kernel/trace/trace_hw_branches.c

   1 /*
   2  * h/w branch tracer for x86 based on bts
   3  *
   4  * Copyright (C) 2008 Markus Metzger <markus.t.metzger@gmail.com>
   5  *
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/fs.h>
  10 #include <linux/debugfs.h>
  11 #include <linux/ftrace.h>
  12 #include <linux/kallsyms.h>
  13
  14 #include <asm/ds.h>
  15
  16 #include "trace.h"
  17
  18
  19 #define SIZEOF_BTS (1 << 13)
  20
  21 static DEFINE_PER_CPU(struct bts_tracer *, tracer);
  22 static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer);
  23
  24 #define this_tracer per_cpu(tracer, smp_processor_id())
  25 #define this_buffer per_cpu(buffer, smp_processor_id())
  26
  27
  28 static void bts_trace_start_cpu(void *arg)
  29 {
  30         if (this_tracer)
  31                 ds_release_bts(this_tracer);
  32
  33         this_tracer =
  34                 ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS,
  35                                /* ovfl = */ NULL, /* th = */ (size_t)-1,
  36                                BTS_KERNEL);
  37         if (IS_ERR(this_tracer)) {
  38                 this_tracer = NULL;
  39                 return;
  40         }
  41 }
  42
  43 static void bts_trace_start(struct trace_array *tr)
  44 {
  45         int cpu;
  46
  47         tracing_reset_online_cpus(tr);
  48
  49         for_each_cpu(cpu, cpu_possible_mask)
  50                 smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
  51 }
  52
  53 static void bts_trace_stop_cpu(void *arg)
  54 {
  55         if (this_tracer) {
  56                 ds_release_bts(this_tracer);
  57                 this_tracer = NULL;
  58         }
  59 }
  60
  61 static void bts_trace_stop(struct trace_array *tr)
  62 {
  63         int cpu;
  64
  65         for_each_cpu(cpu, cpu_possible_mask)
  66                 smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
  67 }
  68
  69 static int bts_trace_init(struct trace_array *tr)
  70 {
  71         tracing_reset_online_cpus(tr);
  72         bts_trace_start(tr);
  73
  74         return 0;
  75 }
  76
  77 static void bts_trace_print_header(struct seq_file *m)
  78 {
  79         seq_puts(m,
  80                  "# CPU#        FROM                   TO         FUNCTION\n");
  81         seq_puts(m,
  82                  "#  |           |                     |             |\n");
  83 }
  84
  85 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
  86 {
  87         struct trace_entry *entry = iter->ent;
  88         struct trace_seq *seq = &iter->seq;
  89         struct hw_branch_entry *it;
  90
  91         trace_assign_type(it, entry);
  92
  93         if (entry->type == TRACE_HW_BRANCHES) {
  94                 if (trace_seq_printf(seq, "%4d  ", entry->cpu) &&
  95                     trace_seq_printf(seq, "0x%016llx -> 0x%016llx ",
  96                                      it->from, it->to) &&
  97                     (!it->from ||
  98                      seq_print_ip_sym(seq, it->from, /* sym_flags = */ 0)) &&
  99                     trace_seq_printf(seq, "\n"))
 100                         return TRACE_TYPE_HANDLED;
 101                 return TRACE_TYPE_PARTIAL_LINE;;
 102         }
 103         return TRACE_TYPE_UNHANDLED;
 104 }
 105
 106 void trace_hw_branch(struct trace_array *tr, u64 from, u64 to)
 107 {
 108         struct ring_buffer_event *event;
 109         struct hw_branch_entry *entry;
 110         unsigned long irq;
 111
 112         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry), &irq);
 113         if (!event)
 114                 return;
 115         entry   = ring_buffer_event_data(event);
 116         tracing_generic_entry_update(&entry->ent, 0, from);
 117         entry->ent.type = TRACE_HW_BRANCHES;
 118         entry->ent.cpu = smp_processor_id();
 119         entry->from = from;
 120         entry->to   = to;
 121         ring_buffer_unlock_commit(tr->buffer, event, irq);
 122 }
 123
 124 static void trace_bts_at(struct trace_array *tr,
 125                          const struct bts_trace *trace, void *at)
 126 {
 127         struct bts_struct bts;
 128         int err = 0;
 129
 130         WARN_ON_ONCE(!trace->read);
 131         if (!trace->read)
 132                 return;
 133
 134         err = trace->read(this_tracer, at, &bts);
 135         if (err < 0)
 136                 return;
 137
 138         switch (bts.qualifier) {
 139         case BTS_BRANCH:
 140                 trace_hw_branch(tr, bts.variant.lbr.from, bts.variant.lbr.to);
 141                 break;
 142         }
 143 }
 144
 145 static void trace_bts_cpu(void *arg)
 146 {
 147         struct trace_array *tr = (struct trace_array *) arg;
 148         const struct bts_trace *trace;
 149         unsigned char *at;
 150
 151         if (!this_tracer)
 152                 return;
 153
 154         ds_suspend_bts(this_tracer);
 155         trace = ds_read_bts(this_tracer);
 156         if (!trace)
 157                 goto out;
 158
 159         for (at = trace->ds.top; (void *)at < trace->ds.end;
 160              at += trace->ds.size)
 161                 trace_bts_at(tr, trace, at);
 162
 163         for (at = trace->ds.begin; (void *)at < trace->ds.top;
 164              at += trace->ds.size)
 165                 trace_bts_at(tr, trace, at);
 166
 167 out:
 168         ds_resume_bts(this_tracer);
 169 }
 170
 171 static void trace_bts_prepare(struct trace_iterator *iter)
 172 {
 173         int cpu;
 174
 175         for_each_cpu(cpu, cpu_possible_mask)
 176                 smp_call_function_single(cpu, trace_bts_cpu, iter->tr, 1);
 177 }
 178
 179 struct tracer bts_tracer __read_mostly =
 180 {
 181         .name           = "hw-branch-tracer",
 182         .init           = bts_trace_init,
 183         .reset          = bts_trace_stop,
 184         .print_header   = bts_trace_print_header,
 185         .print_line     = bts_trace_print_line,
 186         .start          = bts_trace_start,
 187         .stop           = bts_trace_stop,
 188         .open           = trace_bts_prepare
 189 };
 190
 191 __init static int init_bts_trace(void)
 192 {
 193         return register_tracer(&bts_tracer);
 194 }
 195 device_initcall(init_bts_trace);