter_type == FILTER_OTHER)
         field->filter_type = filter_assign_type(type);
     else
         field->filter_type = filter_type;
 
     field->offset = offset;
     field->size = size;
     field->is_signed = is_signed;
 
     list_add(&field->link, head);
 
     return 0;
 }
 
 int trace_define_field(struct trace_event_call *call, const char *type,
                const char *name, int offset, int size, int is_signed,
                int filter_type)
 {
     struct list_head *head;
 
     if (WARN_ON(!call->class))
         return 0;
 
     head = trace_get_fields(call);
     return __trace_define_field(head, type, name, offset, size,
                     is_signed, filter_type);
 }
 EXPORT_SYMBOL_GPL(trace_define_field);
 
 #define __generic_field(type, item, filter_type)            \
     ret = __trace_define_field(&ftrace_generic_fields, #type,   \
                    #item, 0, 0, is_signed_type(type),   \
                    filter_type);            \
     if (ret)                            \
         return ret;
 
 #define __common_field(type, item)                  \
     ret = __trace_define_field(&ftrace_common_fields, #type,    \
                    "common_" #item,         \
                    offsetof(typeof(ent), item),     \
                    sizeof(ent.item),            \
                    is_signed_type(type), FILTER_OTHER); \
     if (ret)                            \
         return ret;
 
 static int trace_define_generic_fields(void)
 {
     int ret;
 
     __generic_field(int, CPU, FILTER_CPU);
     __generic_field(int, cpu, FILTER_CPU);
     __generic_field(int, common_cpu, FILTER_CPU);
     __generic_field(char *, COMM, FILTER_COMM);
     __generic_field(char *, comm, FILTER_COMM);
 
     return ret;
 }
 
 static int trace_define_common_fields(void)
 {
     int ret;
     struct trace_entry ent;
 
     __common_field(unsigned short, type);
     __common_field(unsigned char, flags);
     /* Holds both preempt_count and migrate_disable */
     __common_field(unsigned char, preempt_count);
     __common_field(int, pid);
 
     return ret;
 }
 
 static void trace_destroy_fields(struct trace_event_call *call)
 {
     struct ftrace_event_field *field, *next;
     struct list_head *head;
 
     head = trace_get_fields(call);
     list_for_each_entry_safe(field, next, head, link) {
         list_del(&field->link);
         kmem_cache_free(field_cachep, field);
     }
 }
 
 /*
  * run-time version of trace_event_get_offsets_<call>() that returns the last
  * accessible offset of trace fields excluding __dynamic_array bytes
  */
 int trace_event_get_offsets(struct trace_event_call *call)
 {
     struct ftrace_event_field *tail;
     struct list_head *head;
 
     head = trace_get_fields(call);
     /*
      * head->next points to the last field with the largest offset,
      * since it was added last by trace_define_field()
      */
     tail = list_first_entry(head, struct ftrace_event_field, link);
     return tail->offset + tail->size;
 }
 
 /*
  * Check if the referenced field is an array and return true,
  * as arrays are OK to dereference.
  */
 static bool test_field(const char *fmt, struct trace_event_call *call)
 {
     struct trace_event_fields *field = call->class->fields_array;
     const char *array_descriptor;
     const char *p = fmt;
     int len;
 
     if (!(len = str_has_prefix(fmt, "REC->")))
         return false;
     fmt += len;
     for (p = fmt; *p; p++) {
         if (!isalnum(*p) && *p != '_')
             break;
     }
     len = p - fmt;
 
     for (; field->type; field++) {
         if (strncmp(field->name, fmt, len) ||
             field->name[len])
             continue;
         array_descriptor = strchr(field->type, '[');
         /* This is an array and is OK to dereference. */
         return array_descriptor != NULL;
     }
     return false;
 }
 
 /*
  * Examine the print fmt of the event looking for unsafe dereference
  * pointers using %p* that could be recorded in the trace event and
  * much later referenced after the pointer was freed. Dereferencing
  * pointers are OK, if it is dereferenced into the event itself.
  */
 static void test_event_printk(struct trace_event_call *call)
 {
     u64 dereference_flags = 0;
     bool first = true;
     const char *fmt, *c, *r, *a;
     int parens = 0;
     char in_quote = 0;
     int start_arg = 0;
     int arg = 0;
     int i;
 
     fmt = call->print_fmt;
 
     if (!fmt)
         return;
 
     for (i = 0; fmt[i]; i++) {
         switch (fmt[i]) {
         case '\\':
             i++;
             if (!fmt[i])
                 return;
             continue;
         case '"':
         case '\'':
             /*
              * The print fmt starts with a string that
              * is processed first to find %p* usage,
              * then after the first string, the print fmt
              * contains arguments that are used to check
              * if the dereferenced %p* usage is safe.
              */
             if (first) {
                 if (fmt[i] == '\'')
                     continue;
                 if (in_quote) {
                     arg = 0;
                     first = false;
                     /*
                      * If there was no %p* uses
                      * the fmt is OK.
                      */
                     if (!dereference_flags)
                         return;
                 }
             }
             if (in_quote) {
                 if (in_quote == fmt[i])
                     in_quote = 0;
             } else {
                 in_quote = fmt[i];
             }
             continue;
         case '%':
             if (!first || !in_quote)
                 continue;
             i++;
             if (!fmt[i])
                 return;
             switch (fmt[i]) {
             case '%':
                 continue;
             case 'p':
                 /* Find dereferencing fields */
                 switch (fmt[i + 1]) {
                 case 'B': case 'R': case 'r':
                 case 'b': case 'M': case 'm':
                 case 'I': case 'i': case 'E':
                 case 'U': case 'V': case 'N':
                 case 'a': case 'd': case 'D':
                 case 'g': case 't': case 'C':
                 case 'O': case 'f':
                     if (WARN_ONCE(arg == 63,
                               "Too many args for event: %s",
                               trace_event_name(call)))
                         return;
                     dereference_flags |= 1ULL << arg;
                 }
                 break;
             default:
             {
                 bool star = false;
                 int j;
 
                 /* Increment arg if %*s exists. */
                 for (j = 0; fmt[i + j]; j++) {
                     if (isdigit(fmt[i + j]) ||
                         fmt[i + j] == '.')
                         continue;
                     if (fmt[i + j] == '*') {
                         star = true;
                         continue;
                     }
                     if ((fmt[i + j] == 's') && star)
                         arg++;
                     break;
                 }
                 break;
             } /* default */
 
             } /* switch */
             arg++;
             continue;
         case '(':
             if (in_quote)
                 continue;
             parens++;
             continue;
         case ')':
             if (in_quote)
                 continue;
             parens--;
             if (WARN_ONCE(parens < 0,
                       "Paren mismatch for event: %s\narg='%s'\n%*s",
                       trace_event_name(call),
                       fmt + start_arg,
                       (i - start_arg) + 5, "^"))
                 return;
             continue;
         case ',':
             if (in_quote || parens)
                 continue;
             i++;
             while (isspace(fmt[i]))
                 i++;
             start_arg = i;
             if (!(dereference_flags & (1ULL << arg)))
                 goto next_arg;
 
             /* Find the REC-> in the argument */
             c = strchr(fmt + i, ',');
             r = strstr(fmt + i, "REC->");
             if (r && (!c || r < c)) {
                 /*
                  * Addresses of events on the buffer,
                  * or an array on the buffer is
                  * OK to dereference.
                  * There's ways to fool this, but
                  * this is to catch common mistakes,
                  * not malicious code.
                  */
                 a = strchr(fmt + i, '&');
                 if ((a && (a < r)) || test_field(r, call))
                     dereference_flags &= ~(1ULL << arg);
             } else if ((r = strstr(fmt + i, "__get_dynamic_array(")) &&
                    (!c || r < c)) {
                 dereference_flags &= ~(1ULL << arg);
             } else if ((r = strstr(fmt + i, "__get_sockaddr(")) &&
                    (!c || r < c)) {
                 dereference_flags &= ~(1ULL << arg);
             }
 
         next_arg:
             i--;
             arg++;
         }
     }
 
     /*
      * If you triggered the below warning, the trace event reported
      * uses an unsafe dereference pointer %p*. As the data stored
      * at the trace event time may no longer exist when the trace
      * event is printed, dereferencing to the original source is
      * unsafe. The source of the dereference must be copied into the
      * event itself, and the dereference must access the copy instead.
      */
     if (WARN_ON_ONCE(dereference_flags)) {
         arg = 1;
         while (!(dereference_flags & 1)) {
             dereference_flags >>= 1;
             arg++;
         }
         pr_warn("event %s has unsafe dereference of argument %d\n",
             trace_event_name(call), arg);
         pr_warn("print_fmt: %s\n", fmt);
     }
 }
 
 int trace_event_raw_init(struct trace_event_call *call)
 {
     int id;
 
     id = register_trace_event(&call->event);
     if (!id)
         return -ENODEV;
 
     test_event_printk(call);
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(trace_event_raw_init);
 
 bool trace_event_ignore_this_pid(struct trace_event_file *trace_file)
 {
     struct trace_array *tr = trace_file->tr;
     struct trace_array_cpu *data;
     struct trace_pid_list *no_pid_list;
     struct trace_pid_list *pid_list;
 
     pid_list = rcu_dereference_raw(tr->filtered_pids);
     no_pid_list = rcu_dereference_raw(tr->filtered_no_pids);
 
     if (!pid_list && !no_pid_list)
         return false;
 
     data = this_cpu_ptr(tr->array_buffer.data);
 
     return data->ignore_pid;
 }
 EXPORT_SYMBOL_GPL(trace_event_ignore_this_pid);
 
 void *trace_event_buffer_reserve(struct trace_event_buffer *fbuffer,
                  struct trace_event_file *trace_file,
                  unsigned long len)
 {
     struct trace_event_call *event_call = trace_file->event_call;
 
     if ((trace_file->flags & EVENT_FILE_FL_PID_FILTER) &&
         trace_event_ignore_this_pid(trace_file))
         return NULL;
 
     /*
      * If CONFIG_PREEMPTION is enabled, then the tracepoint itself disables
      * preemption (adding one to the preempt_count). Since we are
      * interested in the preempt_count at the time the tracepoint was
      * hit, we need to subtract one to offset the increment.
      */
     fbuffer->trace_ctx = tracing_gen_ctx_dec();
     fbuffer->trace_file = trace_file;
 
     fbuffer->event =
         trace_event_buffer_lock_reserve(&fbuffer->buffer, trace_file,
                         event_call->event.type, len,
                         fbuffer->trace_ctx);
     if (!fbuffer->event)
         return NULL;
 
     fbuffer->regs = NULL;
     fbuffer->entry = ring_buffer_event_data(fbuffer->event);
     return fbuffer->entry;
 }
 EXPORT_SYMBOL_GPL(trace_event_buffer_reserve);
 
 int trace_event_reg(struct trace_event_call *call,
             enum trace_reg type, void *data)
 {
     struct trace_event_file *file = data;
 
     WARN_ON(!(call->flags & TRACE_EVENT_FL_TRACEPOINT));
     switch (type) {
     case TRACE_REG_REGISTER:
         return tracepoint_probe_register(call->tp,
                          call->class->probe,
                          file);
     case TRACE_REG_UNREGISTER:
         tracepoint_probe_unregister(call->tp,
                         call->class->probe,
                         file);
         return 0;
 
 #ifdef CONFIG_PERF_EVENTS
     case TRACE_REG_PERF_REGISTER:
         return tracepoint_probe_register(call->tp,
                          call->class->perf_probe,
                          call);
     case TRACE_REG_PERF_UNREGISTER:
         tracepoint_probe_unregister(call->tp,
                         call->class->perf_probe,
                         call);
         return 0;
     case TRACE_REG_PERF_OPEN:
     case TRACE_REG_PERF_CLOSE:
     case TRACE_REG_PERF_ADD:
     case TRACE_REG_PERF_DEL:
         return 0;
 #endif
     }
     return 0;
 }
 EXPORT_SYMBOL_GPL(trace_event_reg);
 
 void trace_event_enable_cmd_record(bool enable)
 {
     struct trace_event_file *file;
     struct trace_array *tr;
 
     lockdep_assert_held(&event_mutex);
 
     do_for_each_event_file(tr, file) {
 
         if (!(file->flags & EVENT_FILE_FL_ENABLED))
             continue;
 
         if (enable) {
             tracing_start_cmdline_record();
             set_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
         } else {
             tracing_stop_cmdline_record();
             clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
         }
     } while_for_each_event_file();
 }
 
 void trace_event_enable_tgid_record(bool enable)
 {
     struct trace_event_file *file;
     struct trace_array *tr;
 
     lockdep_assert_held(&event_mutex);
 
     do_for_each_event_file(tr, file) {
         if (!(file->flags & EVENT_FILE_FL_ENABLED))
             continue;
 
         if (enable) {
             tracing_start_tgid_record();
             set_bit(EVENT_FILE_FL_RECORDED_TGID_BIT, &file->flags);
         } else {
             tracing_stop_tgid_record();
             clear_bit(EVENT_FILE_FL_RECORDED_TGID_BIT,
                   &file->flags);
         }
     } while_for_each_event_file();
 }
 
 static int __ftrace_event_enable_disable(struct trace_event_file *file,
                      int enable, int soft_disable)
 {
     struct trace_event_call *call = file->event_call;
     struct trace_array *tr = file->tr;
     unsigned long file_flags = file->flags;
     int ret = 0;
     int disable;
 
     switch (enable) {
     case 0:
         /*
          * When soft_disable is set and enable is cleared, the sm_ref
          * reference counter is decremented. If it reaches 0, we want
          * to clear the SOFT_DISABLED flag but leave the event in the
          * state that it was. That is, if the event was enabled and
          * SOFT_DISABLED isn't set, then do nothing. But if SOFT_DISABLED
          * is set we do not want the event to be enabled before we
          * clear the bit.
          *
          * When soft_disable is not set but the SOFT_MODE flag is,
          * we do nothing. Do not disable the tracepoint, otherwise
          * "soft enable"s (clearing the SOFT_DISABLED bit) wont work.
          */
         if (soft_disable) {
             if (atomic_dec_return(&file->sm_ref) > 0)
                 break;
             disable = file->flags & EVENT_FILE_FL_SOFT_DISABLED;
             clear_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags);
         } else
             disable = !(file->flags & EVENT_FILE_FL_SOFT_MODE);
 
         if (disable && (file->flags & EVENT_FILE_FL_ENABLED)) {
             clear_bit(EVENT_FILE_FL_ENABLED_BIT, &file->flags);
             if (file->flags & EVENT_FILE_FL_RECORDED_CMD) {
                 tracing_stop_cmdline_record();
                 clear_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
             }
 
             if (file->flags & EVENT_FILE_FL_RECORDED_TGID) {
                 tracing_stop_tgid_record();
                 clear_bit(EVENT_FILE_FL_RECORDED_TGID_BIT, &file->flags);
             }
 
             call->class->reg(call, TRACE_REG_UNREGISTER, file);
         }
         /* If in SOFT_MODE, just set the SOFT_DISABLE_BIT, else clear it */
         if (file->flags & EVENT_FILE_FL_SOFT_MODE)
             set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
         else
             clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
         break;
     case 1:
         /*
          * When soft_disable is set and enable is set, we want to
          * register the tracepoint for the event, but leave the event
          * as is. That means, if the event was already enabled, we do
          * nothing (but set SOFT_MODE). If the event is disabled, we
          * set SOFT_DISABLED before enabling the event tracepoint, so
          * it still seems to be disabled.
          */
         if (!soft_disable)
             clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
         else {
             if (atomic_inc_return(&file->sm_ref) > 1)
                 break;
             set_bit(EVENT_FILE_FL_SOFT_MODE_BIT, &file->flags);
         }
 
         if (!(file->flags & EVENT_FILE_FL_ENABLED)) {
             bool cmd = false, tgid = false;
 
