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 static struct trace_array *hw_branch_trace __read_mostly;
  44
  45
  46 /*
  47  * Start tracing on the current cpu.
  48  * The argument is ignored.
  49  *
  50  * pre: bts_tracer_mutex must be locked.
  51  */
  52 static void bts_trace_start_cpu(void *arg)
  53 {
  54         if (this_tracer)
  55                 ds_release_bts(this_tracer);
  56
  57         this_tracer =
  58                 ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS,
  59                                /* ovfl = */ NULL, /* th = */ (size_t)-1,
  60                                BTS_KERNEL);
  61         if (IS_ERR(this_tracer)) {
  62                 this_tracer = NULL;
  63                 return;
  64         }
  65 }
  66
  67 static void bts_trace_start(struct trace_array *tr)
  68 {
  69         mutex_lock(&bts_tracer_mutex);
  70
  71         on_each_cpu(bts_trace_start_cpu, NULL, 1);
  72         trace_hw_branches_enabled = 1;
  73
  74         mutex_unlock(&bts_tracer_mutex);
  75 }
  76
  77 /*
  78  * Start tracing on the current cpu.
  79  * The argument is ignored.
  80  *
  81  * pre: bts_tracer_mutex must be locked.
  82  */
  83 static void bts_trace_stop_cpu(void *arg)
  84 {
  85         if (this_tracer) {
  86                 ds_release_bts(this_tracer);
  87                 this_tracer = NULL;
  88         }
  89 }
  90
  91 static void bts_trace_stop(struct trace_array *tr)
  92 {
  93         mutex_lock(&bts_tracer_mutex);
  94
  95         trace_hw_branches_enabled = 0;
  96         on_each_cpu(bts_trace_stop_cpu, NULL, 1);
  97
  98         mutex_unlock(&bts_tracer_mutex);
  99 }
 100
 101 static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
 102                                      unsigned long action, void *hcpu)
 103 {
 104         unsigned int cpu = (unsigned long)hcpu;
 105
 106         mutex_lock(&bts_tracer_mutex);
 107
 108         if (!trace_hw_branches_enabled)
 109                 goto out;
 110
 111         switch (action) {
 112         case CPU_ONLINE:
 113         case CPU_DOWN_FAILED:
 114                 smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
 115                 break;
 116         case CPU_DOWN_PREPARE:
 117                 smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
 118                 break;
 119         }
 120
 121  out:
 122         mutex_unlock(&bts_tracer_mutex);
 123         return NOTIFY_DONE;
 124 }
 125
 126 static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
 127         .notifier_call = bts_hotcpu_handler
 128 };
 129
 130 static int bts_trace_init(struct trace_array *tr)
 131 {
 132         hw_branch_trace = tr;
 133
 134         register_hotcpu_notifier(&bts_hotcpu_notifier);
 135         bts_trace_start(tr);
 136
 137         return 0;
 138 }
 139
 140 static void bts_trace_reset(struct trace_array *tr)
 141 {
 142         bts_trace_stop(tr);
 143         unregister_hotcpu_notifier(&bts_hotcpu_notifier);
 144 }
 145
 146 static void bts_trace_print_header(struct seq_file *m)
 147 {
 148         seq_puts(m, "# CPU#        TO  <-  FROM\n");
 149 }
 150
 151 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 152 {
 153         struct trace_entry *entry = iter->ent;
 154         struct trace_seq *seq = &iter->seq;
 155         struct hw_branch_entry *it;
 156         unsigned long symflags = TRACE_ITER_SYM_OFFSET;
 157
 158         trace_assign_type(it, entry);
 159
 160         if (entry->type == TRACE_HW_BRANCHES) {
 161                 if (trace_seq_printf(seq, "%4d  ", iter->cpu) &&
 162                     seq_print_ip_sym(seq, it->to, symflags) &&
 163                     trace_seq_printf(seq, "\t  <-  ") &&
 164                     seq_print_ip_sym(seq, it->from, symflags) &&
 165                     trace_seq_printf(seq, "\n"))
 166                         return TRACE_TYPE_HANDLED;
