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.h"
  19 #include "trace_output.h"
  20
  21
  22 #define SIZEOF_BTS (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[SIZEOF_BTS], 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 __read_mostly trace_hw_branches_enabled;
  42 static struct trace_array *hw_branch_trace __read_mostly;
  43
  44
  45 /*
  46  * Start tracing on the current cpu.
  47  * The argument is ignored.
  48  *
  49  * pre: bts_tracer_lock 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         spin_lock(&bts_tracer_lock);
  69
  70         on_each_cpu(bts_trace_start_cpu, NULL, 1);
  71         trace_hw_branches_enabled = 1;
  72
  73         spin_unlock(&bts_tracer_lock);
  74 }
  75
  76 /*
  77  * Stop tracing on the current cpu.
  78  * The argument is ignored.
  79  *
  80  * pre: bts_tracer_lock 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         spin_lock(&bts_tracer_lock);
  93
  94         trace_hw_branches_enabled = 0;
  95         on_each_cpu(bts_trace_stop_cpu, NULL, 1);
  96
  97         spin_unlock(&bts_tracer_lock);
  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         spin_lock(&bts_tracer_lock);
 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         spin_unlock(&bts_tracer_lock);
 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         hw_branch_trace = tr;
 132
 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 }
 142
 143 static void bts_trace_print_header(struct seq_file *m)
 144 {
 145         seq_puts(m, "# CPU#        TO  <-  FROM\n");
 146 }
 147
 148 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
 149 {
 150         struct trace_entry *entry = iter->ent;
 151         struct trace_seq *seq = &iter->seq;
 152         struct hw_branch_entry *it;
 153         unsigned long symflags = TRACE_ITER_SYM_OFFSET;
 154
 155         trace_assign_type(it, entry);
 156
 157         if (entry->type == TRACE_HW_BRANCHES) {
 158                 if (trace_seq_printf(seq, "%4d  ", iter->cpu) &&
 159                     seq_print_ip_sym(seq, it->to, symflags) &&
 160                     trace_seq_printf(seq, "\t  <-  ") &&
 161                     seq_print_ip_sym(seq, it->from, symflags) &&
 162                     trace_seq_printf(seq, "\n"))
 163                         return TRACE_TYPE_HANDLED;
 164                 return TRACE_TYPE_PARTIAL_LINE;;
 165         }
 166         return TRACE_TYPE_UNHANDLED;
 167 }
 168
 169 void trace_hw_branch(u64 from, u64 to)
 170 {
 171         struct trace_array *tr = hw_branch_trace;
 172         struct ring_buffer_event *event;
 173         struct hw_branch_entry *entry;
 174         unsigned long irq1;
 175         int cpu;
 176
 177         if (unlikely(!tr))
 178                 return;
 179
 180         if (unlikely(!trace_hw_branches_enabled))
 181                 return;
 182
 183         local_irq_save(irq1);
 184         cpu = raw_smp_processor_id();
 185         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
 186                 goto out;
 187
 188         event = trace_buffer_lock_reserve(tr, TRACE_HW_BRANCHES,
 189                                           sizeof(*entry), 0, 0);
 190         if (!event)
 191                 goto out;
 192         entry   = ring_buffer_event_data(event);
 193         tracing_generic_entry_update(&entry->ent, 0, from);
 194         entry->ent.type = TRACE_HW_BRANCHES;
 195         entry->from = from;
 196         entry->to   = to;
 197         trace_buffer_unlock_commit(tr, event, 0, 0);
 198
 199  out:
 200         atomic_dec(&tr->data[cpu]->disabled);
 201         local_irq_restore(irq1);
 202 }
 203
 204 static void trace_bts_at(const struct bts_trace *trace, void *at)
 205 {
 206         struct bts_struct bts;
 207         int err = 0;
 208
 209         WARN_ON_ONCE(!trace->read);
 210         if (!trace->read)
 211                 return;
 212
 213         err = trace->read(this_tracer, at, &bts);
 214         if (err < 0)
 215                 return;
 216
 217         switch (bts.qualifier) {
 218         case BTS_BRANCH:
 219                 trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
 220                 break;
 221         }
 222 }
 223
 224 /*
 225  * Collect the trace on the current cpu and write it into the ftrace buffer.
 226  *
 227  * pre: bts_tracer_lock must be locked
 228  */
 229 static void trace_bts_cpu(void *arg)
 230 {
 231         struct trace_array *tr = (struct trace_array *) arg;
 232         const struct bts_trace *trace;
 233         unsigned char *at;
 234
 235         if (unlikely(!tr))
 236                 return;
 237
 238         if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
 239                 return;
 240
 241         if (unlikely(!this_tracer))
 242                 return;
 243
 244         ds_suspend_bts(this_tracer);
 245         trace = ds_read_bts(this_tracer);
 246         if (!trace)
 247                 goto out;
 248
 249         for (at = trace->ds.top; (void *)at < trace->ds.end;
 250              at += trace->ds.size)
 251                 trace_bts_at(trace, at);
 252
 253         for (at = trace->ds.begin; (void *)at < trace->ds.top;
 254              at += trace->ds.size)
 255                 trace_bts_at(trace, at);
 256
 257 out:
 258         ds_resume_bts(this_tracer);
 259 }
 260
 261 static void trace_bts_prepare(struct trace_iterator *iter)
 262 {
 263         spin_lock(&bts_tracer_lock);
 264
 265         on_each_cpu(trace_bts_cpu, iter->tr, 1);
 266
 267         spin_unlock(&bts_tracer_lock);
 268 }
 269
 270 static void trace_bts_close(struct trace_iterator *iter)
 271 {
 272         tracing_reset_online_cpus(iter->tr);
 273 }
 274
 275 void trace_hw_branch_oops(void)
 276 {
 277         spin_lock(&bts_tracer_lock);
 278
 279         trace_bts_cpu(hw_branch_trace);
 280
 281         spin_unlock(&bts_tracer_lock);
 282 }
 283
 284 struct tracer bts_tracer __read_mostly =
 285 {
 286         .name           = "hw-branch-tracer",
 287         .init           = bts_trace_init,
 288         .reset          = bts_trace_reset,
 289         .print_header   = bts_trace_print_header,
 290         .print_line     = bts_trace_print_line,
 291         .start          = bts_trace_start,
 292         .stop           = bts_trace_stop,
 293         .open           = trace_bts_prepare,
 294         .close          = trace_bts_close
 295 };
 296
 297 __init static int init_bts_trace(void)
 298 {
 299         register_hotcpu_notifier(&bts_hotcpu_notifier);
 300         return register_tracer(&bts_tracer);
 301 }
 302 device_initcall(init_bts_trace);