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 #include <linux/spinlock.h>
   8 #include <linux/kallsyms.h>
   9 #include <linux/debugfs.h>
  10 #include <linux/ftrace.h>
  11 #include <linux/module.h>
  12 #include <linux/cpu.h>
  13 #include <linux/smp.h>
  14 #include <linux/fs.h>
  15
  16 #include <asm/ds.h>
  17
  18 #include "trace_output.h"
  19 #include "trace.h"
  20
  21
  22 #define BTS_BUFFER_SIZE (1 << 13)
  23
  24 /*
  25  * The tracer lock protects the below per-cpu tracer array.
  26  * It needs to be held to:
  27  * - start tracing on all cpus
  28  * - stop tracing on all cpus
  29  * - start tracing on a single hotplug cpu
  30  * - stop tracing on a single hotplug cpu
  31  * - read the trace from all cpus
  32  * - read the trace from a single cpu
  33  */
  34 static DEFINE_SPINLOCK(bts_tracer_lock);
  35 static DEFINE_PER_CPU(struct bts_tracer *, tracer);
  36 static DEFINE_PER_CPU(unsigned char[BTS_BUFFER_SIZE], buffer);
  37
  38 #define this_tracer per_cpu(tracer, smp_processor_id())
  39 #define this_buffer per_cpu(buffer, smp_processor_id())
  40
  41 static int trace_hw_branches_enabled __read_mostly;
  42 static int trace_hw_branches_suspended __read_mostly;
  43 static struct trace_array *hw_branch_trace __read_mostly;
  44
  45
  46 /*
  47  * Initialize the tracer for the current cpu.
  48  * The argument is ignored.
  49  *
  50  * pre: bts_tracer_lock must be locked.
  51  */
  52 static void bts_trace_init_cpu(void *arg)
  53 {
  54         if (this_tracer)
  55                 ds_release_bts(this_tracer);
  56
  57         this_tracer = ds_request_bts(NULL, this_buffer, BTS_BUFFER_SIZE,
  58                                      NULL, (size_t)-1, BTS_KERNEL);
  59         if (IS_ERR(this_tracer)) {
  60                 this_tracer = NULL;
  61                 return;
  62         }
  63 }
  64
  65 static int bts_trace_init(struct trace_array *tr)
  66 {
  67         int cpu, avail;
  68
  69         spin_lock(&bts_tracer_lock);
  70
  71         hw_branch_trace = tr;
  72
  73         on_each_cpu(bts_trace_init_cpu, NULL, 1);
  74
  75         /* Check on how many cpus we could enable tracing */
  76         avail = 0;
  77         for_each_online_cpu(cpu)
  78                 if (per_cpu(tracer, cpu))
  79                         avail++;
  80
  81         trace_hw_branches_enabled = (avail ? 1 : 0);
  82         trace_hw_branches_suspended = 0;
  83
  84         spin_unlock(&bts_tracer_lock);
  85
  86
  87         /* If we could not enable tracing on a single cpu, we fail. */
  88         return avail ? 0 : -EOPNOTSUPP;
  89 }
  90
  91 /*
  92  * Release the tracer for the current cpu.
  93  * The argument is ignored.
  94  *
  95  * pre: bts_tracer_lock must be locked.
  96  */
  97 static void bts_trace_release_cpu(void *arg)
  98 {
  99         if (this_tracer) {
 100                 ds_release_bts(this_tracer);
 101                 this_tracer = NULL;
 102         }
 103 }
 104
 105 static void bts_trace_reset(struct trace_array *tr)
 106 {
 107         spin_lock(&bts_tracer_lock);
 108
 109         on_each_cpu(bts_trace_release_cpu, NULL, 1);
 110         trace_hw_branches_enabled = 0;
 111         trace_hw_branches_suspended = 0;
 112
 113         spin_unlock(&bts_tracer_lock);
 114 }
 115
 116 /*
 117  * Resume tracing on the current cpu.
 118  * The argument is ignored.
 119  *
 120  * pre: bts_tracer_lock must be locked.
