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 EXPORT_SYMBOL_GPL(perf_arch_fetch_caller_regs); 13 14 static char *perf_trace_buf[4]; 15 16 /* 17 * Force it to be aligned to unsigned long to avoid misaligned accesses 18 * suprises 19 */ 20 typedef typeof(unsigned long [PERF_MAX_TRACE_SIZE / sizeof(unsigned long)]) 21 perf_trace_t; 22 23 /* Count the events in use (per event id, not per instance) */ 24 static int total_ref_count; 25 26 static int perf_trace_event_init(struct ftrace_event_call *tp_event, 27 struct perf_event *p_event) 28 { 29 struct hlist_head *list; 30 int ret = -ENOMEM; 31 int cpu; 32 33 p_event->tp_event = tp_event; 34 if (tp_event->perf_refcount++ > 0) 35 return 0; 36 37 list = alloc_percpu(struct hlist_head); 38 if (!list) 39 goto fail; 40 41 for_each_possible_cpu(cpu) 42 INIT_HLIST_HEAD(per_cpu_ptr(list, cpu)); 43 44 tp_event->perf_events = list; 45 46 if (!total_ref_count) { 47 char *buf; 48 int i; 49 50 for (i = 0; i < 4; i++) { 51 buf = (char *)alloc_percpu(perf_trace_t); 52 if (!buf) 53 goto fail; 54 55 perf_trace_buf[i] = buf; 56 } 57 } 58 59 if (tp_event->class->reg) 60 ret = tp_event->class->reg(tp_event, TRACE_REG_PERF_REGISTER); 61 else 62 ret = tracepoint_probe_register(tp_event->name, 63 tp_event->class->perf_probe, 64 tp_event); 65 66 if (ret) 67 goto fail; 68 69 total_ref_count++; 70 return 0; 71 72 fail: 73 if (!total_ref_count) { 74 int i; 75 76 for (i = 0; i < 4; i++) { 77 free_percpu(perf_trace_buf[i]); 78 perf_trace_buf[i] = NULL; 79 } 80 } 81 82 if (!--tp_event->perf_refcount) { 83 free_percpu(tp_event->perf_events); 84 tp_event->perf_events = NULL; 85 } 86 87 return ret; 88 } 89 90 int perf_trace_init(struct perf_event *p_event) 91 { 92 struct ftrace_event_call *tp_event; 93 int event_id = p_event->attr.config; 94 int ret = -EINVAL; 95 96 mutex_lock(&event_mutex); 97 list_for_each_entry(tp_event, &ftrace_events, list) { 98 if (tp_event->event.type == event_id && 99 tp_event->class && tp_event->class->perf_probe && 100 try_module_get(tp_event->mod)) { 101 ret = perf_trace_event_init(tp_event, p_event); 102 break; 103 } 104 } 105 mutex_unlock(&event_mutex); 106 107 return ret; 108 } 109 110 int perf_trace_enable(struct perf_event *p_event) 111 { 112 struct ftrace_event_call *tp_event = p_event->tp_event; 113 struct hlist_head *list; 114 115 list = tp_event->perf_events; 116 if (WARN_ON_ONCE(!list)) 117 return -EINVAL; 118 119 list = this_cpu_ptr(list); 120 hlist_add_head_rcu(&p_event->hlist_entry, list); 121 122 return 0; 123 } 124 125 void perf_trace_disable(struct perf_event *p_event) 126 { 127 hlist_del_rcu(&p_event->hlist_entry); 128 } 129 130 void perf_trace_destroy(struct perf_event *p_event) 131 { 132 struct ftrace_event_call *tp_event = p_event->tp_event; 133 int i; 134 135 mutex_lock(&event_mutex); 136 if (--tp_event->perf_refcount > 0) 137 goto out; 138 139 if (tp_event->class->reg) 140 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER); 141 else 142 tracepoint_probe_unregister(tp_event->name, 143 tp_event->class->perf_probe, 144 tp_event); 145 146 /* 147 * Ensure our callback won't be called anymore. See 148 * tracepoint_probe_unregister() and __DO_TRACE(). 149 */ 150 synchronize_sched(); 151 152 free_percpu(tp_event->perf_events); 153 tp_event->perf_events = NULL; 154 155 if (!--total_ref_count) { 156 for (i = 0; i < 4; i++) { 157 free_percpu(perf_trace_buf[i]); 158 perf_trace_buf[i] = NULL; 159 } 160 } 161 out: 162 mutex_unlock(&event_mutex); 163 } 164 165 __kprobes void *perf_trace_buf_prepare(int size, unsigned short type, 166 struct pt_regs *regs, int *rctxp) 167 { 168 struct trace_entry *entry; 169 unsigned long flags; 170 char *raw_data; 171 int pc; 172 173 BUILD_BUG_ON(PERF_MAX_TRACE_SIZE % sizeof(unsigned long)); 174 175 pc = preempt_count(); 176 177 *rctxp = perf_swevent_get_recursion_context(); 178 if (*rctxp < 0) 179 return NULL; 180 181 raw_data = this_cpu_ptr(perf_trace_buf[*rctxp]); 182 183 /* zero the dead bytes from align to not leak stack to user */ 184 memset(&raw_data[size - sizeof(u64)], 0, sizeof(u64)); 185 186 entry = (struct trace_entry *)raw_data; 187 local_save_flags(flags); 188 tracing_generic_entry_update(entry, flags, pc); 189 entry->type = type; 190 191 return raw_data; 192 } 193 EXPORT_SYMBOL_GPL(perf_trace_buf_prepare); 194