             /* Keep the event disabled, when going to SOFT_MODE. */
             if (soft_disable)
                 set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &file->flags);
 
             if (tr->trace_flags & TRACE_ITER_RECORD_CMD) {
                 cmd = true;
                 tracing_start_cmdline_record();
                 set_bit(EVENT_FILE_FL_RECORDED_CMD_BIT, &file->flags);
             }
 
             if (tr->trace_flags & TRACE_ITER_RECORD_TGID) {
                 tgid = true;
                 tracing_start_tgid_record();
                 set_bit(EVENT_FILE_FL_RECORDED_TGID_BIT, &file->flags);
             }
 
             ret = call->class->reg(call, TRACE_REG_REGISTER, file);
             if (ret) {
                 if (cmd)
                     tracing_stop_cmdline_record();
                 if (tgid)
                     tracing_stop_tgid_record();
                 pr_info("event trace: Could not enable event "
                     "%s\n", trace_event_name(call));
                 break;
             }
             set_bit(EVENT_FILE_FL_ENABLED_BIT, &file->flags);
 
             /* WAS_ENABLED gets set but never cleared. */
             set_bit(EVENT_FILE_FL_WAS_ENABLED_BIT, &file->flags);
         }
         break;
     }
 
     /* Enable or disable use of trace_buffered_event */
     if ((file_flags & EVENT_FILE_FL_SOFT_DISABLED) !=
         (file->flags & EVENT_FILE_FL_SOFT_DISABLED)) {
         if (file->flags & EVENT_FILE_FL_SOFT_DISABLED)
             trace_buffered_event_enable();
         else
             trace_buffered_event_disable();
     }
 
     return ret;
 }
 
 int trace_event_enable_disable(struct trace_event_file *file,
                    int enable, int soft_disable)
 {
     return __ftrace_event_enable_disable(file, enable, soft_disable);
 }
 
 static int ftrace_event_enable_disable(struct trace_event_file *file,
                        int enable)
 {
     return __ftrace_event_enable_disable(file, enable, 0);
 }
 
 static void ftrace_clear_events(struct trace_array *tr)
 {
     struct trace_event_file *file;
 
     mutex_lock(&event_mutex);
     list_for_each_entry(file, &tr->events, list) {
         ftrace_event_enable_disable(file, 0);
     }
     mutex_unlock(&event_mutex);
 }
 
 static void
 event_filter_pid_sched_process_exit(void *data, struct task_struct *task)
 {
     struct trace_pid_list *pid_list;
     struct trace_array *tr = data;
 
     pid_list = rcu_dereference_raw(tr->filtered_pids);
     trace_filter_add_remove_task(pid_list, NULL, task);
 
     pid_list = rcu_dereference_raw(tr->filtered_no_pids);
     trace_filter_add_remove_task(pid_list, NULL, task);
 }
 
 static void
 event_filter_pid_sched_process_fork(void *data,
                     struct task_struct *self,
                     struct task_struct *task)
 {
     struct trace_pid_list *pid_list;
     struct trace_array *tr = data;
 
     pid_list = rcu_dereference_sched(tr->filtered_pids);
     trace_filter_add_remove_task(pid_list, self, task);
 
     pid_list = rcu_dereference_sched(tr->filtered_no_pids);
     trace_filter_add_remove_task(pid_list, self, task);
 }
 
 void trace_event_follow_fork(struct trace_array *tr, bool enable)
 {
     if (enable) {
         register_trace_prio_sched_process_fork(event_filter_pid_sched_process_fork,
                                tr, INT_MIN);
         register_trace_prio_sched_process_free(event_filter_pid_sched_process_exit,
                                tr, INT_MAX);
     } else {
         unregister_trace_sched_process_fork(event_filter_pid_sched_process_fork,
                             tr);
         unregister_trace_sched_process_free(event_filter_pid_sched_process_exit,
                             tr);
     }
 }
 
 static void
 event_filter_pid_sched_switch_probe_pre(void *data, bool preempt,
                     struct task_struct *prev,
                     struct task_struct *next,
                     unsigned int prev_state)
 {
     struct trace_array *tr = data;
     struct trace_pid_list *no_pid_list;
     struct trace_pid_list *pid_list;
     bool ret;
 
     pid_list = rcu_dereference_sched(tr->filtered_pids);
     no_pid_list = rcu_dereference_sched(tr->filtered_no_pids);
 
     /*
      * Sched switch is funny, as we only want to ignore it
      * in the notrace case if both prev and next should be ignored.
      */
     ret = trace_ignore_this_task(NULL, no_pid_list, prev) &&
         trace_ignore_this_task(NULL, no_pid_list, next);
 
     this_cpu_write(tr->array_buffer.data->ignore_pid, ret ||
                (trace_ignore_this_task(pid_list, NULL, prev) &&
             trace_ignore_this_task(pid_list, NULL, next)));
 }
 
 static void
 event_filter_pid_sched_switch_probe_post(void *data, bool preempt,
                      struct task_struct *prev,
                      struct task_struct *next,
                      unsigned int prev_state)
 {
     struct trace_array *tr = data;
     struct trace_pid_list *no_pid_list;
     struct trace_pid_list *pid_list;
 
     pid_list = rcu_dereference_sched(tr->filtered_pids);
     no_pid_list = rcu_dereference_sched(tr->filtered_no_pids);
 
     this_cpu_write(tr->array_buffer.data->ignore_pid,
                trace_ignore_this_task(pid_list, no_pid_list, next));
 }
 
 static void
 event_filter_pid_sched_wakeup_probe_pre(void *data, struct task_struct *task)
 {
     struct trace_array *tr = data;
     struct trace_pid_list *no_pid_list;
     struct trace_pid_list *pid_list;
 
     /* Nothing to do if we are already tracing */
     if (!this_cpu_read(tr->array_buffer.data->ignore_pid))
         return;
 
     pid_list = rcu_dereference_sched(tr->filtered_pids);
     no_pid_list = rcu_dereference_sched(tr->filtered_no_pids);
 
     this_cpu_write(tr->array_buffer.data->ignore_pid,
                trace_ignore_this_task(pid_list, no_pid_list, task));
 }
 
 static void
 event_filter_pid_sched_wakeup_probe_post(void *data, struct task_struct *task)
 {
     struct trace_array *tr = data;
     struct trace_pid_list *no_pid_list;
     struct trace_pid_list *pid_list;
 
     /* Nothing to do if we are not tracing */
     if (this_cpu_read(tr->array_buffer.data->ignore_pid))
         return;
 
     pid_list = rcu_dereference_sched(tr->filtered_pids);
     no_pid_list = rcu_dereference_sched(tr->filtered_no_pids);
 
     /* Set tracing if current is enabled */
     this_cpu_write(tr->array_buffer.data->ignore_pid,
                trace_ignore_this_task(pid_list, no_pid_list, current));
 }
 
 static void unregister_pid_events(struct trace_array *tr)
 {
     unregister_trace_sched_switch(event_filter_pid_sched_switch_probe_pre, tr);
     unregister_trace_sched_switch(event_filter_pid_sched_switch_probe_post, tr);
 
     unregister_trace_sched_wakeup(event_filter_pid_sched_wakeup_probe_pre, tr);
     unregister_trace_sched_wakeup(event_filter_pid_sched_wakeup_probe_post, tr);
 
     unregister_trace_sched_wakeup_new(event_filter_pid_sched_wakeup_probe_pre, tr);
     unregister_trace_sched_wakeup_new(event_filter_pid_sched_wakeup_probe_post, tr);
 
     unregister_trace_sched_waking(event_filter_pid_sched_wakeup_probe_pre, tr);
     unregister_trace_sched_waking(event_filter_pid_sched_wakeup_probe_post, tr);
 }
 
 static void __ftrace_clear_event_pids(struct trace_array *tr, int type)
 {
     struct trace_pid_list *pid_list;
     struct trace_pid_list *no_pid_list;
     struct trace_event_file *file;
     int cpu;
 
     pid_list = rcu_dereference_protected(tr->filtered_pids,
                          lockdep_is_held(&event_mutex));
     no_pid_list = rcu_dereference_protected(tr->filtered_no_pids,
                          lockdep_is_held(&event_mutex));
 
     /* Make sure there's something to do */
     if (!pid_type_enabled(type, pid_list, no_pid_list))
         return;
 
     if (!still_need_pid_events(type, pid_list, no_pid_list)) {
         unregister_pid_events(tr);
 
         list_for_each_entry(file, &tr->events, list) {
             clear_bit(EVENT_FILE_FL_PID_FILTER_BIT, &file->flags);
         }
 
         for_each_possible_cpu(cpu)
             per_cpu_ptr(tr->array_buffer.data, cpu)->ignore_pid = false;
     }
 
     if (type & TRACE_PIDS)
         rcu_assign_pointer(tr->filtered_pids, NULL);
 
     if (type & TRACE_NO_PIDS)
         rcu_assign_pointer(tr->filtered_no_pids, NULL);
 
     /* Wait till all users are no longer using pid filtering */
     tracepoint_synchronize_unregister();
 
     if ((type & TRACE_PIDS) && pid_list)
         trace_pid_list_free(pid_list);
 
     if ((type & TRACE_NO_PIDS) && no_pid_list)
         trace_pid_list_free(no_pid_list);
 }
 
 static void ftrace_clear_event_pids(struct trace_array *tr, int type)
 {
     mutex_lock(&event_mutex);
     __ftrace_clear_event_pids(tr, type);
     mutex_unlock(&event_mutex);
 }
 
 static void __put_system(struct event_subsystem *system)
 {
     struct event_filter *filter = system->filter;
 
     WARN_ON_ONCE(system_refcount(system) == 0);
     if (system_refcount_dec(system))
         return;
 
     list_del(&system->list);
 
     if (filter) {
         kfree(filter->filter_string);
         kfree(filter);
     }
     kfree_const(system->name);
     kfree(system);
 }
 
 static void __get_system(struct event_subsystem *system)
 {
     WARN_ON_ONCE(system_refcount(system) == 0);
     system_refcount_inc(system);
 }
 
 static void __get_system_dir(struct trace_subsystem_dir *dir)
 {
     WARN_ON_ONCE(dir->ref_count == 0);
     dir->ref_count++;
     __get_system(dir->subsystem);
 }
 
 static void __put_system_dir(struct trace_subsystem_dir *dir)
 {
     WARN_ON_ONCE(dir->ref_count == 0);
     /* If the subsystem is about to be freed, the dir must be too */
     WARN_ON_ONCE(system_refcount(dir->subsystem) == 1 && dir->ref_count != 1);
 
     __put_system(dir->subsystem);
     if (!--dir->ref_count)
         kfree(dir);
 }
 
 static void put_system(struct trace_subsystem_dir *dir)
 {
     mutex_lock(&event_mutex);
     __put_system_dir(dir);
     mutex_unlock(&event_mutex);
 }
 
 static void remove_subsystem(struct trace_subsystem_dir *dir)
 {
     if (!dir)
         return;
 
     if (!--dir->nr_events) {
         tracefs_remove(dir->entry);
         list_del(&dir->list);
         __put_system_dir(dir);
     }
 }
 
 static void remove_event_file_dir(struct trace_event_file *file)
 {
     struct dentry *dir = file->dir;
     struct dentry *child;
 
     if (dir) {
         spin_lock(&dir->d_lock);    /* probably unneeded */
         list_for_each_entry(child, &dir->d_subdirs, d_child) {
             if (d_really_is_positive(child))    /* probably unneeded */
                 d_inode(child)->i_private = NULL;
         }
         spin_unlock(&dir->d_lock);
 
         tracefs_remove(dir);
     }
 
     list_del(&file->list);
     remove_subsystem(file->system);
     free_event_filter(file->filter);
     kmem_cache_free(file_cachep, file);
 }
 
