/*
* h/w branch tracer for x86 based on BTS
*
* Copyright (C) 2008-2009 Intel Corporation.
* Markus Metzger <markus.t.metzger@gmail.com>, 2008-2009
*/
#include <linux/kallsyms.h>
#include <linux/debugfs.h>
#include <linux/ftrace.h>
#include <linux/module.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/fs.h>
#include <asm/ds.h>
#include "trace_output.h"
#include "trace.h"
#define BTS_BUFFER_SIZE (1 << 13)
static DEFINE_PER_CPU(struct bts_tracer *, tracer);
static DEFINE_PER_CPU(unsigned char[BTS_BUFFER_SIZE], buffer);
#define this_tracer per_cpu(tracer, smp_processor_id())
static int trace_hw_branches_enabled __read_mostly;
static int trace_hw_branches_suspended __read_mostly;
static struct trace_array *hw_branch_trace __read_mostly;
static void bts_trace_init_cpu(int cpu)
{
per_cpu(tracer, cpu) =
ds_request_bts_cpu(cpu, per_cpu(buffer, cpu), BTS_BUFFER_SIZE,
NULL, (size_t)-1, BTS_KERNEL);
if (IS_ERR(per_cpu(tracer, cpu)))
per_cpu(tracer, cpu) = NULL;
}
static int bts_trace_init(struct trace_array *tr)
{
int cpu;
hw_branch_trace = tr;
trace_hw_branches_enabled = 0;
get_online_cpus();
for_each_online_cpu(cpu) {
bts_trace_init_cpu(cpu);
if (likely(per_cpu(tracer, cpu)))
trace_hw_branches_enabled = 1;
}
trace_hw_branches_suspended = 0;
put_online_cpus();
/* If we could not enable tracing on a single cpu, we fail. */
return trace_hw_branches_enabled ? 0 : -EOPNOTSUPP;
}
static void bts_trace_reset(struct trace_array *tr)
{
int cpu;
get_online_cpus();
for_each_online_cpu(cpu) {
if (likely(per_cpu(tracer, cpu))) {
ds_release_bts(per_cpu(tracer, cpu));
per_cpu(tracer, cpu) = NULL;
}
}
trace_hw_branches_enabled = 0;
trace_hw_branches_suspended = 0;
put_online_cpus();
}
static void bts_trace_start(struct trace_array *tr)
{
int cpu;
get_online_cpus();
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_resume_bts(per_cpu(tracer, cpu));
trace_hw_branches_suspended = 0;
put_online_cpus();
}
static void bts_trace_stop(struct trace_array *tr)
{
int cpu;
get_online_cpus();
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_suspend_bts(per_cpu(tracer, cpu));
trace_hw_branches_suspended = 1;
put_online_cpus();
}
static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
switch (action) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
/* The notification is sent with interrupts enabled. */
if (trace_hw_branches_enabled) {
bts_trace_init_cpu(cpu);
if (trace_hw_branches_suspended &&
likely(per_cpu(tracer, cpu)))
ds_suspend_bts(per_cpu(tracer, cpu));
}
break;
case CPU_DOWN_PREPARE:
/* The notification is sent with interrupts enabled. */
if (likely(per_cpu(tracer, cpu))) {
ds_release_bts(per_cpu(tracer, cpu));
per_cpu(tracer, cpu) = NULL;
}
}
return NOTIFY_DONE;
}
static struct notifier_block bts_hotcpu_notifier __cpuinitdata = {
.notifier_call = bts_hotcpu_handler
};
static void bts_trace_print_header(struct seq_file *m)
{
seq_puts(m, "# CPU# TO <- FROM\n");
}
static enum print_line_t bts_trace_print_line(struct trace_iterator *iter)
{
unsigned long symflags = TRACE_ITER_SYM_OFFSET;
struct trace_entry *entry = iter->ent;
struct trace_seq *seq = &iter->seq;
struct hw_branch_entry *it;
trace_assign_type(it, entry);
if (entry->type == TRACE_HW_BRANCHES) {
if (trace_seq_printf(seq, "%4d ", iter->cpu) &&
seq_print_ip_sym(seq, it->to, symflags) &&
trace_seq_printf(seq, "\t <- ") &&
seq_print_ip_sym(seq, it->from, symflags) &&
