kernel/trace/trace_functions.c

   1 /*
   2  * ring buffer based function tracer
   3  *
   4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
   6  *
   7  * Based on code from the latency_tracer, that is:
   8  *
   9  *  Copyright (C) 2004-2006 Ingo Molnar
  10  *  Copyright (C) 2004 William Lee Irwin III
  11  */
  12 #include <linux/debugfs.h>
  13 #include <linux/uaccess.h>
  14 #include <linux/ftrace.h>
  15 #include <linux/fs.h>
  16
  17 #include "trace.h"
  18
  19 /* function tracing enabled */
  20 static int                      ftrace_function_enabled;
  21
  22 static struct trace_array       *func_trace;
  23
  24 static void tracing_start_function_trace(void);
  25 static void tracing_stop_function_trace(void);
  26
  27 static int function_trace_init(struct trace_array *tr)
  28 {
  29         func_trace = tr;
  30         tr->cpu = get_cpu();
  31         put_cpu();
  32
  33         tracing_start_cmdline_record();
  34         tracing_start_function_trace();
  35         return 0;
  36 }
  37
  38 static void function_trace_reset(struct trace_array *tr)
  39 {
  40         tracing_stop_function_trace();
  41         tracing_stop_cmdline_record();
  42 }
  43
  44 static void function_trace_start(struct trace_array *tr)
  45 {
  46         tracing_reset_online_cpus(tr);
  47 }
  48
  49 static void
  50 function_trace_call_preempt_only(unsigned long ip, unsigned long parent_ip)
  51 {
  52         struct trace_array *tr = func_trace;
  53         struct trace_array_cpu *data;
  54         unsigned long flags;
  55         long disabled;
  56         int cpu, resched;
  57         int pc;
  58
  59         if (unlikely(!ftrace_function_enabled))
  60                 return;
  61
  62         pc = preempt_count();
  63         resched = ftrace_preempt_disable();
  64         local_save_flags(flags);
  65         cpu = raw_smp_processor_id();
  66         data = tr->data[cpu];
  67         disabled = atomic_inc_return(&data->disabled);
  68
  69         if (likely(disabled == 1))
  70                 trace_function(tr, ip, parent_ip, flags, pc);
  71
  72         atomic_dec(&data->disabled);
  73         ftrace_preempt_enable(resched);
  74 }
  75
  76 static void
  77 function_trace_call(unsigned long ip, unsigned long parent_ip)
  78 {
  79         struct trace_array *tr = func_trace;
  80         struct trace_array_cpu *data;
  81         unsigned long flags;
  82         long disabled;
  83         int cpu;
  84         int pc;
  85
  86         if (unlikely(!ftrace_function_enabled))
  87                 return;
  88
  89         /*
  90          * Need to use raw, since this must be called before the
  91          * recursive protection is performed.
  92          */
  93         local_irq_save(flags);
  94         cpu = raw_smp_processor_id();
  95         data = tr->data[cpu];
  96         disabled = atomic_inc_return(&data->disabled);
  97
  98         if (likely(disabled == 1)) {
  99                 pc = preempt_count();
 100                 trace_function(tr, ip, parent_ip, flags, pc);
 101         }
 102
 103         atomic_dec(&data->disabled);
 104         local_irq_restore(flags);
 105 }
 106
 107 static void
 108 function_stack_trace_call(unsigned long ip, unsigned long parent_ip)
 109 {
 110         struct trace_array *tr = func_trace;
 111         struct trace_array_cpu *data;
 112         unsigned long flags;
 113         long disabled;
 114         int cpu;
 115         int pc;
 116
 117         if (unlikely(!ftrace_function_enabled))
 118                 return;
 119
 120         /*
 121          * Need to use raw, since this must be called before the
 122          * recursive protection is performed.
 123          */
 124         local_irq_save(flags);
 125         cpu = raw_smp_processor_id();
 126         data = tr->data[cpu];
 127         disabled = atomic_inc_return(&data->disabled);
 128
 129         if (likely(disabled == 1)) {
 130                 pc = preempt_count();
 131                 trace_function(tr, ip, parent_ip, flags, pc);
 132                 /*
 133                  * skip over 5 funcs:
 134                  *    __ftrace_trace_stack,
 135                  *    __trace_stack,
 136                  *    function_stack_trace_call
 137                  *    ftrace_list_func
 138                  *    ftrace_call
 139                  */
 140                 __trace_stack(tr, flags, 5, pc);
 141         }
 142
 143         atomic_dec(&data->disabled);
 144         local_irq_restore(flags);
 145 }
 146
 147
 148 static struct ftrace_ops trace_ops __read_mostly =
 149 {
 150         .func = function_trace_call,
 151 };
 152
 153 static struct ftrace_ops trace_stack_ops __read_mostly =
 154 {
 155         .func = function_stack_trace_call,
 156 };
 157
 158 /* Our two options */
 159 enum {
 160         TRACE_FUNC_OPT_STACK = 0x1,
 161 };
 162
 163 static struct tracer_opt func_opts[] = {
 164 #ifdef CONFIG_STACKTRACE
 165         { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
 166 #endif
 167         { } /* Always set a last empty entry */
 168 };
 169
 170 static struct tracer_flags func_flags = {
 171         .val = 0, /* By default: all flags disabled */
 172         .opts = func_opts
 173 };
 174
 175 static void tracing_start_function_trace(void)
 176 {
 177         ftrace_function_enabled = 0;
 178
 179         if (trace_flags & TRACE_ITER_PREEMPTONLY)
 180                 trace_ops.func = function_trace_call_preempt_only;
 181         else
 182                 trace_ops.func = function_trace_call;
 183
 184         if (func_flags.val & TRACE_FUNC_OPT_STACK)
 185                 register_ftrace_function(&trace_stack_ops);
 186         else
 187                 register_ftrace_function(&trace_ops);
 188
 189         ftrace_function_enabled = 1;
 190 }
 191
 192 static void tracing_stop_function_trace(void)
 193 {
 194         ftrace_function_enabled = 0;
 195         /* OK if they are not registered */
 196         unregister_ftrace_function(&trace_stack_ops);
 197         unregister_ftrace_function(&trace_ops);
 198 }
 199
 200 static int func_set_flag(u32 old_flags, u32 bit, int set)
 201 {
 202         if (bit == TRACE_FUNC_OPT_STACK) {
 203                 /* do nothing if already set */
 204                 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
 205                         return 0;
 206
 207                 if (set) {
 208                         unregister_ftrace_function(&trace_ops);
 209                         register_ftrace_function(&trace_stack_ops);
 210                 } else {
 211                         unregister_ftrace_function(&trace_stack_ops);
 212                         register_ftrace_function(&trace_ops);
 213                 }
 214
 215                 return 0;
 216         }
 217
 218         return -EINVAL;
 219 }
 220
 221 static struct tracer function_trace __read_mostly =
 222 {
 223         .name           = "function",
 224         .init           = function_trace_init,
 225         .reset          = function_trace_reset,
 226         .start          = function_trace_start,
 227         .flags          = &func_flags,
 228         .set_flag       = func_set_flag,
 229 #ifdef CONFIG_FTRACE_SELFTEST
 230         .selftest       = trace_selftest_startup_function,
 231 #endif
 232 };
 233
 234 static __init int init_function_trace(void)
 235 {
 236         return register_tracer(&function_trace);
 237 }
 238
 239 device_initcall(init_function_trace);