 /*
  * __ftrace_set_clr_event(NULL, NULL, NULL, set) will set/unset all events.
  */
 static int
 __ftrace_set_clr_event_nolock(struct trace_array *tr, const char *match,
                   const char *sub, const char *event, int set)
 {
     struct trace_event_file *file;
     struct trace_event_call *call;
     const char *name;
     int ret = -EINVAL;
     int eret = 0;
 
     list_for_each_entry(file, &tr->events, list) {
 
         call = file->event_call;
         name = trace_event_name(call);
 
         if (!name || !call->class || !call->class->reg)
             continue;
 
         if (call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
             continue;
 
         if (match &&
             strcmp(match, name) != 0 &&
             strcmp(match, call->class->system) != 0)
             continue;
 
         if (sub && strcmp(sub, call->class->system) != 0)
             continue;
 
         if (event && strcmp(event, name) != 0)
             continue;
 
         ret = ftrace_event_enable_disable(file, set);
 
         /*
          * Save the first error and return that. Some events
          * may still have been enabled, but let the user
          * know that something went wrong.
          */
         if (ret && !eret)
             eret = ret;
 
         ret = eret;
     }
 
     return ret;
 }
 
 static int __ftrace_set_clr_event(struct trace_array *tr, const char *match,
                   const char *sub, const char *event, int set)
 {
     int ret;
 
     mutex_lock(&event_mutex);
     ret = __ftrace_set_clr_event_nolock(tr, match, sub, event, set);
     mutex_unlock(&event_mutex);
 
     return ret;
 }
 
 int ftrace_set_clr_event(struct trace_array *tr, char *buf, int set)
 {
     char *event = NULL, *sub = NULL, *match;
     int ret;
 
     if (!tr)
         return -ENOENT;
     /*
      * The buf format can be <subsystem>:<event-name>
      *  *:<event-name> means any event by that name.
      *  :<event-name> is the same.
      *
      *  <subsystem>:* means all events in that subsystem
      *  <subsystem>: means the same.
      *
      *  <name> (no ':') means all events in a subsystem with
      *  the name <name> or any event that matches <name>
      */
 
     match = strsep(&buf, ":");
     if (buf) {
         sub = match;
         event = buf;
         match = NULL;
 
         if (!strlen(sub) || strcmp(sub, "*") == 0)
             sub = NULL;
         if (!strlen(event) || strcmp(event, "*") == 0)
             event = NULL;
     }
 
     ret = __ftrace_set_clr_event(tr, match, sub, event, set);
 
     /* Put back the colon to allow this to be called again */
     if (buf)
         *(buf - 1) = ':';
 
     return ret;
 }
 
 /**
  * trace_set_clr_event - enable or disable an event
  * @system: system name to match (NULL for any system)
  * @event: event name to match (NULL for all events, within system)
  * @set: 1 to enable, 0 to disable
  *
  * This is a way for other parts of the kernel to enable or disable
  * event recording.
  *
  * Returns 0 on success, -EINVAL if the parameters do not match any
  * registered events.
  */
 int trace_set_clr_event(const char *system, const char *event, int set)
 {
     struct trace_array *tr = top_trace_array();
 
     if (!tr)
         return -ENODEV;
 
     return __ftrace_set_clr_event(tr, NULL, system, event, set);
 }
 EXPORT_SYMBOL_GPL(trace_set_clr_event);
 
 /**
  * trace_array_set_clr_event - enable or disable an event for a trace array.
  * @tr: concerned trace array.
  * @system: system name to match (NULL for any system)
  * @event: event name to match (NULL for all events, within system)
  * @enable: true to enable, false to disable
  *
  * This is a way for other parts of the kernel to enable or disable
  * event recording.
  *
  * Returns 0 on success, -EINVAL if the parameters do not match any
  * registered events.
  */
 int trace_array_set_clr_event(struct trace_array *tr, const char *system,
         const char *event, bool enable)
 {
     int set;
 
     if (!tr)
         return -ENOENT;
 
     set = (enable == true) ? 1 : 0;
     return __ftrace_set_clr_event(tr, NULL, system, event, set);
 }
 EXPORT_SYMBOL_GPL(trace_array_set_clr_event);
 
 /* 128 should be much more than enough */
 #define EVENT_BUF_SIZE      127
 
 static ssize_t
 ftrace_event_write(struct file *file, const char __user *ubuf,
            size_t cnt, loff_t *ppos)
 {
     struct trace_parser parser;
     struct seq_file *m = file->private_data;
     struct trace_array *tr = m->private;
     ssize_t read, ret;
 
     if (!cnt)
         return 0;
 
     ret = tracing_update_buffers();
     if (ret < 0)
         return ret;
 
     if (trace_parser_get_init(&parser, EVENT_BUF_SIZE + 1))
         return -ENOMEM;
 
     read = trace_get_user(&parser, ubuf, cnt, ppos);
 
     if (read >= 0 && trace_parser_loaded((&parser))) {
         int set = 1;
 
         if (*parser.buffer == '!')
             set = 0;
 
         ret = ftrace_set_clr_event(tr, parser.buffer + !set, set);
         if (ret)
             goto out_put;
     }
 
     ret = read;
 
  out_put:
     trace_parser_put(&parser);
 
     return ret;
 }
 
 static void *
 t_next(struct seq_file *m, void *v, loff_t *pos)
 {
     struct trace_event_file *file = v;
     struct trace_event_call *call;
     struct trace_array *tr = m->private;
 
     (*pos)++;
 
     list_for_each_entry_continue(file, &tr->events, list) {
         call = file->event_call;
         /*
          * The ftrace subsystem is for showing formats only.
          * They can not be enabled or disabled via the event files.
          */
         if (call->class && call->class->reg &&
             !(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
             return file;
     }
 
     return NULL;
 }
 
 static void *t_start(struct seq_file *m, loff_t *pos)
 {
     struct trace_event_file *file;
     struct trace_array *tr = m->private;
     loff_t l;
 
     mutex_lock(&event_mutex);
 
     file = list_entry(&tr->events, struct trace_event_file, list);
     for (l = 0; l <= *pos; ) {
         file = t_next(m, file, &l);
         if (!file)
             break;
     }
     return file;
 }
 
 static void *
 s_next(struct seq_file *m, void *v, loff_t *pos)
 {
     struct trace_event_file *file = v;
     struct trace_array *tr = m->private;
 
     (*pos)++;
 
     list_for_each_entry_continue(file, &tr->events, list) {
         if (file->flags & EVENT_FILE_FL_ENABLED)
             return file;
     }
 
     return NULL;
 }
 
 static void *s_start(struct seq_file *m, loff_t *pos)
 {
     struct trace_event_file *file;
     struct trace_array *tr = m->private;
     loff_t l;
 
     mutex_lock(&event_mutex);
 
     file = list_entry(&tr->events, struct trace_event_file, list);
     for (l = 0; l <= *pos; ) {
         file = s_next(m, file, &l);
         if (!file)
             break;
     }
     return file;
 }
 
 static int t_show(struct seq_file *m, void *v)
 {
     struct trace_event_file *file = v;
     struct trace_event_call *call = file->event_call;
 
     if (strcmp(call->class->system, TRACE_SYSTEM) != 0)
         seq_printf(m, "%s:", call->class->system);
     seq_printf(m, "%s\n", trace_event_name(call));
 
     return 0;
 }
 
 static void t_stop(struct seq_file *m, void *p)
 {
     mutex_unlock(&event_mutex);
 }
 
 static void *
 __next(struct seq_file *m, void *v, loff_t *pos, int type)
 {
     struct trace_array *tr = m->private;
     struct trace_pid_list *pid_list;
 
     if (type == TRACE_PIDS)
         pid_list = rcu_dereference_sched(tr->filtered_pids);
     else
         pid_list = rcu_dereference_sched(tr->filtered_no_pids);
 
     return trace_pid_next(pid_list, v, pos);
 }
 
 static void *
 p_next(struct seq_file *m, void *v, loff_t *pos)
 {
     return __next(m, v, pos, TRACE_PIDS);
 }
 
 static void *
 np_next(struct seq_file *m, void *v, loff_t *pos)
 {
     return __next(m, v, pos, TRACE_NO_PIDS);
 }
 
 static void *__start(struct seq_file *m, loff_t *pos, int type)
     __acquires(RCU)
 {
     struct trace_pid_list *pid_list;
     struct trace_array *tr = m->private;
 
     /*
      * Grab the mutex, to keep calls to p_next() having the same
      * tr->filtered_pids as p_start() has.
      * If we just passed the tr->filtered_pids around, then RCU would
      * have been enough, but doing that makes things more complex.
      */
     mutex_lock(&event_mutex);
     rcu_read_lock_sched();
 
     if (type == TRACE_PIDS)
         pid_list = rcu_dereference_sched(tr->filtered_pids);
     else
         pid_list = rcu_dereference_sched(tr->filtered_no_pids);
 
     if (!pid_list)
         return NULL;
 
     return trace_pid_start(pid_list, pos);
 }
 
 static void *p_start(struct seq_file *m, loff_t *pos)
     __acquires(RCU)
 {
     return __start(m, pos, TRACE_PIDS);
 }
 
 static void *np_start(struct seq_file *m, loff_t *pos)
     __acquires(RCU)
 {
     return __start(m, pos, TRACE_NO_PIDS);
 }
 
 static void p_stop(struct seq_file *m, void *p)
     __releases(RCU)
 {
     rcu_read_unlock_sched();
     mutex_unlock(&event_mutex);
 }
 
 static ssize_t
 event_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
           loff_t *ppos)
 {
     struct trace_event_file *file;
     unsigned long flags;
     char buf[4] = "0";
 
     mutex_lock(&event_mutex);
     file = event_file_data(filp);
     if (likely(file))
         flags = file->flags;
     mutex_unlock(&event_mutex);
 
     if (!file)
         return -ENODEV;
 
     if (flags & EVENT_FILE_FL_ENABLED &&
         !(flags & EVENT_FILE_FL_SOFT_DISABLED))
         strcpy(buf, "1");
 
     if (flags & EVENT_FILE_FL_SOFT_DISABLED ||
         flags & EVENT_FILE_FL_SOFT_MODE)
         strcat(buf, "*");
 
     strcat(buf, "\n");
 
     return simple_read_from_buffer(ubuf, cnt, ppos, buf, strlen(buf));
 }
 
 static ssize_t
 event_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
            loff_t *ppos)
 {
     struct trace_event_file *file;
     unsigned long val;
     int ret;
 
     ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
     if (ret)
         return ret;
 
     ret = tracing_update_buffers();
     if (ret < 0)
         return ret;
 
     switch (val) {
     case 0:
     case 1:
         ret = -ENODEV;
         mutex_lock(&event_mutex);
         file = event_file_data(filp);
         if (likely(file))
             ret = ftrace_event_enable_disable(file, val);
         mutex_unlock(&event_mutex);
         break;
 
     default:
         return -EINVAL;
     }
 
     *ppos += cnt;
 
     return ret ? ret : cnt;
 }
 
 static ssize_t
 system_enable_read(struct file *filp, char __user *ubuf, size_t cnt,
            loff_t *ppos)
 {
     const char set_to_char[4] = { '?', '0', '1', 'X' };
     struct trace_subsystem_dir *dir = filp->private_data;
     struct event_subsystem *system = dir->subsystem;
     struct trace_event_call *call;
     struct trace_event_file *file;
     struct trace_array *tr = dir->tr;
     char buf[2];
     int set = 0;
     int ret;
 
     mutex_lock(&event_mutex);
     list_for_each_entry(file, &tr->events, list) {
         call = file->event_call;
         if ((call->flags & TRACE_EVENT_FL_IGNORE_ENABLE) ||
             !trace_event_name(call) || !call->class || !call->class->reg)
             continue;
 
         if (system && strcmp(call->class->system, system->name) != 0)
             continue;
 
         /*
          * We need to find out if all the events are set
          * or if all events or cleared, or if we have
          * a mixture.
          */
         set |= (1 << !!(file->flags & EVENT_FILE_FL_ENABLED));
 
         /*
          * If we have a mixture, no need to look further.
          */
         if (set == 3)
             break;
     }
     mutex_unlock(&event_mutex);
 
     buf[0] = set_to_char[set];
     buf[1] = '\n';
 
     ret = simple_read_from_buffer(ubuf, cnt, ppos, buf, 2);
 
     return ret;
 }
 
 static ssize_t
 system_enable_write(struct file *filp, const char __user *ubuf, size_t cnt,
             loff_t *ppos)
 {
     struct trace_subsystem_dir *dir = filp->private_data;
     struct event_subsystem *system = dir->subsystem;
     const char *name = NULL;
     unsigned long val;
     ssize_t ret;
 
     ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
     if (ret)
         return ret;
 
     ret = tracing_update_buffers();
     if (ret < 0)
         return ret;
 
     if (val != 0 && val != 1)
         return -EINVAL;
 
     /*
      * Opening of "enable" adds a ref count to system,
      * so the name is safe to use.
      */
     if (system)
         name = system->name;
 
     ret = __ftrace_set_clr_event(dir->tr, NULL, name, NULL, val);
     if (ret)
         goto out;
 
     ret = cnt;
 
 out:
     *ppos += cnt;
 
     return ret;
 }
 
 enum {
     FORMAT_HEADER       = 1,
     FORMAT_FIELD_SEPERATOR  = 2,
     FORMAT_PRINTFMT     = 3,
 };
 
 static void *f_next(struct seq_file *m, void *v, loff_t *pos)
 {
     struct trace_event_call *call = event_file_data(m->private);
     struct list_head *common_head = &ftrace_common_fields;
     struct list_head *head = trace_get_fields(call);
     struct list_head *node = v;
 
