1 /* 2 * trace event based perf event profiling/tracing 3 * 4 * Copyright (C) 2009 Red Hat Inc, Peter Zijlstra <pzijlstr@redhat.com> 5 * Copyright (C) 2009-2010 Frederic Weisbecker <fweisbec@gmail.com> 6 */ 7 8 #include <linux/module.h> 9 #include <linux/kprobes.h> 10 #include "trace.h" 11 12 DEFINE_PER_CPU(struct pt_regs, perf_trace_regs); 13 EXPORT_PER_CPU_SYMBOL_GPL(perf_trace_regs); 14 15 static char *perf_trace_buf; 16 static char *perf_trace_buf_nmi; 17 18 typedef typeof(char [PERF_MAX_TRACE_SIZE]) perf_trace_t ; 19 20 /* Count the events in use (per event id, not per instance) */ 21 static int total_ref_count; 22 23 static int perf_trace_event_enable(struct ftrace_event_call *event) 24 { 25 char *buf; 26 int ret = -ENOMEM; 27 28 if (event->perf_refcount++ > 0) 29 return 0; 30 31 if (!total_ref_count) { 32 buf = (char *)alloc_percpu(perf_trace_t); 33 if (!buf) 34 goto fail_buf; 35 36 rcu_assign_pointer(perf_trace_buf, buf); 37 38 buf = (char *)alloc_percpu(perf_trace_t); 39 if (!buf) 40 goto fail_buf_nmi; 41 42 rcu_assign_pointer(perf_trace_buf_nmi, buf); 43 } 44 45 ret = event->perf_event_enable(event); 46 if (!ret) { 47 total_ref_count++; 48 return 0; 49 } 50 51 fail_buf_nmi: 52 if (!total_ref_count) { 53 free_percpu(perf_trace_buf_nmi); 54 free_percpu(perf_trace_buf); 55 perf_trace_buf_nmi = NULL; 56 perf_trace_buf = NULL; 57 } 58 fail_buf: 59 event->perf_refcount--; 60 61 return ret; 62 } 63 64 int perf_trace_enable(int event_id) 65 { 66 struct ftrace_event_call *event; 67 int ret = -EINVAL; 68 69 mutex_lock(&event_mutex); 70 list_for_each_entry(event, &ftrace_events, list) { 71 if (event->id == event_id && event->perf_event_enable && 72 try_module_get(event->mod)) { 73 ret = perf_trace_event_enable(event); 74 break; 75 } 76 } 77 mutex_unlock(&event_mutex); 78 79 return ret; 80 } 81 82 static void perf_trace_event_disable(struct ftrace_event_call *event) 83 { 84 char *buf, *nmi_buf; 85 86 if (--event->perf_refcount > 0) 87 return; 88 89 event->perf_event_disable(event); 90 91 if (!--total_ref_count) { 92 buf = perf_trace_buf; 93 rcu_assign_pointer(perf_trace_buf, NULL); 94 95 nmi_buf = perf_trace_buf_nmi; 96 rcu_assign_pointer(perf_trace_buf_nmi, NULL); 97 98 /* 99 * Ensure every events in profiling have finished before 100 * releasing the buffers 101 */ 102 synchronize_sched(); 103 104 free_percpu(buf); 105 free_percpu(nmi_buf); 106 } 107 } 108 109 void perf_trace_disable(int event_id) 110 { 111 struct ftrace_event_call *event; 112 113 mutex_lock(&event_mutex); 114 list_for_each_entry(event, &ftrace_events, list) { 115 if (event->id == event_id) { 116 perf_trace_event_disable(event); 117 module_put(event->mod); 118 break; 119 } 120 } 121 mutex_unlock(&event_mutex); 122 } 123 124 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, 125 int *rctxp, unsigned long *irq_flags) 126 { 127 struct trace_entry *entry; 128 char *trace_buf, *raw_data; 129 int pc, cpu; 130 131 pc = preempt_count(); 132 133 /* Protect the per cpu buffer, begin the rcu read side */ 134 local_irq_save(*irq_flags); 135 136 *rctxp = perf_swevent_get_recursion_context(); 137 if (*rctxp < 0) 138 goto err_recursion; 139 140 cpu = smp_processor_id(); 141 142 if (in_nmi()) 143 trace_buf = rcu_dereference(perf_trace_buf_nmi); 144 else 145 trace_buf = rcu_dereference(perf_trace_buf); 146 147 if (!trace_buf) 148 goto err; 149 150 raw_data = per_cpu_ptr(trace_buf, cpu); 151 152 /* zero the dead bytes from align to not leak stack to user */ 153 *(u64 *)(&raw_data[size - sizeof(u64)]) = 0ULL; 154 155 entry = (struct trace_entry *)raw_data; 156 tracing_generic_entry_update(entry, *irq_flags, pc); 157 entry->type = type; 158 159 return raw_data; 160 err: 161 perf_swevent_put_recursion_context(*rctxp); 162 err_recursion: 163 local_irq_restore(*irq_flags); 164 return NULL; 165 } 166 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); 167