kernel/trace/trace_hw_branches.c

   1 /*
   2  * h/w branch tracer for x86 based on bts
   3  *
   4  * Copyright (C) 2008-2009 Intel Corporation.
   5  * Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
   6  *
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/fs.h>
  11 #include <linux/debugfs.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/kallsyms.h>
  14 #include <linux/mutex.h>
  15 #include <linux/cpu.h>
  16 #include <linux/smp.h>
  17
  18 #include <asm/ds.h>
  19
  20 #include "trace.h"
  21 #include "trace_output.h"
  22
  23
  24 #define SIZEOF_BTS (1 << 13)
  25
  26 /* The tracer mutex protects the below per-cpu tracer array.
  27    It needs to be held to:
  28    - start tracing on all cpus
  29    - stop tracing on all cpus
  30    - start tracing on a single hotplug cpu
  31    - stop tracing on a single hotplug cpu
  32    - read the trace from all cpus
  33    - read the trace from a single cpu
  34 */
  35 static DEFINE_MUTEX(bts_tracer_mutex);
  36 static DEFINE_PER_CPU(struct bts_tracer *, tracer);
  37 static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
  38
  39 #define this_tracer per_cpu(tracer, smp_processor_id())
  40 #define this_buffer per_cpu(buffer, smp_processor_id())
  41
  42 static int __read_mostly trace_hw_branches_enabled;
  43
  44
  45 /*
  46  * Start tracing on the current cpu.
  47  * The argument is ignored.
  48  *
  49  * pre: bts_tracer_mutex must be locked.
  50  */
  51 static void bts_trace_start_cpu(void *arg)
  52 {
  53         if (this_tracer)
  54                 ds_release_bts(this_tracer);
  55
  56         this_tracer =
  57                 ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS,
  58                                /* ovfl = */ NULL, /* th = */ (size_t)-1,
  59                                BTS_KERNEL);
  60         if (IS_ERR(this_tracer)) {
  61                 this_tracer = NULL;
  62                 return;
  63         }
  64 }
  65
  66 static void bts_trace_start(struct trace_array *tr)
  67 {
  68         mutex_lock(&bts_tracer_mutex);
  69
  70         on_each_cpu(bts_trace_start_cpu, NULL, 1);
  71         trace_hw_branches_enabled = 1;
  72
  73         mutex_unlock(&bts_tracer_mutex);
  74 }
  75
  76 /*
  77  * Start tracing on the current cpu.
  78  * The argument is ignored.
  79  *
  80  * pre: bts_tracer_mutex must be locked.
  81  */
  82 static void bts_trace_stop_cpu(void *arg)
  83 {
  84         if (this_tracer) {
  85                 ds_release_bts(this_tracer);
  86                 this_tracer = NULL;
  87         }
  88 }
  89
  90 static void bts_trace_stop(struct trace_array *tr)
  91 {
  92         mutex_lock(&bts_tracer_mutex);
  93
  94         trace_hw_branches_enabled = 0;
  95         on_each_cpu(bts_trace_stop_cpu, NULL, 1);
  96
  97         mutex_unlock(&bts_tracer_mutex);
  98 }
  99
 100 static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
 101                                      unsigned long action, void *hcpu)
 102 {
 103         unsigned int cpu = (unsigned long)hcpu;
 104
 105         mutex_lock(&bts_tracer_mutex);
 106
 107         if (!trace_hw_branches_enabled)
 108                 goto out;
 109
 110         switch (action) {
 111         case CPU_ONLINE:
 112         case CPU_DOWN_FAILED:
 113                 smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
 114                 break;
 115         case CPU_DOWN_PREPARE:
 116                 smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
 117                 break;
 118         }
 119
 120  out:
 121         mutex_unlock(&bts_tracer_mutex);
 122         return NOTIFY_DONE;
 123 }
 124
 125 static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
 126         .notifier_call = bts_hotcpu_handler
 127 };
 128
 129 static int bts_trace_init(struct trace_array *tr)
 130 {
 131         register_hotcpu_notifier(&bts_hotcpu_notifier);
 132         tracing_reset_online_cpus(tr);
 133         bts_trace_start(tr);
 134
 135         return 0;
 136 }
 137
 138 static void bts_trace_reset(struct trace_array *tr)
 139 {
 140         bts_trace_stop(tr);
 141         unregister_hotcpu_notifier(&bts_hotcpu_notifier);
 142 }
 143
 144 static void bts_trace_print_header(struct seq_file *m)
 145 {
 146         seq_puts(m,
 147                  "# CPU#        FROM                   TO         FUNCTION\n");
 148         seq_puts(m,
 149                  "#  |           |                     |             |\n");
 150 }
 151