     (*pos)++;
 
     switch ((unsigned long)v) {
     case FORMAT_HEADER:
         node = common_head;
         break;
 
     case FORMAT_FIELD_SEPERATOR:
         node = head;
         break;
 
     case FORMAT_PRINTFMT:
         /* all done */
         return NULL;
     }
 
     node = node->prev;
     if (node == common_head)
         return (void *)FORMAT_FIELD_SEPERATOR;
     else if (node == head)
         return (void *)FORMAT_PRINTFMT;
     else
         return node;
 }
 
 static int f_show(struct seq_file *m, void *v)
 {
     struct trace_event_call *call = event_file_data(m->private);
     struct ftrace_event_field *field;
     const char *array_descriptor;
 
     switch ((unsigned long)v) {
     case FORMAT_HEADER:
         seq_printf(m, "name: %s\n", trace_event_name(call));
         seq_printf(m, "ID: %d\n", call->event.type);
         seq_puts(m, "format:\n");
         return 0;
 
     case FORMAT_FIELD_SEPERATOR:
         seq_putc(m, '\n');
         return 0;
 
     case FORMAT_PRINTFMT:
         seq_printf(m, "\nprint fmt: %s\n",
                call->print_fmt);
         return 0;
     }
 
     field = list_entry(v, struct ftrace_event_field, link);
     /*
      * Smartly shows the array type(except dynamic array).
      * Normal:
      *  field:TYPE VAR
      * If TYPE := TYPE[LEN], it is shown:
      *  field:TYPE VAR[LEN]
      */
     array_descriptor = strchr(field->type, '[');
 
     if (str_has_prefix(field->type, "__data_loc"))
         array_descriptor = NULL;
 
     if (!array_descriptor)
         seq_printf(m, "\tfield:%s %s;\toffset:%u;\tsize:%u;\tsigned:%d;\n",
                field->type, field->name, field->offset,
                field->size, !!field->is_signed);
     else
         seq_printf(m, "\tfield:%.*s %s%s;\toffset:%u;\tsize:%u;\tsigned:%d;\n",
                (int)(array_descriptor - field->type),
                field->type, field->name,
                array_descriptor, field->offset,
                field->size, !!field->is_signed);
 
     return 0;
 }
 
 static void *f_start(struct seq_file *m, loff_t *pos)
 {
     void *p = (void *)FORMAT_HEADER;
     loff_t l = 0;
 
     /* ->stop() is called even if ->start() fails */
     mutex_lock(&event_mutex);
     if (!event_file_data(m->private))
         return ERR_PTR(-ENODEV);
 
     while (l < *pos && p)
         p = f_next(m, p, &l);
 
     return p;
 }
 
 static void f_stop(struct seq_file *m, void *p)
 {
     mutex_unlock(&event_mutex);
 }
 
 static const struct seq_operations trace_format_seq_ops = {
     .start      = f_start,
     .next       = f_next,
     .stop       = f_stop,
     .show       = f_show,
 };
 
 static int trace_format_open(struct inode *inode, struct file *file)
 {
     struct seq_file *m;
     int ret;
 
     /* Do we want to hide event format files on tracefs lockdown? */
 
     ret = seq_open(file, &trace_format_seq_ops);
     if (ret < 0)
         return ret;
 
     m = file->private_data;
     m->private = file;
 
     return 0;
 }
 
 static ssize_t
 event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
 {
     int id = (long)event_file_data(filp);
     char buf[32];
     int len;
 
     if (unlikely(!id))
         return -ENODEV;
 
     len = sprintf(buf, "%d\n", id);
 
     return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
 }
 
 static ssize_t
 event_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
           loff_t *ppos)
 {
     struct trace_event_file *file;
     struct trace_seq *s;
     int r = -ENODEV;
 
     if (*ppos)
         return 0;
 
     s = kmalloc(sizeof(*s), GFP_KERNEL);
 
     if (!s)
         return -ENOMEM;
 
     trace_seq_init(s);
 
     mutex_lock(&event_mutex);
     file = event_file_data(filp);
     if (file)
         print_event_filter(file, s);
     mutex_unlock(&event_mutex);
 
     if (file)
         r = simple_read_from_buffer(ubuf, cnt, ppos,
                         s->buffer, trace_seq_used(s));
 
     kfree(s);
 
     return r;
 }
 
 static ssize_t
 event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
            loff_t *ppos)
 {
     struct trace_event_file *file;
     char *buf;
     int err = -ENODEV;
 
     if (cnt >= PAGE_SIZE)
         return -EINVAL;
 
     buf = memdup_user_nul(ubuf, cnt);
     if (IS_ERR(buf))
         return PTR_ERR(buf);
 
     mutex_lock(&event_mutex);
     file = event_file_data(filp);
     if (file)
         err = apply_event_filter(file, buf);
     mutex_unlock(&event_mutex);
 
     kfree(buf);
     if (err < 0)
         return err;
 
     *ppos += cnt;
 
     return cnt;
 }
 
 static LIST_HEAD(event_subsystems);
 
 static int subsystem_open(struct inode *inode, struct file *filp)
 {
     struct trace_subsystem_dir *dir = NULL, *iter_dir;
     struct trace_array *tr = NULL, *iter_tr;
     struct event_subsystem *system = NULL;
     int ret;
 
     if (tracing_is_disabled())
         return -ENODEV;
 
     /* Make sure the system still exists */
     mutex_lock(&event_mutex);
     mutex_lock(&trace_types_lock);
     list_for_each_entry(iter_tr, &ftrace_trace_arrays, list) {
         list_for_each_entry(iter_dir, &iter_tr->systems, list) {
             if (iter_dir == inode->i_private) {
                 /* Don't open systems with no events */
                 tr = iter_tr;
                 dir = iter_dir;
                 if (dir->nr_events) {
                     __get_system_dir(dir);
                     system = dir->subsystem;
                 }
                 goto exit_loop;
             }
         }
     }
  exit_loop:
     mutex_unlock(&trace_types_lock);
     mutex_unlock(&event_mutex);
 
     if (!system)
         return -ENODEV;
 
     /* Still need to increment the ref count of the system */
     if (trace_array_get(tr) < 0) {
         put_system(dir);
         return -ENODEV;
     }
 
     ret = tracing_open_generic(inode, filp);
     if (ret < 0) {
         trace_array_put(tr);
         put_system(dir);
     }
 
     return ret;
 }
 
 static int system_tr_open(struct inode *inode, struct file *filp)
 {
     struct trace_subsystem_dir *dir;
     struct trace_array *tr = inode->i_private;
     int ret;
 
     /* Make a temporary dir that has no system but points to tr */
     dir = kzalloc(sizeof(*dir), GFP_KERNEL);
     if (!dir)
         return -ENOMEM;
 
     ret = tracing_open_generic_tr(inode, filp);
     if (ret < 0) {
         kfree(dir);
         return ret;
     }
     dir->tr = tr;
     filp->private_data = dir;
 
     return 0;
 }
 
 static int subsystem_release(struct inode *inode, struct file *file)
 {
     struct trace_subsystem_dir *dir = file->private_data;
 
     trace_array_put(dir->tr);
 
     /*
      * If dir->subsystem is NULL, then this is a temporary
      * descriptor that was made for a trace_array to enable
      * all subsystems.
      */
     if (dir->subsystem)
         put_system(dir);
     else
         kfree(dir);
 
     return 0;
 }
 
 static ssize_t
 subsystem_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
               loff_t *ppos)
 {
     struct trace_subsystem_dir *dir = filp->private_data;
     struct event_subsystem *system = dir->subsystem;
     struct trace_seq *s;
     int r;
 
     if (*ppos)
         return 0;
 
     s = kmalloc(sizeof(*s), GFP_KERNEL);
     if (!s)
         return -ENOMEM;
 
     trace_seq_init(s);
 
     print_subsystem_event_filter(system, s);
     r = simple_read_from_buffer(ubuf, cnt, ppos,
                     s->buffer, trace_seq_used(s));
 
     kfree(s);
 
     return r;
 }
 
 static ssize_t
 subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
                loff_t *ppos)
 {
     struct trace_subsystem_dir *dir = filp->private_data;
     char *buf;
     int err;
 
     if (cnt >= PAGE_SIZE)
         return -EINVAL;
 
     buf = memdup_user_nul(ubuf, cnt);
     if (IS_ERR(buf))
         return PTR_ERR(buf);
 
     err = apply_subsystem_event_filter(dir, buf);
     kfree(buf);
     if (err < 0)
         return err;
 
     *ppos += cnt;
 
     return cnt;
 }
 
 static ssize_t
 show_header(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
 {
     int (*func)(struct trace_seq *s) = filp->private_data;
     struct trace_seq *s;
     int r;
 
     if (*ppos)
         return 0;
 
     s = kmalloc(sizeof(*s), GFP_KERNEL);
     if (!s)
         return -ENOMEM;
 
     trace_seq_init(s);
 
     func(s);
     r = simple_read_from_buffer(ubuf, cnt, ppos,
                     s->buffer, trace_seq_used(s));
 
     kfree(s);
 
     return r;
 }
 
 static void ignore_task_cpu(void *data)
 {
     struct trace_array *tr = data;
     struct trace_pid_list *pid_list;
     struct trace_pid_list *no_pid_list;
 
     /*
      * This function is called by on_each_cpu() while the
      * event_mutex is held.
      */
     pid_list = rcu_dereference_protected(tr->filtered_pids,
                          mutex_is_locked(&event_mutex));
     no_pid_list = rcu_dereference_protected(tr->filtered_no_pids,
                          mutex_is_locked(&event_mutex));
 
     this_cpu_write(tr->array_buffer.data->ignore_pid,
                trace_ignore_this_task(pid_list, no_pid_list, current));
 }
 
 static void register_pid_events(struct trace_array *tr)
 {
     /*
      * Register a probe that is called before all other probes
      * to set ignore_pid if next or prev do not match.
      * Register a probe this is called after all other probes
      * to only keep ignore_pid set if next pid matches.
      */
     register_trace_prio_sched_switch(event_filter_pid_sched_switch_probe_pre,
                      tr, INT_MAX);
     register_trace_prio_sched_switch(event_filter_pid_sched_switch_probe_post,
                      tr, 0);
 
     register_trace_prio_sched_wakeup(event_filter_pid_sched_wakeup_probe_pre,
                      tr, INT_MAX);
     register_trace_prio_sched_wakeup(event_filter_pid_sched_wakeup_probe_post,
                      tr, 0);
 
     register_trace_prio_sched_wakeup_new(event_filter_pid_sched_wakeup_probe_pre,
                          tr, INT_MAX);
     register_trace_prio_sched_wakeup_new(event_filter_pid_sched_wakeup_probe_post,
                          tr, 0);
 
     register_trace_prio_sched_waking(event_filter_pid_sched_wakeup_probe_pre,
                      tr, INT_MAX);
     register_trace_prio_sched_waking(event_filter_pid_sched_wakeup_probe_post,
                      tr, 0);
 }
 
 static ssize_t
 event_pid_write(struct file *filp, const char __user *ubuf,
         size_t cnt, loff_t *ppos, int type)
 {
     struct seq_file *m = filp->private_data;
     struct trace_array *tr = m->private;
     struct trace_pid_list *filtered_pids = NULL;
     struct trace_pid_list *other_pids = NULL;
     struct trace_pid_list *pid_list;
     struct trace_event_file *file;
     ssize_t ret;
 
     if (!cnt)
         return 0;
 
     ret = tracing_update_buffers();
     if (ret < 0)
         return ret;
 
     mutex_lock(&event_mutex);
 
     if (type == TRACE_PIDS) {
         filtered_pids = rcu_dereference_protected(tr->filtered_pids,
                               lockdep_is_held(&event_mutex));
         other_pids = rcu_dereference_protected(tr->filtered_no_pids,
                               lockdep_is_held(&event_mutex));
     } else {
         filtered_pids = rcu_dereference_protected(tr->filtered_no_pids,
                               lockdep_is_held(&event_mutex));
         other_pids = rcu_dereference_protected(tr->filtered_pids,
                               lockdep_is_held(&event_mutex));
     }
 
     ret = trace_pid_write(filtered_pids, &pid_list, ubuf, cnt);
     if (ret < 0)
         goto out;
 
     if (type == TRACE_PIDS)
         rcu_assign_pointer(tr->filtered_pids, pid_list);
     else
         rcu_assign_pointer(tr->filtered_no_pids, pid_list);
 
     list_for_each_entry(file, &tr->events, list) {
         set_bit(EVENT_FILE_FL_PID_FILTER_BIT, &file->flags);
     }
 
     if (filtered_pids) {
         tracepoint_synchronize_unregister();
         trace_pid_list_free(filtered_pids);
     } else if (pid_list && !other_pids) {
         register_pid_events(tr);
     }
 