trace_seq_printf(seq, "\n"))
return TRACE_TYPE_HANDLED;
return TRACE_TYPE_PARTIAL_LINE;
}
return TRACE_TYPE_UNHANDLED;
}
void trace_hw_branch(u64 from, u64 to)
{
struct ftrace_event_call *call = &event_hw_branch;
struct trace_array *tr = hw_branch_trace;
struct ring_buffer_event *event;
struct ring_buffer *buf;
struct hw_branch_entry *entry;
unsigned long irq1;
int cpu;
if (unlikely(!tr))
return;
if (unlikely(!trace_hw_branches_enabled))
return;
local_irq_save(irq1);
cpu = raw_smp_processor_id();
if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
goto out;
buf = tr->buffer;
event = trace_buffer_lock_reserve(buf, TRACE_HW_BRANCHES,
sizeof(*entry), 0, 0);
if (!event)
goto out;
entry = ring_buffer_event_data(event);
tracing_generic_entry_update(&entry->ent, 0, from);
entry->ent.type = TRACE_HW_BRANCHES;
entry->from = from;
entry->to = to;
if (!filter_check_discard(call, entry, buf, event))
trace_buffer_unlock_commit(buf, event, 0, 0);
out:
atomic_dec(&tr->data[cpu]->disabled);
local_irq_restore(irq1);
}
static void trace_bts_at(const struct bts_trace *trace, void *at)
{
struct bts_struct bts;
int err = 0;
WARN_ON_ONCE(!trace->read);
if (!trace->read)
return;
err = trace->read(this_tracer, at, &bts);
if (err < 0)
return;
switch (bts.qualifier) {
case BTS_BRANCH:
trace_hw_branch(bts.variant.lbr.from, bts.variant.lbr.to);
break;
}
}
/*
* Collect the trace on the current cpu and write it into the ftrace buffer.
*
* pre: tracing must be suspended on the current cpu
*/
static void trace_bts_cpu(void *arg)
{
struct trace_array *tr = (struct trace_array *)arg;
const struct bts_trace *trace;
unsigned char *at;
if (unlikely(!tr))
return;
if (unlikely(atomic_read(&tr->data[raw_smp_processor_id()]->disabled)))
return;
if (unlikely(!this_tracer))
return;
trace = ds_read_bts(this_tracer);
if (!trace)
return;
for (at = trace->ds.top; (void *)at < trace->ds.end;
at += trace->ds.size)
trace_bts_at(trace, at);
for (at = trace->ds.begin; (void *)at < trace->ds.top;
at += trace->ds.size)
trace_bts_at(trace, at);
}
static void trace_bts_prepare(struct trace_iterator *iter)
{
int cpu;
get_online_cpus();
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_suspend_bts(per_cpu(tracer, cpu));
/*
* We need to collect the trace on the respective cpu since ftrace
* implicitly adds the record for the current cpu.
* Once that is more flexible, we could collect the data from any cpu.
*/
on_each_cpu(trace_bts_cpu, iter->tr, 1);
for_each_online_cpu(cpu)
if (likely(per_cpu(tracer, cpu)))
ds_resume_bts(per_cpu(tracer, cpu));
put_online_cpus();
}
static void trace_bts_close(struct trace_iterator *iter)
{
tracing_reset_online_cpus(iter->tr);
}
void trace_hw_branch_oops(void)
{
if (this_tracer) {
ds_suspend_bts_noirq(this_tracer);
trace_bts_cpu(hw_branch_trace);
ds_resume_bts_noirq(this_tracer);
}
}
struct tracer bts_tracer __read_mostly =
{
.name = "hw-branch-tracer",
.init = bts_trace_init,
.reset = bts_trace_reset,
.print_header = bts_trace_print_header,
.print_line = bts_trace_print_line,
.start = bts_trace_start,
.stop = bts_trace_stop,
.open = trace_bts_prepare,
.close = trace_bts_close,
#ifdef CONFIG_FTRACE_SELFTEST
.selftest = trace_selftest_startup_hw_branches,
#endif /* CONFIG_FTRACE_SELFTEST */
};
__init static int init_bts_trace(void)
{
register_hotcpu_notifier(&bts_hotcpu_notifier);
return register_tracer(&bts_tracer);
}
device_initcall(init_bts_trace);