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