     /*
      * Ignoring of pids is done at task switch. But we have to
      * check for those tasks that are currently running.
      * Always do this in case a pid was appended or removed.
      */
     on_each_cpu(ignore_task_cpu, tr, 1);
 
  out:
     mutex_unlock(&event_mutex);
 
     if (ret > 0)
         *ppos += ret;
 
     return ret;
 }
 
 static ssize_t
 ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
                size_t cnt, loff_t *ppos)
 {
     return event_pid_write(filp, ubuf, cnt, ppos, TRACE_PIDS);
 }
 
 static ssize_t
 ftrace_event_npid_write(struct file *filp, const char __user *ubuf,
             size_t cnt, loff_t *ppos)
 {
     return event_pid_write(filp, ubuf, cnt, ppos, TRACE_NO_PIDS);
 }
 
 static int ftrace_event_avail_open(struct inode *inode, struct file *file);
 static int ftrace_event_set_open(struct inode *inode, struct file *file);
 static int ftrace_event_set_pid_open(struct inode *inode, struct file *file);
 static int ftrace_event_set_npid_open(struct inode *inode, struct file *file);
 static int ftrace_event_release(struct inode *inode, struct file *file);
 
 static const struct seq_operations show_event_seq_ops = {
     .start = t_start,
     .next = t_next,
     .show = t_show,
     .stop = t_stop,
 };
 
 static const struct seq_operations show_set_event_seq_ops = {
     .start = s_start,
     .next = s_next,
     .show = t_show,
     .stop = t_stop,
 };
 
 static const struct seq_operations show_set_pid_seq_ops = {
     .start = p_start,
     .next = p_next,
     .show = trace_pid_show,
     .stop = p_stop,
 };
 
 static const struct seq_operations show_set_no_pid_seq_ops = {
     .start = np_start,
     .next = np_next,
     .show = trace_pid_show,
     .stop = p_stop,
 };
 
 static const struct file_operations ftrace_avail_fops = {
     .open = ftrace_event_avail_open,
     .read = seq_read,
     .llseek = seq_lseek,
     .release = seq_release,
 };
 
 static const struct file_operations ftrace_set_event_fops = {
     .open = ftrace_event_set_open,
     .read = seq_read,
     .write = ftrace_event_write,
     .llseek = seq_lseek,
     .release = ftrace_event_release,
 };
 
 static const struct file_operations ftrace_set_event_pid_fops = {
     .open = ftrace_event_set_pid_open,
     .read = seq_read,
     .write = ftrace_event_pid_write,
     .llseek = seq_lseek,
     .release = ftrace_event_release,
 };
 
 static const struct file_operations ftrace_set_event_notrace_pid_fops = {
     .open = ftrace_event_set_npid_open,
     .read = seq_read,
     .write = ftrace_event_npid_write,
     .llseek = seq_lseek,
     .release = ftrace_event_release,
 };
 
 static const struct file_operations ftrace_enable_fops = {
     .open = tracing_open_generic,
     .read = event_enable_read,
     .write = event_enable_write,
     .llseek = default_llseek,
 };
 
 static const struct file_operations ftrace_event_format_fops = {
     .open = trace_format_open,
     .read = seq_read,
     .llseek = seq_lseek,
     .release = seq_release,
 };
 
 static const struct file_operations ftrace_event_id_fops = {
     .read = event_id_read,
     .llseek = default_llseek,
 };
 
 static const struct file_operations ftrace_event_filter_fops = {
     .open = tracing_open_generic,
     .read = event_filter_read,
     .write = event_filter_write,
     .llseek = default_llseek,
 };
 
 static const struct file_operations ftrace_subsystem_filter_fops = {
     .open = subsystem_open,
     .read = subsystem_filter_read,
     .write = subsystem_filter_write,
     .llseek = default_llseek,
     .release = subsystem_release,
 };
 
 static const struct file_operations ftrace_system_enable_fops = {
     .open = subsystem_open,
     .read = system_enable_read,
     .write = system_enable_write,
     .llseek = default_llseek,
     .release = subsystem_release,
 };
 
 static const struct file_operations ftrace_tr_enable_fops = {
     .open = system_tr_open,
     .read = system_enable_read,
     .write = system_enable_write,
     .llseek = default_llseek,
     .release = subsystem_release,
 };
 
 static const struct file_operations ftrace_show_header_fops = {
     .open = tracing_open_generic,
     .read = show_header,
     .llseek = default_llseek,
 };
 
 static int
 ftrace_event_open(struct inode *inode, struct file *file,
           const struct seq_operations *seq_ops)
 {
     struct seq_file *m;
     int ret;
 
     ret = security_locked_down(LOCKDOWN_TRACEFS);
     if (ret)
         return ret;
 
     ret = seq_open(file, seq_ops);
     if (ret < 0)
         return ret;
     m = file->private_data;
     /* copy tr over to seq ops */
     m->private = inode->i_private;
 
     return ret;
 }
 
 static int ftrace_event_release(struct inode *inode, struct file *file)
 {
     struct trace_array *tr = inode->i_private;
 
     trace_array_put(tr);
 
     return seq_release(inode, file);
 }
 
 static int
 ftrace_event_avail_open(struct inode *inode, struct file *file)
 {
     const struct seq_operations *seq_ops = &show_event_seq_ops;
 
     /* Checks for tracefs lockdown */
     return ftrace_event_open(inode, file, seq_ops);
 }
 
 static int
 ftrace_event_set_open(struct inode *inode, struct file *file)
 {
     const struct seq_operations *seq_ops = &show_set_event_seq_ops;
     struct trace_array *tr = inode->i_private;
     int ret;
 
     ret = tracing_check_open_get_tr(tr);
     if (ret)
         return ret;
 
     if ((file->f_mode & FMODE_WRITE) &&
         (file->f_flags & O_TRUNC))
         ftrace_clear_events(tr);
 
     ret = ftrace_event_open(inode, file, seq_ops);
     if (ret < 0)
         trace_array_put(tr);
     return ret;
 }
 
 static int
 ftrace_event_set_pid_open(struct inode *inode, struct file *file)
 {
     const struct seq_operations *seq_ops = &show_set_pid_seq_ops;
     struct trace_array *tr = inode->i_private;
     int ret;
 
     ret = tracing_check_open_get_tr(tr);
     if (ret)
         return ret;
 
     if ((file->f_mode & FMODE_WRITE) &&
         (file->f_flags & O_TRUNC))
         ftrace_clear_event_pids(tr, TRACE_PIDS);
 
     ret = ftrace_event_open(inode, file, seq_ops);
     if (ret < 0)
         trace_array_put(tr);
     return ret;
 }
 
 static int
 ftrace_event_set_npid_open(struct inode *inode, struct file *file)
 {
     const struct seq_operations *seq_ops = &show_set_no_pid_seq_ops;
     struct trace_array *tr = inode->i_private;
     int ret;
 
     ret = tracing_check_open_get_tr(tr);
     if (ret)
         return ret;
 
     if ((file->f_mode & FMODE_WRITE) &&
         (file->f_flags & O_TRUNC))
         ftrace_clear_event_pids(tr, TRACE_NO_PIDS);
 
     ret = ftrace_event_open(inode, file, seq_ops);
     if (ret < 0)
         trace_array_put(tr);
     return ret;
 }
 
 static struct event_subsystem *
 create_new_subsystem(const char *name)
 {
     struct event_subsystem *system;
 
     /* need to create new entry */
     system = kmalloc(sizeof(*system), GFP_KERNEL);
     if (!system)
         return NULL;
 
     system->ref_count = 1;
 
     /* Only allocate if dynamic (kprobes and modules) */
     system->name = kstrdup_const(name, GFP_KERNEL);
     if (!system->name)
         goto out_free;
 
     system->filter = NULL;
 
     system->filter = kzalloc(sizeof(struct event_filter), GFP_KERNEL);
     if (!system->filter)
         goto out_free;
 
     list_add(&system->list, &event_subsystems);
 
     return system;
 
  out_free:
     kfree_const(system->name);
     kfree(system);
     return NULL;
 }
 
 static struct dentry *
 event_subsystem_dir(struct trace_array *tr, const char *name,
             struct trace_event_file *file, struct dentry *parent)
 {
     struct event_subsystem *system, *iter;
     struct trace_subsystem_dir *dir;
     struct dentry *entry;
 
     /* First see if we did not already create this dir */
     list_for_each_entry(dir, &tr->systems, list) {
         system = dir->subsystem;
         if (strcmp(system->name, name) == 0) {
             dir->nr_events++;
             file->system = dir;
             return dir->entry;
         }
     }
 
     /* Now see if the system itself exists. */
     system = NULL;
     list_for_each_entry(iter, &event_subsystems, list) {
         if (strcmp(iter->name, name) == 0) {
             system = iter;
             break;
         }
     }
 
     dir = kmalloc(sizeof(*dir), GFP_KERNEL);
     if (!dir)
         goto out_fail;
 
     if (!system) {
         system = create_new_subsystem(name);
         if (!system)
             goto out_free;
     } else
         __get_system(system);
 
     dir->entry = tracefs_create_dir(name, parent);
     if (!dir->entry) {
         pr_warn("Failed to create system directory %s\n", name);
         __put_system(system);
         goto out_free;
     }
 
     dir->tr = tr;
     dir->ref_count = 1;
     dir->nr_events = 1;
     dir->subsystem = system;
     file->system = dir;
 
     /* the ftrace system is special, do not create enable or filter files */
     if (strcmp(name, "ftrace") != 0) {
 
         entry = tracefs_create_file("filter", TRACE_MODE_WRITE,
                         dir->entry, dir,
                         &ftrace_subsystem_filter_fops);
         if (!entry) {
             kfree(system->filter);
             system->filter = NULL;
             pr_warn("Could not create tracefs '%s/filter' entry\n", name);
         }
 
         trace_create_file("enable", TRACE_MODE_WRITE, dir->entry, dir,
                   &ftrace_system_enable_fops);
     }
 
     list_add(&dir->list, &tr->systems);
 
     return dir->entry;
 
  out_free:
     kfree(dir);
  out_fail:
     /* Only print this message if failed on memory allocation */
     if (!dir || !system)
         pr_warn("No memory to create event subsystem %s\n", name);
     return NULL;
 }
 
 static int
 event_define_fields(struct trace_event_call *call)
 {
     struct list_head *head;
     int ret = 0;
 
     /*
      * Other events may have the same class. Only update
      * the fields if they are not already defined.
      */
     head = trace_get_fields(call);
     if (list_empty(head)) {
         struct trace_event_fields *field = call->class->fields_array;
         unsigned int offset = sizeof(struct trace_entry);
 
         for (; field->type; field++) {
             if (field->type == TRACE_FUNCTION_TYPE) {
                 field->define_fields(call);
                 break;
             }
 
             offset = ALIGN(offset, field->align);
             ret = trace_define_field(call, field->type, field->name,
                          offset, field->size,
                          field->is_signed, field->filter_type);
             if (WARN_ON_ONCE(ret)) {
                 pr_err("error code is %d\n", ret);
                 break;
             }
 
             offset += field->size;
         }
     }
 
     return ret;
 }
 
 static int
 event_create_dir(struct dentry *parent, struct trace_event_file *file)
 {
     struct trace_event_call *call = file->event_call;
     struct trace_array *tr = file->tr;
     struct dentry *d_events;
     const char *name;
     int ret;
 
     /*
      * If the trace point header did not define TRACE_SYSTEM
      * then the system would be called "TRACE_SYSTEM".
      */
     if (strcmp(call->class->system, TRACE_SYSTEM) != 0) {
         d_events = event_subsystem_dir(tr, call->class->system, file, parent);
         if (!d_events)
             return -ENOMEM;
     } else
         d_events = parent;
 
     name = trace_event_name(call);
     file->dir = tracefs_create_dir(name, d_events);
     if (!file->dir) {
         pr_warn("Could not create tracefs '%s' directory\n", name);
         return -1;
     }
 
     if (call->class->reg && !(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE))
         trace_create_file("enable", TRACE_MODE_WRITE, file->dir, file,
                   &ftrace_enable_fops);
 
 #ifdef CONFIG_PERF_EVENTS
     if (call->event.type && call->class->reg)
         trace_create_file("id", TRACE_MODE_READ, file->dir,
                   (void *)(long)call->event.type,
                   &ftrace_event_id_fops);
 #endif
 
     ret = event_define_fields(call);
     if (ret < 0) {
         pr_warn("Could not initialize trace point events/%s\n", name);
         return ret;
     }
 
     /*
      * Only event directories that can be enabled should have
      * triggers or filters.
      */
     if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)) {
         trace_create_file("filter", TRACE_MODE_WRITE, file->dir,
                   file, &ftrace_event_filter_fops);
 
         trace_create_file("trigger", TRACE_MODE_WRITE, file->dir,
                   file, &event_trigger_fops);
     }
 
 #ifdef CONFIG_HIST_TRIGGERS
     trace_create_file("hist", TRACE_MODE_READ, file->dir, file,
               &event_hist_fops);
 #endif
 #ifdef CONFIG_HIST_TRIGGERS_DEBUG
     trace_create_file("hist_debug", TRACE_MODE_READ, file->dir, file,
               &event_hist_debug_fops);
 #endif
     trace_create_file("format", TRACE_MODE_READ, file->dir, call,
               &ftrace_event_format_fops);
 
 #ifdef CONFIG_TRACE_EVENT_INJECT
     if (call->event.type && call->class->reg)
         trace_create_file("inject", 0200, file->dir, file,
                   &event_inject_fops);
 #endif
 
     return 0;
 }
 
 static void remove_event_from_tracers(struct trace_event_call *call)
 {
     struct trace_event_file *file;
     struct trace_array *tr;
 
     do_for_each_event_file_safe(tr, file) {
         if (file->event_call != call)
             continue;
 
         remove_event_file_dir(file);
         /*
          * The do_for_each_event_file_safe() is
          * a double loop. After finding the call for this
          * trace_array, we use break to jump to the next
          * trace_array.
          */
         break;
     } while_for_each_event_file();
 }
 
 static void event_remove(struct trace_event_call *call)
 {
     struct trace_array *tr;
     struct trace_event_file *file;
 
     do_for_each_event_file(tr, file) {
         if (file->event_call != call)
             continue;
 
         if (file->flags & EVENT_FILE_FL_WAS_ENABLED)
             tr->clear_trace = true;
 
         ftrace_event_enable_disable(file, 0);
         /*
          * The do_for_each_event_file() is
          * a double loop. After finding the call for this
          * trace_array, we use break to jump to the next
          * trace_array.
          */
         break;
     } while_for_each_event_file();
 
     if (call->event.funcs)
         __unregister_trace_event(&call->event);
     remove_event_from_tracers(call);
     list_del(&call->list);
 }
 
 static int event_init(struct trace_event_call *call)
 {
     int ret = 0;
     const char *name;
 
     name = trace_event_name(call);
     if (WARN_ON(!name))
         return -EINVAL;
 
     if (call->class->raw_init) {
         ret = call->class->raw_init(call);
         if (ret < 0 && ret != -ENOSYS)
             pr_warn("Could not initialize trace events/%s\n", name);
     }
 
     return ret;
 }
 
 static int
 __register_event(struct trace_event_call *call, struct module *mod)
 {
     int ret;
 
     ret = event_init(call);
     if (ret < 0)
         return ret;
 
     list_add(&call->list, &ftrace_events);
     if (call->flags & TRACE_EVENT_FL_DYNAMIC)
         atomic_set(&call->refcnt, 0);
     else
         call->module = mod;
 
     return 0;
 }
 
 static char *eval_replace(char *ptr, struct trace_eval_map *map, int len)
 {
     int rlen;
     int elen;
 