 121  */
 122 static void bts_trace_resume_cpu(void *arg)
 123 {
 124         if (this_tracer)
 125                 ds_resume_bts(this_tracer);
 126 }
 127
 128 static void bts_trace_start(struct trace_array *tr)
 129 {
 130         spin_lock(&bts_tracer_lock);
 131
 132         on_each_cpu(bts_trace_resume_cpu, NULL, 1);
 133         trace_hw_branches_suspended = 0;
 134
 135         spin_unlock(&bts_tracer_lock);
 136 }
 137
 138 /*
 139  * Suspend tracing on the current cpu.
 140  * The argument is ignored.
 141  *
 142  * pre: bts_tracer_lock must be locked.
 143  */
 144 static void bts_trace_suspend_cpu(void *arg)
 145 {
 146         if (this_tracer)
 147                 ds_suspend_bts(this_tracer);
 148 }
 149
 150 static void bts_trace_stop(struct trace_array *tr)
 151 {
 152         spin_lock(&bts_tracer_lock);
 153
 154         on_each_cpu(bts_trace_suspend_cpu, NULL, 1);
 155         trace_hw_branches_suspended = 1;
 156
 157         spin_unlock(&bts_tracer_lock);
 158 }
 159
 160 static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
 161                                      unsigned long action, void *hcpu)
 162 {
 163         unsigned int cpu = (unsigned long)hcpu;
 164
 165         spin_lock(&bts_tracer_lock);
 166
 167         if (!trace_hw_branches_enabled)
 168                 goto out;
 169
 170         switch (action) {
 171         case CPU_ONLINE:
 172         case CPU_DOWN_FAILED:
 173                 smp_call_function_single(cpu, bts_trace_init_cpu, NULL, 1);
 174
 175                 if (trace_hw_branches_suspended)
 176                         smp_call_function_single(cpu, bts_trace_suspend_cpu,
 177                                                  NULL, 1);
 178                 break;
 179         case CPU_DOWN_PREPARE:
 180                 smp_call_function_single(cpu, bts_trace_release_cpu, NULL, 1);
 181                 break;
 182         }
 183
 184  out:
 185         spin_unlock(&bts_tracer_lock);
 186         return NOTIFY_DONE;
 187 }
 188
 189 static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
 190         .notifier_call = bts_hotcpu_handler
 191 };
 192
 193 static void bts_trace_print_header(struct seq_file *m)
 194 {
 195         seq_puts(m, "# CPU#        TO  <-  FROM\n");
 196 }
 197
 198 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 199 {
 200         unsigned long symflags = TRACE_ITER_SYM_OFFSET;
 201         struct trace_entry *entry = iter->ent;
 202         struct trace_seq *seq = &iter->seq;
 203         struct hw_branch_entry *it;
 204
 205         trace_assign_type(it, entry);
 206
 207         if (entry->type == TRACE_HW_BRANCHES) {
 208                 if (trace_seq_printf(seq, "%4d  ", iter->cpu) &&
 209                     seq_print_ip_sym(seq, it->to, symflags) &&
 210                     trace_seq_printf(seq, "\t  <-  ") &&
 211                     seq_print_ip_sym(seq, it->from, symflags) &&
 212                     trace_seq_printf(seq, "\n"))
 213                         return TRACE_TYPE_HANDLED;
 214                 return TRACE_TYPE_PARTIAL_LINE;;
 215         }
 216         return TRACE_TYPE_UNHANDLED;
 217 }
 218
 219 void trace_hw_branch(u64 from, u64 to)
 220 {
 221         struct trace_array *tr = hw_branch_trace;
 222         struct ring_buffer_event *event;
 223         struct hw_branch_entry *entry;
 224         unsigned long irq1;
 225         int cpu;
 226
 227         if (unlikely(!tr))
 228                 return;
 229
 230         if (unlikely(!trace_hw_branches_enabled))
 231                 return;
 232
 233         local_irq_save(irq1);
 234         cpu = raw_smp_processor_id();
 235         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
 236                 goto out;
 237