 167                 return TRACE_TYPE_PARTIAL_LINE;;
 168         }
 169         return TRACE_TYPE_UNHANDLED;
 170 }
 171
 172 void trace_hw_branch(u64 from, u64 to)
 173 {
 174         struct trace_array *tr = hw_branch_trace;
 175         struct ring_buffer_event *event;
 176         struct hw_branch_entry *entry;
 177         unsigned long irq1;
 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 = trace_buffer_lock_reserve(tr, TRACE_HW_BRANCHES,
 192                                           sizeof(*entry), 0, 0);
 193         if (!event)
 194                 goto out;
 195         entry   = ring_buffer_event_data(event);
 196         tracing_generic_entry_update(&entry->ent, 0, from);
 197         entry->ent.type = TRACE_HW_BRANCHES;
 198         entry->from = from;
 199         entry->to   = to;
 200         trace_buffer_unlock_commit(tr, event, 0, 0);
 201
 202  out:
 203         atomic_dec(&tr->data[cpu]->disabled);
 204         local_irq_restore(irq1);
 205 }
 206
 207 static void trace_bts_at(const struct bts_trace *trace, void *at)
 208 {
 209         struct bts_struct bts;
 210         int err = 0;
 211
 212         WARN_ON_ONCE(!trace->read);
 213         if (!trace->read)
 214                 return;
 215
 216         err = trace->read(this_tracer, at, &bts);
 217         if (err < 0)
 218                 return;
 219
 220         switch (bts.qualifier) {
 221         case BTS_BRANCH:
 222                 trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
 223                 break;
 224         }
 225 }
 226
 227 /*
 228  * Collect the trace on the current cpu and write it into the ftrace buffer.
 229  *
 230  * pre: bts_tracer_mutex must be locked
 231  */
 232 static void trace_bts_cpu(void *arg)
 233 {
 234         struct trace_array *tr = (struct trace_array *) arg;
 235         const struct bts_trace *trace;
 236         unsigned char *at;
 237
 238         if (unlikely(!tr))
 239                 return;
 240
 241         if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
 242                 return;
 243
 244         if (unlikely(!this_tracer))
 245                 return;
 246
 247         ds_suspend_bts(this_tracer);
 248         trace = ds_read_bts(this_tracer);
 249         if (!trace)
 250                 goto out;
 251
 252         for (at = trace->ds.top; (void *)at < trace->ds.end;
 253              at += trace->ds.size)
 254                 trace_bts_at(trace, at);
 255
 256         for (at = trace->ds.begin; (void *)at < trace->ds.top;
 257              at += trace->ds.size)
 258                 trace_bts_at(trace, at);
 259
 260 out:
 261         ds_resume_bts(this_tracer);
 262 }
 263
 264 static void trace_bts_prepare(struct trace_iterator *iter)
 265 {
 266         mutex_lock(&bts_tracer_mutex);
 267
 268         on_each_cpu(trace_bts_cpu, iter->tr, 1);
 269
 270         mutex_unlock(&bts_tracer_mutex);
 271 }
 272
 273 static void trace_bts_close(struct trace_iterator *iter)
 274 {
 275         tracing_reset_online_cpus(iter->tr);
 276 }
 277
 278 void trace_hw_branch_oops(void)
 279 {
 280         mutex_lock(&bts_tracer_mutex);
 281
 282         trace_bts_cpu(hw_branch_trace);
 283
 284         mutex_unlock(&bts_tracer_mutex);
 285 }
 286
 287 struct tracer bts_tracer __read_mostly =
 288 {
 289         .name           = "hw-branch-tracer",
 290         .init           = bts_trace_init,
 291         .reset          = bts_trace_reset,
 292         .print_header   = bts_trace_print_header,
 293         .print_line     = bts_trace_print_line,
 294         .start          = bts_trace_start,
 295         .stop           = bts_trace_stop,
 296         .open           = trace_bts_prepare,
 297         .close          = trace_bts_close
 298 };
 299
 300 __init static int init_bts_trace(void)
 301 {
 302         return register_tracer(&bts_tracer);
 303 }
 304 device_initcall(init_bts_trace);