/* * h/w branch tracer for x86 based on bts * * Copyright (C) 2008-2009 Intel Corporation. * Markus Metzger , 2008-2009 */ #include #include #include #include #include #include #include #include #include #include "trace.h" #include "trace_output.h" #define SIZEOF_BTS (1 << 13) /* * The tracer lock protects the below per-cpu tracer array. * It needs to be held to: * - start tracing on all cpus * - stop tracing on all cpus * - start tracing on a single hotplug cpu * - stop tracing on a single hotplug cpu * - read the trace from all cpus * - read the trace from a single cpu */ static DEFINE_SPINLOCK(bts_tracer_lock); static DEFINE_PER_CPU(struct bts_tracer *, tracer); static DEFINE_PER_CPU(unsigned char[SIZEOF_BTS], buffer); #define this_tracer per_cpu(tracer, smp_processor_id()) #define this_buffer per_cpu(buffer, smp_processor_id()) static int __read_mostly trace_hw_branches_enabled; static struct trace_array *hw_branch_trace __read_mostly; /* * Start tracing on the current cpu. * The argument is ignored. * * pre: bts_tracer_lock must be locked. */ static void bts_trace_start_cpu(void *arg) { if (this_tracer) ds_release_bts(this_tracer); this_tracer = ds_request_bts(/* task = */ NULL, this_buffer, SIZEOF_BTS, /* ovfl = */ NULL, /* th = */ (size_t)-1, BTS_KERNEL); if (IS_ERR(this_tracer)) { this_tracer = NULL; return; } } static void bts_trace_start(struct trace_array *tr) { spin_lock(&bts_tracer_lock); on_each_cpu(bts_trace_start_cpu, NULL, 1); trace_hw_branches_enabled = 1; spin_unlock(&bts_tracer_lock); } /* * Stop tracing on the current cpu. * The argument is ignored. * * pre: bts_tracer_lock must be locked. */ static void bts_trace_stop_cpu(void *arg) { if (this_tracer) { ds_release_bts(this_tracer); this_tracer = NULL; } } static void bts_trace_stop(struct trace_array *tr) { spin_lock(&bts_tracer_lock); trace_hw_branches_enabled = 0; on_each_cpu(bts_trace_stop_cpu, NULL, 1); spin_unlock(&bts_tracer_lock); } static int __cpuinit bts_hotcpu_handler(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned long)hcpu; spin_lock(&bts_tracer_lock); if (!trace_hw_branches_enabled) goto out; switch (action) { case CPU_ONLINE: case CPU_DOWN_FAILED: smp_call_function_single(cpu, bts_trace_start_cpu, NULL, 1); break; case CPU_DOWN_PREPARE: smp_call_function_single(cpu, bts_trace_stop_cpu, NULL, 1); break; } out: spin_unlock(&bts_tracer_lock); return NOTIFY_DONE; } static struct notifier_block bts_hotcpu_notifier __cpuinitdata = { .notifier_call = bts_hotcpu_handler }; static int bts_trace_init(struct trace_array *tr) { hw_branch_trace = tr; bts_trace_start(tr); return 0; } static void bts_trace_reset(struct trace_array *tr) { bts_trace_stop(tr); } 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) { struct trace_entry *entry = iter->ent; struct trace_seq *seq = &iter->seq; struct hw_branch_entry *it; unsigned long symflags = TRACE_ITER_SYM_OFFSET; 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 trace_array *tr = hw_branch_trace; struct ring_buffer_event *event; 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; event = trace_buffer_lock_reserve(tr, 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; trace_buffer_unlock_commit(tr, 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: bts_tracer_lock must be locked */ 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; ds_suspend_bts(this_tracer); trace = ds_read_bts(this_tracer); if (!trace) goto out; 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); out: ds_resume_bts(this_tracer); } static void trace_bts_prepare(struct trace_iterator *iter) { spin_lock(&bts_tracer_lock); on_each_cpu(trace_bts_cpu, iter->tr, 1); spin_unlock(&bts_tracer_lock); } static void trace_bts_close(struct trace_iterator *iter) { tracing_reset_online_cpus(iter->tr); } void trace_hw_branch_oops(void) { spin_lock(&bts_tracer_lock); trace_bts_cpu(hw_branch_trace); spin_unlock(&bts_tracer_lock); } 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 }; __init static int init_bts_trace(void) { register_hotcpu_notifier(&bts_hotcpu_notifier); return register_tracer(&bts_tracer); } device_initcall(init_bts_trace);