 238         event = trace_buffer_lock_reserve(tr, TRACE_HW_BRANCHES,
 239                                           sizeof(*entry), 0, 0);
 240         if (!event)
 241                 goto out;
 242         entry   = ring_buffer_event_data(event);
 243         tracing_generic_entry_update(&entry->ent, 0, from);
 244         entry->ent.type = TRACE_HW_BRANCHES;
 245         entry->from = from;
 246         entry->to   = to;
 247         trace_buffer_unlock_commit(tr, event, 0, 0);
 248
 249  out:
 250         atomic_dec(&tr->data[cpu]->disabled);
 251         local_irq_restore(irq1);
 252 }
 253
 254 static void trace_bts_at(const struct bts_trace *trace, void *at)
 255 {
 256         struct bts_struct bts;
 257         int err = 0;
 258
 259         WARN_ON_ONCE(!trace->read);
 260         if (!trace->read)
 261                 return;
 262
 263         err = trace->read(this_tracer, at, &bts);
 264         if (err < 0)
 265                 return;
 266
 267         switch (bts.qualifier) {
 268         case BTS_BRANCH:
 269                 trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
 270                 break;
 271         }
 272 }
 273
 274 /*
 275  * Collect the trace on the current cpu and write it into the ftrace buffer.
 276  *
 277  * pre: bts_tracer_lock must be locked
 278  */
 279 static void trace_bts_cpu(void *arg)
 280 {
 281         struct trace_array *tr = (struct trace_array *)arg;
 282         const struct bts_trace *trace;
 283         unsigned char *at;
 284
 285         if (unlikely(!tr))
 286                 return;
 287
 288         if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
 289                 return;
 290
 291         if (unlikely(!this_tracer))
 292                 return;
 293
 294         ds_suspend_bts(this_tracer);
 295         trace = ds_read_bts(this_tracer);
 296         if (!trace)
 297                 goto out;
 298
 299         for (at = trace->ds.top; (void *)at < trace->ds.end;
 300              at += trace->ds.size)
 301                 trace_bts_at(trace, at);
 302
 303         for (at = trace->ds.begin; (void *)at < trace->ds.top;
 304              at += trace->ds.size)
 305                 trace_bts_at(trace, at);
 306
 307 out:
 308         ds_resume_bts(this_tracer);
 309 }
 310
 311 static void trace_bts_prepare(struct trace_iterator *iter)
 312 {
 313         spin_lock(&bts_tracer_lock);
 314
 315         on_each_cpu(trace_bts_cpu, iter->tr, 1);
 316
 317         spin_unlock(&bts_tracer_lock);
 318 }
 319
 320 static void trace_bts_close(struct trace_iterator *iter)
 321 {
 322         tracing_reset_online_cpus(iter->tr);
 323 }
 324
 325 void trace_hw_branch_oops(void)
 326 {
 327         spin_lock(&bts_tracer_lock);
 328
 329         if (trace_hw_branches_enabled)
 330                 trace_bts_cpu(hw_branch_trace);
 331
 332         spin_unlock(&bts_tracer_lock);
 333 }
 334
 335 struct tracer bts_tracer __read_mostly =
 336 {
 337         .name           = "hw-branch-tracer",
 338         .init           = bts_trace_init,
 339         .reset          = bts_trace_reset,
 340         .print_header   = bts_trace_print_header,
 341         .print_line     = bts_trace_print_line,
 342         .start          = bts_trace_start,
 343         .stop           = bts_trace_stop,
 344         .open           = trace_bts_prepare,
 345         .close          = trace_bts_close,
 346 #ifdef CONFIG_FTRACE_SELFTEST
 347         .selftest       = trace_selftest_startup_hw_branches,
 348 #endif /* CONFIG_FTRACE_SELFTEST */
 349 };
 350
 351 __init static int init_bts_trace(void)
 352 {
 353         register_hotcpu_notifier(&bts_hotcpu_notifier);
 354         return register_tracer(&bts_tracer);
 355 }
 356 device_initcall(init_bts_trace);