 152 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 153 {
 154         struct trace_entry *entry = iter->ent;
 155         struct trace_seq *seq = &iter->seq;
 156         struct hw_branch_entry *it;
 157
 158         trace_assign_type(it, entry);
 159
 160         if (entry->type == TRACE_HW_BRANCHES) {
 161                 if (trace_seq_printf(seq, "%4d  ", entry->cpu) &&
 162                     trace_seq_printf(seq, "0x%016llx -> 0x%016llx ",
 163                                      it->from, it->to) &&
 164                     (!it->from ||
 165                      seq_print_ip_sym(seq, it->from, /* sym_flags = */ 0)) &&
 166                     trace_seq_printf(seq, "\n"))
 167                         return TRACE_TYPE_HANDLED;
 168                 return TRACE_TYPE_PARTIAL_LINE;;
 169         }
 170         return TRACE_TYPE_UNHANDLED;
 171 }
 172
 173 void trace_hw_branch(struct trace_array *tr, u64 from, u64 to)
 174 {
 175         struct ring_buffer_event *event;
 176         struct hw_branch_entry *entry;
 177         unsigned long irq1, irq2;
 178         int cpu;
 179
 180         if (unlikely(!tr))
 181                 return;
 182
 183         if (unlikely(!trace_hw_branches_enabled))
 184                 return;
 185
 186         local_irq_save(irq1);
 187         cpu = raw_smp_processor_id();
 188         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
 189                 goto out;
 190
 191         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq2);
 192         if (!event)
 193                 goto out;
 194         entry   = ring_buffer_event_data(event);
 195         tracing_generic_entry_update(&entry->ent, 0, from);
 196         entry->ent.type = TRACE_HW_BRANCHES;
 197         entry->ent.cpu = cpu;
 198         entry->from = from;
 199         entry->to   = to;
 200         ring_buffer_unlock_commit(tr->buffer, event, irq2);
 201
 202  out:
 203         atomic_dec(&tr->data[cpu]->disabled);
 204         local_irq_restore(irq1);
 205 }
 206
 207 static void trace_bts_at(struct trace_array *tr,
 208                          const struct bts_trace *trace, void *at)
 209 {
 210         struct bts_struct bts;
 211         int err = 0;
 212
 213         WARN_ON_ONCE(!trace->read);
 214         if (!trace->read)
 215                 return;
 216
 217         err = trace->read(this_tracer, at, &bts);
 218         if (err < 0)
 219                 return;
 220
 221         switch (bts.qualifier) {
 222         case BTS_BRANCH:
 223                 trace_hw_branch(tr, bts.variant.lbr.from, bts.variant.lbr.to);
 224                 break;
 225         }
 226 }
 227
 228 /*
 229  * Collect the trace on the current cpu and write it into the ftrace buffer.
 230  *
 231  * pre: bts_tracer_mutex must be locked
 232  */
 233 static void trace_bts_cpu(void *arg)
 234 {
 235         struct trace_array *tr = (struct trace_array *) arg;
 236         const struct bts_trace *trace;
 237         unsigned char *at;
 238
 239         if (!this_tracer)
 240                 return;
 241
 242         if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
 243                 return;
 244
 245         ds_suspend_bts(this_tracer);
 246         trace = ds_read_bts(this_tracer);
 247         if (!trace)
 248                 goto out;
 249
 250         for (at = trace->ds.top; (void *)at < trace->ds.end;
 251              at += trace->ds.size)
 252                 trace_bts_at(tr, trace, at);
 253
 254         for (at = trace->ds.begin; (void *)at < trace->ds.top;
 255              at += trace->ds.size)
 256                 trace_bts_at(tr, trace, at);
 257
 258 out:
 259         ds_resume_bts(this_tracer);
 260 }
 261
 262 static void trace_bts_prepare(struct trace_iterator *iter)
 263 {
 264         mutex_lock(&bts_tracer_mutex);
 265
 266         on_each_cpu(trace_bts_cpu, iter->tr, 1);
 267
 268         mutex_unlock(&bts_tracer_mutex);
 269 }
 270
 271 struct tracer bts_tracer __read_mostly =
 272 {
 273         .name           = "hw-branch-tracer",
 274         .init           = bts_trace_init,
 275         .reset          = bts_trace_reset,
 276         .print_header   = bts_trace_print_header,
 277         .print_line     = bts_trace_print_line,
 278         .start          = bts_trace_start,
 279         .stop           = bts_trace_stop,
 280         .open           = trace_bts_prepare
 281 };
 282
 283 __init static int init_bts_trace(void)
 284 {
 285         return register_tracer(&bts_tracer);
 286 }
 287 device_initcall(init_bts_trace);