2 * h/w branch tracer for x86 based on bts
4 * Copyright (C) 2008-2009 Intel Corporation.
5 * Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
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>
19 #include "trace_output.h"
22 #define SIZEOF_BTS (1 << 13)
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
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);
38 #define this_tracer per_cpu(tracer, smp_processor_id())
39 #define this_buffer per_cpu(buffer, smp_processor_id())
41 static int __read_mostly trace_hw_branches_enabled;
42 static struct trace_array *hw_branch_trace __read_mostly;
46 * Start tracing on the current cpu.
47 * The argument is ignored.
49 * pre: bts_tracer_lock must be locked.
51 static void bts_trace_start_cpu(void *arg)
54 ds_release_bts(this_tracer);
57 ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS,
58 /* ovfl = */ NULL, /* th = */ (size_t)-1,
60 if (IS_ERR(this_tracer)) {
66 static void bts_trace_start(struct trace_array *tr)
68 spin_lock(&bts_tracer_lock);
70 on_each_cpu(bts_trace_start_cpu, NULL, 1);
71 trace_hw_branches_enabled = 1;
73 spin_unlock(&bts_tracer_lock);
77 * Stop tracing on the current cpu.
78 * The argument is ignored.
80 * pre: bts_tracer_lock must be locked.
82 static void bts_trace_stop_cpu(void *arg)
85 ds_release_bts(this_tracer);
90 static void bts_trace_stop(struct trace_array *tr)
92 spin_lock(&bts_tracer_lock);
94 trace_hw_branches_enabled = 0;
95 on_each_cpu(bts_trace_stop_cpu, NULL, 1);
97 spin_unlock(&bts_tracer_lock);
100 static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
101 unsigned long action, void *hcpu)
103 unsigned int cpu = (unsigned long)hcpu;
105 spin_lock(&bts_tracer_lock);
107 if (!trace_hw_branches_enabled)
112 case CPU_DOWN_FAILED:
113 smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1);
115 case CPU_DOWN_PREPARE:
116 smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1);
121 spin_unlock(&bts_tracer_lock);
125 static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
126 .notifier_call = bts_hotcpu_handler
129 static int bts_trace_init(struct trace_array *tr)
131 hw_branch_trace = tr;
138 static void bts_trace_reset(struct trace_array *tr)
143 static void bts_trace_print_header(struct seq_file *m)
145 seq_puts(m, "# CPU# TO <- FROM\n");
148 static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
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;
155 trace_assign_type(it, entry);
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;;
166 return TRACE_TYPE_UNHANDLED;
169 void trace_hw_branch(u64 from, u64 to)
171 struct ftrace_event_call *call = &event_hw_branch;
172 struct trace_array *tr = hw_branch_trace;
173 struct ring_buffer_event *event;
174 struct hw_branch_entry *entry;
181 if (unlikely(!trace_hw_branches_enabled))
184 local_irq_save(irq1);
185 cpu = raw_smp_processor_id();
186 if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
189 event = trace_buffer_lock_reserve(tr, TRACE_HW_BRANCHES,
190 sizeof(*entry), 0, 0);
193 entry = ring_buffer_event_data(event);
194 tracing_generic_entry_update(&entry->ent, 0, from);
195 entry->ent.type = TRACE_HW_BRANCHES;
198 filter_check_discard(call, entry, event);
199 trace_buffer_unlock_commit(tr, event, 0, 0);
202 atomic_dec(&tr->data[cpu]->disabled);
203 local_irq_restore(irq1);
206 static void trace_bts_at(const struct bts_trace *trace, void *at)
208 struct bts_struct bts;
211 WARN_ON_ONCE(!trace->read);
215 err = trace->read(this_tracer, at, &bts);
219 switch (bts.qualifier) {
221 trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
227 * Collect the trace on the current cpu and write it into the ftrace buffer.
229 * pre: bts_tracer_lock must be locked
231 static void trace_bts_cpu(void *arg)
233 struct trace_array *tr = (struct trace_array *) arg;
234 const struct bts_trace *trace;
240 if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
243 if (unlikely(!this_tracer))
246 ds_suspend_bts(this_tracer);
247 trace = ds_read_bts(this_tracer);
251 for (at = trace->ds.top; (void *)at < trace->ds.end;
252 at += trace->ds.size)
253 trace_bts_at(trace, at);
255 for (at = trace->ds.begin; (void *)at < trace->ds.top;
256 at += trace->ds.size)
257 trace_bts_at(trace, at);
260 ds_resume_bts(this_tracer);
263 static void trace_bts_prepare(struct trace_iterator *iter)
265 spin_lock(&bts_tracer_lock);
267 on_each_cpu(trace_bts_cpu, iter->tr, 1);
269 spin_unlock(&bts_tracer_lock);
272 static void trace_bts_close(struct trace_iterator *iter)
274 tracing_reset_online_cpus(iter->tr);
277 void trace_hw_branch_oops(void)
279 spin_lock(&bts_tracer_lock);
281 trace_bts_cpu(hw_branch_trace);
283 spin_unlock(&bts_tracer_lock);
286 struct tracer bts_tracer __read_mostly =
288 .name = "hw-branch-tracer",
289 .init = bts_trace_init,
290 .reset = bts_trace_reset,
291 .print_header = bts_trace_print_header,
292 .print_line = bts_trace_print_line,
293 .start = bts_trace_start,
294 .stop = bts_trace_stop,
295 .open = trace_bts_prepare,
296 .close = trace_bts_close
299 __init static int init_bts_trace(void)
301 register_hotcpu_notifier(&bts_hotcpu_notifier);
302 return register_tracer(&bts_tracer);
304 device_initcall(init_bts_trace);