     /* Find the length of the eval value as a string */
     elen = snprintf(ptr, 0, "%ld", map->eval_value);
     /* Make sure there's enough room to replace the string with the value */
     if (len < elen)
         return NULL;
 
     snprintf(ptr, elen + 1, "%ld", map->eval_value);
 
     /* Get the rest of the string of ptr */
     rlen = strlen(ptr + len);
     memmove(ptr + elen, ptr + len, rlen);
     /* Make sure we end the new string */
     ptr[elen + rlen] = 0;
 
     return ptr + elen;
 }
 
 static void update_event_printk(struct trace_event_call *call,
                 struct trace_eval_map *map)
 {
     char *ptr;
     int quote = 0;
     int len = strlen(map->eval_string);
 
     for (ptr = call->print_fmt; *ptr; ptr++) {
         if (*ptr == '\\') {
             ptr++;
             /* paranoid */
             if (!*ptr)
                 break;
             continue;
         }
         if (*ptr == '"') {
             quote ^= 1;
             continue;
         }
         if (quote)
             continue;
         if (isdigit(*ptr)) {
             /* skip numbers */
             do {
                 ptr++;
                 /* Check for alpha chars like ULL */
             } while (isalnum(*ptr));
             if (!*ptr)
                 break;
             /*
              * A number must have some kind of delimiter after
              * it, and we can ignore that too.
              */
             continue;
         }
         if (isalpha(*ptr) || *ptr == '_') {
             if (strncmp(map->eval_string, ptr, len) == 0 &&
                 !isalnum(ptr[len]) && ptr[len] != '_') {
                 ptr = eval_replace(ptr, map, len);
                 /* enum/sizeof string smaller than value */
                 if (WARN_ON_ONCE(!ptr))
                     return;
                 /*
                  * No need to decrement here, as eval_replace()
                  * returns the pointer to the character passed
                  * the eval, and two evals can not be placed
                  * back to back without something in between.
                  * We can skip that something in between.
                  */
                 continue;
             }
         skip_more:
             do {
                 ptr++;
             } while (isalnum(*ptr) || *ptr == '_');
             if (!*ptr)
                 break;
             /*
              * If what comes after this variable is a '.' or
              * '->' then we can continue to ignore that string.
              */
             if (*ptr == '.' || (ptr[0] == '-' && ptr[1] == '>')) {
                 ptr += *ptr == '.' ? 1 : 2;
                 if (!*ptr)
                     break;
                 goto skip_more;
             }
             /*
              * Once again, we can skip the delimiter that came
              * after the string.
              */
             continue;
         }
     }
 }
 
 static void add_str_to_module(struct module *module, char *str)
 {
     struct module_string *modstr;
 
     modstr = kmalloc(sizeof(*modstr), GFP_KERNEL);
 
     /*
      * If we failed to allocate memory here, then we'll just
      * let the str memory leak when the module is removed.
      * If this fails to allocate, there's worse problems than
      * a leaked string on module removal.
      */
     if (WARN_ON_ONCE(!modstr))
         return;
 
     modstr->module = module;
     modstr->str = str;
 
     list_add(&modstr->next, &module_strings);
 }
 
 static void update_event_fields(struct trace_event_call *call,
                 struct trace_eval_map *map)
 {
     struct ftrace_event_field *field;
     struct list_head *head;
     char *ptr;
     char *str;
     int len = strlen(map->eval_string);
 
     /* Dynamic events should never have field maps */
     if (WARN_ON_ONCE(call->flags & TRACE_EVENT_FL_DYNAMIC))
         return;
 
     head = trace_get_fields(call);
     list_for_each_entry(field, head, link) {
         ptr = strchr(field->type, '[');
         if (!ptr)
             continue;
         ptr++;
 
         if (!isalpha(*ptr) && *ptr != '_')
             continue;
 
         if (strncmp(map->eval_string, ptr, len) != 0)
             continue;
 
         str = kstrdup(field->type, GFP_KERNEL);
         if (WARN_ON_ONCE(!str))
             return;
         ptr = str + (ptr - field->type);
         ptr = eval_replace(ptr, map, len);
         /* enum/sizeof string smaller than value */
         if (WARN_ON_ONCE(!ptr)) {
             kfree(str);
             continue;
         }
 
         /*
          * If the event is part of a module, then we need to free the string
          * when the module is removed. Otherwise, it will stay allocated
          * until a reboot.
          */
         if (call->module)
             add_str_to_module(call->module, str);
 
         field->type = str;
     }
 }
 
 void trace_event_eval_update(struct trace_eval_map **map, int len)
 {
     struct trace_event_call *call, *p;
     const char *last_system = NULL;
     bool first = false;
     int last_i;
     int i;
 
     down_write(&trace_event_sem);
     list_for_each_entry_safe(call, p, &ftrace_events, list) {
         /* events are usually grouped together with systems */
         if (!last_system || call->class->system != last_system) {
             first = true;
             last_i = 0;
             last_system = call->class->system;
         }
 
         /*
          * Since calls are grouped by systems, the likelihood that the
          * next call in the iteration belongs to the same system as the
          * previous call is high. As an optimization, we skip searching
          * for a map[] that matches the call's system if the last call
          * was from the same system. That's what last_i is for. If the
          * call has the same system as the previous call, then last_i
          * will be the index of the first map[] that has a matching
          * system.
          */
         for (i = last_i; i < len; i++) {
             if (call->class->system == map[i]->system) {
                 /* Save the first system if need be */
                 if (first) {
                     last_i = i;
                     first = false;
                 }
                 update_event_printk(call, map[i]);
                 update_event_fields(call, map[i]);
             }
         }
     }
     up_write(&trace_event_sem);
 }
 
 static struct trace_event_file *
 trace_create_new_event(struct trace_event_call *call,
                struct trace_array *tr)
 {
     struct trace_pid_list *no_pid_list;
     struct trace_pid_list *pid_list;
     struct trace_event_file *file;
     unsigned int first;
 
     file = kmem_cache_alloc(file_cachep, GFP_TRACE);
     if (!file)
         return NULL;
 
     pid_list = rcu_dereference_protected(tr->filtered_pids,
                          lockdep_is_held(&event_mutex));
     no_pid_list = rcu_dereference_protected(tr->filtered_no_pids,
                          lockdep_is_held(&event_mutex));
 
     if (!trace_pid_list_first(pid_list, &first) ||
         !trace_pid_list_first(no_pid_list, &first))
         file->flags |= EVENT_FILE_FL_PID_FILTER;
 
     file->event_call = call;
     file->tr = tr;
     atomic_set(&file->sm_ref, 0);
     atomic_set(&file->tm_ref, 0);
     INIT_LIST_HEAD(&file->triggers);
     list_add(&file->list, &tr->events);
 
     return file;
 }
 
 /* Add an event to a trace directory */
 static int
 __trace_add_new_event(struct trace_event_call *call, struct trace_array *tr)
 {
     struct trace_event_file *file;
 
     file = trace_create_new_event(call, tr);
     if (!file)
         return -ENOMEM;
 
     if (eventdir_initialized)
         return event_create_dir(tr->event_dir, file);
     else
         return event_define_fields(call);
 }
 
 /*
  * Just create a descriptor for early init. A descriptor is required
  * for enabling events at boot. We want to enable events before
  * the filesystem is initialized.
  */
 static int
 __trace_early_add_new_event(struct trace_event_call *call,
                 struct trace_array *tr)
 {
     struct trace_event_file *file;
 
     file = trace_create_new_event(call, tr);
     if (!file)
         return -ENOMEM;
 
     return event_define_fields(call);
 }
 
 struct ftrace_module_file_ops;
 static void __add_event_to_tracers(struct trace_event_call *call);
 
 /* Add an additional event_call dynamically */
 int trace_add_event_call(struct trace_event_call *call)
 {
     int ret;
     lockdep_assert_held(&event_mutex);
 
     mutex_lock(&trace_types_lock);
 
     ret = __register_event(call, NULL);
     if (ret >= 0)
         __add_event_to_tracers(call);
 
     mutex_unlock(&trace_types_lock);
     return ret;
 }
 EXPORT_SYMBOL_GPL(trace_add_event_call);
 
 /*
  * Must be called under locking of trace_types_lock, event_mutex and
  * trace_event_sem.
  */
 static void __trace_remove_event_call(struct trace_event_call *call)
 {
     event_remove(call);
     trace_destroy_fields(call);
     free_event_filter(call->filter);
     call->filter = NULL;
 }
 
 static int probe_remove_event_call(struct trace_event_call *call)
 {
     struct trace_array *tr;
     struct trace_event_file *file;
 
 #ifdef CONFIG_PERF_EVENTS
     if (call->perf_refcount)
         return -EBUSY;
 #endif
     do_for_each_event_file(tr, file) {
         if (file->event_call != call)
             continue;
         /*
          * We can't rely on ftrace_event_enable_disable(enable => 0)
          * we are going to do, EVENT_FILE_FL_SOFT_MODE can suppress
          * TRACE_REG_UNREGISTER.
          */
         if (file->flags & EVENT_FILE_FL_ENABLED)
             return -EBUSY;
         /*
          * The do_for_each_event_file_safe() is
          * a double loop. After finding the call for this
          * trace_array, we use break to jump to the next
          * trace_array.
          */
         break;
     } while_for_each_event_file();
 
     __trace_remove_event_call(call);
 
     return 0;
 }
 
 /* Remove an event_call */
 int trace_remove_event_call(struct trace_event_call *call)
 {
     int ret;
 
     lockdep_assert_held(&event_mutex);
 
     mutex_lock(&trace_types_lock);
     down_write(&trace_event_sem);
     ret = probe_remove_event_call(call);
     up_write(&trace_event_sem);
     mutex_unlock(&trace_types_lock);
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(trace_remove_event_call);
 
 #define for_each_event(event, start, end)           \
     for (event = start;                 \
          (unsigned long)event < (unsigned long)end;     \
          event++)
 
 #ifdef CONFIG_MODULES
 
 static void trace_module_add_events(struct module *mod)
 {
     struct trace_event_call **call, **start, **end;
 
     if (!mod->num_trace_events)
         return;
 
     /* Don't add infrastructure for mods without tracepoints */
     if (trace_module_has_bad_taint(mod)) {
         pr_err("%s: module has bad taint, not creating trace events\n",
                mod->name);
         return;
     }
 
     start = mod->trace_events;
     end = mod->trace_events + mod->num_trace_events;
 
     for_each_event(call, start, end) {
         __register_event(*call, mod);
         __add_event_to_tracers(*call);
     }
 }
 
 static void trace_module_remove_events(struct module *mod)
 {
     struct trace_event_call *call, *p;
     struct module_string *modstr, *m;
 
     down_write(&trace_event_sem);
     list_for_each_entry_safe(call, p, &ftrace_events, list) {
         if ((call->flags & TRACE_EVENT_FL_DYNAMIC) || !call->module)
             continue;
         if (call->module == mod)
             __trace_remove_event_call(call);
     }
     /* Check for any strings allocade for this module */
     list_for_each_entry_safe(modstr, m, &module_strings, next) {
         if (modstr->module != mod)
             continue;
         list_del(&modstr->next);
         kfree(modstr->str);
         kfree(modstr);
     }
     up_write(&trace_event_sem);
 
     /*
      * It is safest to reset the ring buffer if the module being unloaded
      * registered any events that were used. The only worry is if
      * a new module gets loaded, and takes on the same id as the events
      * of this module. When printing out the buffer, traced events left
      * over from this module may be passed to the new module events and
      * unexpected results may occur.
      */
     tracing_reset_all_online_cpus();
 }
 
 static int trace_module_notify(struct notifier_block *self,
                    unsigned long val, void *data)
 {
     struct module *mod = data;
 
     mutex_lock(&event_mutex);
     mutex_lock(&trace_types_lock);
     switch (val) {
     case MODULE_STATE_COMING:
         trace_module_add_events(mod);
         break;
     case MODULE_STATE_GOING:
         trace_module_remove_events(mod);
         break;
     }
     mutex_unlock(&trace_types_lock);
     mutex_unlock(&event_mutex);
 
     return NOTIFY_OK;
 }
 
 static struct notifier_block trace_module_nb = {
     .notifier_call = trace_module_notify,
     .priority = 1, /* higher than trace.c module notify */
 };
 #endif /* CONFIG_MODULES */
 
 /* Create a new event directory structure for a trace directory. */
 static void
 __trace_add_event_dirs(struct trace_array *tr)
 {
     struct trace_event_call *call;
     int ret;
 
     list_for_each_entry(call, &ftrace_events, list) {
         ret = __trace_add_new_event(call, tr);
         if (ret < 0)
             pr_warn("Could not create directory for event %s\n",
                 trace_event_name(call));
     }
 }
 
 /* Returns any file that matches the system and event */
 struct trace_event_file *
 __find_event_file(struct trace_array *tr, const char *system, const char *event)
 {
     struct trace_event_file *file;
     struct trace_event_call *call;
     const char *name;
 
     list_for_each_entry(file, &tr->events, list) {
 
         call = file->event_call;
         name = trace_event_name(call);
 
         if (!name || !call->class)
             continue;
 
         if (strcmp(event, name) == 0 &&
             strcmp(system, call->class->system) == 0)
             return file;
     }
     return NULL;
 }
 
