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