 /* Returns valid trace event files that match system and event */
 struct trace_event_file *
 find_event_file(struct trace_array *tr, const char *system, const char *event)
 {
     struct trace_event_file *file;
 
     file = __find_event_file(tr, system, event);
     if (!file || !file->event_call->class->reg ||
         file->event_call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)
         return NULL;
 
     return file;
 }
 
 /**
  * trace_get_event_file - Find and return a trace event file
  * @instance: The name of the trace instance containing the event
  * @system: The name of the system containing the event
  * @event: The name of the event
  *
  * Return a trace event file given the trace instance name, trace
  * system, and trace event name.  If the instance name is NULL, it
  * refers to the top-level trace array.
  *
  * This function will look it up and return it if found, after calling
  * trace_array_get() to prevent the instance from going away, and
  * increment the event's module refcount to prevent it from being
  * removed.
  *
  * To release the file, call trace_put_event_file(), which will call
  * trace_array_put() and decrement the event's module refcount.
  *
  * Return: The trace event on success, ERR_PTR otherwise.
  */
 struct trace_event_file *trace_get_event_file(const char *instance,
                           const char *system,
                           const char *event)
 {
     struct trace_array *tr = top_trace_array();
     struct trace_event_file *file = NULL;
     int ret = -EINVAL;
 
     if (instance) {
         tr = trace_array_find_get(instance);
         if (!tr)
             return ERR_PTR(-ENOENT);
     } else {
         ret = trace_array_get(tr);
         if (ret)
             return ERR_PTR(ret);
     }
 
     mutex_lock(&event_mutex);
 
     file = find_event_file(tr, system, event);
     if (!file) {
         trace_array_put(tr);
         ret = -EINVAL;
         goto out;
     }
 
     /* Don't let event modules unload while in use */
     ret = trace_event_try_get_ref(file->event_call);
     if (!ret) {
         trace_array_put(tr);
         ret = -EBUSY;
         goto out;
     }
 
     ret = 0;
  out:
     mutex_unlock(&event_mutex);
 
     if (ret)
         file = ERR_PTR(ret);
 
     return file;
 }
 EXPORT_SYMBOL_GPL(trace_get_event_file);
 
 /**
  * trace_put_event_file - Release a file from trace_get_event_file()
  * @file: The trace event file
  *
  * If a file was retrieved using trace_get_event_file(), this should
  * be called when it's no longer needed.  It will cancel the previous
  * trace_array_get() called by that function, and decrement the
  * event's module refcount.
  */
 void trace_put_event_file(struct trace_event_file *file)
 {
     mutex_lock(&event_mutex);
     trace_event_put_ref(file->event_call);
     mutex_unlock(&event_mutex);
 
     trace_array_put(file->tr);
 }
 EXPORT_SYMBOL_GPL(trace_put_event_file);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 /* Avoid typos */
 #define ENABLE_EVENT_STR    "enable_event"
 #define DISABLE_EVENT_STR   "disable_event"
 
 struct event_probe_data {
     struct trace_event_file *file;
     unsigned long           count;
     int             ref;
     bool                enable;
 };
 
 static void update_event_probe(struct event_probe_data *data)
 {
     if (data->enable)
         clear_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &data->file->flags);
     else
         set_bit(EVENT_FILE_FL_SOFT_DISABLED_BIT, &data->file->flags);
 }
 
 static void
 event_enable_probe(unsigned long ip, unsigned long parent_ip,
            struct trace_array *tr, struct ftrace_probe_ops *ops,
            void *data)
 {
     struct ftrace_func_mapper *mapper = data;
     struct event_probe_data *edata;
     void **pdata;
 
     pdata = ftrace_func_mapper_find_ip(mapper, ip);
     if (!pdata || !*pdata)
         return;
 
     edata = *pdata;
     update_event_probe(edata);
 }
 
 static void
 event_enable_count_probe(unsigned long ip, unsigned long parent_ip,
              struct trace_array *tr, struct ftrace_probe_ops *ops,
              void *data)
 {
     struct ftrace_func_mapper *mapper = data;
     struct event_probe_data *edata;
     void **pdata;
 
     pdata = ftrace_func_mapper_find_ip(mapper, ip);
     if (!pdata || !*pdata)
         return;
 
     edata = *pdata;
 
     if (!edata->count)
         return;
 
     /* Skip if the event is in a state we want to switch to */
     if (edata->enable == !(edata->file->flags & EVENT_FILE_FL_SOFT_DISABLED))
         return;
 
     if (edata->count != -1)
         (edata->count)--;
 
     update_event_probe(edata);
 }
 
 static int
 event_enable_print(struct seq_file *m, unsigned long ip,
            struct ftrace_probe_ops *ops, void *data)
 {
     struct ftrace_func_mapper *mapper = data;
     struct event_probe_data *edata;
     void **pdata;
 
     pdata = ftrace_func_mapper_find_ip(mapper, ip);
 
     if (WARN_ON_ONCE(!pdata || !*pdata))
         return 0;
 
     edata = *pdata;
 
     seq_printf(m, "%ps:", (void *)ip);
 
     seq_printf(m, "%s:%s:%s",
            edata->enable ? ENABLE_EVENT_STR : DISABLE_EVENT_STR,
            edata->file->event_call->class->system,
            trace_event_name(edata->file->event_call));
 
     if (edata->count == -1)
         seq_puts(m, ":unlimited\n");
     else
         seq_printf(m, ":count=%ld\n", edata->count);
 
     return 0;
 }
 
 static int
 event_enable_init(struct ftrace_probe_ops *ops, struct trace_array *tr,
           unsigned long ip, void *init_data, void **data)
 {
     struct ftrace_func_mapper *mapper = *data;
     struct event_probe_data *edata = init_data;
     int ret;
 
     if (!mapper) {
         mapper = allocate_ftrace_func_mapper();
         if (!mapper)
             return -ENODEV;
         *data = mapper;
     }
 
     ret = ftrace_func_mapper_add_ip(mapper, ip, edata);
     if (ret < 0)
         return ret;
 
     edata->ref++;
 
     return 0;
 }
 
 static int free_probe_data(void *data)
 {
     struct event_probe_data *edata = data;
 
     edata->ref--;
     if (!edata->ref) {
         /* Remove the SOFT_MODE flag */
         __ftrace_event_enable_disable(edata->file, 0, 1);
         trace_event_put_ref(edata->file->event_call);
         kfree(edata);
     }
     return 0;
 }
 
 static void
 event_enable_free(struct ftrace_probe_ops *ops, struct trace_array *tr,
           unsigned long ip, void *data)
 {
     struct ftrace_func_mapper *mapper = data;
     struct event_probe_data *edata;
 
     if (!ip) {
         if (!mapper)
             return;
         free_ftrace_func_mapper(mapper, free_probe_data);
         return;
     }
 
     edata = ftrace_func_mapper_remove_ip(mapper, ip);
 
     if (WARN_ON_ONCE(!edata))
         return;
 
     if (WARN_ON_ONCE(edata->ref <= 0))
         return;
 
     free_probe_data(edata);
 }
 
 static struct ftrace_probe_ops event_enable_probe_ops = {
     .func           = event_enable_probe,
     .print          = event_enable_print,
     .init           = event_enable_init,
     .free           = event_enable_free,
 };
 
 static struct ftrace_probe_ops event_enable_count_probe_ops = {
     .func           = event_enable_count_probe,
     .print          = event_enable_print,
     .init           = event_enable_init,
     .free           = event_enable_free,
 };
 
 static struct ftrace_probe_ops event_disable_probe_ops = {
     .func           = event_enable_probe,
     .print          = event_enable_print,
     .init           = event_enable_init,
     .free           = event_enable_free,
 };
 
 static struct ftrace_probe_ops event_disable_count_probe_ops = {
     .func           = event_enable_count_probe,
     .print          = event_enable_print,
     .init           = event_enable_init,
     .free           = event_enable_free,
 };
 
 static int
 event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
           char *glob, char *cmd, char *param, int enabled)
 {
     struct trace_event_file *file;
     struct ftrace_probe_ops *ops;
     struct event_probe_data *data;
     const char *system;
     const char *event;
     char *number;
     bool enable;
     int ret;
 
     if (!tr)
         return -ENODEV;
 
     /* hash funcs only work with set_ftrace_filter */
     if (!enabled || !param)
         return -EINVAL;
 
     system = strsep(&param, ":");
     if (!param)
         return -EINVAL;
 
     event = strsep(&param, ":");
 
     mutex_lock(&event_mutex);
 
     ret = -EINVAL;
     file = find_event_file(tr, system, event);
     if (!file)
         goto out;
 
     enable = strcmp(cmd, ENABLE_EVENT_STR) == 0;
 
     if (enable)
         ops = param ? &event_enable_count_probe_ops : &event_enable_probe_ops;
     else
         ops = param ? &event_disable_count_probe_ops : &event_disable_probe_ops;
 
     if (glob[0] == '!') {
         ret = unregister_ftrace_function_probe_func(glob+1, tr, ops);
         goto out;
     }
 
     ret = -ENOMEM;
 
     data = kzalloc(sizeof(*data), GFP_KERNEL);
     if (!data)
         goto out;
 
     data->enable = enable;
     data->count = -1;
     data->file = file;
 
     if (!param)
         goto out_reg;
 
     number = strsep(&param, ":");
 
     ret = -EINVAL;
     if (!strlen(number))
         goto out_free;
 
     /*
      * We use the callback data field (which is a pointer)
      * as our counter.
      */
     ret = kstrtoul(number, 0, &data->count);
     if (ret)
         goto out_free;
 
  out_reg:
     /* Don't let event modules unload while probe registered */
     ret = trace_event_try_get_ref(file->event_call);
     if (!ret) {
         ret = -EBUSY;
         goto out_free;
     }
 
     ret = __ftrace_event_enable_disable(file, 1, 1);
     if (ret < 0)
         goto out_put;
 
     ret = register_ftrace_function_probe(glob, tr, ops, data);
     /*
      * The above returns on success the # of functions enabled,
      * but if it didn't find any functions it returns zero.
      * Consider no functions a failure too.
      */
     if (!ret) {
         ret = -ENOENT;
         goto out_disable;
     } else if (ret < 0)
         goto out_disable;
     /* Just return zero, not the number of enabled functions */
     ret = 0;
  out:
     mutex_unlock(&event_mutex);
     return ret;
 
  out_disable:
     __ftrace_event_enable_disable(file, 0, 1);
  out_put:
     trace_event_put_ref(file->event_call);
  out_free:
     kfree(data);
     goto out;
 }
 
 static struct ftrace_func_command event_enable_cmd = {
     .name           = ENABLE_EVENT_STR,
     .func           = event_enable_func,
 };
 
 static struct ftrace_func_command event_disable_cmd = {
     .name           = DISABLE_EVENT_STR,
     .func           = event_enable_func,
 };
 
 static __init int register_event_cmds(void)
 {
     int ret;
 
     ret = register_ftrace_command(&event_enable_cmd);
     if (WARN_ON(ret < 0))
         return ret;
     ret = register_ftrace_command(&event_disable_cmd);
     if (WARN_ON(ret < 0))
         unregister_ftrace_command(&event_enable_cmd);
     return ret;
 }
 #else
 static inline int register_event_cmds(void) { return 0; }
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 /*
  * The top level array and trace arrays created by boot-time tracing
  * have already had its trace_event_file descriptors created in order
  * to allow for early events to be recorded.
  * This function is called after the tracefs has been initialized,
  * and we now have to create the files associated to the events.
  */
 static void __trace_early_add_event_dirs(struct trace_array *tr)
 {
     struct trace_event_file *file;
     int ret;
 
 
     list_for_each_entry(file, &tr->events, list) {
         ret = event_create_dir(tr->event_dir, file);
         if (ret < 0)
             pr_warn("Could not create directory for event %s\n",
                 trace_event_name(file->event_call));
     }
 }
 
 /*
  * For early boot up, the top trace array and the trace arrays created
  * by boot-time tracing require to have a list of events that can be
  * enabled. This must be done before the filesystem is set up in order
  * to allow events to be traced early.
  */
 void __trace_early_add_events(struct trace_array *tr)
 {
     struct trace_event_call *call;
     int ret;
 
     list_for_each_entry(call, &ftrace_events, list) {
         /* Early boot up should not have any modules loaded */
         if (!(call->flags & TRACE_EVENT_FL_DYNAMIC) &&
             WARN_ON_ONCE(call->module))
             continue;
 
         ret = __trace_early_add_new_event(call, tr);
         if (ret < 0)
             pr_warn("Could not create early event %s\n",
                 trace_event_name(call));
     }
 }
 
 /* Remove the event directory structure for a trace directory. */
 static void
 __trace_remove_event_dirs(struct trace_array *tr)
 {
     struct trace_event_file *file, *next;
 
     list_for_each_entry_safe(file, next, &tr->events, list)
         remove_event_file_dir(file);
 }
 
 static void __add_event_to_tracers(struct trace_event_call *call)
 {
     struct trace_array *tr;
 
     list_for_each_entry(tr, &ftrace_trace_arrays, list)
         __trace_add_new_event(call, tr);
 }
 
 extern struct trace_event_call *__start_ftrace_events[];
 extern struct trace_event_call *__stop_ftrace_events[];
 
 static char bootup_event_buf[COMMAND_LINE_SIZE] __initdata;
 
 static __init int setup_trace_event(char *str)
 {
     strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
     ring_buffer_expanded = true;
     disable_tracing_selftest("running event tracing");
 
     return 1;
 }
 __setup("trace_event=", setup_trace_event);
 
 /* Expects to have event_mutex held when called */
 static int
 create_event_toplevel_files(struct dentry *parent, struct trace_array *tr)
 {
     struct dentry *d_events;
     struct dentry *entry;
 
     entry = trace_create_file("set_event", TRACE_MODE_WRITE, parent,
                   tr, &ftrace_set_event_fops);
     if (!entry)
         return -ENOMEM;
 
     d_events = tracefs_create_dir("events", parent);
     if (!d_events) {
         pr_warn("Could not create tracefs 'events' directory\n");
         return -ENOMEM;
     }
 
     entry = trace_create_file("enable", TRACE_MODE_WRITE, d_events,
                   tr, &ftrace_tr_enable_fops);
     if (!entry)
         return -ENOMEM;
 
     /* There are not as crucial, just warn if they are not created */
 
     trace_create_file("set_event_pid", TRACE_MODE_WRITE, parent,
               tr, &ftrace_set_event_pid_fops);
 
     trace_create_file("set_event_notrace_pid",
               TRACE_MODE_WRITE, parent, tr,
               &ftrace_set_event_notrace_pid_fops);
 
     /* ring buffer internal formats */
     trace_create_file("header_page", TRACE_MODE_READ, d_events,
                   ring_buffer_print_page_header,
                   &ftrace_show_header_fops);
 
     trace_create_file("header_event", TRACE_MODE_READ, d_events,
                   ring_buffer_print_entry_header,
                   &ftrace_show_header_fops);
 
     tr->event_dir = d_events;
 
     return 0;
 }
 
 /**
  * event_trace_add_tracer - add a instance of a trace_array to events
  * @parent: The parent dentry to place the files/directories for events in
  * @tr: The trace array associated with these events
  *
  * When a new instance is created, it needs to set up its events
  * directory, as well as other files associated with events. It also
  * creates the event hierarchy in the @parent/events directory.
  *
  * Returns 0 on success.
  *
  * Must be called with event_mutex held.
  */
 int event_trace_add_tracer(struct dentry *parent, struct trace_array *tr)
 {
     int ret;
 
     lockdep_assert_held(&event_mutex);
 
     ret = create_event_toplevel_files(parent, tr);
     if (ret)
         goto out;
 
     down_write(&trace_event_sem);
     /* If tr already has the event list, it is initialized in early boot. */
     if (unlikely(!list_empty(&tr->events)))
         __trace_early_add_event_dirs(tr);
     else
         __trace_add_event_dirs(tr);
     up_write(&trace_event_sem);
 
  out:
     return ret;
 }
 
 /*
  * The top trace array already had its file descriptors created.
  * Now the files themselves need to be created.
  */
 static __init int
 early_event_add_tracer(struct dentry *parent, struct trace_array *tr)
 {
     int ret;
 
     mutex_lock(&event_mutex);
 
     ret = create_event_toplevel_files(parent, tr);
     if (ret)
         goto out_unlock;
 
     down_write(&trace_event_sem);
     __trace_early_add_event_dirs(tr);
     up_write(&trace_event_sem);
 
  out_unlock:
     mutex_unlock(&event_mutex);
 
     return ret;
 }
 
 /* Must be called with event_mutex held */
 int event_trace_del_tracer(struct trace_array *tr)
 {
     lockdep_assert_held(&event_mutex);
 
     /* Disable any event triggers and associated soft-disabled events */
     clear_event_triggers(tr);
 
     /* Clear the pid list */
     __ftrace_clear_event_pids(tr, TRACE_PIDS | TRACE_NO_PIDS);
 
     /* Disable any running events */
     __ftrace_set_clr_event_nolock(tr, NULL, NULL, NULL, 0);
 
     /* Make sure no more events are being executed */
     tracepoint_synchronize_unregister();
 
     down_write(&trace_event_sem);
     __trace_remove_event_dirs(tr);
     tracefs_remove(tr->event_dir);
     up_write(&trace_event_sem);
 
     tr->event_dir = NULL;
 
     return 0;
 }
 
 static __init int event_trace_memsetup(void)
 {
     field_cachep = KMEM_CACHE(ftrace_event_field, SLAB_PANIC);
     file_cachep = KMEM_CACHE(trace_event_file, SLAB_PANIC);
     return 0;
 }
 
 static __init void
 early_enable_events(struct trace_array *tr, bool disable_first)
 {
     char *buf = bootup_event_buf;
     char *token;
     int ret;
 
     while (true) {
         token = strsep(&buf, ",");
 
         if (!token)
             break;
 
         if (*token) {
             /* Restarting syscalls requires that we stop them first */
             if (disable_first)
                 ftrace_set_clr_event(tr, token, 0);
 
             ret = ftrace_set_clr_event(tr, token, 1);
             if (ret)
                 pr_warn("Failed to enable trace event: %s\n", token);
         }
 
         /* Put back the comma to allow this to be called again */
         if (buf)
             *(buf - 1) = ',';
     }
 }
 
 static __init int event_trace_enable(void)
 {
     struct trace_array *tr = top_trace_array();
     struct trace_event_call **iter, *call;
     int ret;
 
     if (!tr)
         return -ENODEV;
 
     for_each_event(iter, __start_ftrace_events, __stop_ftrace_events) {
 
         call = *iter;
         ret = event_init(call);
         if (!ret)
             list_add(&call->list, &ftrace_events);
     }
 
     /*
      * We need the top trace array to have a working set of trace
      * points at early init, before the debug files and directories
      * are created. Create the file entries now, and attach them
      * to the actual file dentries later.
      */
     __trace_early_add_events(tr);
 
     early_enable_events(tr, false);
 
     trace_printk_start_comm();
 
     register_event_cmds();
 
     register_trigger_cmds();
 
     return 0;
 }
 
 /*
  * event_trace_enable() is called from trace_event_init() first to
  * initialize events and perhaps start any events that are on the
  * command line. Unfortunately, there are some events that will not
  * start this early, like the system call tracepoints that need
  * to set the %SYSCALL_WORK_SYSCALL_TRACEPOINT flag of pid 1. But
  * event_trace_enable() is called before pid 1 starts, and this flag
  * is never set, making the syscall tracepoint never get reached, but
  * the event is enabled regardless (and not doing anything).
  */
 static __init int event_trace_enable_again(void)
 {
     struct trace_array *tr;
 
     tr = top_trace_array();
     if (!tr)
         return -ENODEV;
 
     early_enable_events(tr, true);
 
     return 0;
 }
 
 early_initcall(event_trace_enable_again);
 
 /* Init fields which doesn't related to the tracefs */
 static __init int event_trace_init_fields(void)
 {
     if (trace_define_generic_fields())
         pr_warn("tracing: Failed to allocated generic fields");
 
     if (trace_define_common_fields())
         pr_warn("tracing: Failed to allocate common fields");
 
     return 0;
 }
 
 __init int event_trace_init(void)
 {
     struct trace_array *tr;
     int ret;
 
     tr = top_trace_array();
     if (!tr)
         return -ENODEV;
 
     trace_create_file("available_events", TRACE_MODE_READ,
               NULL, tr, &ftrace_avail_fops);
 
     ret = early_event_add_tracer(NULL, tr);
     if (ret)
         return ret;
 
 #ifdef CONFIG_MODULES
     ret = register_module_notifier(&trace_module_nb);
     if (ret)
         pr_warn("Failed to register trace events module notifier\n");
 #endif
 
     eventdir_initialized = true;
 
     return 0;
 }
 
 void __init trace_event_init(void)
 {
     event_trace_memsetup();
     init_ftrace_syscalls();
     event_trace_enable();
     event_trace_init_fields();
 }
 
 #ifdef CONFIG_EVENT_TRACE_STARTUP_TEST
 
 static DEFINE_SPINLOCK(test_spinlock);
 static DEFINE_SPINLOCK(test_spinlock_irq);
 static DEFINE_MUTEX(test_mutex);
 
 static __init void test_work(struct work_struct *dummy)
 {
     spin_lock(&test_spinlock);
     spin_lock_irq(&test_spinlock_irq);
     udelay(1);
     spin_unlock_irq(&test_spinlock_irq);
     spin_unlock(&test_spinlock);
 
     mutex_lock(&test_mutex);
     msleep(1);
     mutex_unlock(&test_mutex);
 }
 
 static __init int event_test_thread(void *unused)
 {
     void *test_malloc;
 
     test_malloc = kmalloc(1234, GFP_KERNEL);
     if (!test_malloc)
         pr_info("failed to kmalloc\n");
 
     schedule_on_each_cpu(test_work);
 
     kfree(test_malloc);
 
     set_current_state(TASK_INTERRUPTIBLE);
     while (!kthread_should_stop()) {
         schedule();
         set_current_state(TASK_INTERRUPTIBLE);
     }
     __set_current_state(TASK_RUNNING);
 
     return 0;
 }
 
 /*
  * Do various things that may trigger events.
  */
 static __init void event_test_stuff(void)
 {
     struct task_struct *test_thread;
 
     test_thread = kthread_run(event_test_thread, NULL, "test-events");
     msleep(1);
     kthread_stop(test_thread);
 }
 
 /*
  * For every trace event defined, we will test each trace point separately,
  * and then by groups, and finally all trace points.
  */
 static __init void event_trace_self_tests(void)
 {
     struct trace_subsystem_dir *dir;
     struct trace_event_file *file;
     struct trace_event_call *call;
     struct event_subsystem *system;
     struct trace_array *tr;
     int ret;
 
     tr = top_trace_array();
     if (!tr)
         return;
 
     pr_info("Running tests on trace events:\n");
 
     list_for_each_entry(file, &tr->events, list) {
 
         call = file->event_call;
 
         /* Only test those that have a probe */
         if (!call->class || !call->class->probe)
             continue;
 
 /*
  * Testing syscall events here is pretty useless, but
  * we still do it if configured. But this is time consuming.
  * What we really need is a user thread to perform the
  * syscalls as we test.
  */
 #ifndef CONFIG_EVENT_TRACE_TEST_SYSCALLS
         if (call->class->system &&
             strcmp(call->class->system, "syscalls") == 0)
             continue;
 #endif
 
         pr_info("Testing event %s: ", trace_event_name(call));
 
         /*
          * If an event is already enabled, someone is using
          * it and the self test should not be on.
          */
         if (file->flags & EVENT_FILE_FL_ENABLED) {
             pr_warn("Enabled event during self test!\n");
             WARN_ON_ONCE(1);
             continue;
         }
 
         ftrace_event_enable_disable(file, 1);
         event_test_stuff();
         ftrace_event_enable_disable(file, 0);
 
         pr_cont("OK\n");
     }
 
     /* Now test at the sub system level */
 
     pr_info("Running tests on trace event systems:\n");
 
     list_for_each_entry(dir, &tr->systems, list) {
 
         system = dir->subsystem;
 
         /* the ftrace system is special, skip it */
         if (strcmp(system->name, "ftrace") == 0)
             continue;
 
         pr_info("Testing event system %s: ", system->name);
 
         ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 1);
         if (WARN_ON_ONCE(ret)) {
             pr_warn("error enabling system %s\n",
                 system->name);
             continue;
         }
 
         event_test_stuff();
 
         ret = __ftrace_set_clr_event(tr, NULL, system->name, NULL, 0);
         if (WARN_ON_ONCE(ret)) {
             pr_warn("error disabling system %s\n",
                 system->name);
             continue;
         }
 
         pr_cont("OK\n");
     }
 
     /* Test with all events enabled */
 
     pr_info("Running tests on all trace events:\n");
     pr_info("Testing all events: ");
 
     ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 1);
     if (WARN_ON_ONCE(ret)) {
         pr_warn("error enabling all events\n");
         return;
     }
 
     event_test_stuff();
 
     /* reset sysname */
     ret = __ftrace_set_clr_event(tr, NULL, NULL, NULL, 0);
     if (WARN_ON_ONCE(ret)) {
         pr_warn("error disabling all events\n");
         return;
     }
 
     pr_cont("OK\n");
 }
 
 #ifdef CONFIG_FUNCTION_TRACER
 
 static DEFINE_PER_CPU(atomic_t, ftrace_test_event_disable);
 
 static struct trace_event_file event_trace_file __initdata;
 
 static void __init
 function_test_events_call(unsigned long ip, unsigned long parent_ip,
               struct ftrace_ops *op, struct ftrace_regs *regs)
 {
     struct trace_buffer *buffer;
     struct ring_buffer_event *event;
     struct ftrace_entry *entry;
     unsigned int trace_ctx;
     long disabled;
     int cpu;
 
     trace_ctx = tracing_gen_ctx();
     preempt_disable_notrace();
     cpu = raw_smp_processor_id();
     disabled = atomic_inc_return(&per_cpu(ftrace_test_event_disable, cpu));
 
     if (disabled != 1)
         goto out;
 
     event = trace_event_buffer_lock_reserve(&buffer, &event_trace_file,
                         TRACE_FN, sizeof(*entry),
                         trace_ctx);
     if (!event)
         goto out;
     entry   = ring_buffer_event_data(event);
     entry->ip           = ip;
     entry->parent_ip        = parent_ip;
 
     event_trigger_unlock_commit(&event_trace_file, buffer, event,
                     entry, trace_ctx);
  out:
     atomic_dec(&per_cpu(ftrace_test_event_disable, cpu));
     preempt_enable_notrace();
 }
 
 static struct ftrace_ops trace_ops __initdata  =
 {
     .func = function_test_events_call,
 };
 
 static __init void event_trace_self_test_with_function(void)
 {
     int ret;
 
     event_trace_file.tr = top_trace_array();
     if (WARN_ON(!event_trace_file.tr))
         return;
 
     ret = register_ftrace_function(&trace_ops);
     if (WARN_ON(ret < 0)) {
         pr_info("Failed to enable function tracer for event tests\n");
         return;
     }
     pr_info("Running tests again, along with the function tracer\n");
     event_trace_self_tests();
     unregister_ftrace_function(&trace_ops);
 }
 #else
 static __init void event_trace_self_test_with_function(void)
 {
 }
 #endif
 
 static __init int event_trace_self_tests_init(void)
 {
     if (!tracing_selftest_disabled) {
         event_trace_self_tests();
         event_trace_self_test_with_function();
     }
 
     return 0;
 }
 
 late_initcall(event_trace_self_tests_init);
 
 #endif